Add some tests for the new executor system

And fix a couple of bugs picked up by said tests

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,16 @@
+---
+name: Bug report
+about: Report some misbehaviour in the mod
+
+---
+
+<!--
+## Before reporting
+ - Search for the bug both here and [on the ComputerCraft issues page](https://github.com/dan200/ComputerCraft/issues?utf8=%E2%9C%93&q=is%3Aissue+)
+ - If possible, try to reproduce on vanilla ComputerCraft. If it still occurs, [report on the ComputerCraft repo](https://github.com/dan200/ComputerCraft/issues/new) instead.
+-->
+
+## Useful information to include:
+ - Minecraft version
+ - CC: Tweaked version
+ - Detailed reproduction steps!** Sometimes I can spot a bug pretty easily, but often it's much more obscure. Anything you can give which will help reproduce it means it'll get fixed quicker.

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,15 @@
+---
+name: Feature request
+about: Suggest an idea or improvement
+
+---
+
+<!--
+## Before reporting
+ - Search for the suggestion both here and [on the ComputerCraft issues page](https://github.com/dan200/ComputerCraft/issues?utf8=%E2%9C%93&q=is%3Aissue+). It's possible someone's suggested it before!
+ - Unless something is specific to CC:Tweaked, try to [suggest them on the ComputerCraft repo](https://github.com/dan200/ComputerCraft/issues/new). There's a lot more people watching it, so it allows the wider community to contribute.
+-->
+
+## Useful information to include:
+ - Explanation of how the feature/change chould work.
+ - Some rationale/use case for a feature. I'd like to keep CC:T as minimal

.github/pull_request_template.md

@@ -0,0 +1,9 @@
+<!--
+Unless this feature is specific to CC:Tweaked, try to [target the original ComputerCraft repo](https://github.com/dan200/ComputerCraft/) instead. There's a lot more people watching it, so it allows the wider community to contribute.
+-->
+
+## Useful information to include:
+ - Brief explanation of the changes you've made.
+ - Rationale of why this change has been made/reasoning behind it.
+
+The more information you can provide, the easier it is to review something now _and_ to see why a change was made, when the code needs updating in the future.

README.md

@@ -6,26 +6,42 @@ features of the mod. For a more stable experience, I recommend checking out the
 [original mod](https://github.com/dan200/ComputerCraft).
 
 ## What?
-CC: Tweaked does not aim to create a competing fork of ComputerCraft, nor am I planning to take it in in a vastly
-different direction to the original mod. In fact, CC: Tweaked aims to be a nurturing ground for various features, with
-a pull request against the original mod being the end goal.
+CC: Tweaked (or CC:T for short) does not aim to create a competing fork of ComputerCraft, nor am I planning to take it
+in in a vastly different direction to the original mod. In fact, CC:T aims to be a nurturing ground for various
+features, with a pull request against the original mod being the end goal.
 
-CC: Tweaked also includes many pull requests from the community which have not yet been merged, offering a large number
+CC:T also includes many pull requests from the community which have not yet been merged, offering a large number
 of additional bug fixes and features over the original mod.
 
+## Features
+CC: Tweaked contains the all features of the latest alpha, as well as numerous fixes, performance improvements and
+several additional features. I'd recommend checking out [the releases page](https://github.com/SquidDev-CC/CC-Tweaked/releases)
+to see the full changes, but here's a couple of the more interesting changes:
+
+ - Replace LuaJ with Cobalt.
+ - Allow running multiple computers at the same time.
+ - Websocket support in the HTTP library.
+ - Wired modems and cables act more like multiparts.
+ - Add map-like rendering for pocket computers and printed pages/books.
+ - Adds the `/computercraft` command, offering various diagnostic tools for server owners. This allows operators to
+   track which computers are hogging resources, turn on and shutdown multiple computers at once and interact with
+   computers remotely.
+ - Add full-block wired modems, allowing one to wrap non-solid peripherals (such as turtles, or chests if Plethora is
+   installed).
+
 ## Relation to CCTweaks?
-This mod has nothing to do with CCTweaks, though there is no denying the name is a throwback to it. However, I do plan
-to migrate some features of CCTweaks into CC: Tweaked.
+This mod has nothing to do with CCTweaks, though there is no denying the name is a throwback to it. That being said,
+several features have been included, such as full block modems, the Cobalt runtime and map-like rendering for pocket
+computers.
 
 ## Contributing
 Any contribution is welcome, be that using the mod, reporting bugs or contributing code. If you do wish to contribute
 code, do consider submitting it to the ComputerCraft repository instead.
 
-That being said, in order to start helping develop CC: Tweaked, you'll need to follow these steps:
+That being said, in order to start helping develop CC:T, you'll need to follow these steps:
 
  - **Clone the repository:** `git clone https://github.com/SquidDev-CC/CC-Tweaked.git && cd CC-Tweaked`
  - **Setup Forge:** `./gradlew setupDecompWorkspace`
  - **Test your changes:** `./gradlew runClient` (or run the `GradleStart` class from your IDE).
- 
-If you want to run CC: Tweaked in a normal Minecraft instance, run `./gradlew build` and copy the `.jar` from 
-`build/libs`.
+
+If you want to run CC:T in a normal Minecraft instance, run `./gradlew build` and copy the `.jar` from `build/libs`.

build.gradle

@@ -23,12 +23,12 @@ apply plugin: 'org.ajoberstar.grgit'
 apply plugin: 'maven-publish'
 apply plugin: 'maven'
 
-version = "1.80pr1.6"
+version = "1.80pr1.8"
 group = "org.squiddev"
 archivesBaseName = "cc-tweaked"
 
 minecraft {
-    version = "1.12.2-14.23.2.2634"
+    version = "1.12.2-14.23.4.2749"
     runDir = "run"
     replace '${version}', project.version
 
@@ -37,11 +37,12 @@ minecraft {
     // stable_#            stables are built at the discretion of the MCP team.
     // Use non-default mappings at your own risk. they may not allways work.
     // simply re-run your setup task after changing the mappings to update your workspace.
-    mappings = "snapshot_20180324"
+    mappings = "snapshot_20180724"
     // makeObfSourceJar = false // an Srg named sources jar is made by default. uncomment this to disable.
 }
 
 repositories {
+    mavenLocal()
     maven {
         name = "JEI"
         url  = "http://dvs1.progwml6.com/files/maven"
@@ -50,6 +51,8 @@ repositories {
         name = "squiddev"
         url = "https://dl.bintray.com/squiddev/maven"
     }
+
+    ivy { artifactPattern "https://asie.pl/files/mods/Charset/LibOnly/[module]-[revision](-[classifier]).[ext]" }
 }
 
 configurations {
@@ -60,8 +63,11 @@ configurations {
 
 dependencies {
     deobfProvided "mezz.jei:jei_1.12.2:4.8.5.159:api"
+    deobfProvided "pl.asie:Charset-Lib:0.5.4.6"
+
     runtime "mezz.jei:jei_1.12.2:4.8.5.159"
-    shade 'org.squiddev:Cobalt:0.3.1'
+
+    shade 'org.squiddev:Cobalt:0.3.2-nothread'
 
     testCompile 'junit:junit:4.11'
 
@@ -191,3 +197,9 @@ gradle.projectsEvaluated {
 
 runClient.outputs.upToDateWhen { false }
 runServer.outputs.upToDateWhen { false }
+
+test {
+    testLogging {
+        events "failed", "standardOut", "standardError"
+    }
+}

src/main/java/dan200/computercraft/ComputerCraft.java

@@ -98,6 +98,7 @@ import java.net.MalformedURLException;
 import java.net.URISyntaxException;
 import java.net.URL;
 import java.util.*;
+import java.util.function.Function;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipFile;
 
@@ -1124,13 +1125,18 @@ public class ComputerCraft
         turtleProxy.addAllUpgradedTurtles( list );
     }
 
-    public static void setEntityDropConsumer( Entity entity, IEntityDropConsumer consumer )
+    public static void setDropConsumer( Entity entity, Function<ItemStack, ItemStack> consumer )
     {
-        turtleProxy.setEntityDropConsumer( entity, consumer );
+        turtleProxy.setDropConsumer( entity, consumer );
     }
 
-    public static void clearEntityDropConsumer( Entity entity )
+    public static void setDropConsumer( World world, BlockPos pos, Function<ItemStack, ItemStack> consumer )
     {
-        turtleProxy.clearEntityDropConsumer( entity );
+        turtleProxy.setDropConsumer( world, pos, consumer );
+    }
+
+    public static List<ItemStack> clearDropConsumer( )
+    {
+        return turtleProxy.clearDropConsumer();
     }
 }

src/main/java/dan200/computercraft/api/lua/ICallContext.java

@@ -0,0 +1,31 @@
+/*
+ * This file is part of the public ComputerCraft API - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. This API may be redistributed unmodified and in full only.
+ * For help using the API, and posting your mods, visit the forums at computercraft.info.
+ */
+
+package dan200.computercraft.api.lua;
+
+import javax.annotation.Nonnull;
+
+/**
+ * An interface passed to peripherals and {@link ILuaObject}s by computers or turtles, providing methods that allow the
+ * method to interact with the invoking computer.
+ */
+public interface ICallContext
+{
+    /**
+     * Queue a task to be executed on the main server thread at the beginning of next tick, but do not wait for it to
+     * complete. This should be used when you need to interact with the world in a thread-safe manner but do not care
+     * about the result or you wish to run asynchronously.
+     *
+     * When the task has finished, it will enqueue a {@code task_completed} event, which takes the task id, a success
+     * value and the return values, or an error message if it failed. If you need to wait on this event, it may be
+     * better to use {@link MethodResult#onMainThread(ILuaCallable)}.
+     *
+     * @param task The task to execute on the main thread.
+     * @return The "id" of the task. This will be the first argument to the {@code task_completed} event.
+     * @throws LuaException If the task could not be queued.
+     */
+    long issueMainThreadTask( @Nonnull ILuaTask task ) throws LuaException;
+}

src/main/java/dan200/computercraft/api/lua/ILuaCallable.java

@@ -0,0 +1,31 @@
+/*
+ * This file is part of the public ComputerCraft API - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. This API may be redistributed unmodified and in full only.
+ * For help using the API, and posting your mods, visit the forums at computercraft.info.
+ */
+
+package dan200.computercraft.api.lua;
+
+import javax.annotation.Nonnull;
+
+/**
+ * A function which calls performs an action in a specific context (such as on the server thread) and returns a result.
+ *
+ * @see MethodResult#onMainThread(ILuaCallable)
+ * @see ILuaContext#executeMainThreadTask(ILuaTask)
+ */
+@FunctionalInterface
+public interface ILuaCallable
+{
+    /**
+     * Run the code within the specified context and return the result to continue with.
+     *
+     * @return The result of executing this function. Note that this may not be evaluated within the same context as
+     * this call is.
+     * @throws LuaException If you throw any exception from this function, a lua error will be raised with the
+     *                      same message as your exception. Use this to throw appropriate errors if the wrong
+     *                      arguments are supplied to your method.
+     */
+    @Nonnull
+    MethodResult execute() throws LuaException;
+}

src/main/java/dan200/computercraft/api/lua/ILuaContext.java

@@ -1,6 +1,6 @@
 /*
  * This file is part of the public ComputerCraft API - http://www.computercraft.info
- * Copyright Daniel Ratcliffe, 2011-2017. This API may be redistributed unmodified and in full only.
+ * Copyright Daniel Ratcliffe, 2011-2018. This API may be redistributed unmodified and in full only.
  * For help using the API, and posting your mods, visit the forums at computercraft.info.
  */
 
@@ -13,8 +13,11 @@ import javax.annotation.Nullable;
  * An interface passed to peripherals and {@link ILuaObject}s by computers or turtles, providing methods
  * that allow the peripheral call to wait for events before returning, just like in lua. This is very useful if you need
  * to signal work to be performed on the main thread, and don't want to return until the work has been completed.
+ *
+ * This interface mostly exists for integrating with older code. One should use {@link MethodResult} instead, as this
+ * encourages an asynchronous way of interacting with Lua coroutines.
  */
-public interface ILuaContext
+public interface ILuaContext extends ICallContext
 {
     /**
      * Wait for an event to occur on the computer, suspending the thread until it arises. This method is exactly
@@ -30,8 +33,10 @@ public interface ILuaContext
      * @throws InterruptedException If the user shuts down or reboots the computer while pullEvent() is waiting for an
      *                              event, InterruptedException will be thrown. This exception must not be caught or
      *                              intercepted, or the computer will leak memory and end up in a broken state.
+     * @deprecated Use {@link MethodResult#pullEvent(String, ILuaFunction)}
      */
     @Nonnull
+    @Deprecated
     Object[] pullEvent( @Nullable String filter ) throws LuaException, InterruptedException;
 
     /**
@@ -45,8 +50,10 @@ public interface ILuaContext
      *                              an event, InterruptedException will be thrown. This exception must not be caught or
      *                              intercepted, or the computer will leak memory and end up in a broken state.
      * @see #pullEvent(String)
+     * @deprecated Use {@link MethodResult#pullEventRaw(String, ILuaFunction)}
      */
     @Nonnull
+    @Deprecated
     Object[] pullEventRaw( @Nullable String filter ) throws InterruptedException;
 
     /**
@@ -59,8 +66,10 @@ public interface ILuaContext
      *                              InterruptedException will be thrown. This exception must not be caught or
      *                              intercepted, or the computer will leak memory and end up in a broken state.
      * @see #pullEvent(String)
+     * @deprecated Use {@link MethodResult#pullEventRaw(ILuaFunction)}
      */
     @Nonnull
+    @Deprecated
     Object[] yield( @Nullable Object[] arguments ) throws InterruptedException;
 
     /**
@@ -76,22 +85,9 @@ public interface ILuaContext
      * @throws InterruptedException If the user shuts down or reboots the computer the coroutine is suspended,
      *                              InterruptedException will be thrown. This exception must not be caught or
      *                              intercepted, or the computer will leak memory and end up in a broken state.
+     * @deprecated Use {@link MethodResult#onMainThread(ILuaCallable)}
      */
     @Nullable
+    @Deprecated
     Object[] executeMainThreadTask( @Nonnull ILuaTask task ) throws LuaException, InterruptedException;
-
-    /**
-     * Queue a task to be executed on the main server thread at the beginning of next tick, but do not wait for it to
-     * complete. This should be used when you need to interact with the world in a thread-safe manner but do not care
-     * about the result or you wish to run asynchronously.
-     *
-     * When the task has finished, it will enqueue a {@code task_completed} event, which takes the task id, a success
-     * value and the return values, or an error message if it failed. If you need to wait on this event, it may be
-     * better to use {@link #executeMainThreadTask(ILuaTask)}.
-     *
-     * @param task The task to execute on the main thread.
-     * @return The "id" of the task. This will be the first argument to the {@code task_completed} event.
-     * @throws LuaException If the task could not be queued.
-     */
-    long issueMainThreadTask( @Nonnull ILuaTask task ) throws LuaException;
 }

src/main/java/dan200/computercraft/api/lua/ILuaContextTask.java

@@ -0,0 +1,24 @@
+/*
+ * This file is part of the public ComputerCraft API - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. This API may be redistributed unmodified and in full only.
+ * For help using the API, and posting your mods, visit the forums at computercraft.info.
+ */
+
+package dan200.computercraft.api.lua;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+/**
+ * A function which executes using a {@link ILuaContext}.
+ *
+ * Like {@link ILuaContext}, this is not intended for use in the future - it purely exists as an argument for
+ * {@link MethodResult#withLuaContext(ILuaContextTask)}.
+ */
+@FunctionalInterface
+public interface ILuaContextTask
+{
+    @Nullable
+    @Deprecated
+    Object[] execute( @Nonnull ILuaContext context ) throws LuaException, InterruptedException;
+}

src/main/java/dan200/computercraft/api/lua/ILuaFunction.java

@@ -0,0 +1,33 @@
+/*
+ * This file is part of the public ComputerCraft API - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. This API may be redistributed unmodified and in full only.
+ * For help using the API, and posting your mods, visit the forums at computercraft.info.
+ */
+
+package dan200.computercraft.api.lua;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+/**
+ * A Lua function which consumes some values and returns a result.
+ *
+ * @see MethodResult#then(ILuaFunction)
+ * @see MethodResult#pullEvent(ILuaFunction)
+ * @see MethodResult#pullEventRaw(String)
+ */
+@FunctionalInterface
+public interface ILuaFunction
+{
+    /**
+     * Accept the values and return another method result.
+     *
+     * @param values The inputs for this function.
+     * @return The result of executing this function.
+     * @throws LuaException If you throw any exception from this function, a lua error will be raised with the
+     *                      same message as your exception. Use this to throw appropriate errors if the wrong
+     *                      arguments are supplied to your method.
+     */
+    @Nonnull
+    MethodResult call( @Nullable Object[] values ) throws LuaException;
+}

src/main/java/dan200/computercraft/api/lua/ILuaObject.java

@@ -1,6 +1,6 @@
 /*
  * This file is part of the public ComputerCraft API - http://www.computercraft.info
- * Copyright Daniel Ratcliffe, 2011-2017. This API may be redistributed unmodified and in full only.
+ * Copyright Daniel Ratcliffe, 2011-2018. This API may be redistributed unmodified and in full only.
  * For help using the API, and posting your mods, visit the forums at computercraft.info.
  */
 
@@ -41,16 +41,45 @@ public interface ILuaObject
      *                  wishes to call. The integer indicates the index into the getMethodNames() table
      *                  that corresponds to the string passed into peripheral.call()
      * @param arguments The arguments for this method. See {@link IPeripheral#callMethod(IComputerAccess, ILuaContext, int, Object[])}
-     *                  the possible values and conversion rules.
-     * @return An array of objects, representing the values you wish to return to the Lua program.
-     * See {@link IPeripheral#callMethod(IComputerAccess, ILuaContext, int, Object[])} for the valid values and
-     * conversion rules.
-     * @throws LuaException         If the task could not be queued, or if the task threw an exception.
+     *                  for the possible values and conversion rules.
+     * @return An array of objects, representing the values you wish to return to the Lua program. See
+     * {@link MethodResult#of(Object...)}  for the valid values and conversion rules.
+     * @throws LuaException         If you throw any exception from this function, a lua error will be raised with the
+     *                              same message as your exception. Use this to throw appropriate errors if the wrong
+     *                              arguments are supplied to your method.
      * @throws InterruptedException If the user shuts down or reboots the computer the coroutine is suspended,
      *                              InterruptedException will be thrown. This exception must not be caught or
-     *                              intercepted, or the computer will leak memory and end up in a broken state.w
+     *                              intercepted, or the computer will leak memory and end up in a broken state.
      * @see IPeripheral#callMethod(IComputerAccess, ILuaContext, int, Object[])
+     * @deprecated Use {@link #callMethod(ICallContext, int, Object[])} instead.
      */
     @Nullable
+    @Deprecated
     Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException;
+
+    /**
+     * Called when a user calls one of the methods that this object implements. This works the same as
+     * {@link IPeripheral#callMethod(IComputerAccess, ICallContext, int, Object[])}}. See that method for detailed
+     * documentation.
+     *
+     * @param context   The context of the current call.
+     * @param method    An integer identifying which of the methods from getMethodNames() the computercraft
+     *                  wishes to call. The integer indicates the index into the getMethodNames() table
+     *                  that corresponds to the string passed into peripheral.call()
+     * @param arguments The arguments for this method. See {@link IPeripheral#callMethod(IComputerAccess, ICallContext, int, Object[])}
+     *                  for the possible values and conversion rules.
+     * @return The result of calling this method. Use {@link MethodResult#empty()} to return nothing or
+     * {@link MethodResult#of(Object...)} to return several values.
+     * @throws LuaException         If you throw any exception from this function, a lua error will be raised with the
+     *                              same message as your exception. Use this to throw appropriate errors if the wrong
+     *                              arguments are supplied to your method.
+     * @see IPeripheral#callMethod(IComputerAccess, ICallContext, int, Object[])
+     * @see MethodResult
+     */
+    @Nonnull
+    @SuppressWarnings( { "deprecation" } )
+    default MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] arguments ) throws LuaException
+    {
+        return MethodResult.withLuaContext( lua -> callMethod( lua, method, arguments ) );
+    }
 }

src/main/java/dan200/computercraft/api/lua/LuaContextResultEvaluator.java

@@ -0,0 +1,105 @@
+/*
+ * This file is part of the public ComputerCraft API - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. This API may be redistributed unmodified and in full only.
+ * For help using the API, and posting your mods, visit the forums at computercraft.info.
+ */
+
+package dan200.computercraft.api.lua;
+
+import javax.annotation.Nonnull;
+import java.util.ArrayDeque;
+import java.util.Deque;
+
+/**
+ * Evaluates {@link MethodResult}s within a {@link ILuaContext}.
+ *
+ * @see MethodResult#evaluate(ILuaContext)
+ * @see MethodResult#withLuaContext(ILuaContextTask)
+ * @deprecated This should not be used except to interface between the two call call systems.
+ */
+@Deprecated
+class LuaContextResultEvaluator
+{
+    @Deprecated
+    public static Object[] evaluate( @Nonnull ILuaContext context, @Nonnull MethodResult future ) throws LuaException, InterruptedException
+    {
+        Deque<ILuaFunction> callbacks = null;
+        while( true )
+        {
+            if( future instanceof MethodResult.AndThen )
+            {
+                MethodResult.AndThen then = ((MethodResult.AndThen) future);
+
+                // Thens are "unwrapped", being pushed onto a stack
+                if( callbacks == null ) callbacks = new ArrayDeque<>();
+                callbacks.addLast( then.getCallback() );
+
+                future = then.getPrevious();
+                if( future == null ) throw new NullPointerException( "Null result from " + then.getCallback() );
+            }
+            else if( future instanceof MethodResult.Immediate )
+            {
+                Object[] values = ((MethodResult.Immediate) future).getResult();
+
+                // Immediate values values will attempt to call the previous "then", or return if nothing 
+                // else needs to be done.
+                ILuaFunction callback = callbacks == null ? null : callbacks.pollLast();
+                if( callback == null ) return values;
+
+                future = callback.call( values );
+                if( future == null ) throw new NullPointerException( "Null result from " + callback );
+            }
+            else if( future instanceof MethodResult.OnEvent )
+            {
+                MethodResult.OnEvent onEvent = (MethodResult.OnEvent) future;
+
+                // Poll for an event, and then call the previous "then" or return if nothing else needs 
+                // to be done. 
+                Object[] values = onEvent.isRaw() ? context.pullEventRaw( onEvent.getFilter() ) : context.pullEvent( onEvent.getFilter() );
+
+                ILuaFunction callback = callbacks == null ? null : callbacks.pollLast();
+                if( callback == null ) return values;
+
+                future = callback.call( values );
+                if( future == null ) throw new NullPointerException( "Null result from " + callback );
+            }
+            else if( future instanceof MethodResult.OnMainThread )
+            {
+                MethodResult.OnMainThread onMainThread = (MethodResult.OnMainThread) future;
+
+                // Evaluate our task on the main thread and mark it as the next future to evaluate.
+                Reference temporary = new Reference();
+                context.executeMainThreadTask( () -> {
+                    temporary.value = onMainThread.getTask().execute();
+                    return null;
+                } );
+
+                future = temporary.value;
+                if( future == null ) throw new NullPointerException( "Null result from " + onMainThread.getTask() );
+            }
+            else if( future instanceof MethodResult.WithLuaContext )
+            {
+                MethodResult.WithLuaContext withContext = (MethodResult.WithLuaContext) future;
+
+                // Run the task, and then call the previous "then" or return if nothing else
+                // needs to be done. 
+                Object[] values = withContext.getConsumer().execute( context );
+
+                ILuaFunction callback = callbacks == null ? null : callbacks.pollLast();
+                if( callback == null ) return values;
+                
+                future = callback.call( values );
+                if( future == null ) throw new NullPointerException( "Null result from " + callback );
+            }
+            else
+            {
+                throw new IllegalStateException( "Unknown MethodResult " + future );
+            }
+        }
+    }
+
+    private static class Reference
+    {
+        MethodResult value;
+    }
+}

src/main/java/dan200/computercraft/api/lua/MethodResult.java

@@ -0,0 +1,354 @@
+/*
+ * This file is part of the public ComputerCraft API - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. This API may be redistributed unmodified and in full only.
+ * For help using the API, and posting your mods, visit the forums at computercraft.info.
+ */
+
+package dan200.computercraft.api.lua;
+
+import com.google.common.base.Preconditions;
+import com.google.common.util.concurrent.ListenableFuture;
+import dan200.computercraft.api.peripheral.IComputerAccess;
+import dan200.computercraft.api.peripheral.IPeripheral;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import java.util.Map;
+
+/**
+ * The result of calling a method, such as {@link ILuaObject#callMethod(ICallContext, int, Object[])} or
+ * {@link IPeripheral#callMethod(IComputerAccess, ICallContext, int, Object[])}.
+ *
+ * This is non-dissimilar to a promise or {@link ListenableFuture}. One can either return an immediate value through
+ * {@link #of(Object...)}, wait for an external action with {@link #onMainThread(ILuaCallable)} or {@link #pullEvent()}
+ * and then act on the result of either of those by using {@link #then(ILuaFunction)}.
+ */
+public abstract class MethodResult
+{
+    private static MethodResult empty;
+
+    MethodResult()
+    {
+    }
+
+    /**
+     * A result which returns immediately with no value.
+     *
+     * Use {@link #of(Object...)} if you need to return one or more values.
+     *
+     * @return The empty method result.
+     * @see #of(Object...)
+     */
+    @Nonnull
+    public static MethodResult empty()
+    {
+        if( empty == null ) empty = new Immediate( null );
+        return empty;
+    }
+
+    /**
+     * A result which returns several values.
+     *
+     * @param result The values to return, this may be {@code null}. {@link Number}s, {@link String}s, {@link Boolean}s,
+     *               {@link Map}s, {@link ILuaObject}s, and {@code null} be converted to their corresponding lua type.
+     *               All other types will be converted to nil.
+     * @return A result which will return these values when evaluated.
+     * @see #empty()
+     */
+    @Nonnull
+    public static MethodResult of( Object... result )
+    {
+        return result == null ? empty() : new Immediate( result );
+    }
+
+    /**
+     * Wait for an event to occur on the computer, suspending the coroutine until it arises. This method is equivalent
+     * to {@code os.pullEvent()} in Lua.
+     *
+     * Normally you'll wish to consume the event using {@link #then(ILuaFunction)}. This can be done slightly more
+     * easily with {@link #pullEvent(ILuaFunction)}.
+     *
+     * If you want to listen to a specific event, it's easier to use {@link #pullEvent(String)} rather than
+     * running until the desired event is found.
+     *
+     * @return The constructed method result. This evaluates to the name of the event that occurred, and any event
+     * parameters.
+     * @see #pullEvent(ILuaFunction)
+     * @see #pullEvent(String)
+     */
+    @Nonnull
+    public static MethodResult pullEvent()
+    {
+        return new OnEvent( false, null );
+    }
+
+    /**
+     * Wait for the specified event to occur on the computer, suspending the coroutine until it arises. This method is
+     * equivalent to {@code os.pullEvent(event)} in Lua.
+     *
+     * Normally you'll wish to consume the event using {@link #then(ILuaFunction)}. This can be done slightly more
+     * easily with {@link #pullEvent(String, ILuaFunction)}.
+     *
+     * @param filter The event name to filter on.
+     * @return The constructed method result. This evaluates to the name of the event that occurred, and any event
+     * parameters.
+     * @see #pullEvent(String, ILuaFunction)
+     * @see #pullEvent()
+     */
+    @Nonnull
+    public static MethodResult pullEvent( @Nonnull String filter )
+    {
+        Preconditions.checkNotNull( filter, "event cannot be null" );
+        return new OnEvent( false, filter );
+    }
+
+    /**
+     * Wait for an event to occur on the computer, suspending the coroutine until it arises. This method to
+     * {@link #pullEvent()} and {@link #then(ILuaFunction)}.
+     *
+     * If you want to listen to a specific event, it's easier to use {@link #pullEvent(String, ILuaFunction)} rather
+     * than running until the desired event is found.
+     *
+     * @param callback The function to call when the event is received.
+     * @return The constructed method result. This evaluates to the result of the {@code callback}.
+     * @see #pullEvent()
+     * @see #pullEvent(String, ILuaFunction)
+     */
+    @Nonnull
+    public static MethodResult pullEvent( @Nonnull ILuaFunction callback )
+    {
+        Preconditions.checkNotNull( callback, "callback cannot be null" );
+        return new OnEvent( false, null ).then( callback );
+    }
+
+    /**
+     * Wait for the specified event to occur on the computer, suspending the coroutine until it arises. This method to
+     * {@link #pullEvent(String)} and {@link #then(ILuaFunction)}.
+     *
+     * @param filter   The event name to filter on.
+     * @param callback The function to call when the event is received.
+     * @return The constructed method result. This evaluates to the result of the {@code callback}.
+     * @see #pullEvent(String)
+     * @see #pullEvent(ILuaFunction)
+     */
+    @Nonnull
+    public static MethodResult pullEvent( @Nullable String filter, @Nonnull ILuaFunction callback )
+    {
+        Preconditions.checkNotNull( callback, "callback cannot be null" );
+        return new OnEvent( false, filter ).then( callback );
+    }
+
+    /**
+     * The same as {@link #pullEvent()}, except {@code terminated} events are also passed to the callback, instead of
+     * throwing an error. Only use this if you want to prevent program termination, which is not recommended.
+     *
+     * @return The constructed method result. This evaluates to the name of the event that occurred, and any event
+     * parameters.
+     */
+    @Nonnull
+    public static MethodResult pullEventRaw()
+    {
+        return new OnEvent( true, null );
+    }
+
+    /**
+     * The same as {@link #pullEvent(String)}, except {@code terminated} events are also passed to the callback, instead
+     * of throwing an error. Only use this if you want to prevent program termination, which is not recommended.
+     *
+     * @param filter The event name to filter on.
+     * @return The constructed method result. This evaluates to the name of the event that occurred, and any event
+     * parameters.
+     */
+    @Nonnull
+    public static MethodResult pullEventRaw( @Nonnull String filter )
+    {
+        return new OnEvent( true, filter );
+    }
+
+    /**
+     * The same as {@link #pullEvent(ILuaFunction)}, except {@code terminated} events are also passed to the callback,
+     * instead of throwing an error. Only use this if you want to prevent program termination, which is not recommended.
+     *
+     * @param callback The function to call when the event is received.
+     * @return The constructed method result. This evaluates to the result of the {@code callback}.
+     */
+    @Nonnull
+    public static MethodResult pullEventRaw( @Nonnull ILuaFunction callback )
+    {
+        Preconditions.checkNotNull( callback, "callback cannot be null" );
+        return new OnEvent( true, null ).then( callback );
+    }
+
+    /**
+     * The same as {@link #pullEvent(String, ILuaFunction)}, except {@code terminated} events are also passed to the
+     * callback, instead of throwing an error. Only use this if you want to prevent program termination, which is not
+     * recommended.
+     *
+     * @param filter   The event name to filter on.
+     * @param callback The function to call when the event is received.
+     * @return The constructed method result. This evaluates to the result of the {@code callback}.
+     */
+    @Nonnull
+    public static MethodResult pullEventRaw( @Nullable String filter, @Nonnull ILuaFunction callback )
+    {
+        Preconditions.checkNotNull( callback, "callback cannot be null" );
+        return new OnEvent( true, filter ).then( callback );
+    }
+
+    /**
+     * Queue a task to be executed on the main server thread at the beginning of next tick, waiting for it to complete.
+     * This should be used when you need to interact with the world in a thread-safe manner.
+     *
+     * @param callback The task to execute on the server thread.
+     * @return The constructed method result, which evaluates to the result of the {@code callback}.
+     */
+    @Nonnull
+    public static MethodResult onMainThread( @Nonnull ILuaCallable callback )
+    {
+        Preconditions.checkNotNull( callback, "callback cannot be null" );
+        return new OnMainThread( callback );
+    }
+
+    /**
+     * Consume the result of this {@link MethodResult} and return another result.
+     *
+     * Note this does NOT modify the current method result, rather returning a new (wrapped) one. You must return the
+     * result of this call if you wish to use it.
+     *
+     * @param callback The function which consumes the provided values.
+     * @return The constructed method result.
+     */
+    @Nonnull
+    public final MethodResult then( @Nonnull ILuaFunction callback )
+    {
+        Preconditions.checkNotNull( callback, "callback cannot be null" );
+        return new AndThen( this, callback );
+    }
+
+    /**
+     * Execute a blocking task within a {@link ILuaContext} and return its result.
+     *
+     * @param consumer The task to execute with the provided Lua context.
+     * @return The constructed method result.
+     * @see #evaluate(ILuaContext)
+     * @deprecated This should not be used except to interface between the two call systems.
+     */
+    @Deprecated
+    public static MethodResult withLuaContext( @Nonnull ILuaContextTask consumer )
+    {
+        Preconditions.checkNotNull( consumer, "consumer cannot be null" );
+        return new WithLuaContext( consumer );
+    }
+
+    /**
+     * Evaluate this result task using {@link ILuaContext} and return its result.
+     *
+     * @param context The context to execute with.
+     * @return The resulting values.
+     * @throws LuaException         If an error was thrown while executing one of the methods within this future.
+     * @throws InterruptedException If the user shuts down or reboots the computer while the coroutine is suspended.
+     * @see #withLuaContext(ILuaContextTask)
+     * @deprecated This should not be used except to interface between the two call systems.
+     */
+    @Deprecated
+    public final Object[] evaluate( @Nonnull ILuaContext context ) throws LuaException, InterruptedException
+    {
+        return LuaContextResultEvaluator.evaluate( context, this );
+    }
+
+    public static class Immediate extends MethodResult
+    {
+        @Nullable
+        private final Object[] values;
+
+        @Nullable
+        private Immediate( Object[] values )
+        {
+            this.values = values;
+        }
+
+        public Object[] getResult()
+        {
+            return values;
+        }
+    }
+
+    public static class OnEvent extends MethodResult
+    {
+        private final boolean raw;
+        private final String filter;
+
+        private OnEvent( boolean raw, String filter )
+        {
+            this.raw = raw;
+            this.filter = filter;
+        }
+
+        public boolean isRaw()
+        {
+            return raw;
+        }
+
+        @Nullable
+        public String getFilter()
+        {
+            return filter;
+        }
+    }
+
+    public static class OnMainThread extends MethodResult
+    {
+        private final ILuaCallable task;
+
+        public OnMainThread( ILuaCallable task )
+        {
+            this.task = task;
+        }
+
+        @Nonnull
+        public ILuaCallable getTask()
+        {
+            return task;
+        }
+    }
+
+    public static class AndThen extends MethodResult
+    {
+        private final MethodResult previous;
+        private final ILuaFunction callback;
+
+        private AndThen( MethodResult previous, ILuaFunction callback )
+        {
+            this.previous = previous;
+            this.callback = callback;
+        }
+
+        @Nonnull
+        public MethodResult getPrevious()
+        {
+            return previous;
+        }
+
+        @Nonnull
+        public ILuaFunction getCallback()
+        {
+            return callback;
+        }
+    }
+
+    public static class WithLuaContext extends MethodResult
+    {
+        private final ILuaContextTask consumer;
+
+        private WithLuaContext( ILuaContextTask consumer )
+        {
+            this.consumer = consumer;
+        }
+
+        @Nonnull
+        public ILuaContextTask getConsumer()
+        {
+            return consumer;
+        }
+    }
+}

src/main/java/dan200/computercraft/api/peripheral/IPeripheral.java

@@ -1,13 +1,15 @@
 /*
  * This file is part of the public ComputerCraft API - http://www.computercraft.info
- * Copyright Daniel Ratcliffe, 2011-2017. This API may be redistributed unmodified and in full only.
+ * Copyright Daniel Ratcliffe, 2011-2018. This API may be redistributed unmodified and in full only.
  * For help using the API, and posting your mods, visit the forums at computercraft.info.
  */
 
 package dan200.computercraft.api.peripheral;
 
+import dan200.computercraft.api.lua.ICallContext;
 import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
@@ -70,10 +72,46 @@ public interface IPeripheral
      *                              InterruptedException will be thrown. This exception must not be caught or
      *                              intercepted, or the computer will leak memory and end up in a broken state.
      * @see #getMethodNames
+     * @deprecated Use {@link #callMethod(IComputerAccess, ICallContext, int, Object[])} instead.
      */
     @Nullable
+    @Deprecated
     Object[] callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException;
 
+    /**
+     * This is called when a lua program on an attached computer calls {@code peripheral.call()} with
+     * one of the methods exposed by {@link #getMethodNames()}.
+     *
+     * Be aware that this will be called from the ComputerCraft Lua thread, and must be thread-safe
+     * when interacting with Minecraft objects.
+     *
+     * @param computer  The interface to the computer that is making the call. Remember that multiple
+     *                  computers can be attached to a peripheral at once.
+     * @param context   The context of the current call.
+     * @param method    An integer identifying which of the methods from getMethodNames() the computercraft
+     *                  wishes to call. The integer indicates the index into the getMethodNames() table
+     *                  that corresponds to the string passed into peripheral.call()
+     * @param arguments An array of objects, representing the arguments passed into {@code peripheral.call()}.<br>
+     *                  Lua values of type "string" will be represented by Object type String.<br>
+     *                  Lua values of type "number" will be represented by Object type Double.<br>
+     *                  Lua values of type "boolean" will be represented by Object type Boolean.<br>
+     *                  Lua values of type "table" will be represented by Object type Map.<br>
+     *                  Lua values of any other type will be represented by a null object.<br>
+     *                  This array will be empty if no arguments are passed.
+     * @return The result of calling this method. Use {@link MethodResult#empty()} to return nothing or
+     * {@link MethodResult#of(Object...)} to return several values.
+     * @throws LuaException If you throw any exception from this function, a lua error will be raised with the
+     *                      same message as your exception. Use this to throw appropriate errors if the wrong
+     *                      arguments are supplied to your method.
+     * @see #getMethodNames
+     */
+    @Nonnull
+    @SuppressWarnings({ "deprecation" })
+    default MethodResult callMethod( @Nonnull IComputerAccess computer, @Nonnull ICallContext context, int method, @Nonnull Object[] arguments ) throws LuaException
+    {
+        return MethodResult.withLuaContext( lua -> callMethod( computer, lua, method, arguments ) );
+    }
+
     /**
      * Is called when canAttachToSide has returned true, and a computer is attaching to the peripheral.
      *

src/main/java/dan200/computercraft/api/turtle/ITurtleAccess.java

@@ -9,6 +9,7 @@ package dan200.computercraft.api.turtle;
 import com.mojang.authlib.GameProfile;
 import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import net.minecraft.inventory.IInventory;
 import net.minecraft.nbt.NBTTagCompound;
@@ -238,10 +239,30 @@ public interface ITurtleAccess
      *                                       intercepted, or the computer will leak memory and end up in a broken state.
      * @see ITurtleCommand
      * @see ILuaContext#pullEvent(String)
+     * @deprecated Use {@link #executeCommand(ITurtleCommand)} instead.
      */
     @Nonnull
+    @Deprecated
     Object[] executeCommand( @Nonnull ILuaContext context, @Nonnull ITurtleCommand command ) throws LuaException, InterruptedException;
 
+    /**
+     * Adds a custom command to the turtles command queue. Unlike peripheral methods, these custom commands will be
+     * executed on the main thread, so are guaranteed to be able to access Minecraft objects safely, and will be queued
+     * up with the turtles standard movement and tool commands.
+     *
+     * An issued command will return an unique integer, which will be supplied as a parameter to a "turtle_response"
+     * event issued to the turtle after the command has completed. Look at the Lua source code for "rom/apis/turtle" for
+     * how to build a Lua wrapper around this functionality.
+     *
+     * @param command An object which will execute the custom command when its point in the queue is reached
+     * @return The constructed method result. This evaluates to the result of the provided {@code command}.
+     * @throws UnsupportedOperationException When attempting to execute a command on the client side.
+     * @see ITurtleCommand
+     * @see MethodResult#pullEvent(String)
+     */
+    @Nonnull
+    MethodResult executeCommand( @Nonnull ITurtleCommand command );
+
     /**
      * Start playing a specific animation. This will prevent other turtle commands from executing until
      * it is finished.

src/main/java/dan200/computercraft/api/turtle/ITurtleUpgrade.java

@@ -133,7 +133,7 @@ public interface ITurtleUpgrade
      * @return The model that you wish to be used to render your upgrade, and a transformation to apply to it. Returning
      * a transformation of {@code null} has the same effect as the identify matrix.
      */
-    @SideOnly(Side.CLIENT)
+    @SideOnly( Side.CLIENT )
     @Nonnull
     Pair<IBakedModel, Matrix4f> getModel( @Nullable ITurtleAccess turtle, @Nonnull TurtleSide side );
 

src/main/java/dan200/computercraft/client/gui/GuiPrintout.java

@@ -6,25 +6,19 @@
 
 package dan200.computercraft.client.gui;
 
-import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.core.terminal.TextBuffer;
 import dan200.computercraft.shared.media.inventory.ContainerHeldItem;
 import dan200.computercraft.shared.media.items.ItemPrintout;
-import dan200.computercraft.shared.util.Palette;
 import net.minecraft.client.gui.inventory.GuiContainer;
 import net.minecraft.client.renderer.GlStateManager;
-import net.minecraft.util.ResourceLocation;
 import org.lwjgl.input.Mouse;
 
 import java.io.IOException;
 
+import static dan200.computercraft.client.render.PrintoutRenderer.*;
+
 public class GuiPrintout extends GuiContainer
 {
-    private static final ResourceLocation background = new ResourceLocation( "computercraft", "textures/gui/printout.png" );
-    
-    private static final int xSize = 172;
-    private static final int ySize = 209;
-    
     private final boolean m_book;
     private final int m_pages;
     private final TextBuffer[] m_text;
@@ -34,23 +28,18 @@ public class GuiPrintout extends GuiContainer
     public GuiPrintout( ContainerHeldItem container )
     {
         super( container );
-        m_book = (ItemPrintout.getType( container.getStack() ) == ItemPrintout.Type.Book);
 
         String[] text = ItemPrintout.getText( container.getStack() );
         m_text = new TextBuffer[ text.length ];
-        for( int i=0; i<m_text.length; ++i )
-        {
-            m_text[i] = new TextBuffer( text[i] );
-        }
+        for( int i = 0; i < m_text.length; ++i ) m_text[ i ] = new TextBuffer( text[ i ] );
+
         String[] colours = ItemPrintout.getColours( container.getStack() );
         m_colours = new TextBuffer[ colours.length ];
-        for( int i=0; i<m_colours.length; ++i )
-        {
-            m_colours[i] = new TextBuffer( colours[i] );
-        }
+        for( int i = 0; i < m_colours.length; ++i ) m_colours[ i ] = new TextBuffer( colours[ i ] );
 
-        m_pages = Math.max( m_text.length / ItemPrintout.LINES_PER_PAGE, 1 );
         m_page = 0;
+        m_pages = Math.max( m_text.length / ItemPrintout.LINES_PER_PAGE, 1 );
+        m_book = ItemPrintout.getType( container.getStack() ) == ItemPrintout.Type.Book;
     }
 
     @Override
@@ -78,25 +67,19 @@ public class GuiPrintout extends GuiContainer
     }
 
     @Override
-    protected void keyTyped(char c, int k) throws IOException
+    protected void keyTyped( char c, int k ) throws IOException
     {
         super.keyTyped( c, k );
 
         if( k == 205 )
         {
             // Right
-            if( m_page < m_pages - 1 )
-            {
-                m_page = m_page + 1;
-            }
+            if( m_page < m_pages - 1 ) m_page++;
         }
         else if( k == 203 )
         {
-             // Left
-            if( m_page > 0 )
-            {
-                m_page = m_page - 1;
-            }
+            // Left
+            if( m_page > 0 ) m_page--;
         }
     }
 
@@ -106,21 +89,15 @@ public class GuiPrintout extends GuiContainer
         super.handleMouseInput();
 
         int mouseWheelChange = Mouse.getEventDWheel();
-        if (mouseWheelChange < 0)
+        if( mouseWheelChange < 0 )
         {
             // Up
-            if( m_page < m_pages - 1 )
-            {
-                m_page = m_page + 1;
-            }
+            if( m_page < m_pages - 1 ) m_page++;
         }
-        else if (mouseWheelChange > 0) 
+        else if( mouseWheelChange > 0 )
         {
             // Down
-            if( m_page > 0 )
-            {
-                m_page = m_page - 1;
-            }
+            if( m_page > 0 ) m_page--;
         }
     }
 
@@ -135,78 +112,20 @@ public class GuiPrintout extends GuiContainer
     }
 
     @Override
-    public void drawScreen(int mouseX, int mouseY, float f)
+    public void drawScreen( int mouseX, int mouseY, float f )
     {
         // Draw background
+        zLevel = zLevel - 1;
         drawDefaultBackground();
-        
+        zLevel = zLevel + 1;
+
         // Draw the printout
         GlStateManager.color( 1.0f, 1.0f, 1.0f, 1.0f );
-        this.mc.getTextureManager().bindTexture( background );
-        
-        int startY = (height - ySize) / 2;
-        //int startX = (width - xSize) / 2 - (m_page * 8);
-        int startX = (width - (xSize + (m_pages - 1)*8)) / 2;
-        
-        if( m_book )
-        {
-            // Border
-            drawTexturedModalRect( startX - 8, startY - 8, xSize + 48, 0, 12, ySize + 24);
-            drawTexturedModalRect( startX + xSize + (m_pages - 1)*8 - 4, startY - 8, xSize + 48 + 12, 0, 12, ySize + 24);
-            
-            drawTexturedModalRect( startX, startY - 8, 0, ySize, xSize, 12);
-            drawTexturedModalRect( startX, startY + ySize - 4, 0, ySize + 12, xSize, 12);
-            for( int n=1; n<m_pages; ++n )
-            {
-                drawTexturedModalRect( startX + xSize + (n-1)*8, startY - 8, 0, ySize, 8, 12);
-                drawTexturedModalRect( startX + xSize + (n-1)*8, startY + ySize - 4, 0, ySize + 12, 8, 12);
-            }
-        }
-            
-        // Left half
-        if( m_page == 0 )
-        {            
-            drawTexturedModalRect( startX, startY, 24, 0, xSize / 2, ySize);
-            drawTexturedModalRect( startX, startY, 0, 0, 12, ySize);
-        }
-        else
-        {
-            drawTexturedModalRect( startX, startY, 0, 0, 12, ySize);
-            for( int n=1; n<m_page; ++n )
-            {
-                drawTexturedModalRect( startX + n*8, startY, 12, 0, 12, ySize);                
-            }
-            drawTexturedModalRect( startX + m_page*8, startY, 24, 0, xSize / 2, ySize);
-        }
-        
-        // Right half
-        if( m_page == (m_pages - 1) )
-        {
-            drawTexturedModalRect( startX + m_page*8 + xSize/2, startY, 24 + xSize / 2, 0, xSize / 2, ySize);
-            drawTexturedModalRect( startX + m_page*8 + (xSize - 12), startY, 24 + xSize + 12, 0, 12, ySize);
-        }
-        else 
-        {
-            drawTexturedModalRect( startX + (m_pages - 1)*8 + (xSize - 12), startY, 24 + xSize + 12, 0, 12, ySize);
-            for( int n=m_pages-2; n>=m_page; --n )
-            {
-                drawTexturedModalRect( startX + n*8 + (xSize - 12), startY, 24 + xSize, 0, 12, ySize);
-            }
-            drawTexturedModalRect( startX + m_page*8 + xSize/2, startY, 24 + xSize / 2, 0, xSize / 2, ySize);
-        }
 
-        // Draw the text
-        FixedWidthFontRenderer fontRenderer = (FixedWidthFontRenderer)ComputerCraft.getFixedWidthFontRenderer();
-        int x = startX + m_page * 8 + 13;
-        int y = startY + 11;
-        for( int line=0; line<ItemPrintout.LINES_PER_PAGE; ++line )
-        {
-            int lineIdx = ItemPrintout.LINES_PER_PAGE * m_page + line;
-            if( lineIdx >= 0 && lineIdx < m_text.length )
-            {
-                fontRenderer.drawString( m_text[lineIdx], x, y, m_colours[lineIdx], null, 0, 0, false, Palette.DEFAULT );
-            }
-            y = y + FixedWidthFontRenderer.FONT_HEIGHT;
-        }
+        int startY = (height - Y_SIZE) / 2;
+        int startX = (width - X_SIZE) / 2;
+
+        drawBorder( startX, startY, zLevel, m_page, m_pages, m_book );
+        drawText( startX + X_TEXT_MARGIN, startY + Y_TEXT_MARGIN, ItemPrintout.LINES_PER_PAGE * m_page, m_text, m_colours );
     }
 }

src/main/java/dan200/computercraft/client/proxy/ComputerCraftProxyClient.java

@@ -9,6 +9,7 @@ package dan200.computercraft.client.proxy;
 import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.client.gui.*;
 import dan200.computercraft.client.render.ItemPocketRenderer;
+import dan200.computercraft.client.render.ItemPrintoutRenderer;
 import dan200.computercraft.client.render.RenderOverlayCable;
 import dan200.computercraft.client.render.TileEntityCableRenderer;
 import dan200.computercraft.client.render.TileEntityMonitorRenderer;
@@ -497,6 +498,7 @@ public class ComputerCraftProxyClient extends ComputerCraftProxyCommon
         MinecraftForge.EVENT_BUS.register( handlers );
         MinecraftForge.EVENT_BUS.register( new RenderOverlayCable() );
         MinecraftForge.EVENT_BUS.register( new ItemPocketRenderer() );
+        MinecraftForge.EVENT_BUS.register( new ItemPrintoutRenderer() );
     }
 
     public class ForgeHandlers

src/main/java/dan200/computercraft/client/render/ItemPrintoutRenderer.java

@@ -0,0 +1,197 @@
+package dan200.computercraft.client.render;
+
+import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.shared.media.items.ItemPrintout;
+import net.minecraft.client.Minecraft;
+import net.minecraft.client.renderer.GlStateManager;
+import net.minecraft.client.renderer.ItemRenderer;
+import net.minecraft.entity.player.EntityPlayer;
+import net.minecraft.item.ItemStack;
+import net.minecraft.util.EnumHand;
+import net.minecraft.util.EnumHandSide;
+import net.minecraft.util.math.MathHelper;
+import net.minecraftforge.client.event.RenderItemInFrameEvent;
+import net.minecraftforge.client.event.RenderSpecificHandEvent;
+import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;
+
+import static dan200.computercraft.client.gui.FixedWidthFontRenderer.FONT_HEIGHT;
+import static dan200.computercraft.client.gui.FixedWidthFontRenderer.FONT_WIDTH;
+import static dan200.computercraft.client.render.PrintoutRenderer.*;
+import static dan200.computercraft.shared.media.items.ItemPrintout.LINES_PER_PAGE;
+import static dan200.computercraft.shared.media.items.ItemPrintout.LINE_MAX_LENGTH;
+
+public class ItemPrintoutRenderer
+{
+    @SubscribeEvent
+    public void onRenderInHand( RenderSpecificHandEvent event )
+    {
+        ItemStack stack = event.getItemStack();
+        if( stack.getItem() != ComputerCraft.Items.printout ) return;
+
+        event.setCanceled( true );
+
+        EntityPlayer player = Minecraft.getMinecraft().player;
+
+        GlStateManager.pushMatrix();
+        if( event.getHand() == EnumHand.MAIN_HAND && player.getHeldItemOffhand().isEmpty() )
+        {
+            renderPrintoutFirstPersonCentre(
+                event.getInterpolatedPitch(),
+                event.getEquipProgress(),
+                event.getSwingProgress(),
+                stack
+            );
+        }
+        else
+        {
+            renderPrintoutFirstPersonSide(
+                event.getHand() == EnumHand.MAIN_HAND ? player.getPrimaryHand() : player.getPrimaryHand().opposite(),
+                event.getEquipProgress(),
+                event.getSwingProgress(),
+                stack
+            );
+        }
+        GlStateManager.popMatrix();
+    }
+
+    /**
+     * Renders a pocket computer to one side of the player.
+     *
+     * @param side          The side to render on
+     * @param equipProgress The equip progress of this item
+     * @param swingProgress The swing progress of this item
+     * @param stack         The stack to render
+     * @see ItemRenderer#renderMapFirstPersonSide(float, EnumHandSide, float, ItemStack)
+     */
+    private void renderPrintoutFirstPersonSide( EnumHandSide side, float equipProgress, float swingProgress, ItemStack stack )
+    {
+        Minecraft minecraft = Minecraft.getMinecraft();
+        float offset = side == EnumHandSide.RIGHT ? 1f : -1f;
+        GlStateManager.translate( offset * 0.125f, -0.125f, 0f );
+
+        // If the player is not invisible then render a single arm
+        if( !minecraft.player.isInvisible() )
+        {
+            GlStateManager.pushMatrix();
+            GlStateManager.rotate( offset * 10f, 0f, 0f, 1f );
+            minecraft.getItemRenderer().renderArmFirstPerson( equipProgress, swingProgress, side );
+            GlStateManager.popMatrix();
+        }
+
+        // Setup the appropriate transformations. This is just copied from the
+        // corresponding method in ItemRenderer. 
+        GlStateManager.pushMatrix();
+        GlStateManager.translate( offset * 0.51f, -0.08f + equipProgress * -1.2f, -0.75f );
+        float f1 = MathHelper.sqrt( swingProgress );
+        float f2 = MathHelper.sin( f1 * (float) Math.PI );
+        float f3 = -0.5f * f2;
+        float f4 = 0.4f * MathHelper.sin( f1 * ((float) Math.PI * 2f) );
+        float f5 = -0.3f * MathHelper.sin( swingProgress * (float) Math.PI );
+        GlStateManager.translate( offset * f3, f4 - 0.3f * f2, f5 );
+        GlStateManager.rotate( f2 * -45f, 1f, 0f, 0f );
+        GlStateManager.rotate( offset * f2 * -30f, 0f, 1f, 0f );
+
+        renderPrintoutFirstPerson( stack );
+
+        GlStateManager.popMatrix();
+    }
+
+    /**
+     * Render an item in the middle of the screen
+     *
+     * @param pitch         The pitch of the player
+     * @param equipProgress The equip progress of this item
+     * @param swingProgress The swing progress of this item
+     * @param stack         The stack to render
+     * @see ItemRenderer#renderMapFirstPerson(float, float, float)
+     */
+    private void renderPrintoutFirstPersonCentre( float pitch, float equipProgress, float swingProgress, ItemStack stack )
+    {
+        ItemRenderer itemRenderer = Minecraft.getMinecraft().getItemRenderer();
+
+        // Setup the appropriate transformations. This is just copied from the
+        // corresponding method in ItemRenderer.
+        float swingRt = MathHelper.sqrt( swingProgress );
+        float tX = -0.2f * MathHelper.sin( swingProgress * (float) Math.PI );
+        float tZ = -0.4f * MathHelper.sin( swingRt * (float) Math.PI );
+        GlStateManager.translate( 0f, -tX / 2f, tZ );
+        float pitchAngle = itemRenderer.getMapAngleFromPitch( pitch );
+        GlStateManager.translate( 0f, 0.04f + equipProgress * -1.2f + pitchAngle * -0.5f, -0.72f );
+        GlStateManager.rotate( pitchAngle * -85f, 1f, 0f, 0f );
+        itemRenderer.renderArms();
+        float rX = MathHelper.sin( swingRt * (float) Math.PI );
+        GlStateManager.rotate( rX * 20f, 1f, 0f, 0f );
+        GlStateManager.scale( 2f, 2f, 2f );
+
+        renderPrintoutFirstPerson( stack );
+    }
+
+
+    private static void renderPrintoutFirstPerson( ItemStack stack )
+    {
+        // Setup various transformations. Note that these are partially adapated from the corresponding method
+        // in ItemRenderer.renderMapFirstPerson
+        GlStateManager.disableLighting();
+
+        GlStateManager.rotate( 180f, 0f, 1f, 0f );
+        GlStateManager.rotate( 180f, 0f, 0f, 1f );
+        GlStateManager.scale( 0.42f, 0.42f, -0.42f );
+        GlStateManager.translate( -0.5f, -0.48f, 0.0f );
+
+        drawPrintout( stack );
+
+        GlStateManager.enableLighting();
+    }
+
+    @SubscribeEvent
+    public void onRenderInFrame( RenderItemInFrameEvent event )
+    {
+        ItemStack stack = event.getItem();
+        if( stack.getItem() != ComputerCraft.Items.printout ) return;
+
+        event.setCanceled( true );
+
+        GlStateManager.disableLighting();
+
+        // Move a little bit forward to ensure we're not clipping with the frame
+        GlStateManager.translate( 0.0f, 0.0f, -0.001f );
+        GlStateManager.rotate( 180f, 0f, 0f, 1f );
+        GlStateManager.scale( 0.95f, 0.95f, -0.95f );
+        GlStateManager.translate( -0.5f, -0.5f, 0.0f );
+
+        drawPrintout( stack );
+
+        GlStateManager.enableLighting();
+    }
+
+    private static void drawPrintout( ItemStack stack )
+    {
+        int pages = ItemPrintout.getPageCount( stack );
+        boolean book = ItemPrintout.getType( stack ) == ItemPrintout.Type.Book;
+
+        double width = LINE_MAX_LENGTH * FONT_WIDTH + X_TEXT_MARGIN * 2;
+        double height = LINES_PER_PAGE * FONT_HEIGHT + Y_TEXT_MARGIN * 2;
+
+        // Non-books will be left aligned
+        if( !book ) width += offsetAt( pages );
+
+        double visualWidth = width, visualHeight = height;
+
+        // Meanwhile books will be centred
+        if( book )
+        {
+            visualWidth += 2 * COVER_SIZE + 2 * offsetAt( pages );
+            visualHeight += 2 * COVER_SIZE;
+        }
+
+        double max = Math.max( visualHeight, visualWidth );
+
+        // Scale the printout to fit correctly.
+        double scale = 1.0 / max;
+        GlStateManager.scale( scale, scale, scale );
+        GlStateManager.translate( (max - width) / 2.0f, (max - height) / 2.0f, 0.0f );
+
+        drawBorder( 0, 0, -0.01, 0, pages, book );
+        drawText( X_TEXT_MARGIN, Y_TEXT_MARGIN, 0, ItemPrintout.getText( stack ), ItemPrintout.getColours( stack ) );
+    }
+}

src/main/java/dan200/computercraft/client/render/PrintoutRenderer.java

@@ -0,0 +1,169 @@
+package dan200.computercraft.client.render;
+
+import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.client.gui.FixedWidthFontRenderer;
+import dan200.computercraft.core.terminal.TextBuffer;
+import dan200.computercraft.shared.util.Palette;
+import net.minecraft.client.Minecraft;
+import net.minecraft.client.renderer.BufferBuilder;
+import net.minecraft.client.renderer.GlStateManager;
+import net.minecraft.client.renderer.Tessellator;
+import net.minecraft.client.renderer.vertex.DefaultVertexFormats;
+import net.minecraft.util.ResourceLocation;
+import org.lwjgl.opengl.GL11;
+
+import static dan200.computercraft.client.gui.FixedWidthFontRenderer.FONT_HEIGHT;
+import static dan200.computercraft.shared.media.items.ItemPrintout.LINES_PER_PAGE;
+
+public class PrintoutRenderer
+{
+    private static final ResourceLocation BG = new ResourceLocation( "computercraft", "textures/gui/printout.png" );
+    private static final double BG_SIZE = 256.0;
+
+    /**
+     * Width of a page
+     */
+    public static final int X_SIZE = 172;
+
+    /**
+     * Height of a page
+     */
+    public static final int Y_SIZE = 209;
+
+    /**
+     * Padding between the left and right of a page and the text
+     */
+    public static final int X_TEXT_MARGIN = 13;
+
+    /**
+     * Padding between the top and bottom of a page and the text
+     */
+    public static final int Y_TEXT_MARGIN = 11;
+
+    /**
+     * Width of the extra page texture
+     */
+    private static final int X_FOLD_SIZE = 12;
+
+    /**
+     * Size of the leather cover
+     */
+    public static final int COVER_SIZE = 12;
+
+    private static final int COVER_Y = Y_SIZE;
+    private static final int COVER_X = X_SIZE + 4 * X_FOLD_SIZE;
+
+    public static void drawText( int x, int y, int start, TextBuffer[] text, TextBuffer[] colours )
+    {
+        FixedWidthFontRenderer fontRenderer = (FixedWidthFontRenderer) ComputerCraft.getFixedWidthFontRenderer();
+
+        for( int line = 0; line < LINES_PER_PAGE && line < text.length; ++line )
+        {
+            fontRenderer.drawString( text[ start + line ], x, y + line * FONT_HEIGHT, colours[ start + line ], null, 0, 0, false, Palette.DEFAULT );
+        }
+    }
+
+    public static void drawText( int x, int y, int start, String[] text, String[] colours )
+    {
+        GlStateManager.color( 1.0f, 1.0f, 1.0f, 1.0f );
+        GlStateManager.enableBlend();
+        GlStateManager.enableTexture2D();
+
+        FixedWidthFontRenderer fontRenderer = (FixedWidthFontRenderer) ComputerCraft.getFixedWidthFontRenderer();
+
+        for( int line = 0; line < LINES_PER_PAGE && line < text.length; ++line )
+        {
+            fontRenderer.drawString( new TextBuffer( text[ start + line ] ), x, y + line * FONT_HEIGHT, new TextBuffer( colours[ start + line ] ), null, 0, 0, false, Palette.DEFAULT );
+        }
+    }
+
+    public static void drawBorder( double x, double y, double z, int page, int pages, boolean isBook )
+    {
+        GlStateManager.color( 1.0f, 1.0f, 1.0f, 1.0f );
+        GlStateManager.enableBlend();
+        GlStateManager.enableTexture2D();
+
+        Minecraft.getMinecraft().getTextureManager().bindTexture( BG );
+
+        Tessellator tessellator = Tessellator.getInstance();
+        BufferBuilder buffer = tessellator.getBuffer();
+        buffer.begin( GL11.GL_QUADS, DefaultVertexFormats.POSITION_TEX );
+
+        int leftPages = page;
+        int rightPages = pages - page - 1;
+
+        if( isBook )
+        {
+            // Border
+            double offset = offsetAt( pages );
+            final double left = x - 4 - offset;
+            final double right = x + X_SIZE + offset - 4;
+
+            // Left and right border
+            drawTexture( buffer, left - 4, y - 8, z - 0.02, COVER_X, 0, COVER_SIZE, Y_SIZE + COVER_SIZE * 2 );
+            drawTexture( buffer, right, y - 8, z - 0.02, COVER_X + COVER_SIZE, 0, COVER_SIZE, Y_SIZE + COVER_SIZE * 2 );
+
+            // Draw centre panel (just stretched texture, sorry).
+            drawTexture( buffer,
+                x - offset, y, z - 0.02, X_SIZE + offset * 2, Y_SIZE,
+                COVER_X + COVER_SIZE / 2, COVER_SIZE, COVER_SIZE, Y_SIZE
+            );
+
+            double borderX = left;
+            while( borderX < right )
+            {
+                double thisWidth = Math.min( right - borderX, X_SIZE );
+                drawTexture( buffer, borderX, y - 8, z - 0.02, 0, COVER_Y, thisWidth, COVER_SIZE );
+                drawTexture( buffer, borderX, y + Y_SIZE - 4, z - 0.02, 0, COVER_Y + COVER_SIZE, thisWidth, COVER_SIZE );
+                borderX += thisWidth;
+            }
+        }
+
+        // Left half
+        drawTexture( buffer, x, y, z, X_FOLD_SIZE * 2, 0, X_SIZE / 2, Y_SIZE );
+        for( int n = 0; n <= leftPages; n++ )
+        {
+            drawTexture( buffer,
+                x - offsetAt( n ), y, z - 1e-3 * n,
+                // Use the left "bold" fold for the outermost page
+                n == leftPages ? 0 : X_FOLD_SIZE, 0,
+                X_FOLD_SIZE, Y_SIZE
+            );
+        }
+
+        // Right half
+        drawTexture( buffer, x + X_SIZE / 2, y, z, X_FOLD_SIZE * 2 + X_SIZE / 2, 0, X_SIZE / 2, Y_SIZE );
+        for( int n = 0; n <= rightPages; n++ )
+        {
+            drawTexture( buffer,
+                x + (X_SIZE - X_FOLD_SIZE) + offsetAt( n ), y, z - 1e-3 * n,
+                // Two folds, then the main page. Use the right "bold" fold for the outermost page.
+                X_FOLD_SIZE * 2 + X_SIZE + (n == rightPages ? X_FOLD_SIZE : 0), 0,
+                X_FOLD_SIZE, Y_SIZE
+            );
+        }
+
+        tessellator.draw();
+    }
+
+    private static void drawTexture( BufferBuilder buffer, double x, double y, double z, double u, double v, double width, double height )
+    {
+        buffer.pos( x, y + height, z ).tex( u / BG_SIZE, (v + height) / BG_SIZE ).endVertex();
+        buffer.pos( x + width, y + height, z ).tex( (u + width) / BG_SIZE, (v + height) / BG_SIZE ).endVertex();
+        buffer.pos( x + width, y, z ).tex( (u + width) / BG_SIZE, v / BG_SIZE ).endVertex();
+        buffer.pos( x, y, z ).tex( u / BG_SIZE, v / BG_SIZE ).endVertex();
+    }
+
+    private static void drawTexture( BufferBuilder buffer, double x, double y, double z, double width, double height, double u, double v, double tWidth, double tHeight )
+    {
+        buffer.pos( x, y + height, z ).tex( u / BG_SIZE, (v + tHeight) / BG_SIZE ).endVertex();
+        buffer.pos( x + width, y + height, z ).tex( (u + tWidth) / BG_SIZE, (v + tHeight) / BG_SIZE ).endVertex();
+        buffer.pos( x + width, y, z ).tex( (u + tWidth) / BG_SIZE, v / BG_SIZE ).endVertex();
+        buffer.pos( x, y, z ).tex( u / BG_SIZE, v / BG_SIZE ).endVertex();
+    }
+
+    public static double offsetAt( int page )
+    {
+        return 32 * (1 - Math.pow( 1.2, -page ));
+    }
+}

src/main/java/dan200/computercraft/client/render/TileEntityCableRenderer.java

@@ -71,7 +71,7 @@ public class TileEntityCableRenderer extends TileEntitySpecialRenderer<TileCable
         buffer.setTranslation( x - pos.getX(), y - pos.getY(), z - pos.getZ() );
         buffer.noColor();
 
-        ForgeHooksClient.setRenderLayer( block.getBlockLayer() );
+        ForgeHooksClient.setRenderLayer( block.getRenderLayer() );
 
         // See BlockRendererDispatcher#renderBlockDamage
         TextureAtlasSprite breakingTexture = mc.getTextureMapBlocks().getAtlasSprite( "minecraft:blocks/destroy_stage_" + destroyStage );

src/main/java/dan200/computercraft/core/apis/BufferAPI.java

@@ -6,13 +6,12 @@
 
 package dan200.computercraft.core.apis;
 
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.api.lua.ILuaAPI;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.ILuaObject;
-import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.core.terminal.TextBuffer;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 
 import static dan200.computercraft.core.apis.ArgumentHelper.getString;
 import static dan200.computercraft.core.apis.ArgumentHelper.optInt;
@@ -41,27 +40,28 @@ public class BufferAPI implements ILuaAPI
             };
         }
 
+        @Nonnull
         @Override
-        public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+        public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] arguments ) throws LuaException
         {
             switch( method )
             {
                 case 0:
                 {
                     // len
-                    return new Object[] { m_buffer.length() };
+                    return MethodResult.of( m_buffer.length() );
                 }
                 case 1:
                 {
                     // tostring
-                    return new Object[] { m_buffer.toString() };
+                    return MethodResult.of( m_buffer.toString() );
                 }
                 case 2:
                 {
                     // read
                     int start = optInt( arguments, 0, 0 );
                     int end = optInt( arguments, 1, m_buffer.length() );
-                    return new Object[] { m_buffer.read( start, end ) };
+                    return MethodResult.of( m_buffer.read( start, end ) );
                 }
                 case 3:
                 {
@@ -70,7 +70,7 @@ public class BufferAPI implements ILuaAPI
                     int start = optInt( arguments, 1, 0 );
                     int end = optInt( arguments, 2, start + text.length() );
                     m_buffer.write( text, start, end );
-                    return null;
+                    return MethodResult.empty();
                 }
                 case 4:
                 {
@@ -79,14 +79,22 @@ public class BufferAPI implements ILuaAPI
                     int start = optInt( arguments, 1, 0 );
                     int end = optInt( arguments, 2, m_buffer.length() );
                     m_buffer.fill( text, start, end );
-                    return null;
+                    return MethodResult.empty();
                 }
                 default:
                 {
-                    return null;
+                    return MethodResult.empty();
                 }
             }
         }
+
+        @Nullable
+        @Override
+        @Deprecated
+        public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+        {
+            return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+        }
     }
 
     public BufferAPI( IAPIEnvironment _env )
@@ -110,8 +118,9 @@ public class BufferAPI implements ILuaAPI
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] arguments ) throws LuaException
     {
         switch( method )
         {
@@ -124,12 +133,20 @@ public class BufferAPI implements ILuaAPI
                     throw ArgumentHelper.badArgument( 1, "positive number", Integer.toString( repetitions ) );
                 }
                 TextBuffer buffer = new TextBuffer( text, repetitions );
-                return new Object[] { new BufferLuaObject( buffer ) };
+                return MethodResult.of( new BufferLuaObject( buffer ) );
             }
             default:
             {
-                return null;
+                return MethodResult.empty();
             }
         }
     }
+
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
 }

src/main/java/dan200/computercraft/core/apis/ComputerAccess.java

@@ -3,14 +3,17 @@ package dan200.computercraft.core.apis;
 import dan200.computercraft.api.filesystem.IMount;
 import dan200.computercraft.api.filesystem.IWritableMount;
 import dan200.computercraft.api.peripheral.IComputerAccess;
+import dan200.computercraft.core.computer.Computer;
+import dan200.computercraft.core.computer.IComputerOwned;
 import dan200.computercraft.core.filesystem.FileSystem;
 import dan200.computercraft.core.filesystem.FileSystemException;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.util.HashSet;
 import java.util.Set;
 
-public abstract class ComputerAccess implements IComputerAccess
+public abstract class ComputerAccess implements IComputerAccess, IComputerOwned
 {
     private final IAPIEnvironment m_environment;
     private final Set<String> m_mounts = new HashSet<>();
@@ -133,6 +136,13 @@ public abstract class ComputerAccess implements IComputerAccess
         m_environment.queueEvent( event, arguments );
     }
 
+    @Nullable
+    @Override
+    public Computer getComputer()
+    {
+        return m_environment.getComputer();
+    }
+
     private String findFreeLocation( String desiredLoc )
     {
         try

src/main/java/dan200/computercraft/core/apis/FSAPI.java

@@ -6,9 +6,8 @@
 
 package dan200.computercraft.core.apis;
 
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.api.lua.ILuaAPI;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.core.apis.handles.BinaryInputHandle;
 import dan200.computercraft.core.apis.handles.BinaryOutputHandle;
 import dan200.computercraft.core.apis.handles.EncodedInputHandle;
@@ -18,6 +17,7 @@ import dan200.computercraft.core.filesystem.FileSystemException;
 import dan200.computercraft.core.tracking.TrackingField;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.util.HashMap;
@@ -80,8 +80,9 @@ public class FSAPI implements ILuaAPI
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -96,7 +97,7 @@ public class FSAPI implements ILuaAPI
                     for(int i=0; i<results.length; ++i ) {
                         table.put( i+1, results[i] );
                     }
-                    return new Object[] { table };
+                    return MethodResult.of( table );
                 }
                 catch( FileSystemException e )
                 {
@@ -108,13 +109,13 @@ public class FSAPI implements ILuaAPI
                 // combine
                 String pathA = getString( args, 0 );
                 String pathB = getString( args, 1 );
-                return new Object[] { m_fileSystem.combine( pathA, pathB ) };
+                return MethodResult.of( m_fileSystem.combine( pathA, pathB ) );
             }
             case 2:
             {
                 // getName
                 String path = getString( args, 0 );
-                return new Object[]{ FileSystem.getName( path ) };
+                return MethodResult.of( FileSystem.getName( path ) );
             }
             case 3:
             {
@@ -122,7 +123,7 @@ public class FSAPI implements ILuaAPI
                 String path = getString( args, 0 );
                 try
                 {
-                    return new Object[]{ m_fileSystem.getSize( path ) };
+                    return MethodResult.of( m_fileSystem.getSize( path ) );
                 }
                 catch( FileSystemException e )
                 {
@@ -134,9 +135,9 @@ public class FSAPI implements ILuaAPI
                 // exists
                 String path = getString( args, 0 );
                 try {
-                    return new Object[]{ m_fileSystem.exists( path ) };
+                    return MethodResult.of( m_fileSystem.exists( path ) );
                 } catch( FileSystemException e ) {
-                    return new Object[]{ false };
+                    return MethodResult.of( false );
                 }
             }
             case 5:
@@ -144,9 +145,9 @@ public class FSAPI implements ILuaAPI
                 // isDir
                 String path = getString( args, 0 );
                 try {
-                    return new Object[]{ m_fileSystem.isDir( path ) };
+                    return MethodResult.of( m_fileSystem.isDir( path ) );
                 } catch( FileSystemException e ) {
-                    return new Object[]{ false };
+                    return MethodResult.of( false );
                 }
             }
             case 6:
@@ -154,9 +155,9 @@ public class FSAPI implements ILuaAPI
                 // isReadOnly
                 String path = getString( args, 0 );
                 try {
-                    return new Object[]{ m_fileSystem.isReadOnly( path ) };
+                    return MethodResult.of( m_fileSystem.isReadOnly( path ) );
                 } catch( FileSystemException e ) {
-                    return new Object[]{ false };
+                    return MethodResult.of( false );
                 }
             }
             case 7:
@@ -166,7 +167,7 @@ public class FSAPI implements ILuaAPI
                 try {
                     m_env.addTrackingChange( TrackingField.FS_OPS );
                     m_fileSystem.makeDir( path );
-                    return null;
+                    return MethodResult.empty();
                 } catch( FileSystemException e ) {
                     throw new LuaException( e.getMessage() );
                 }
@@ -179,7 +180,7 @@ public class FSAPI implements ILuaAPI
                 try {
                     m_env.addTrackingChange( TrackingField.FS_OPS );
                     m_fileSystem.move( path, dest );
-                    return null;
+                    return MethodResult.empty();
                 } catch( FileSystemException e ) {
                     throw new LuaException( e.getMessage() );
                 }
@@ -192,7 +193,7 @@ public class FSAPI implements ILuaAPI
                 try {
                     m_env.addTrackingChange( TrackingField.FS_OPS );
                     m_fileSystem.copy( path, dest );
-                    return null;
+                    return MethodResult.empty();
                 } catch( FileSystemException e ) {
                     throw new LuaException( e.getMessage() );
                 }
@@ -204,7 +205,7 @@ public class FSAPI implements ILuaAPI
                 try {
                     m_env.addTrackingChange( TrackingField.FS_OPS );
                     m_fileSystem.delete( path );
-                    return null;
+                    return MethodResult.empty();
                 } catch( FileSystemException e ) {
                     throw new LuaException( e.getMessage() );
                 }
@@ -222,43 +223,43 @@ public class FSAPI implements ILuaAPI
                         {
                             // Open the file for reading, then create a wrapper around the reader
                             InputStream reader = m_fileSystem.openForRead( path );
-                            return new Object[] { new EncodedInputHandle( reader ) };
+                            return MethodResult.of( new EncodedInputHandle( reader ) );
                         }
                         case "w":
                         {
                             // Open the file for writing, then create a wrapper around the writer
                             OutputStream writer = m_fileSystem.openForWrite( path, false );
-                            return new Object[] { new EncodedOutputHandle( writer ) };
+                            return MethodResult.of( new EncodedOutputHandle( writer ) );
                         }
                         case "a":
                         {
                             // Open the file for appending, then create a wrapper around the writer
                             OutputStream writer = m_fileSystem.openForWrite( path, true );
-                            return new Object[] { new EncodedOutputHandle( writer ) };
+                            return MethodResult.of( new EncodedOutputHandle( writer ) );
                         }
                         case "rb":
                         {
                             // Open the file for binary reading, then create a wrapper around the reader
                             InputStream reader = m_fileSystem.openForRead( path );
-                            return new Object[] { new BinaryInputHandle( reader ) };
+                            return MethodResult.of( new BinaryInputHandle( reader ) );
                         }
                         case "wb":
                         {
                             // Open the file for binary writing, then create a wrapper around the writer
                             OutputStream writer = m_fileSystem.openForWrite( path, false );
-                            return new Object[] { new BinaryOutputHandle( writer ) };
+                            return MethodResult.of( new BinaryOutputHandle( writer ) );
                         }
                         case "ab":
                         {
                             // Open the file for binary appending, then create a wrapper around the reader
                             OutputStream writer = m_fileSystem.openForWrite( path, true );
-                            return new Object[] { new BinaryOutputHandle( writer ) };
+                            return MethodResult.of( new BinaryOutputHandle( writer ) );
                         }
                         default:
                             throw new LuaException( "Unsupported mode" );
                     }
                 } catch( FileSystemException e ) {
-                    return new Object[] { null, e.getMessage() };
+                    return MethodResult.of( null, e.getMessage() );
                 }
             }
             case 12:
@@ -268,9 +269,9 @@ public class FSAPI implements ILuaAPI
                 try {
                     if( !m_fileSystem.exists( path ) )
                     {
-                        return null;
+                        return MethodResult.empty();
                     }
-                    return new Object[]{ m_fileSystem.getMountLabel( path ) };
+                    return MethodResult.of( m_fileSystem.getMountLabel( path ) );
                 } catch( FileSystemException e ) {
                     throw new LuaException( e.getMessage() );
                 }
@@ -283,9 +284,9 @@ public class FSAPI implements ILuaAPI
                     long freeSpace = m_fileSystem.getFreeSpace( path );
                     if( freeSpace >= 0 )
                     {
-                        return new Object[]{ freeSpace };
+                        return MethodResult.of( freeSpace );
                     }
-                    return new Object[]{ "unlimited" };
+                    return MethodResult.of( "unlimited" );
                 } catch( FileSystemException e ) {
                     throw new LuaException( e.getMessage() );
                 }
@@ -301,7 +302,7 @@ public class FSAPI implements ILuaAPI
                     for(int i=0; i<results.length; ++i ) {
                         table.put( i+1, results[i] );
                     }
-                    return new Object[] { table };
+                    return MethodResult.of( table );
                 } catch( FileSystemException e ) {
                     throw new LuaException( e.getMessage() );
                 }
@@ -310,13 +311,21 @@ public class FSAPI implements ILuaAPI
             {
                 // getDir
                 String path = getString( args, 0 );
-                return new Object[]{ FileSystem.getDirectory( path ) };
+                return MethodResult.of( FileSystem.getDirectory( path ) );
             }
             default:
             {
                 assert( false );
-                return null;
+                return MethodResult.empty();
             }
         }
     }
+
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
 }

src/main/java/dan200/computercraft/core/apis/HTTPAPI.java

@@ -8,12 +8,12 @@ package dan200.computercraft.core.apis;
 
 import com.google.common.collect.ImmutableSet;
 import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.api.lua.ILuaAPI;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.core.apis.http.*;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.io.Closeable;
 import java.io.IOException;
 import java.net.URI;
@@ -102,8 +102,9 @@ public class HTTPAPI implements ILuaAPI
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -164,11 +165,11 @@ public class HTTPAPI implements ILuaAPI
                     {
                         m_httpTasks.add( HTTPExecutor.EXECUTOR.submit( request ) );
                     }
-                    return new Object[]{ true };
+                    return MethodResult.of(true);
                 }
                 catch( HTTPRequestException e )
                 {
-                    return new Object[]{ false, e.getMessage() };
+                    return MethodResult.of( false, e.getMessage() );
                 }
             }
             case 1:
@@ -186,11 +187,11 @@ public class HTTPAPI implements ILuaAPI
                     {
                         m_httpTasks.add( HTTPExecutor.EXECUTOR.submit( check ) );
                     }
-                    return new Object[]{ true };
+                    return MethodResult.of( true );
                 }
                 catch( HTTPRequestException e )
                 {
-                    return new Object[]{ false, e.getMessage() };
+                    return MethodResult.of( false, e.getMessage() );
                 }
             }
             case 2: // websocket
@@ -223,20 +224,28 @@ public class HTTPAPI implements ILuaAPI
                     {
                         m_httpTasks.add( connector );
                     }
-                    return new Object[]{ true };
+                    return MethodResult.of(true);
                 }
                 catch( HTTPRequestException e )
                 {
-                    return new Object[]{ false, e.getMessage() };
+                    return MethodResult.of( false, e.getMessage() );
                 }
             }
             default:
             {
-                return null;
+                return MethodResult.empty();
             }
         }
     }
 
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
+
     public void addCloseable( Closeable closeable )
     {
         synchronized( m_closeables )

src/main/java/dan200/computercraft/core/apis/IAPIEnvironment.java

@@ -9,17 +9,19 @@ package dan200.computercraft.core.apis;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.core.computer.Computer;
 import dan200.computercraft.core.computer.IComputerEnvironment;
+import dan200.computercraft.core.computer.IComputerOwned;
 import dan200.computercraft.core.filesystem.FileSystem;
 import dan200.computercraft.core.terminal.Terminal;
 import dan200.computercraft.core.tracking.TrackingField;
 
-public interface IAPIEnvironment
+public interface IAPIEnvironment extends IComputerOwned
 {
     interface IPeripheralChangeListener
     {
         void onPeripheralChanged( int side, IPeripheral newPeripheral );
     }
-    
+
+    @Override
     Computer getComputer();
     int getComputerID();
     IComputerEnvironment getComputerEnvironment();

src/main/java/dan200/computercraft/core/apis/OSAPI.java

@@ -6,12 +6,12 @@
 
 package dan200.computercraft.core.apis;
 
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.api.lua.ILuaAPI;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.shared.util.StringUtil;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.util.*;
 
 import static dan200.computercraft.core.apis.ArgumentHelper.*;
@@ -221,7 +221,8 @@ public class OSAPI implements ILuaAPI
     }
 
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
+    @Nonnull
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -229,7 +230,7 @@ public class OSAPI implements ILuaAPI
             {
                 // queueEvent
                 queueLuaEvent( getString( args, 0 ), trimArray( args, 1 ) );
-                return null;
+                return MethodResult.empty();
             }
             case 1:
             {
@@ -238,7 +239,7 @@ public class OSAPI implements ILuaAPI
                 synchronized( m_timers )
                 {
                     m_timers.put( m_nextTimerToken, new Timer( (int)Math.round( timer / 0.05 ) ) );
-                    return new Object[] { m_nextTimerToken++ };
+                    return MethodResult.of( m_nextTimerToken++ );
                 }
             }
             case 2:
@@ -253,33 +254,33 @@ public class OSAPI implements ILuaAPI
                 {
                     int day = (time > m_time) ? m_day : (m_day + 1);
                     m_alarms.put( m_nextAlarmToken, new Alarm( time, day ) );
-                    return new Object[] { m_nextAlarmToken++ };
+                    return MethodResult.of( m_nextAlarmToken++ );
                 }
             }
             case 3:
             {
                 // shutdown
                 m_apiEnvironment.shutdown();
-                return null;
+                return MethodResult.empty();
             }
             case 4:
             {
                 // reboot
                 m_apiEnvironment.reboot();
-                return null;
+                return MethodResult.empty();
             }
             case 5:
             case 6:
             {
                 // computerID/getComputerID
-                return new Object[] { getComputerID() };
+                return MethodResult.of( getComputerID() );
             }
             case 7:
             {
                 // setComputerLabel
                 String label = optString( args, 0, null );
                 m_apiEnvironment.setLabel( StringUtil.normaliseLabel( label ) );
-                return null;
+                return MethodResult.empty();
             }
             case 8:
             case 9:
@@ -288,16 +289,16 @@ public class OSAPI implements ILuaAPI
                 String label = m_apiEnvironment.getLabel();
                 if( label != null )
                 {
-                    return new Object[] { label };
+                    return MethodResult.of( label );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 10:
             {
                 // clock
                 synchronized( m_timers )
                 {
-                    return new Object[] { m_clock * 0.05 };
+                    return MethodResult.of( m_clock * 0.05 );
                 }
             }
             case 11:
@@ -310,19 +311,19 @@ public class OSAPI implements ILuaAPI
                     {
                         // Get Hour of day (UTC)
                         Calendar c = Calendar.getInstance( TimeZone.getTimeZone( "UTC" ) );
-                        return new Object[] { getTimeForCalendar( c ) };
+                        return MethodResult.of( getTimeForCalendar( c ) );
                     }
                     case "local":
                     {
                         // Get Hour of day (local time)
                         Calendar c = Calendar.getInstance();
-                        return new Object[] { getTimeForCalendar( c ) };
+                        return MethodResult.of( getTimeForCalendar( c ) );
                     }
                     case "ingame":
                         // Get ingame hour
                         synchronized( m_alarms )
                         {
-                            return new Object[] { m_time };
+                            return MethodResult.of( m_time );
                         }
                     default:
                         throw new LuaException( "Unsupported operation" );
@@ -338,19 +339,19 @@ public class OSAPI implements ILuaAPI
                     {
                         // Get numbers of days since 1970-01-01 (utc)
                         Calendar c = Calendar.getInstance( TimeZone.getTimeZone( "UTC" ) );
-                        return new Object[] { getDayForCalendar( c ) };
+                        return MethodResult.of( getDayForCalendar( c ) );
                     }
                     case "local":
                     {
                         // Get numbers of days since 1970-01-01 (local time)
                         Calendar c = Calendar.getInstance();
-                        return new Object[] { getDayForCalendar( c ) };
+                        return MethodResult.of( getDayForCalendar( c ) );
                     }
                     case "ingame":
                         // Get game day
                         synchronized( m_alarms )
                         {
-                            return new Object[] { m_day };
+                            return MethodResult.of( m_day );
                         }
                     default:
                         throw new LuaException( "Unsupported operation" );
@@ -367,7 +368,7 @@ public class OSAPI implements ILuaAPI
                         m_timers.remove( token );
                     }
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 14:
             {
@@ -380,7 +381,7 @@ public class OSAPI implements ILuaAPI
                         m_alarms.remove( token );
                     }
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 15:
             {
@@ -392,21 +393,21 @@ public class OSAPI implements ILuaAPI
                     {
                         // Get utc epoch
                         Calendar c = Calendar.getInstance( TimeZone.getTimeZone( "UTC" ) );
-                        return new Object[] { getEpochForCalendar( c ) };
+                        return MethodResult.of( getEpochForCalendar( c ) );
                     }
                     case "local":
                     {
                         // Get local epoch
                         Calendar c = Calendar.getInstance();
-                        return new Object[] { getEpochForCalendar( c ) };
+                        return MethodResult.of( getEpochForCalendar( c ) );
                     }
                     case "ingame":
                         // Get in-game epoch
                         synchronized( m_alarms )
                         {
-                            return new Object[] {
+                            return MethodResult.of(
                                 m_day * 86400000 + (int) (m_time * 3600000.0f)
-                            };
+                            );
                         }
                     default:
                         throw new LuaException( "Unsupported operation" );
@@ -414,11 +415,18 @@ public class OSAPI implements ILuaAPI
             }
             default:
             {
-                return null;
+                return MethodResult.empty();
             }
         }
     }
 
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
     // Private methods
 
     private void queueLuaEvent( String event, Object[] args )

src/main/java/dan200/computercraft/core/apis/PeripheralAPI.java

@@ -8,9 +8,8 @@ package dan200.computercraft.core.apis;
 
 import dan200.computercraft.api.filesystem.IMount;
 import dan200.computercraft.api.filesystem.IWritableMount;
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.api.lua.ILuaAPI;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.core.computer.Computer;
 import dan200.computercraft.core.computer.ComputerThread;
@@ -98,7 +97,7 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
             m_attached = false;
         }
 
-        public Object[] call( ILuaContext context, String methodName, Object[] arguments ) throws LuaException, InterruptedException
+        public MethodResult call( ICallContext context, String methodName, Object[] arguments ) throws LuaException
         {
             int method = -1;
             synchronized( this )
@@ -368,8 +367,9 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException, InterruptedException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -389,7 +389,7 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
                         }
                     }
                 }
-                return new Object[] { present };
+                return MethodResult.of( present );
             }
             case 1:
             {
@@ -408,10 +408,10 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
                     }
                     if( type != null )
                     {
-                        return new Object[] { type };
+                        return MethodResult.of( type );
                     }
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 2:
             {
@@ -435,9 +435,9 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
                     for(int i=0; i<methods.length; ++i ) {
                         table.put( i+1, methods[i] );
                     }
-                    return new Object[] { table };
+                    return MethodResult.of( table );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 3:
             {
@@ -462,11 +462,19 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
             }
             default:
             {
-                return null;
+                return MethodResult.empty();
             }
         }
     }
 
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
+    
     // Privates
 
     private int parseSide( Object[] args ) throws LuaException

src/main/java/dan200/computercraft/core/apis/RedstoneAPI.java

@@ -6,12 +6,12 @@
 
 package dan200.computercraft.core.apis;
 
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.api.lua.ILuaAPI;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.core.computer.Computer;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -56,8 +56,9 @@ public class RedstoneAPI implements ILuaAPI
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -69,7 +70,7 @@ public class RedstoneAPI implements ILuaAPI
                 {
                     table.put( i+1, Computer.s_sideNames[i] );
                 }
-                return new Object[] { table };
+                return MethodResult.of( table );
             }
             case 1:
             {
@@ -77,19 +78,19 @@ public class RedstoneAPI implements ILuaAPI
                 int side = parseSide( args );
                 boolean output = getBoolean( args, 1 );
                 m_environment.setOutput( side, output ? 15 : 0 );
-                return null;
+                return MethodResult.empty();
             }
             case 2:
             {
                 // getOutput
                 int side = parseSide( args );
-                return new Object[] { m_environment.getOutput( side ) > 0 };
+                return MethodResult.of( m_environment.getOutput( side ) > 0 );
             }
             case 3:
             {
                 // getInput
                 int side = parseSide( args );
-                return new Object[] { m_environment.getInput( side ) > 0 };
+                return MethodResult.of( m_environment.getInput( side ) > 0 );
             }
             case 4:
             {
@@ -97,19 +98,19 @@ public class RedstoneAPI implements ILuaAPI
                 int side = parseSide( args );
                 int output = getInt( args, 1 );
                 m_environment.setBundledOutput( side, output );
-                return null;
+                return MethodResult.empty();
             }
             case 5:
             {
                 // getBundledOutput
                 int side = parseSide( args );
-                return new Object[] { m_environment.getBundledOutput( side ) };
+                return MethodResult.of( m_environment.getBundledOutput( side ) );
             }
             case 6:
             {
                 // getBundledInput
                 int side = parseSide( args );
-                return new Object[] { m_environment.getBundledInput( side ) };
+                return MethodResult.of( m_environment.getBundledInput( side ) );
             }
             case 7:
             {
@@ -117,7 +118,7 @@ public class RedstoneAPI implements ILuaAPI
                 int side = parseSide( args );
                 int mask = getInt( args, 1 );
                 int input = m_environment.getBundledInput( side );
-                return new Object[] { ((input & mask) == mask) };
+                return MethodResult.of( ((input & mask) == mask) );
             }
             case 8:
             case 9:
@@ -130,28 +131,36 @@ public class RedstoneAPI implements ILuaAPI
                     throw new LuaException( "Expected number in range 0-15" );
                 }
                 m_environment.setOutput( side, output );
-                return null;
+                return MethodResult.empty();
             }
             case 10:
             case 11:
             {
                 // getAnalogOutput/getAnalogueOutput
                 int side = parseSide( args );
-                return new Object[] { m_environment.getOutput( side ) };
+                return MethodResult.of( m_environment.getOutput( side ) );
             }
             case 12:
             case 13:
             {
                 // getAnalogInput/getAnalogueInput
                 int side = parseSide( args );
-                return new Object[] { m_environment.getInput( side ) };
+                return MethodResult.of( m_environment.getInput( side ) );
             }
             default:
             {
-                return null;
+                return MethodResult.empty();
             }
         }
     }
+
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
     
     private int parseSide( Object[] args ) throws LuaException
     {

src/main/java/dan200/computercraft/core/apis/TermAPI.java

@@ -6,15 +6,15 @@
 
 package dan200.computercraft.core.apis;
 
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.api.lua.ILuaAPI;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.core.computer.IComputerEnvironment;
 import dan200.computercraft.core.terminal.Terminal;
 import dan200.computercraft.shared.util.Palette;
 import org.apache.commons.lang3.ArrayUtils;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 
 import static dan200.computercraft.core.apis.ArgumentHelper.*;
 
@@ -83,11 +83,9 @@ public class TermAPI implements ILuaAPI
         return colour;
     }
 
-    public static Object[] encodeColour( int colour ) throws LuaException
+    public static MethodResult encodeColour( int colour )
     {
-        return new Object[] {
-            1 << colour
-        };
+        return MethodResult.of( 1 << colour );
     }
 
     public static void setColour( Terminal terminal, int colour, double r, double g, double b )
@@ -99,8 +97,9 @@ public class TermAPI implements ILuaAPI
         }
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -119,7 +118,7 @@ public class TermAPI implements ILuaAPI
                     m_terminal.write( text );
                     m_terminal.setCursorPos( m_terminal.getCursorX() + text.length(), m_terminal.getCursorY() );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 1:
             {
@@ -129,7 +128,7 @@ public class TermAPI implements ILuaAPI
                 {
                     m_terminal.scroll(y);
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 2:
             {
@@ -140,7 +139,7 @@ public class TermAPI implements ILuaAPI
                 {
                     m_terminal.setCursorPos( x, y );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 3:
             {
@@ -150,7 +149,7 @@ public class TermAPI implements ILuaAPI
                 {
                     m_terminal.setCursorBlink( b );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 4:
             {
@@ -161,7 +160,7 @@ public class TermAPI implements ILuaAPI
                     x = m_terminal.getCursorX();
                     y = m_terminal.getCursorY();
                 }
-                return new Object[] { x + 1, y + 1 };
+                return MethodResult.of( x + 1, y + 1 );
             }
             case 5:
             {
@@ -172,7 +171,7 @@ public class TermAPI implements ILuaAPI
                     width = m_terminal.getWidth();
                     height = m_terminal.getHeight();
                 }                
-                return new Object[] { width, height };
+                return MethodResult.of( width, height );
             }
             case 6:
             {
@@ -181,7 +180,7 @@ public class TermAPI implements ILuaAPI
                 {
                     m_terminal.clear();
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 7:
             {
@@ -190,7 +189,7 @@ public class TermAPI implements ILuaAPI
                 {
                     m_terminal.clearLine();
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 8:
             case 9:
@@ -201,7 +200,7 @@ public class TermAPI implements ILuaAPI
                 {
                     m_terminal.setTextColour( colour );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 10:
             case 11:
@@ -212,13 +211,13 @@ public class TermAPI implements ILuaAPI
                 {
                     m_terminal.setBackgroundColour( colour );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 12:
             case 13:
             {
                 // isColour/isColor
-                return new Object[] { m_environment.isColour() };
+                return MethodResult.of( m_environment.isColour() );
             }
             case 14:
             case 15:
@@ -248,7 +247,7 @@ public class TermAPI implements ILuaAPI
                     m_terminal.blit( text, textColour, backgroundColour );
                     m_terminal.setCursorPos( m_terminal.getCursorX() + text.length(), m_terminal.getCursorY() );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 19:
             case 20:
@@ -268,7 +267,7 @@ public class TermAPI implements ILuaAPI
                     double b = getReal( args, 3 );
                     setColour( m_terminal, colour, r, g, b );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 21:
             case 22:
@@ -279,18 +278,26 @@ public class TermAPI implements ILuaAPI
                 {
                     if ( m_terminal.getPalette() != null )
                     {
-                        return ArrayUtils.toObject( m_terminal.getPalette().getColour( colour ) );
+                        return MethodResult.of( (Object[]) ArrayUtils.toObject( m_terminal.getPalette().getColour( colour ) ) );
                     }
                 }
-                return null;
+                return MethodResult.empty();
             }
             default:
             {
-                return null;
+                return MethodResult.empty();
             }
         }
     }
-    
+
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
+
     private static int getHighestBit( int group )
     {
         int bit = 0;

src/main/java/dan200/computercraft/core/apis/handles/BinaryInputHandle.java

@@ -1,8 +1,9 @@
 package dan200.computercraft.core.apis.handles;
 
 import com.google.common.io.ByteStreams;
-import dan200.computercraft.api.lua.ILuaContext;
+import dan200.computercraft.api.lua.ICallContext;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 
 import javax.annotation.Nonnull;
 import java.io.ByteArrayOutputStream;
@@ -35,8 +36,9 @@ public class BinaryInputHandle extends HandleGeneric
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -60,9 +62,9 @@ public class BinaryInputHandle extends HandleGeneric
                             byte[] bytes = new byte[ count ];
                             int read = m_stream.read( bytes );
 
-                            if( read < 0 ) return null;
+                            if( read < 0 ) return MethodResult.empty();
                             if( read < count ) bytes = Arrays.copyOf( bytes, read );
-                            return new Object[] { bytes };
+                            return MethodResult.of( bytes );
                         }
                         else
                         {
@@ -86,18 +88,18 @@ public class BinaryInputHandle extends HandleGeneric
                                 out.write( buffer, 0, read );
                             }
 
-                            return new Object[] { out.toByteArray() };
+                            return MethodResult.of( new Object[]{ out.toByteArray() } );
                         }
                     }
                     else
                     {
                         int b = m_stream.read();
-                        return b == -1 ? null : new Object[] { b };
+                        return b == -1 ? MethodResult.empty() : MethodResult.of( b );
                     }
                 }
                 catch( IOException e )
                 {
-                    return null;
+                    return MethodResult.empty();
                 }
             case 1:
                 // readAll
@@ -105,18 +107,18 @@ public class BinaryInputHandle extends HandleGeneric
                 try
                 {
                     byte[] out = ByteStreams.toByteArray( m_stream );
-                    return out == null ? null : new Object[] { out };
+                    return out == null ? MethodResult.empty() : MethodResult.of( out );
                 }
                 catch( IOException e )
                 {
-                    return null;
+                    return MethodResult.empty();
                 }
             case 2:
                 //close
                 close();
-                return null;
+                return MethodResult.empty();
             default:
-                return null;
+                return MethodResult.empty();
         }
     }
 }

src/main/java/dan200/computercraft/core/apis/handles/BinaryOutputHandle.java

@@ -1,7 +1,8 @@
 package dan200.computercraft.core.apis.handles;
 
-import dan200.computercraft.api.lua.ILuaContext;
+import dan200.computercraft.api.lua.ICallContext;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 import dan200.computercraft.core.apis.ArgumentHelper;
 import dan200.computercraft.shared.util.StringUtil;
 
@@ -30,8 +31,9 @@ public class BinaryOutputHandle extends HandleGeneric
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -54,7 +56,7 @@ public class BinaryOutputHandle extends HandleGeneric
                     {
                         throw ArgumentHelper.badArgument( 0, "string or number", args.length > 0 ? args[ 0 ] : null );
                     }
-                    return null;
+                    return MethodResult.empty();
                 }
                 catch( IOException e )
                 {
@@ -66,18 +68,18 @@ public class BinaryOutputHandle extends HandleGeneric
                 try
                 {
                     m_writer.flush();
-                    return null;
+                    return MethodResult.empty();
                 }
                 catch( IOException e )
                 {
-                    return null;
+                    return MethodResult.empty();
                 }
             case 2:
                 //close
                 close();
-                return null;
+                return MethodResult.empty();
             default:
-                return null;
+                return MethodResult.empty();
         }
     }
 }

src/main/java/dan200/computercraft/core/apis/handles/EncodedInputHandle.java

@@ -1,7 +1,8 @@
 package dan200.computercraft.core.apis.handles;
 
-import dan200.computercraft.api.lua.ILuaContext;
+import dan200.computercraft.api.lua.ICallContext;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 
 import javax.annotation.Nonnull;
 import java.io.*;
@@ -57,8 +58,9 @@ public class EncodedInputHandle extends HandleGeneric
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -70,16 +72,16 @@ public class EncodedInputHandle extends HandleGeneric
                     String line = m_reader.readLine();
                     if( line != null )
                     {
-                        return new Object[] { line };
+                        return MethodResult.of( line );
                     }
                     else
                     {
-                        return null;
+                        return MethodResult.empty();
                     }
                 }
                 catch( IOException e )
                 {
-                    return null;
+                    return MethodResult.empty();
                 }
             case 1:
                 // readAll
@@ -97,16 +99,16 @@ public class EncodedInputHandle extends HandleGeneric
                             result.append( "\n" );
                         }
                     }
-                    return new Object[] { result.toString() };
+                    return MethodResult.of( result.toString() );
                 }
                 catch( IOException e )
                 {
-                    return null;
+                    return MethodResult.empty();
                 }
             case 2:
                 // close
                 close();
-                return null;
+                return MethodResult.empty();
             case 3:
                 // read
                 checkOpen();
@@ -125,7 +127,7 @@ public class EncodedInputHandle extends HandleGeneric
                         char[] chars = new char[ count ];
                         int read = m_reader.read( chars );
 
-                        return read < 0 ? null : new Object[] { new String( chars, 0, read ) };
+                        return read < 0 ? MethodResult.empty() : MethodResult.of( new String( chars, 0, read ) );
                     }
                     else
                     {
@@ -150,15 +152,15 @@ public class EncodedInputHandle extends HandleGeneric
                             out.append( buffer, 0, read );
                         }
 
-                        return new Object[] { out.toString() };
+                        return MethodResult.of( out.toString() );
                     }
                 }
                 catch( IOException e )
                 {
-                    return null;
+                    return MethodResult.empty();
                 }
             default:
-                return null;
+                return MethodResult.empty();
         }
     }
 }

src/main/java/dan200/computercraft/core/apis/handles/EncodedOutputHandle.java

@@ -1,7 +1,8 @@
 package dan200.computercraft.core.apis.handles;
 
-import dan200.computercraft.api.lua.ILuaContext;
+import dan200.computercraft.api.lua.ICallContext;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 
 import javax.annotation.Nonnull;
 import java.io.*;
@@ -53,8 +54,9 @@ public class EncodedOutputHandle extends HandleGeneric
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -74,7 +76,7 @@ public class EncodedOutputHandle extends HandleGeneric
                 try
                 {
                     m_writer.write( text, 0, text.length() );
-                    return null;
+                    return MethodResult.empty();
                 }
                 catch( IOException e )
                 {
@@ -98,7 +100,7 @@ public class EncodedOutputHandle extends HandleGeneric
                 {
                     m_writer.write( text, 0, text.length() );
                     m_writer.newLine();
-                    return null;
+                    return MethodResult.empty();
                 }
                 catch( IOException e )
                 {
@@ -111,18 +113,18 @@ public class EncodedOutputHandle extends HandleGeneric
                 try
                 {
                     m_writer.flush();
-                    return null;
+                    return MethodResult.empty();
                 }
                 catch( IOException e )
                 {
-                    return null;
+                    return MethodResult.empty();
                 }
             case 3:
                 // close
                 close();
-                return null;
+                return MethodResult.empty();
             default:
-                return null;
+                return MethodResult.empty();
         }
     }
 }

src/main/java/dan200/computercraft/core/apis/handles/HandleGeneric.java

@@ -1,8 +1,12 @@
 package dan200.computercraft.core.apis.handles;
 
+import dan200.computercraft.api.lua.ICallContext;
+import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.ILuaObject;
 import dan200.computercraft.api.lua.LuaException;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.io.Closeable;
 import java.io.IOException;
 
@@ -32,4 +36,12 @@ public abstract class HandleGeneric implements ILuaObject
         {
         }
     }
+
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
 }

src/main/java/dan200/computercraft/core/apis/http/HTTPRequest.java

@@ -9,15 +9,14 @@ package dan200.computercraft.core.apis.http;
 import com.google.common.base.Joiner;
 import com.google.common.io.ByteStreams;
 import dan200.computercraft.ComputerCraft;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.ILuaObject;
-import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.core.apis.IAPIEnvironment;
 import dan200.computercraft.core.apis.handles.BinaryInputHandle;
 import dan200.computercraft.core.apis.handles.EncodedInputHandle;
 import dan200.computercraft.core.tracking.TrackingField;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.io.*;
 import java.net.*;
 import java.util.Arrays;
@@ -236,8 +235,9 @@ public class HTTPRequest implements Runnable
                 return newMethods;
             }
 
+            @Nonnull
             @Override
-            public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException, InterruptedException
+            public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
             {
                 if( method < methodOffset )
                 {
@@ -248,19 +248,27 @@ public class HTTPRequest implements Runnable
                     case 0:
                     {
                         // getResponseCode
-                        return new Object[]{ responseCode };
+                        return MethodResult.of( responseCode );
                     }
                     case 1:
                     {
                         // getResponseHeaders
-                        return new Object[]{ responseHeaders };
+                        return MethodResult.of( responseHeaders );
                     }
                     default:
                     {
-                        return null;
+                        return MethodResult.empty();
                     }
                 }
             }
+
+            @Nullable
+            @Override
+            @Deprecated
+            public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+            {
+                return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+            }
         };
     }
 

src/main/java/dan200/computercraft/core/apis/http/WebsocketConnection.java

@@ -7,9 +7,7 @@
 package dan200.computercraft.core.apis.http;
 
 import com.google.common.base.Objects;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.ILuaObject;
-import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.core.apis.HTTPAPI;
 import dan200.computercraft.core.apis.IAPIEnvironment;
 import dan200.computercraft.core.tracking.TrackingField;
@@ -156,33 +154,48 @@ public class WebsocketConnection extends SimpleChannelInboundHandler<Object> imp
 
     @Nullable
     @Override
+    @Deprecated
     public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
+
+    @Nonnull
+    @Override
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] arguments ) throws LuaException
     {
         switch( method )
         {
             case 0:
-                while( true )
+                checkOpen();
+                return MethodResult.pullEvent( MESSAGE_EVENT, new ILuaFunction()
                 {
-                    checkOpen();
-                    Object[] event = context.pullEvent( MESSAGE_EVENT );
-                    if( event.length >= 3 && Objects.equal( event[1], url ) )
+                    @Nonnull
+                    @Override
+                    public MethodResult call( @Nullable Object[] event ) throws LuaException
                     {
-                        return new Object[]{ event[2] };
+                        if( event != null && event.length >= 3 && Objects.equal( event[1], url ) )
+                        {
+                            return MethodResult.of( event[2] );
+                        }
+
+                        checkOpen();
+                        return MethodResult.pullEvent( MESSAGE_EVENT, this );
                     }
-                }
+                } );
             case 1:
             {
                 checkOpen();
                 String text = arguments.length > 0 && arguments[0] != null ? arguments[0].toString() : "";
                 computer.addTrackingChange( TrackingField.WEBSOCKET_OUTGOING, text.length() );
                 channel.writeAndFlush( new TextWebSocketFrame( text ) );
-                return null;
+                return MethodResult.empty();
             }
             case 2:
                 close( true );
-                return null;
+                return MethodResult.empty();
             default:
-                return null;
+                return MethodResult.empty();
         }
     }
 

src/main/java/dan200/computercraft/core/computer/Computer.java

@@ -265,10 +265,18 @@ public class Computer
 
         @Nullable
         @Override
+        @Deprecated
         public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
         {
             return delegate.callMethod( context, method, arguments );
         }
+
+        @Nonnull
+        @Override
+        public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] arguments ) throws LuaException
+        {
+            return delegate.callMethod( context, method, arguments );
+        }
     }
 
     private static IMount s_romMount = null;
@@ -960,7 +968,7 @@ public class Computer
                 return;
             }
         }
-            
+
         final Computer computer = this;
         ITask task = new ITask() {
             @Override

src/main/java/dan200/computercraft/core/computer/IComputerOwned.java

@@ -0,0 +1,9 @@
+package dan200.computercraft.core.computer;
+
+import javax.annotation.Nullable;
+
+public interface IComputerOwned
+{
+    @Nullable
+    Computer getComputer();
+}

src/main/java/dan200/computercraft/core/lua/CobaltCallContext.java

@@ -0,0 +1,87 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.core.lua;
+
+import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.api.lua.ICallContext;
+import dan200.computercraft.api.lua.ILuaTask;
+import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.core.computer.Computer;
+import dan200.computercraft.core.computer.ITask;
+import dan200.computercraft.core.computer.MainThread;
+
+import javax.annotation.Nonnull;
+
+class CobaltCallContext implements ICallContext
+{
+    private final Computer computer;
+
+    CobaltCallContext( Computer computer )
+    {
+        this.computer = computer;
+    }
+
+    @Override
+    public long issueMainThreadTask( @Nonnull final ILuaTask task ) throws LuaException
+    {
+        // Issue command
+        final long taskID = MainThread.getUniqueTaskID();
+        final ITask iTask = new ITask()
+        {
+            @Override
+            public Computer getOwner()
+            {
+                return computer;
+            }
+
+            @Override
+            public void execute()
+            {
+                try
+                {
+                    Object[] results = task.execute();
+                    if( results != null )
+                    {
+                        Object[] eventArguments = new Object[results.length + 2];
+                        eventArguments[0] = taskID;
+                        eventArguments[1] = true;
+                        System.arraycopy( results, 0, eventArguments, 2, results.length );
+                        computer.queueEvent( "task_complete", eventArguments );
+                    }
+                    else
+                    {
+                        computer.queueEvent( "task_complete", new Object[]{ taskID, true } );
+                    }
+                }
+                catch( LuaException e )
+                {
+                    computer.queueEvent( "task_complete", new Object[]{
+                        taskID, false, e.getMessage()
+                    } );
+                }
+                catch( Throwable t )
+                {
+                    if( ComputerCraft.logPeripheralErrors )
+                    {
+                        ComputerCraft.log.error( "Error running task", t );
+                    }
+                    computer.queueEvent( "task_complete", new Object[]{
+                        taskID, false, "Java Exception Thrown: " + t.toString()
+                    } );
+                }
+            }
+        };
+        if( MainThread.queueTask( iTask ) )
+        {
+            return taskID;
+        }
+        else
+        {
+            throw new LuaException( "Task limit exceeded" );
+        }
+    }
+}

src/main/java/dan200/computercraft/core/lua/CobaltLuaContext.java

@@ -0,0 +1,191 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.core.lua;
+
+import dan200.computercraft.api.lua.ILuaContext;
+import dan200.computercraft.api.lua.ILuaContextTask;
+import dan200.computercraft.api.lua.ILuaTask;
+import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.core.computer.Computer;
+import org.squiddev.cobalt.LuaError;
+import org.squiddev.cobalt.LuaState;
+import org.squiddev.cobalt.LuaThread;
+import org.squiddev.cobalt.UnwindThrowable;
+
+import javax.annotation.Nonnull;
+import java.lang.ref.WeakReference;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.SynchronousQueue;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ * An ugly wrapper for {@link ILuaContext} style calls, which executes them on a separate thread.
+ */
+class CobaltLuaContext extends CobaltCallContext implements ILuaContext
+{
+    private static final ThreadGroup group = new ThreadGroup( "ComputerCraft-Lua" );
+    private static final AtomicInteger threadCounter = new AtomicInteger();
+    private static final ExecutorService threads = new ThreadPoolExecutor(
+        4, Integer.MAX_VALUE, 60L, TimeUnit.SECONDS, new SynchronousQueue<>(),
+        task -> {
+            Thread thread = new Thread( group, task, group.getName() + "-" + threadCounter.incrementAndGet() );
+            if( !thread.isDaemon() ) thread.setDaemon( true );
+            if( thread.getPriority() != Thread.NORM_PRIORITY ) thread.setPriority( Thread.NORM_PRIORITY );
+            return thread;
+        }
+    );
+
+    private boolean done = false;
+    private Object[] values;
+    private LuaError exception;
+    private final Semaphore yield = new Semaphore();
+    private final Semaphore resume = new Semaphore();
+    private WeakReference<LuaThread> thread;
+
+    CobaltLuaContext( Computer computer, LuaState state )
+    {
+        super( computer );
+        this.thread = state.getCurrentThread().getReference();
+    }
+
+    @Nonnull
+    @Override
+    @Deprecated
+    public Object[] pullEvent( String filter ) throws LuaException, InterruptedException
+    {
+        Object[] results = pullEventRaw( filter );
+        if( results.length >= 1 && results[0].equals( "terminate" ) )
+        {
+            throw new LuaException( "Terminated", 0 );
+        }
+        return results;
+    }
+
+    @Nonnull
+    @Override
+    @Deprecated
+    public Object[] pullEventRaw( String filter ) throws InterruptedException
+    {
+        return yield( new Object[]{ filter } );
+    }
+
+    @Nonnull
+    @Override
+    @Deprecated
+    public Object[] yield( Object[] yieldArgs ) throws InterruptedException
+    {
+        if( done ) throw new IllegalStateException( "Cannot yield when complete" );
+
+        values = yieldArgs;
+        yield.signal();
+
+        // Every 30 seconds check to see if the coroutine has been GCed
+        // if so then abort this task.
+        while( !resume.await( 30000 ) )
+        {
+            if( thread.get() == null ) throw new InterruptedException( "Orphaned async task" );
+        }
+
+        return values;
+    }
+
+    @Override
+    @Deprecated
+    public Object[] executeMainThreadTask( @Nonnull final ILuaTask task ) throws LuaException, InterruptedException
+    {
+        // Issue task
+        final long taskID = issueMainThreadTask( task );
+
+        // Wait for response
+        while( true )
+        {
+            Object[] response = pullEvent( "task_complete" );
+            if( response.length >= 3 && response[1] instanceof Number && response[2] instanceof Boolean )
+            {
+                if( ((Number) response[1]).intValue() == taskID )
+                {
+                    Object[] returnValues = new Object[response.length - 3];
+                    if( (Boolean) response[2] )
+                    {
+                        // Extract the return values from the event and return them
+                        System.arraycopy( response, 3, returnValues, 0, returnValues.length );
+                        return returnValues;
+                    }
+                    else
+                    {
+                        // Extract the error message from the event and raise it
+                        if( response.length >= 4 && response[3] instanceof String )
+                        {
+                            throw new LuaException( (String) response[3] );
+                        }
+                        else
+                        {
+                            throw new LuaException();
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    void execute( ILuaContextTask task )
+    {
+        threads.submit( () -> {
+            try
+            {
+                values = task.execute( this );
+            }
+            catch( LuaException e )
+            {
+                exception = new LuaError( e.getMessage(), e.getLevel() );
+            }
+            catch( InterruptedException e )
+            {
+                exception = new LuaError( "Java Exception Thrown: " + e.toString(), 0 );
+            }
+            finally
+            {
+                done = true;
+                yield.signal();
+            }
+        } );
+    }
+
+    void resume( Object[] args )
+    {
+        values = args;
+        resume.signal();
+    }
+
+    Object[] await( LuaState state, CobaltLuaMachine machine ) throws LuaError, UnwindThrowable
+    {
+        if( !done )
+        {
+            try
+            {
+                yield.await();
+            }
+            catch( InterruptedException e )
+            {
+                throw new LuaError( "Java Exception Thrown: " + e.toString(), 0 );
+            }
+        }
+
+        if( done )
+        {
+            if( exception != null ) throw exception;
+            return values;
+        }
+        else
+        {
+            LuaThread.yield( state, machine.toValues( values ) );
+            throw new IllegalStateException( "Unreachable" );
+        }
+    }
+}

src/main/java/dan200/computercraft/core/lua/CobaltLuaMachine.java

@@ -7,14 +7,9 @@
 package dan200.computercraft.core.lua;
 
 import dan200.computercraft.ComputerCraft;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.ILuaObject;
-import dan200.computercraft.api.lua.ILuaTask;
-import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.api.lua.ILuaAPI;
+import dan200.computercraft.api.lua.ILuaObject;
 import dan200.computercraft.core.computer.Computer;
-import dan200.computercraft.core.computer.ITask;
-import dan200.computercraft.core.computer.MainThread;
 import org.squiddev.cobalt.*;
 import org.squiddev.cobalt.compiler.CompileException;
 import org.squiddev.cobalt.compiler.LoadState;
@@ -27,7 +22,6 @@ import org.squiddev.cobalt.function.VarArgFunction;
 import org.squiddev.cobalt.lib.*;
 import org.squiddev.cobalt.lib.platform.AbstractResourceManipulator;
 
-import javax.annotation.Nonnull;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
@@ -76,7 +70,7 @@ public class CobaltLuaMachine implements ILuaMachine
                 int count = ++this.count;
                 if( count > 100000 )
                 {
-                    if( m_hardAbortMessage != null ) LuaThread.yield( state, NONE );
+                    if( m_hardAbortMessage != null ) throw new LuaError( m_hardAbortMessage );
                     this.count = 0;
                 }
                 else
@@ -90,7 +84,7 @@ public class CobaltLuaMachine implements ILuaMachine
             @Override
             public void poll() throws LuaError
             {
-                if( m_hardAbortMessage != null ) LuaThread.yield( state, NONE );
+                if( m_hardAbortMessage != null ) throw new LuaError( m_hardAbortMessage );
                 handleSoftAbort();
             }
 
@@ -125,7 +119,7 @@ public class CobaltLuaMachine implements ILuaMachine
         if( ComputerCraft.debug_enable ) m_globals.load( state, new DebugLib() );
 
         // Register custom load/loadstring provider which automatically adds prefixes.
-        LibFunction.bind( state, m_globals, PrefixLoader.class, new String[]{ "load", "loadstring" } );
+        LibFunction.bind( m_globals, PrefixLoader.class, new String[]{ "load", "loadstring" } );
 
         // Remove globals we don't want to expose
         m_globals.rawset( "collectgarbage", Constants.NIL );
@@ -216,18 +210,13 @@ public class CobaltLuaMachine implements ILuaMachine
                 resumeArgs = varargsOf( valueOf( eventName ), toValues( arguments ) );
             }
 
-            Varargs results = m_mainRoutine.resume( resumeArgs );
+            LuaValue filter = LuaThread.run( m_mainRoutine, resumeArgs ).first();
             if( m_hardAbortMessage != null )
             {
                 throw new LuaError( m_hardAbortMessage );
             }
-            else if( !results.first().checkBoolean() )
-            {
-                throw new LuaError( results.arg( 2 ).checkString() );
-            }
             else
             {
-                LuaValue filter = results.arg( 2 );
                 if( filter.isString() )
                 {
                     m_eventFilter = filter.toString();
@@ -246,6 +235,7 @@ public class CobaltLuaMachine implements ILuaMachine
         }
         catch( LuaError e )
         {
+            if( ComputerCraft.logPeripheralErrors ) ComputerCraft.log.error( "Main thread crashed", e );
             m_mainRoutine.abandon();
             m_mainRoutine = null;
         }
@@ -302,181 +292,12 @@ public class CobaltLuaMachine implements ILuaMachine
     {
         LuaTable table = new LuaTable();
         String[] methods = object.getMethodNames();
-        for( int i = 0; i < methods.length; ++i )
+        for( int method = 0; method < methods.length; method++ )
         {
-            if( methods[ i ] != null )
+            if( methods[method] != null )
             {
-                final int method = i;
-                final ILuaObject apiObject = object;
-                final String methodName = methods[ i ];
-                table.rawset( methodName, new VarArgFunction()
-                {
-                    @Override
-                    public Varargs invoke( final LuaState state, Varargs _args ) throws LuaError
-                    {
-                        Object[] arguments = toObjects( _args, 1 );
-                        Object[] results;
-                        try
-                        {
-                            results = apiObject.callMethod( new ILuaContext()
-                            {
-                                @Nonnull
-                                @Override
-                                public Object[] pullEvent( String filter ) throws LuaException, InterruptedException
-                                {
-                                    Object[] results = pullEventRaw( filter );
-                                    if( results.length >= 1 && results[ 0 ].equals( "terminate" ) )
-                                    {
-                                        throw new LuaException( "Terminated", 0 );
-                                    }
-                                    return results;
-                                }
-
-                                @Nonnull
-                                @Override
-                                public Object[] pullEventRaw( String filter ) throws InterruptedException
-                                {
-                                    return yield( new Object[] { filter } );
-                                }
-
-                                @Nonnull
-                                @Override
-                                public Object[] yield( Object[] yieldArgs ) throws InterruptedException
-                                {
-                                    try
-                                    {
-                                        Varargs results = LuaThread.yield( state, toValues( yieldArgs ) );
-                                        return toObjects( results, 1 );
-                                    }
-                                    catch( OrphanedThread e )
-                                    {
-                                        throw new InterruptedException();
-                                    }
-                                    catch( Throwable e )
-                                    {
-                                        throw new RuntimeException( e );
-                                    }
-                                }
-
-                                @Override
-                                public long issueMainThreadTask( @Nonnull final ILuaTask task ) throws LuaException
-                                {
-                                    // Issue command
-                                    final long taskID = MainThread.getUniqueTaskID();
-                                    final ITask iTask = new ITask()
-                                    {
-                                        @Override
-                                        public Computer getOwner()
-                                        {
-                                            return m_computer;
-                                        }
-
-                                        @Override
-                                        public void execute()
-                                        {
-                                            try
-                                            {
-                                                Object[] results = task.execute();
-                                                if( results != null )
-                                                {
-                                                    Object[] eventArguments = new Object[ results.length + 2 ];
-                                                    eventArguments[ 0 ] = taskID;
-                                                    eventArguments[ 1 ] = true;
-                                                    System.arraycopy( results, 0, eventArguments, 2, results.length );
-                                                    m_computer.queueEvent( "task_complete", eventArguments );
-                                                }
-                                                else
-                                                {
-                                                    m_computer.queueEvent( "task_complete", new Object[] { taskID, true } );
-                                                }
-                                            }
-                                            catch( LuaException e )
-                                            {
-                                                m_computer.queueEvent( "task_complete", new Object[] {
-                                                    taskID, false, e.getMessage()
-                                                } );
-                                            }
-                                            catch( Throwable t )
-                                            {
-                                                if( ComputerCraft.logPeripheralErrors )
-                                                {
-                                                    ComputerCraft.log.error( "Error running task", t );
-                                                }
-                                                m_computer.queueEvent( "task_complete", new Object[] {
-                                                    taskID, false, "Java Exception Thrown: " + t.toString()
-                                                } );
-                                            }
-                                        }
-                                    };
-                                    if( MainThread.queueTask( iTask ) )
-                                    {
-                                        return taskID;
-                                    }
-                                    else
-                                    {
-                                        throw new LuaException( "Task limit exceeded" );
-                                    }
-                                }
-
-                                @Override
-                                public Object[] executeMainThreadTask( @Nonnull final ILuaTask task ) throws LuaException, InterruptedException
-                                {
-                                    // Issue task
-                                    final long taskID = issueMainThreadTask( task );
-
-                                    // Wait for response
-                                    while( true )
-                                    {
-                                        Object[] response = pullEvent( "task_complete" );
-                                        if( response.length >= 3 && response[ 1 ] instanceof Number && response[ 2 ] instanceof Boolean )
-                                        {
-                                            if( ((Number) response[ 1 ]).intValue() == taskID )
-                                            {
-                                                Object[] returnValues = new Object[ response.length - 3 ];
-                                                if( (Boolean) response[ 2 ] )
-                                                {
-                                                    // Extract the return values from the event and return them
-                                                    System.arraycopy( response, 3, returnValues, 0, returnValues.length );
-                                                    return returnValues;
-                                                }
-                                                else
-                                                {
-                                                    // Extract the error message from the event and raise it
-                                                    if( response.length >= 4 && response[ 3 ] instanceof String )
-                                                    {
-                                                        throw new LuaException( (String) response[ 3 ] );
-                                                    }
-                                                    else
-                                                    {
-                                                        throw new LuaException();
-                                                    }
-                                                }
-                                            }
-                                        }
-                                    }
-
-                                }
-                            }, method, arguments );
-                        }
-                        catch( InterruptedException e )
-                        {
-                            throw new OrphanedThread();
-                        }
-                        catch( LuaException e )
-                        {
-                            throw new LuaError( e.getMessage(), e.getLevel() );
-                        }
-                        catch( Throwable t )
-                        {
-                            if( ComputerCraft.logPeripheralErrors )
-                            {
-                                ComputerCraft.log.error( "Error calling " + methodName + " on " + apiObject, t );
-                            }
-                            throw new LuaError( "Java Exception Thrown: " + t.toString(), 0 );
-                        }
-                        return toValues( results );
-                    }
-                } );
+                final String methodName = methods[method];
+                table.rawset( methodName, new CobaltWrapperFunction( this, m_computer, object, method, methodName ) );
             }
         }
         return table;
@@ -544,7 +365,7 @@ public class CobaltLuaMachine implements ILuaMachine
         }
     }
 
-    private Varargs toValues( Object[] objects )
+    Varargs toValues( Object[] objects )
     {
         if( objects == null || objects.length == 0 )
         {
@@ -635,7 +456,7 @@ public class CobaltLuaMachine implements ILuaMachine
         }
     }
 
-    private static Object[] toObjects( Varargs values, int startIdx )
+    static Object[] toObjects( Varargs values, int startIdx )
     {
         int count = values.count();
         Object[] objects = new Object[ count - startIdx + 1 ];
@@ -703,13 +524,23 @@ public class CobaltLuaMachine implements ILuaMachine
             if( remaining <= 0 )
             {
                 LuaValue s;
+                state.getCurrentThread().disableYield();
                 try
                 {
                     s = OperationHelper.call( state, func );
-                } catch (LuaError e)
+                }
+                catch( UnwindThrowable e )
+                {
+                    throw new IOException( "Impossible yield within load" );
+                }
+                catch( LuaError e )
                 {
                     throw new IOException( e );
                 }
+                finally
+                {
+                    state.getCurrentThread().enableYield();
+                }
 
                 if( s.isNil() )
                 {
@@ -735,4 +566,5 @@ public class CobaltLuaMachine implements ILuaMachine
             return bytes[offset++];
         }
     }
+
 }

src/main/java/dan200/computercraft/core/lua/CobaltWrapperFunction.java

@@ -0,0 +1,292 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.core.lua;
+
+import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.api.lua.ILuaFunction;
+import dan200.computercraft.api.lua.ILuaObject;
+import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
+import dan200.computercraft.core.computer.Computer;
+import org.squiddev.cobalt.*;
+import org.squiddev.cobalt.debug.DebugState;
+import org.squiddev.cobalt.function.VarArgFunction;
+
+import java.util.ArrayDeque;
+import java.util.Deque;
+
+class CobaltWrapperFunction extends VarArgFunction implements Resumable<CobaltWrapperFunction.State>
+{
+    private final CobaltLuaMachine machine;
+    private final Computer computer;
+    private final CobaltCallContext callContext;
+
+    private final ILuaObject delegate;
+    private final int method;
+    private final String methodName;
+
+    CobaltWrapperFunction( CobaltLuaMachine machine, Computer computer, ILuaObject delegate, int method, String methodName )
+    {
+        this.machine = machine;
+        this.computer = computer;
+        this.callContext = new CobaltCallContext( computer );
+        this.delegate = delegate;
+        this.method = method;
+        this.methodName = methodName;
+    }
+
+    @Override
+    public Varargs invoke( final LuaState state, Varargs args ) throws LuaError, UnwindThrowable
+    {
+        MethodResult future;
+        try
+        {
+            future = delegate.callMethod( callContext, method, CobaltLuaMachine.toObjects( args, 1 ) );
+        }
+        catch( LuaException e )
+        {
+            throw new LuaError( e.getMessage(), e.getLevel() );
+        }
+        catch( Exception e )
+        {
+            if( ComputerCraft.logPeripheralErrors )
+            {
+                ComputerCraft.log.error( "Error calling " + methodName + " on " + delegate, e );
+            }
+            throw new LuaError( "Java Exception Thrown: " + e.toString(), 0 );
+        }
+
+        // Verify we've a "well formed" future
+        if( future == null )
+        {
+            ComputerCraft.log.error( "Null result from " + delegate );
+            throw new LuaError( "Java Exception Thrown: Null result" );
+        }
+
+        // Fast path for immediate results
+        if( future instanceof MethodResult.Immediate )
+        {
+            return machine.toValues( ((MethodResult.Immediate) future).getResult() );
+        }
+
+        State context = new State();
+        try
+        {
+            return runFuture( state, context, future );
+        }
+        catch( UnwindThrowable e )
+        {
+            // Push our state onto the stack if need-be. Normally this wouldn't be safe and we 
+            // should do this at the very beginning, but we know that we won't be calling anything 
+            // else which will push to the resume stack.
+            DebugState ds = state.debug.getDebugState();
+            state.debug.onCall( ds, this, context );
+            throw e;
+        }
+    }
+
+    @Override
+    public Varargs resume( LuaState state, State context, Varargs args ) throws LuaError, UnwindThrowable
+    {
+        Varargs result;
+        try
+        {
+            result = doResume( state, context, args );
+        }
+        catch( LuaError e )
+        {
+            state.debug.onReturn();
+            throw e;
+        }
+        catch( Exception e )
+        {
+            state.debug.onReturn();
+            throw new LuaError( e );
+        }
+
+        state.debug.onReturn();
+        return result;
+    }
+
+    private Varargs doResume( LuaState state, State context, Varargs args ) throws LuaError, UnwindThrowable
+    {
+        MethodResult future = context.pending;
+        if( future instanceof MethodResult.OnEvent )
+        {
+            MethodResult.OnEvent onEvent = (MethodResult.OnEvent) future;
+            if( !onEvent.isRaw() && args.first().toString().equals( "terminate" ) )
+            {
+                throw new LuaError( "Terminated", 0 );
+            }
+
+            return runCallback( state, context, CobaltLuaMachine.toObjects( args, 1 ) );
+        }
+        else if( future instanceof MethodResult.OnMainThread )
+        {
+            if( args.arg( 2 ).isNumber() && args.arg( 3 ).isBoolean() && args.arg( 2 ).toLong() == context.taskId )
+            {
+                if( args.arg( 3 ).toBoolean() )
+                {
+                    // Extract the return values from the event and return them
+                    return runFuture( state, context, context.taskResult );
+                }
+                else
+                {
+                    // Extract the error message from the event and raise it
+                    throw new LuaError( args.arg( 4 ) );
+                }
+            }
+            else
+            {
+                LuaThread.yield( state, ValueFactory.valueOf( "task_complete" ) );
+                throw new IllegalStateException( "Unreachable" );
+            }
+        }
+        else if( future instanceof MethodResult.WithLuaContext )
+        {
+            context.luaContext.resume( CobaltLuaMachine.toObjects( args, 1 ) );
+            return runCallback( state, context, context.luaContext.await( state, machine ) );
+        }
+        else
+        {
+            ComputerCraft.log.error( "Unknown method result " + future );
+            throw new LuaError( "Java Exception Thrown: Unknown method result" );
+        }
+    }
+
+    @Override
+    public Varargs resumeError( LuaState state, State context, LuaError error ) throws LuaError
+    {
+        state.debug.onReturn();
+        throw error;
+    }
+
+    private Varargs runFuture( LuaState state, State context, MethodResult future ) throws LuaError, UnwindThrowable
+    {
+        Deque<ILuaFunction> callbacks = context.callbacks;
+        while( true )
+        {
+            if( future instanceof MethodResult.AndThen )
+            {
+                MethodResult.AndThen then = ((MethodResult.AndThen) future);
+
+                // Thens are "unwrapped", being pushed onto a stack
+                if( callbacks == null ) callbacks = context.callbacks = new ArrayDeque<>();
+                callbacks.addLast( then.getCallback() );
+
+                future = then.getPrevious();
+            }
+            else if( future instanceof MethodResult.Immediate )
+            {
+                Object[] values = ((MethodResult.Immediate) future).getResult();
+
+                // Immediate values values will attempt to call the previous "then", or return if nothing 
+                // else needs to be done.
+                ILuaFunction callback = callbacks == null ? null : callbacks.pollLast();
+                if( callback == null ) return machine.toValues( values );
+
+                future = runFunction( callback, values );
+            }
+            else if( future instanceof MethodResult.OnEvent )
+            {
+                MethodResult.OnEvent onEvent = (MethodResult.OnEvent) future;
+
+                // Mark this future as pending and yield
+                context.pending = future;
+                String filter = onEvent.getFilter();
+                LuaThread.yield( state, filter == null ? Constants.NIL : ValueFactory.valueOf( filter ) );
+                throw new IllegalStateException( "Unreachable" );
+            }
+            else if( future instanceof MethodResult.OnMainThread )
+            {
+                MethodResult.OnMainThread onMainThread = (MethodResult.OnMainThread) future;
+
+                // Mark this future as pending and yield
+                context.pending = future;
+                try
+                {
+                    context.taskId = callContext.issueMainThreadTask( () -> {
+                        context.taskResult = onMainThread.getTask().execute();
+                        return null;
+                    } );
+                }
+                catch( LuaException e )
+                {
+                    throw new LuaError( e.getMessage(), e.getLevel() );
+                }
+
+                LuaThread.yield( state, ValueFactory.valueOf( "task_complete" ) );
+                throw new IllegalStateException( "Unreachable" );
+            }
+            else if( future instanceof MethodResult.WithLuaContext )
+            {
+                MethodResult.WithLuaContext withContext = (MethodResult.WithLuaContext) future;
+
+                // Mark this future as pending and execute on a separate thread.
+                context.pending = future;
+                CobaltLuaContext luaContext = context.luaContext = new CobaltLuaContext( computer, state );
+                luaContext.execute( withContext.getConsumer() );
+                return runCallback( state, context, luaContext.await( state, machine ) );
+            }
+            else
+            {
+                ComputerCraft.log.error( "Unknown method result " + future );
+                throw new LuaError( "Java Exception Thrown: Unknown method result" );
+            }
+        }
+    }
+
+    private Varargs runCallback( LuaState state, State context, Object[] args ) throws LuaError, UnwindThrowable
+    {
+        Deque<ILuaFunction> callbacks = context.callbacks;
+        ILuaFunction callback = callbacks == null ? null : callbacks.pollLast();
+        if( callback == null ) return machine.toValues( args );
+
+        return runFuture( state, context, runFunction( callback, args ) );
+    }
+
+    private MethodResult runFunction( ILuaFunction func, Object[] args ) throws LuaError
+    {
+        MethodResult result;
+        try
+        {
+            result = func.call( args );
+        }
+        catch( LuaException e )
+        {
+            throw new LuaError( e.getMessage(), e.getLevel() );
+        }
+        catch( Exception e )
+        {
+            if( ComputerCraft.logPeripheralErrors )
+            {
+                ComputerCraft.log.error( "Error calling " + methodName + " on " + delegate, e );
+            }
+            throw new LuaError( "Java Exception Thrown: " + e.toString(), 0 );
+        }
+
+        if( result == null )
+        {
+            ComputerCraft.log.error( "Null result from " + func );
+            throw new LuaError( "Java Exception Thrown: Null result" );
+        }
+
+        return result;
+    }
+
+    static class State
+    {
+        Deque<ILuaFunction> callbacks;
+
+        MethodResult pending;
+
+        CobaltLuaContext luaContext;
+
+        long taskId;
+        MethodResult taskResult;
+    }
+}

src/main/java/dan200/computercraft/core/lua/Semaphore.java

@@ -0,0 +1,38 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.core.lua;
+
+/**
+ * A trivial way of signalling
+ */
+public final class Semaphore
+{
+    private volatile boolean state = false;
+
+    public synchronized void signal()
+    {
+        state = true;
+        notify();
+    }
+
+    public synchronized void await() throws InterruptedException
+    {
+        while( !state ) wait();
+        state = false;
+    }
+
+    public synchronized boolean await( long timeout ) throws InterruptedException
+    {
+        if( !state )
+        {
+            wait( timeout );
+            if( !state ) return false;
+        }
+        state = false;
+        return true;
+    }
+}

src/main/java/dan200/computercraft/shared/command/CommandComputerCraft.java

@@ -20,10 +20,10 @@ import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.text.ITextComponent;
 import net.minecraft.util.text.TextComponentString;
 import net.minecraft.world.World;
-import net.minecraftforge.common.util.FakePlayer;
 
 import javax.annotation.Nonnull;
 import java.util.*;
+import java.util.function.Consumer;
 
 import static dan200.computercraft.shared.command.framework.ChatHelpers.*;
 
@@ -59,7 +59,7 @@ public final class CommandComputerCraft extends CommandDelegate
             {
                 if( arguments.size() == 0 )
                 {
-                    TextTable table = new TextTable( DUMP_LIST_ID, "Instance", "Id", "On", "Position" );
+                    TextTable table = new TextTable( DUMP_LIST_ID, "Computer", "On", "Position" );
 
                     List<ServerComputer> computers = new ArrayList<>( ComputerCraft.serverComputerRegistry.getComputers() );
 
@@ -92,8 +92,7 @@ public final class CommandComputerCraft extends CommandDelegate
                     for( ServerComputer computer : computers )
                     {
                         table.addRow(
-                            linkComputer( computer ),
-                            text( Integer.toString( computer.getID() ) ),
+                            linkComputer( context, computer, computer.getID() ),
                             bool( computer.isOn() ),
                             linkPosition( context, computer )
                         );
@@ -149,26 +148,15 @@ public final class CommandComputerCraft extends CommandDelegate
             @Override
             public void execute( @Nonnull CommandContext context, @Nonnull List<String> arguments ) throws CommandException
             {
-                Set<ServerComputer> computers = Sets.newHashSet();
-                if( arguments.size() > 0 )
-                {
-                    for( String arg : arguments )
+                withComputers( arguments, computers -> {
+                    int shutdown = 0;
+                    for( ServerComputer computer : computers )
                     {
-                        computers.addAll( ComputerSelector.getComputers( arg ) );
+                        if( computer.isOn() ) shutdown++;
+                        computer.unload();
                     }
-                }
-                else
-                {
-                    computers.addAll( ComputerCraft.serverComputerRegistry.getComputers() );
-                }
-
-                int shutdown = 0;
-                for( ServerComputer computer : computers )
-                {
-                    if( computer.isOn() ) shutdown++;
-                    computer.unload();
-                }
-                context.getSender().sendMessage( text( "Shutdown " + shutdown + " / " + computers.size() + " computers" ) );
+                    context.getSender().sendMessage( text( "Shutdown " + shutdown + " / " + computers.size() + " computers" ) );
+                } );
             }
 
             @Nonnull
@@ -190,26 +178,15 @@ public final class CommandComputerCraft extends CommandDelegate
             @Override
             public void execute( @Nonnull CommandContext context, @Nonnull List<String> arguments ) throws CommandException
             {
-                Set<ServerComputer> computers = Sets.newHashSet();
-                if( arguments.size() > 0 )
-                {
-                    for( String arg : arguments )
+                withComputers( arguments, computers -> {
+                    int on = 0;
+                    for( ServerComputer computer : computers )
                     {
-                        computers.addAll( ComputerSelector.getComputers( arg ) );
+                        if( !computer.isOn() ) on++;
+                        computer.turnOn();
                     }
-                }
-                else
-                {
-                    computers.addAll( ComputerCraft.serverComputerRegistry.getComputers() );
-                }
-
-                int on = 0;
-                for( ServerComputer computer : computers )
-                {
-                    if( !computer.isOn() ) on++;
-                    computer.turnOn();
-                }
-                context.getSender().sendMessage( text( "Turned on " + on + " / " + computers.size() + " computers" ) );
+                    context.getSender().sendMessage( text( "Turned on " + on + " / " + computers.size() + " computers" ) );
+                } );
             }
 
             @Nonnull
@@ -406,13 +383,46 @@ public final class CommandComputerCraft extends CommandDelegate
         return root;
     }
 
-    private static ITextComponent linkComputer( ServerComputer computer )
+    private static ITextComponent linkComputer( CommandContext context, ServerComputer serverComputer, int computerId )
     {
-        return link(
-            text( Integer.toString( computer.getInstanceID() ) ),
-            "/computercraft dump " + computer.getInstanceID(),
-            "View more info about this computer"
-        );
+        ITextComponent out = new TextComponentString( "" );
+
+        // Append the computer instance
+        if( serverComputer == null )
+        {
+            out.appendSibling( text( "?" ) );
+        }
+        else
+        {
+            out.appendSibling( link(
+                text( Integer.toString( serverComputer.getInstanceID() ) ),
+                "/computercraft dump " + serverComputer.getInstanceID(),
+                "View more info about this computer"
+            ) );
+        }
+
+        // And ID
+        out.appendText( " (id " + computerId + ")" );
+
+        // And, if we're a player, some useful links
+        if( serverComputer != null && UserLevel.OP.canExecute( context ) && context.fromPlayer() )
+        {
+            out
+                .appendText( " " )
+                .appendSibling( link(
+                    text( "\u261b" ),
+                    "/computercraft tp " + serverComputer.getInstanceID(),
+                    "Teleport to this computer"
+                ) )
+                .appendText( " " )
+                .appendSibling( link(
+                    text( "\u20e2" ),
+                    "/computercraft view " + serverComputer.getInstanceID(),
+                    "View this computer"
+                ) );
+        }
+
+        return out;
     }
 
     private static ITextComponent linkPosition( CommandContext context, ServerComputer computer )
@@ -458,9 +468,6 @@ public final class CommandComputerCraft extends CommandDelegate
             if( server.getID() > maxId ) maxId = server.getID();
         }
 
-        ICommandSender sender = context.getSender();
-        boolean isPlayer = sender instanceof EntityPlayerMP && !(sender instanceof FakePlayer);
-
         timings.sort( Comparator.<ComputerTracker, Long>comparing( x -> x.get( field ) ).reversed() );
 
         boolean defaultLayout = field == TrackingField.TASKS || field == TrackingField.TOTAL_TIME
@@ -476,26 +483,7 @@ public final class CommandComputerCraft extends CommandDelegate
             Computer computer = entry.getComputer();
             ServerComputer serverComputer = computer == null ? null : lookup.get( computer );
 
-            ITextComponent computerComponent = new TextComponentString( "" )
-                .appendSibling( serverComputer == null ? text( "?" ) : linkComputer( serverComputer ) )
-                .appendText( " (id " + entry.getComputerId() + ")" );
-
-            if( serverComputer != null && UserLevel.OP.canExecute( context ) && isPlayer )
-            {
-                computerComponent
-                    .appendText( " " )
-                    .appendSibling( link(
-                        text( "\u261b" ),
-                        "/computercraft tp " + serverComputer.getInstanceID(),
-                        "Teleport to this computer"
-                    ) )
-                    .appendText( " " )
-                    .appendSibling( link(
-                        text( "\u20e2" ),
-                        "/computercraft view " + serverComputer.getInstanceID(),
-                        "View this computer"
-                    ) );
-            }
+            ITextComponent computerComponent = linkComputer( context, serverComputer, entry.getComputerId() );
 
             if( defaultLayout )
             {
@@ -515,4 +503,30 @@ public final class CommandComputerCraft extends CommandDelegate
 
         table.displayTo( context.getSender() );
     }
+
+    private static void withComputers( List<String> selectors, Consumer<Collection<ServerComputer>> action ) throws CommandException
+    {
+        Set<ServerComputer> computers = Sets.newHashSet();
+        List<String> failed = new ArrayList<>();
+        if( selectors.isEmpty() )
+        {
+            computers.addAll( ComputerCraft.serverComputerRegistry.getComputers() );
+        }
+        else
+        {
+            for( String selector : selectors )
+            {
+                List<ServerComputer> selected = ComputerSelector.getComputers( selector );
+                computers.addAll( selected );
+                if( selected.isEmpty() ) failed.add( selector );
+            }
+        }
+
+        action.accept( computers );
+
+        if( !failed.isEmpty() )
+        {
+            throw new CommandException( "Could not find computers matching " + String.join( ", ", failed ) );
+        }
+    }
 }

src/main/java/dan200/computercraft/shared/command/ComputerSelector.java

@@ -12,30 +12,22 @@ import java.util.function.Predicate;
 
 public final class ComputerSelector
 {
-    private static List<ServerComputer> getComputers( Predicate<ServerComputer> predicate, String selector ) throws CommandException
+    private static List<ServerComputer> getComputers( Predicate<ServerComputer> predicate ) throws CommandException
     {
         // We copy it to prevent concurrent modifications.
-        List<ServerComputer> computers = Lists.newArrayList( ComputerCraft.serverComputerRegistry.getComputers() );
-        List<ServerComputer> candidates = Lists.newArrayList();
-        for( ServerComputer searchComputer : computers )
-        {
-            if( predicate.test( searchComputer ) ) candidates.add( searchComputer );
-        }
-
-        if( candidates.isEmpty() )
-        {
-            throw new CommandException( "No computer matching " + selector );
-        }
-        else
-        {
-            return candidates;
-        }
+        ArrayList<ServerComputer> computers = new ArrayList<>( ComputerCraft.serverComputerRegistry.getComputers() );
+        computers.removeIf( predicate.negate() );
+        return computers;
     }
 
     public static ServerComputer getComputer( String selector ) throws CommandException
     {
         List<ServerComputer> computers = getComputers( selector );
-        if( computers.size() == 1 )
+        if( computers.size() == 0 )
+        {
+            throw new CommandException( "No computer matching " + selector );
+        }
+        else if( computers.size() == 1 )
         {
             return computers.get( 0 );
         }
@@ -46,7 +38,7 @@ public final class ComputerSelector
 
             for( int i = 0; i < computers.size(); i++ )
             {
-                if( i > 1 ) builder.append( ", " );
+                if( i > 0 ) builder.append( ", " );
                 builder.append( computers.get( i ).getInstanceID() );
             }
             builder.append( ")" );
@@ -71,17 +63,17 @@ public final class ComputerSelector
                 throw new CommandException( "'" + selector + "' is not a valid number" );
             }
 
-            return getComputers( x -> x.getID() == id, selector );
+            return getComputers( x -> x.getID() == id );
         }
         else if( selector.length() > 0 && selector.charAt( 0 ) == '@' )
         {
             String label = selector.substring( 1 );
-            return getComputers( x -> Objects.equals( label, x.getLabel() ), selector );
+            return getComputers( x -> Objects.equals( label, x.getLabel() ) );
         }
         else if( selector.length() > 0 && selector.charAt( 0 ) == '~' )
         {
             String familyName = selector.substring( 1 );
-            return getComputers( x -> x.getFamily().name().equalsIgnoreCase( familyName ), selector );
+            return getComputers( x -> x.getFamily().name().equalsIgnoreCase( familyName ) );
         }
         else
         {
@@ -96,14 +88,7 @@ public final class ComputerSelector
             }
 
             ServerComputer computer = ComputerCraft.serverComputerRegistry.get( instance );
-            if( computer == null )
-            {
-                throw new CommandException( "No such computer for instance id " + instance );
-            }
-            else
-            {
-                return Collections.singletonList( computer );
-            }
+            return computer == null ? Collections.emptyList() : Collections.singletonList( computer );
         }
     }
 

src/main/java/dan200/computercraft/shared/command/framework/CommandContext.java

@@ -2,7 +2,9 @@ package dan200.computercraft.shared.command.framework;
 
 import com.google.common.collect.Lists;
 import net.minecraft.command.ICommandSender;
+import net.minecraft.entity.player.EntityPlayerMP;
 import net.minecraft.server.MinecraftServer;
+import net.minecraftforge.common.util.FakePlayer;
 
 import java.util.Collections;
 import java.util.List;
@@ -90,4 +92,9 @@ public final class CommandContext
     {
         return sender;
     }
+
+    public boolean fromPlayer()
+    {
+        return sender instanceof EntityPlayerMP && !(sender instanceof FakePlayer);
+    }
 }

src/main/java/dan200/computercraft/shared/command/framework/TextFormatter.java

@@ -17,7 +17,6 @@ import static dan200.computercraft.shared.command.framework.ChatHelpers.coloured
  */
 public class TextFormatter
 {
-    private static final int SPACE_WIDTH = 4;
     private static final char PADDING_CHAR = '\u02cc';
 
     /**
@@ -54,7 +53,7 @@ public class TextFormatter
         8, 4,
     };
 
-    private static int getWidth( int codePoint )
+    public static int getWidth( int codePoint )
     {
         // Escape codes
         if( codePoint == 167 ) return -1;
@@ -73,7 +72,7 @@ public class TextFormatter
         return 0;
     }
 
-    private static int getWidth( ITextComponent component )
+    public static int getWidth( ITextComponent component )
     {
         int total = 0;
         if( component instanceof TextComponentString )
@@ -132,19 +131,17 @@ public class TextFormatter
         int width = getWidthFor( entry, sender );
         int delta = maxWidth - width;
 
-        if( delta > 0 )
+        int spaceWidth = getWidthFor( ' ', sender );
+        int spaces = delta / spaceWidth;
+        int extra = delta % spaces;
+
+        // Append a fixed number of spaces
+        if( spaces > 0 ) out.appendSibling( new TextComponentString( StringUtils.repeat( ' ', spaces ) ) );
+
+        // Append several minor characters to pad to a full string 
+        if( extra > 0 )
         {
-            int spaces = delta / SPACE_WIDTH;
-            int extra = delta % SPACE_WIDTH;
-
-            // Append a fixed number of spaces
-            if( spaces > 0 ) out.appendSibling( new TextComponentString( StringUtils.repeat( ' ', spaces ) ) );
-
-            // Append several minor characters to pad to a full string 
-            if( extra > 0 )
-            {
-                out.appendSibling( coloured( StringUtils.repeat( PADDING_CHAR, extra ), TextFormatting.GRAY ) );
-            }
+            out.appendSibling( coloured( StringUtils.repeat( PADDING_CHAR, extra ), TextFormatting.GRAY ) );
         }
     }
 }

src/main/java/dan200/computercraft/shared/command/framework/TextTable.java

@@ -35,7 +35,7 @@ public class TextTable
         this.columns = header.length;
     }
 
-    public TextTable(int id)
+    public TextTable( int id )
     {
         this.id = id;
         this.header = null;
@@ -90,14 +90,15 @@ public class TextTable
             ITextComponent[] row = rows.get( y );
             for( int i = 0; i < row.length; i++ )
             {
-                int width = getWidthFor( row[i], sender ) + 3;
+                int width = getWidthFor( row[i], sender );
                 if( width > maxWidths[i] ) maxWidths[i] = width;
             }
         }
 
-        // Add a small amount of extra padding. We include this here instead of the separator to allow
-        // for "extra" characters
-        for( int i = 0; i < maxWidths.length; i++ ) maxWidths[i] += 4;
+        // Add a small amount of extra padding. This defaults to 3 spaces for players
+        // and 1 for everyone else.
+        int padding = isPlayer( sender ) ? getWidth( ' ' ) * 3 : 1;
+        for( int i = 0; i < maxWidths.length; i++ ) maxWidths[i] += padding;
 
         int totalWidth = (columns - 1) * getWidthFor( SEPARATOR, sender );
         for( int x : maxWidths ) totalWidth += x;
@@ -161,7 +162,7 @@ public class TextTable
             for( int i = 0; i < out.size(); i++ )
             {
                 if( i > 0 ) result.appendSibling( LINE );
-                result.appendSibling( out.get( 0 ) );
+                result.appendSibling( out.get( i ) );
             }
             sender.sendMessage( result );
         }

src/main/java/dan200/computercraft/shared/common/ServerTerminal.java

@@ -54,6 +54,11 @@ public class ServerTerminal implements ITerminal
         }
     }
 
+    protected void markTerminalChanged()
+    {
+        m_terminalChanged = true;
+    }
+
     public void update()
     {
         m_terminalChangedLastFrame = m_terminalChanged || (m_terminal != null && m_terminal.getChanged());

src/main/java/dan200/computercraft/shared/computer/apis/CommandAPI.java

@@ -8,9 +8,7 @@ package dan200.computercraft.shared.computer.apis;
 
 import com.google.common.collect.ImmutableMap;
 import dan200.computercraft.ComputerCraft;
-import dan200.computercraft.api.lua.ILuaAPI;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.shared.computer.blocks.TileCommandComputer;
 import dan200.computercraft.shared.util.WorldUtil;
 import net.minecraft.block.Block;
@@ -24,6 +22,7 @@ import net.minecraft.util.math.BlockPos;
 import net.minecraft.world.World;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -82,7 +81,7 @@ public class CommandAPI implements ILuaAPI
                 sender.clearOutput();
 
                 int result = commandManager.executeCommand( sender, command );
-                return new Object[]{ (result > 0), sender.copyOutput() };
+                return new Object[] { (result > 0), sender.copyOutput() };
             }
             catch( Throwable t )
             {
@@ -90,7 +89,7 @@ public class CommandAPI implements ILuaAPI
                 {
                     ComputerCraft.log.error( "Error running command.", t );
                 }
-                return new Object[]{ false, createOutput( "Java Exception Thrown: " + t.toString() ) };
+                return new Object[] { false, createOutput( "Java Exception Thrown: " + t.toString() ) };
             }
         }
         else
@@ -131,7 +130,8 @@ public class CommandAPI implements ILuaAPI
     }
 
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    @Nonnull
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] arguments ) throws LuaException
     {
         switch( method )
         {
@@ -139,19 +139,19 @@ public class CommandAPI implements ILuaAPI
             {
                 // exec
                 final String command = getString( arguments, 0 );
-                return context.executeMainThreadTask( () -> doCommand( command ) );
+                return MethodResult.onMainThread( () -> MethodResult.of( doCommand( command ) ) );
             }
             case 1:
             {
                 // execAsync
                 final String command = getString( arguments, 0 );
                 long taskID = context.issueMainThreadTask( () -> doCommand( command ) );
-                return new Object[] { taskID };
+                return MethodResult.of( taskID );
             }
             case 2:
             {
                 // list
-                return context.executeMainThreadTask( () ->
+                return MethodResult.onMainThread( () ->
                 {
                     int i = 1;
                     Map<Object, Object> result = new HashMap<>();
@@ -182,7 +182,7 @@ public class CommandAPI implements ILuaAPI
                             }
                         }
                     }
-                    return new Object[]{ result };
+                    return MethodResult.of( result );
                 } );
             }
             case 3:
@@ -190,7 +190,7 @@ public class CommandAPI implements ILuaAPI
                 // getBlockPosition
                 // This is probably safe to do on the Lua thread. Probably.
                 BlockPos pos = m_computer.getPos();
-                return new Object[] { pos.getX(), pos.getY(), pos.getZ() };
+                return MethodResult.of( pos.getX(), pos.getY(), pos.getZ() );
             }
             case 4:
             {
@@ -201,7 +201,7 @@ public class CommandAPI implements ILuaAPI
                 final int maxx = getInt( arguments, 3 );
                 final int maxy = getInt( arguments, 4 );
                 final int maxz = getInt( arguments, 5 );
-                return context.executeMainThreadTask( () ->
+                return MethodResult.onMainThread( () ->
                 {
                     // Get the details of the block
                     World world = m_computer.getWorld();
@@ -236,7 +236,7 @@ public class CommandAPI implements ILuaAPI
                             }
                         }
                     }
-                    return new Object[]{ results };
+                    return MethodResult.of( results );
                 } );
             }
             case 5:
@@ -245,14 +245,14 @@ public class CommandAPI implements ILuaAPI
                 final int x = getInt( arguments, 0 );
                 final int y = getInt( arguments, 1 );
                 final int z = getInt( arguments, 2 );
-                return context.executeMainThreadTask( () ->
+                return MethodResult.onMainThread( () ->
                 {
                     // Get the details of the block
                     World world = m_computer.getWorld();
                     BlockPos position = new BlockPos( x, y, z );
                     if( WorldUtil.isBlockInWorld( world, position ) )
                     {
-                        return new Object[]{ getBlockInfo( world, position ) };
+                        return MethodResult.of( getBlockInfo( world, position ) );
                     }
                     else
                     {
@@ -262,8 +262,16 @@ public class CommandAPI implements ILuaAPI
             }
             default:
             {
-                return null;
+                return MethodResult.empty();
             }
         }
     }
+
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
 }

src/main/java/dan200/computercraft/shared/computer/blocks/BlockCommandComputer.java

@@ -42,7 +42,7 @@ public class BlockCommandComputer extends BlockComputerBase
         super( Material.IRON );
         setBlockUnbreakable();
         setResistance( 6000000.0F );
-        setUnlocalizedName( "computercraft:command_computer" );
+        setTranslationKey( "computercraft:command_computer" );
         setCreativeTab( ComputerCraft.mainCreativeTab );
         setDefaultState( this.blockState.getBaseState()
             .withProperty( Properties.FACING, EnumFacing.NORTH )
@@ -62,7 +62,7 @@ public class BlockCommandComputer extends BlockComputerBase
     @Deprecated
     public IBlockState getStateFromMeta( int meta )
     {
-        EnumFacing dir = EnumFacing.getFront( meta & 0x7 );
+        EnumFacing dir = EnumFacing.byIndex( meta & 0x7 );
         if( dir.getAxis() == EnumFacing.Axis.Y )
         {
             dir = EnumFacing.NORTH;

src/main/java/dan200/computercraft/shared/computer/blocks/BlockComputer.java

@@ -44,7 +44,7 @@ public class BlockComputer extends BlockComputerBase
     {
         super( Material.ROCK );
         setHardness( 2.0f );
-        setUnlocalizedName( "computercraft:computer" );
+        setTranslationKey( "computercraft:computer" );
         setCreativeTab( ComputerCraft.mainCreativeTab );
         setDefaultState( this.blockState.getBaseState()
             .withProperty( Properties.FACING, EnumFacing.NORTH )
@@ -65,7 +65,7 @@ public class BlockComputer extends BlockComputerBase
     @Deprecated
     public IBlockState getStateFromMeta( int meta )
     {
-        EnumFacing dir = EnumFacing.getFront( meta & 0x7 );
+        EnumFacing dir = EnumFacing.byIndex( meta & 0x7 );
         if( dir.getAxis() == EnumFacing.Axis.Y )
         {
             dir = EnumFacing.NORTH;

src/main/java/dan200/computercraft/shared/computer/blocks/ComputerPeripheral.java

@@ -6,11 +6,15 @@
 
 package dan200.computercraft.shared.computer.blocks;
 
+import dan200.computercraft.api.lua.ICallContext;
 import dan200.computercraft.api.lua.ILuaContext;
+import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 import dan200.computercraft.api.peripheral.IComputerAccess;
 import dan200.computercraft.api.peripheral.IPeripheral;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 
 public class ComputerPeripheral
     implements IPeripheral
@@ -23,7 +27,7 @@ public class ComputerPeripheral
         m_type = type;
         m_computer = computer;
     }
-        
+
     // IPeripheral implementation
 
     @Nonnull
@@ -47,8 +51,9 @@ public class ComputerPeripheral
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments )
+    public MethodResult callMethod( @Nonnull IComputerAccess computer, @Nonnull ICallContext context, int method, @Nonnull Object[] arguments )
     {
         switch( method )
         {
@@ -56,42 +61,48 @@ public class ComputerPeripheral
             {
                 // turnOn
                 m_computer.turnOn();
-                return null;
+                return MethodResult.empty();
             }
             case 1:
             {
                 // shutdown
                 m_computer.shutdown();
-                return null;
+                return MethodResult.empty();
             }
             case 2:
             {
                 // reboot
                 m_computer.reboot();
-                return null;
+                return MethodResult.empty();
             }
             case 3:
             {
                 // getID
-                return new Object[] {
-                    m_computer.assignID()
-                };
+                return MethodResult.of( m_computer.assignID() );
             }
             case 4:
             {
                 // isOn
-                return new Object[] { m_computer.isOn() };
+                return MethodResult.of( m_computer.isOn() );
             }
             case 5:
                 // getLabel
-                return new Object[] { m_computer.getLabel() };
+                return MethodResult.of( m_computer.getLabel() );
             default:
             {
-                return null;
+                return MethodResult.empty();
             }
         }
     }
 
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull IComputerAccess access, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( access, (ICallContext) context, method, arguments ).evaluate( context );
+    }
+
     @Override
     public boolean equals( IPeripheral other )
     {

src/main/java/dan200/computercraft/shared/computer/core/ServerComputer.java

@@ -154,7 +154,7 @@ public class ServerComputer extends ServerTerminal
         return packet;
     }
 
-    private ComputerCraftPacket createTerminalPacket() {
+    protected ComputerCraftPacket createTerminalPacket() {
         ComputerCraftPacket packet = new ComputerCraftPacket();
         packet.m_packetType = ComputerCraftPacket.ComputerTerminalChanged;
         packet.m_dataInt = new int[] { getInstanceID() };
@@ -465,7 +465,7 @@ public class ServerComputer extends ServerTerminal
         }
     }
 
-    private boolean isInteracting( EntityPlayer player )
+    protected boolean isInteracting( EntityPlayer player )
     {
         if( player == null ) return false;
 

src/main/java/dan200/computercraft/shared/computer/items/ItemCommandComputer.java

@@ -24,7 +24,7 @@ public class ItemCommandComputer extends ItemComputer
         super( block );
         setMaxStackSize( 64 );
         setHasSubtypes( true );
-        setUnlocalizedName( "computercraft:command_computer" );
+        setTranslationKey( "computercraft:command_computer" );
         setCreativeTab( ComputerCraft.mainCreativeTab );
     }
 

src/main/java/dan200/computercraft/shared/computer/items/ItemComputer.java

@@ -33,7 +33,7 @@ public class ItemComputer extends ItemComputerBase
         super( block );
         setMaxStackSize( 64 );
         setHasSubtypes( true );
-        setUnlocalizedName( "computercraft:computer" );
+        setTranslationKey( "computercraft:computer" );
         setCreativeTab( ComputerCraft.mainCreativeTab );
     }
 
@@ -114,7 +114,7 @@ public class ItemComputer extends ItemComputerBase
 
     @Nonnull
     @Override
-    public String getUnlocalizedName( @Nonnull ItemStack stack )
+    public String getTranslationKey( @Nonnull ItemStack stack )
     {
         switch( getFamily( stack ) )
         {

src/main/java/dan200/computercraft/shared/integration/charset/BundledCapabilityProvider.java

@@ -0,0 +1,88 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.shared.integration.charset;
+
+import dan200.computercraft.shared.common.TileGeneric;
+import net.minecraft.util.EnumFacing;
+import net.minecraftforge.common.capabilities.Capability;
+import net.minecraftforge.common.capabilities.ICapabilityProvider;
+import pl.asie.charset.api.wires.IBundledEmitter;
+import pl.asie.charset.api.wires.IBundledReceiver;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+import static dan200.computercraft.shared.integration.charset.IntegrationCharset.CAPABILITY_EMITTER;
+import static dan200.computercraft.shared.integration.charset.IntegrationCharset.CAPABILITY_RECEIVER;
+
+final class BundledCapabilityProvider implements ICapabilityProvider
+{
+    private final TileGeneric tile;
+    private IBundledReceiver receiver;
+    private IBundledEmitter[] emitters;
+
+    BundledCapabilityProvider( TileGeneric tile )
+    {
+        this.tile = tile;
+    }
+
+    @Override
+    public boolean hasCapability( @Nonnull Capability<?> capability, @Nullable EnumFacing side )
+    {
+        return capability == CAPABILITY_EMITTER || capability == CAPABILITY_RECEIVER;
+    }
+
+    @Nullable
+    @Override
+    public <T> T getCapability( @Nonnull Capability<T> capability, @Nullable EnumFacing side )
+    {
+        if( capability == CAPABILITY_RECEIVER )
+        {
+            IBundledReceiver receiver = this.receiver;
+            if( receiver == null ) receiver = this.receiver = tile::onNeighbourChange;
+
+            return CAPABILITY_RECEIVER.cast( receiver );
+        }
+        else if( capability == CAPABILITY_EMITTER )
+        {
+            IBundledEmitter[] emitters = this.emitters;
+            if( emitters == null ) emitters = this.emitters = new IBundledEmitter[7];
+
+            int index = side == null ? 6 : side.getIndex();
+            IBundledEmitter emitter = emitters[index];
+            if( emitter == null )
+            {
+                if( side == null )
+                {
+                    emitter = emitters[index] = () -> {
+                        int flags = 0;
+                        for( EnumFacing facing : EnumFacing.VALUES ) flags |= tile.getBundledRedstoneOutput( facing );
+                        return toBytes( flags );
+                    };
+                }
+                else
+                {
+                    emitter = emitters[index] = () -> toBytes( tile.getBundledRedstoneOutput( side ) );
+                }
+            }
+            ;
+
+            return CAPABILITY_EMITTER.cast( emitter );
+        }
+        else
+        {
+            return null;
+        }
+    }
+
+    private static byte[] toBytes( int flag )
+    {
+        byte[] channels = new byte[16];
+        for( int i = 0; i < 16; i++ ) channels[i] = (flag & (1 << i)) == 0 ? (byte) 0 : 15;
+        return channels;
+    }
+}

src/main/java/dan200/computercraft/shared/integration/charset/BundledRedstoneProvider.java

@@ -0,0 +1,34 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.shared.integration.charset;
+
+import dan200.computercraft.api.redstone.IBundledRedstoneProvider;
+import net.minecraft.tileentity.TileEntity;
+import net.minecraft.util.EnumFacing;
+import net.minecraft.util.math.BlockPos;
+import net.minecraft.world.World;
+
+import javax.annotation.Nonnull;
+
+import static dan200.computercraft.shared.integration.charset.IntegrationCharset.CAPABILITY_EMITTER;
+
+public class BundledRedstoneProvider implements IBundledRedstoneProvider
+{
+    @Override
+    public int getBundledRedstoneOutput( @Nonnull World world, @Nonnull BlockPos pos, @Nonnull EnumFacing side )
+    {
+        TileEntity tile = world.getTileEntity( pos );
+        if( tile == null || !tile.hasCapability( CAPABILITY_EMITTER, side ) ) return -1;
+
+        byte[] signal = tile.getCapability( CAPABILITY_EMITTER, side ).getBundledSignal();
+        if( signal == null ) return -1;
+
+        int flag = 0;
+        for( int i = 0; i < signal.length; i++ ) flag |= signal[i] > 0 ? (1 << i) : 0;
+        return flag;
+    }
+}

src/main/java/dan200/computercraft/shared/integration/charset/IntegrationCharset.java

@@ -0,0 +1,53 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.shared.integration.charset;
+
+import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.api.ComputerCraftAPI;
+import dan200.computercraft.shared.common.TileGeneric;
+import net.minecraft.tileentity.TileEntity;
+import net.minecraft.util.ResourceLocation;
+import net.minecraftforge.common.MinecraftForge;
+import net.minecraftforge.common.capabilities.Capability;
+import net.minecraftforge.common.capabilities.CapabilityInject;
+import net.minecraftforge.event.AttachCapabilitiesEvent;
+import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;
+import pl.asie.charset.api.wires.IBundledEmitter;
+import pl.asie.charset.api.wires.IBundledReceiver;
+
+public final class IntegrationCharset
+{
+    private static final ResourceLocation CAPABILITY_KEY = new ResourceLocation( ComputerCraft.MOD_ID, "charset" );
+
+    @CapabilityInject( IBundledEmitter.class )
+    public static final Capability<IBundledEmitter> CAPABILITY_EMITTER = null;
+
+    @CapabilityInject( IBundledReceiver.class )
+    public static final Capability<IBundledReceiver> CAPABILITY_RECEIVER = null;
+
+    private IntegrationCharset()
+    {
+    }
+
+    public static void register()
+    {
+        if( CAPABILITY_EMITTER == null || CAPABILITY_RECEIVER == null ) return;
+
+        MinecraftForge.EVENT_BUS.register( new IntegrationCharset() );
+        ComputerCraftAPI.registerBundledRedstoneProvider( new BundledRedstoneProvider() );
+    }
+
+    @SubscribeEvent
+    public void attachGenericCapabilities( AttachCapabilitiesEvent<TileEntity> event)
+    {
+        TileEntity tile = event.getObject();
+        if(tile instanceof TileGeneric)
+        {
+            event.addCapability( CAPABILITY_KEY, new BundledCapabilityProvider( (TileGeneric) tile ) );
+        }
+    }
+}

src/main/java/dan200/computercraft/shared/media/items/ItemDiskLegacy.java

@@ -33,7 +33,7 @@ public class ItemDiskLegacy extends Item
     {
         setMaxStackSize( 1 );
         setHasSubtypes( true );
-        setUnlocalizedName( "computercraft:disk" );
+        setTranslationKey( "computercraft:disk" );
         setCreativeTab( ComputerCraft.mainCreativeTab  );
     }
     

src/main/java/dan200/computercraft/shared/media/items/ItemPrintout.java

@@ -39,7 +39,7 @@ public class ItemPrintout extends Item
     {
         setMaxStackSize( 1 );
         setHasSubtypes( true );
-        setUnlocalizedName( "computercraft:page" );
+        setTranslationKey( "computercraft:page" );
         setCreativeTab( ComputerCraft.mainCreativeTab );
     }
 
@@ -64,7 +64,7 @@ public class ItemPrintout extends Item
 
     @Nonnull
     @Override
-    public String getUnlocalizedName( @Nonnull ItemStack stack )
+    public String getTranslationKey( @Nonnull ItemStack stack )
     {
         Type type = getType( stack );
         switch( type )

src/main/java/dan200/computercraft/shared/media/items/ItemTreasureDisk.java

@@ -34,7 +34,7 @@ public class ItemTreasureDisk extends Item
     {
         setMaxStackSize( 1 );
         setHasSubtypes( true );
-        setUnlocalizedName( "computercraft:treasure_disk" );
+        setTranslationKey( "computercraft:treasure_disk" );
     }
     
     @Override

src/main/java/dan200/computercraft/shared/peripheral/commandblock/CommandBlockPeripheral.java

@@ -6,14 +6,17 @@
 
 package dan200.computercraft.shared.peripheral.commandblock;
 
+import dan200.computercraft.api.lua.ICallContext;
 import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 import dan200.computercraft.api.peripheral.IComputerAccess;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import net.minecraft.tileentity.TileEntityCommandBlock;
 import net.minecraft.util.math.BlockPos;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 
 import static dan200.computercraft.core.apis.ArgumentHelper.getString;
 
@@ -46,17 +49,18 @@ public class CommandBlockPeripheral implements IPeripheral
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull final Object[] arguments ) throws LuaException, InterruptedException
+    public MethodResult callMethod( @Nonnull IComputerAccess computer, @Nonnull ICallContext context, int method, @Nonnull final Object[] arguments ) throws LuaException
     {
-        switch (method)
+        switch( method )
         {
             case 0:
             {
                 // getCommand
-                return context.executeMainThreadTask( () -> new Object[] {
-                    m_commandBlock.getCommandBlockLogic().getCommand()
-                } );
+                return MethodResult.onMainThread( () ->
+                    MethodResult.of( m_commandBlock.getCommandBlockLogic().getCommand() )
+                );
             }
             case 1:
             {
@@ -69,27 +73,35 @@ public class CommandBlockPeripheral implements IPeripheral
                     m_commandBlock.getWorld().markBlockRangeForRenderUpdate( pos, pos );
                     return null;
                 } );
-                return null;
+                return MethodResult.empty();
             }
             case 2:
             {
                 // runCommand
-                return context.executeMainThreadTask( () ->
+                return MethodResult.onMainThread( () ->
                 {
                     m_commandBlock.getCommandBlockLogic().trigger( m_commandBlock.getWorld() );
                     int result = m_commandBlock.getCommandBlockLogic().getSuccessCount();
                     if( result > 0 )
                     {
-                        return new Object[] { true };
+                        return MethodResult.of( true );
                     }
                     else
                     {
-                        return new Object[] { false, "Command failed" };
+                        return MethodResult.of( false, "Command failed" );
                     }
                 } );
             }
         }
-        return null;
+        return MethodResult.empty();
+    }
+
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull IComputerAccess access, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( access, (ICallContext) context, method, arguments ).evaluate( context );
     }
 
     @Override

src/main/java/dan200/computercraft/shared/peripheral/common/BlockCable.java

@@ -55,7 +55,7 @@ public class BlockCable extends BlockPeripheralBase
     public BlockCable()
     {
         setHardness( 1.5f );
-        setUnlocalizedName( "computercraft:cable" );
+        setTranslationKey( "computercraft:cable" );
         setCreativeTab( ComputerCraft.mainCreativeTab );
         setDefaultState( this.blockState.getBaseState()
             .withProperty( Properties.MODEM, BlockCableModemVariant.None )
@@ -94,12 +94,12 @@ public class BlockCable extends BlockPeripheralBase
         if( meta < 6 )
         {
             state = state.withProperty( Properties.CABLE, BlockCableCableVariant.NONE );
-            state = state.withProperty( Properties.MODEM, BlockCableModemVariant.fromFacing( EnumFacing.getFront( meta ) ) );
+            state = state.withProperty( Properties.MODEM, BlockCableModemVariant.fromFacing( EnumFacing.byIndex( meta ) ) );
         }
         else if( meta < 12 )
         {
             state = state.withProperty( Properties.CABLE, BlockCableCableVariant.ANY );
-            state = state.withProperty( Properties.MODEM, BlockCableModemVariant.fromFacing( EnumFacing.getFront( meta - 6 ) ) );
+            state = state.withProperty( Properties.MODEM, BlockCableModemVariant.fromFacing( EnumFacing.byIndex( meta - 6 ) ) );
         }
         else if( meta == 13 )
         {
@@ -296,7 +296,7 @@ public class BlockCable extends BlockPeripheralBase
                 }
             }
 
-            return result == null ? null : new RayTraceResult( result.hitVec.addVector( pos.getX(), pos.getY(), pos.getZ() ), result.sideHit, pos );
+            return result == null ? null : new RayTraceResult( result.hitVec.add( pos.getX(), pos.getY(), pos.getZ() ), result.sideHit, pos );
         }
         else
         {

src/main/java/dan200/computercraft/shared/peripheral/common/BlockPeripheral.java

@@ -44,7 +44,7 @@ public class BlockPeripheral extends BlockPeripheralBase
     public BlockPeripheral()
     {
         setHardness( 2.0f );
-        setUnlocalizedName( "computercraft:peripheral" );
+        setTranslationKey( "computercraft:peripheral" );
         setCreativeTab( ComputerCraft.mainCreativeTab );
         setDefaultState( this.blockState.getBaseState()
             .withProperty( Properties.FACING, EnumFacing.NORTH )
@@ -55,7 +55,7 @@ public class BlockPeripheral extends BlockPeripheralBase
     @Override
     @Nonnull
     @SideOnly( Side.CLIENT)
-    public BlockRenderLayer getBlockLayer()
+    public BlockRenderLayer getRenderLayer()
     {
         return BlockRenderLayer.CUTOUT;
     }
@@ -76,7 +76,7 @@ public class BlockPeripheral extends BlockPeripheralBase
         if( meta >= 2 && meta <= 5 )
         {
             state = state.withProperty( Properties.VARIANT, BlockPeripheralVariant.DiskDriveEmpty );
-            state = state.withProperty( Properties.FACING, EnumFacing.getFront( meta ) );
+            state = state.withProperty( Properties.FACING, EnumFacing.byIndex( meta ) );
         }
         else if( meta <= 9 )
         {
@@ -93,7 +93,7 @@ public class BlockPeripheral extends BlockPeripheralBase
             else
             {
                 state = state.withProperty( Properties.VARIANT, BlockPeripheralVariant.WirelessModemOff );
-                state = state.withProperty( Properties.FACING, EnumFacing.getFront( meta - 4 ) );
+                state = state.withProperty( Properties.FACING, EnumFacing.byIndex( meta - 4 ) );
             }
         }
         else if( meta == 10 )
@@ -651,7 +651,7 @@ public class BlockPeripheral extends BlockPeripheralBase
     public boolean causesSuffocation(IBlockState state)
     {
         // This normally uses the default state 
-        return blockMaterial.blocksMovement() && state.isOpaqueCube();
+        return material.blocksMovement() && state.isOpaqueCube();
     }
 
     @Override

src/main/java/dan200/computercraft/shared/peripheral/common/BlockWiredModemFull.java

@@ -34,7 +34,7 @@ public class BlockWiredModemFull extends BlockPeripheralBase
     public BlockWiredModemFull()
     {
         setHardness( 1.5f );
-        setUnlocalizedName( "computercraft:wired_modem_full" );
+        setTranslationKey( "computercraft:wired_modem_full" );
         setCreativeTab( ComputerCraft.mainCreativeTab );
         setDefaultState( blockState.getBaseState()
             .withProperty( Properties.MODEM_ON, false )

src/main/java/dan200/computercraft/shared/peripheral/common/ItemAdvancedModem.java

@@ -21,7 +21,7 @@ public class ItemAdvancedModem extends ItemPeripheralBase
     public ItemAdvancedModem( Block block )
     {
         super( block );
-        setUnlocalizedName( "computercraft:advanced_modem" );
+        setTranslationKey( "computercraft:advanced_modem" );
         setCreativeTab( ComputerCraft.mainCreativeTab );
     }
 

src/main/java/dan200/computercraft/shared/peripheral/common/ItemCable.java

@@ -28,7 +28,7 @@ public class ItemCable extends ItemPeripheralBase
     public ItemCable( Block block )
     {
         super( block );
-        setUnlocalizedName( "computercraft:cable" );
+        setTranslationKey( "computercraft:cable" );
         setCreativeTab( ComputerCraft.mainCreativeTab );
     }
 

src/main/java/dan200/computercraft/shared/peripheral/common/ItemPeripheral.java

@@ -20,7 +20,7 @@ public class ItemPeripheral extends ItemPeripheralBase
     public ItemPeripheral( Block block )
     {
         super( block );
-        setUnlocalizedName( "computercraft:peripheral" );
+        setTranslationKey( "computercraft:peripheral" );
         setCreativeTab( ComputerCraft.mainCreativeTab );
     }
 

src/main/java/dan200/computercraft/shared/peripheral/common/ItemPeripheralBase.java

@@ -59,7 +59,7 @@ public abstract class ItemPeripheralBase extends ItemBlock implements IPeriphera
 
     @Nonnull
     @Override
-    public String getUnlocalizedName( @Nonnull ItemStack stack )
+    public String getTranslationKey( @Nonnull ItemStack stack )
     {
         PeripheralType type = getPeripheralType( stack );
         switch( type )

src/main/java/dan200/computercraft/shared/peripheral/common/TilePeripheralBase.java

@@ -112,12 +112,12 @@ public abstract class TilePeripheralBase extends TileGeneric
         }
     }
 
-    public synchronized int getAnim()
+    public int getAnim()
     {
         return m_anim;
     }
     
-    public synchronized void setAnim( int anim )
+    public void setAnim( int anim )
     {
         if( anim != m_anim )
         {
@@ -127,12 +127,12 @@ public abstract class TilePeripheralBase extends TileGeneric
     }
 
     @Override    
-    public synchronized void update()
+    public void update()
     {
         if( m_changed )
         {
-            updateBlock();
             m_changed = false;
+            updateBlock();
         }
     }
             
@@ -143,7 +143,7 @@ public abstract class TilePeripheralBase extends TileGeneric
         super.readFromNBT(nbttagcompound);
         if( nbttagcompound.hasKey( "dir" ) )
         {
-            m_dir = EnumFacing.getFront( nbttagcompound.getInteger( "dir" ) );
+            m_dir = EnumFacing.byIndex( nbttagcompound.getInteger( "dir" ) );
         }
         if( nbttagcompound.hasKey( "anim" ) )
         {
@@ -174,7 +174,7 @@ public abstract class TilePeripheralBase extends TileGeneric
     public void readDescription( @Nonnull NBTTagCompound nbttagcompound )
     {
         super.readDescription( nbttagcompound );
-        m_dir = EnumFacing.getFront( nbttagcompound.getInteger( "dir" ) );
+        m_dir = EnumFacing.byIndex( nbttagcompound.getInteger( "dir" ) );
         m_anim = nbttagcompound.getInteger( "anim" );
         if( nbttagcompound.hasKey( "label" ) )
         {

src/main/java/dan200/computercraft/shared/peripheral/diskdrive/DiskDrivePeripheral.java

@@ -6,8 +6,10 @@
 
 package dan200.computercraft.shared.peripheral.diskdrive;
 
+import dan200.computercraft.api.lua.ICallContext;
 import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 import dan200.computercraft.api.media.IMedia;
 import dan200.computercraft.api.peripheral.IComputerAccess;
 import dan200.computercraft.api.peripheral.IPeripheral;
@@ -17,6 +19,7 @@ import net.minecraft.item.Item;
 import net.minecraft.item.ItemStack;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 
 import static dan200.computercraft.core.apis.ArgumentHelper.optString;
 
@@ -55,17 +58,18 @@ public class DiskDrivePeripheral implements IPeripheral
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException
+    public MethodResult callMethod( @Nonnull IComputerAccess computer, @Nonnull ICallContext context, int method, @Nonnull Object[] arguments ) throws LuaException
     {
         switch( method )
         {
             case 0:
             {
                 // isDiskPresent
-                return new Object[] {
+                return MethodResult.of(
                     !m_diskDrive.getDiskStack().isEmpty()
-                };
+                );
             }
             case 1:
             {
@@ -73,9 +77,9 @@ public class DiskDrivePeripheral implements IPeripheral
                 IMedia media = m_diskDrive.getDiskMedia();
                 if( media != null )
                 {
-                    return new Object[] { media.getLabel( m_diskDrive.getDiskStack() ) };
+                    return MethodResult.of( media.getLabel( m_diskDrive.getDiskStack() ) );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 2:
             {
@@ -96,21 +100,21 @@ public class DiskDrivePeripheral implements IPeripheral
                         throw new LuaException( "Disk label cannot be changed" );
                     }
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 3:
             {
                 // hasData
-                return new Object[] {
+                return MethodResult.of(
                     m_diskDrive.getDiskMountPath( computer ) != null
-                };
+                );
             }
             case 4:
             {
                 // getMountPath
-                return new Object[] {
+                return MethodResult.of(
                     m_diskDrive.getDiskMountPath( computer )
-                };
+                );
             }
             case 5:
             {
@@ -118,9 +122,9 @@ public class DiskDrivePeripheral implements IPeripheral
                 IMedia media = m_diskDrive.getDiskMedia();
                 if( media != null )
                 {
-                    return new Object[] { media.getAudio( m_diskDrive.getDiskStack() ) != null };
+                    return MethodResult.of( media.getAudio( m_diskDrive.getDiskStack() ) != null );
                 }
-                return new Object[] { false };
+                return MethodResult.of( false );
             }
             case 6:
             {
@@ -128,27 +132,27 @@ public class DiskDrivePeripheral implements IPeripheral
                 IMedia media = m_diskDrive.getDiskMedia();
                 if( media != null )
                 {
-                    return new Object[] { media.getAudioTitle( m_diskDrive.getDiskStack() ) };
+                    return MethodResult.of( media.getAudioTitle( m_diskDrive.getDiskStack() ) );
                 }
-                return new Object[] { false };
+                return MethodResult.of( false );
             }
             case 7:
             {
                 // playAudio
                 m_diskDrive.playDiskAudio();
-                return null;
+                return MethodResult.empty();
             }
             case 8:
             {
                 // stopAudio
                 m_diskDrive.stopDiskAudio();
-                return null;
+                return MethodResult.empty();
             }
             case 9:
             {
                 // eject
                 m_diskDrive.ejectDisk();
-                return null;
+                return MethodResult.empty();
             }
             case 10:
             {
@@ -159,18 +163,27 @@ public class DiskDrivePeripheral implements IPeripheral
                     Item item = disk.getItem();
                     if( item instanceof ItemDiskLegacy )
                     {
-                        return new Object[] { ((ItemDiskLegacy)item).getDiskID( disk ) };
+                        return MethodResult.of( ((ItemDiskLegacy)item).getDiskID( disk ) );
                     }
                 }
-                return null;
+                return MethodResult.empty();
             }
             default:
             {
-                return null;
+                return MethodResult.empty();
             }
         }
     }
 
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull IComputerAccess access, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( access, (ICallContext) context, method, arguments ).evaluate( context );
+    }
+
+
     @Override
     public void attach( @Nonnull IComputerAccess computer )
     {

src/main/java/dan200/computercraft/shared/peripheral/diskdrive/TileDiskDrive.java

@@ -80,12 +80,9 @@ public class TileDiskDrive extends TilePeripheralBase
     public void destroy()
     {
         ejectContents( true );
-        synchronized( this )
+        if( m_recordPlaying )
         {
-            if( m_recordPlaying )
-            {
-                stopRecord();
-            }
+            stopRecord();
         }
     }
 
@@ -170,13 +167,10 @@ public class TileDiskDrive extends TilePeripheralBase
         super.update();
 
         // Ejection
-        synchronized( this )
+        if( m_ejectQueued )
         {
-            if( m_ejectQueued )
-            {
-                ejectContents( false );
-                m_ejectQueued = false;
-            }
+            ejectContents( false );
+            m_ejectQueued = false;
         }
         
         // Music
@@ -391,10 +385,7 @@ public class TileDiskDrive extends TilePeripheralBase
     @Override
     public void clear()
     {
-        synchronized( this )
-        {
-            setInventorySlotContents( 0, ItemStack.EMPTY );
-        }
+        setInventorySlotContents( 0, ItemStack.EMPTY );
     }
 
     @Override
@@ -425,18 +416,12 @@ public class TileDiskDrive extends TilePeripheralBase
     @Nonnull
     public ItemStack getDiskStack()
     {
-        synchronized( this )
-        {
-            return getStackInSlot( 0 );
-        }
+        return getStackInSlot( 0 );
     }
 
     public void setDiskStack( @Nonnull ItemStack stack )
     {
-        synchronized( this )
-        {
-            setInventorySlotContents( 0, stack );
-        }
+        setInventorySlotContents( 0, stack );
     }
 
     public IMedia getDiskMedia()
@@ -569,7 +554,7 @@ public class TileDiskDrive extends TilePeripheralBase
         }
     }
 
-    private synchronized void updateAnim()
+    private void updateAnim()
     {            
         if( !m_diskStack.isEmpty() )
         {
@@ -605,8 +590,8 @@ public class TileDiskDrive extends TilePeripheralBase
             if( !destroyed )
             {
                 EnumFacing dir = getDirection();
-                xOff = dir.getFrontOffsetX();
-                zOff = dir.getFrontOffsetZ();
+                xOff = dir.getXOffset();
+                zOff = dir.getZOffset();
             }
 
             BlockPos pos = getPos();

src/main/java/dan200/computercraft/shared/peripheral/modem/BlockAdvancedModem.java

@@ -33,7 +33,7 @@ public class BlockAdvancedModem extends BlockPeripheralBase
     public BlockAdvancedModem()
     {
         setHardness( 2.0f );
-        setUnlocalizedName( "computercraft:advanced_modem" );
+        setTranslationKey( "computercraft:advanced_modem" );
         setCreativeTab( ComputerCraft.mainCreativeTab );
         setDefaultState( this.blockState.getBaseState()
             .withProperty( Properties.FACING, EnumFacing.NORTH )
@@ -54,7 +54,7 @@ public class BlockAdvancedModem extends BlockPeripheralBase
     public IBlockState getStateFromMeta( int meta )
     {
         IBlockState state = getDefaultState();
-        state = state.withProperty( Properties.FACING, EnumFacing.getFront( meta ) );
+        state = state.withProperty( Properties.FACING, EnumFacing.byIndex( meta ) );
         state = state.withProperty( Properties.ON, false );
         return state;
     }

src/main/java/dan200/computercraft/shared/peripheral/modem/ModemPeripheral.java

@@ -6,8 +6,10 @@
 
 package dan200.computercraft.shared.peripheral.modem;
 
+import dan200.computercraft.api.lua.ICallContext;
 import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 import dan200.computercraft.api.network.IPacketNetwork;
 import dan200.computercraft.api.network.IPacketReceiver;
 import dan200.computercraft.api.network.IPacketSender;
@@ -20,6 +22,7 @@ import net.minecraft.util.math.Vec3d;
 import net.minecraft.world.World;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 
 import static dan200.computercraft.core.apis.ArgumentHelper.getInt;
 
@@ -75,7 +78,7 @@ public abstract class ModemPeripheral
         m_open = false;
     }
     
-    public synchronized boolean pollChanged()
+    public boolean pollChanged()
     {
         if( m_changed )
         {
@@ -85,9 +88,9 @@ public abstract class ModemPeripheral
         return false;
     }
 
-    public synchronized boolean isActive()
+    public boolean isActive()
     {
-        return (m_computer != null) && m_open;
+        return m_computer != null && m_open;
     }
 
     @Override
@@ -157,8 +160,9 @@ public abstract class ModemPeripheral
         return channel;
     }
     
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    public MethodResult callMethod( @Nonnull IComputerAccess computer, @Nonnull ICallContext context, int method, @Nonnull Object[] arguments ) throws LuaException
     {
         switch( method )
         {
@@ -183,7 +187,7 @@ public abstract class ModemPeripheral
                         }
                     }
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 1:
             {
@@ -192,7 +196,7 @@ public abstract class ModemPeripheral
                 synchronized( this )
                 {
                     boolean open = m_channels.contains( channel );
-                    return new Object[] { open };
+                    return MethodResult.of( open );
                 }
             }
             case 2:
@@ -210,7 +214,7 @@ public abstract class ModemPeripheral
                         }
                     }
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 3:
             {
@@ -228,7 +232,7 @@ public abstract class ModemPeripheral
                         }
                     }
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 4:
             {
@@ -253,7 +257,7 @@ public abstract class ModemPeripheral
                         }
                     }
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 5:
             {
@@ -262,18 +266,26 @@ public abstract class ModemPeripheral
                 {
                     if( m_network != null )
                     {
-                        return new Object[] { m_network.isWireless() };
+                        return MethodResult.of( m_network.isWireless() );
                     }
                 }
-                return new Object[] { false };
+                return MethodResult.of(false);
             }
             default:
             {
-                return null;
+                return MethodResult.empty();
             }
         }
     }
-    
+
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( computer, (ICallContext) context, method, arguments ).evaluate( context );
+    }
+
     @Override
     public synchronized void attach( @Nonnull IComputerAccess computer )
     {

src/main/java/dan200/computercraft/shared/peripheral/modem/TileCable.java

@@ -108,10 +108,11 @@ public class TileCable extends TileModemBase
         m_node = m_cable.getNode();
         return new WiredModemPeripheral( m_cable )
         {
+            @Nonnull
             @Override
-            protected boolean canSeePeripheral( @Nonnull String peripheralName )
+            protected WiredModemLocalPeripheral getLocalPeripheral()
             {
-                return !peripheralName.equals( m_peripheral.getConnectedName() );
+                return m_peripheral;
             }
 
             @Nonnull

src/main/java/dan200/computercraft/shared/peripheral/modem/TileModemBase.java

@@ -37,7 +37,7 @@ public abstract class TileModemBase extends TilePeripheralBase
     protected abstract ModemPeripheral createPeripheral();
             
     @Override
-    public synchronized void destroy()
+    public void destroy()
     {
         if( m_modem != null )
         {

src/main/java/dan200/computercraft/shared/peripheral/modem/TileWiredModemFull.java

@@ -401,12 +401,14 @@ public class TileWiredModemFull extends TilePeripheralBase
         WiredModemPeripheral peripheral = m_modems[side.ordinal()];
         if( peripheral == null )
         {
+            WiredModemLocalPeripheral localPeripheral = m_peripherals[side.ordinal()];
             peripheral = m_modems[side.ordinal()] = new WiredModemPeripheral( m_element )
             {
+                @Nonnull
                 @Override
-                protected boolean canSeePeripheral( @Nonnull String peripheralName )
+                protected WiredModemLocalPeripheral getLocalPeripheral()
                 {
-                    return !peripheralName.equals( m_peripherals[side.ordinal()].getConnectedName() );
+                    return localPeripheral;
                 }
 
                 @Nonnull

src/main/java/dan200/computercraft/shared/peripheral/modem/WiredModemPeripheral.java

@@ -3,13 +3,16 @@ package dan200.computercraft.shared.peripheral.modem;
 import com.google.common.collect.ImmutableMap;
 import dan200.computercraft.api.filesystem.IMount;
 import dan200.computercraft.api.filesystem.IWritableMount;
-import dan200.computercraft.api.lua.ILuaContext;
+import dan200.computercraft.api.lua.ICallContext;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 import dan200.computercraft.api.network.IPacketNetwork;
 import dan200.computercraft.api.network.wired.IWiredNode;
 import dan200.computercraft.api.network.wired.IWiredSender;
 import dan200.computercraft.api.peripheral.IComputerAccess;
 import dan200.computercraft.api.peripheral.IPeripheral;
+import dan200.computercraft.core.computer.Computer;
+import dan200.computercraft.core.computer.IComputerOwned;
 import net.minecraft.world.World;
 
 import javax.annotation.Nonnull;
@@ -56,7 +59,8 @@ public abstract class WiredModemPeripheral extends ModemPeripheral implements IW
         return modem.getWorld();
     }
 
-    protected abstract boolean canSeePeripheral( @Nonnull String peripheralName );
+    @Nonnull
+    protected abstract WiredModemLocalPeripheral getLocalPeripheral();
     //endregion
 
     //region IPeripheral
@@ -65,18 +69,20 @@ public abstract class WiredModemPeripheral extends ModemPeripheral implements IW
     public String[] getMethodNames()
     {
         String[] methods = super.getMethodNames();
-        String[] newMethods = new String[methods.length + 5];
+        String[] newMethods = new String[methods.length + 6];
         System.arraycopy( methods, 0, newMethods, 0, methods.length );
         newMethods[methods.length] = "getNamesRemote";
         newMethods[methods.length + 1] = "isPresentRemote";
         newMethods[methods.length + 2] = "getTypeRemote";
         newMethods[methods.length + 3] = "getMethodsRemote";
         newMethods[methods.length + 4] = "callRemote";
+        newMethods[methods.length + 5] = "getNameLocal";
         return newMethods;
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    public MethodResult callMethod( @Nonnull IComputerAccess computer, @Nonnull ICallContext context, int method, @Nonnull Object[] arguments ) throws LuaException
     {
         String[] methods = super.getMethodNames();
         switch( method - methods.length )
@@ -92,14 +98,14 @@ public abstract class WiredModemPeripheral extends ModemPeripheral implements IW
                     {
                         table.put( idx++, name );
                     }
-                    return new Object[]{ table };
+                    return MethodResult.of( table );
                 }
             }
             case 1:
             {
                 // isPresentRemote
                 String type = getTypeRemote( getString( arguments, 0 ) );
-                return new Object[]{ type != null };
+                return MethodResult.of( type != null );
             }
             case 2:
             {
@@ -107,9 +113,9 @@ public abstract class WiredModemPeripheral extends ModemPeripheral implements IW
                 String type = getTypeRemote( getString( arguments, 0 ) );
                 if( type != null )
                 {
-                    return new Object[]{ type };
+                    return MethodResult.of( type );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 3:
             {
@@ -122,9 +128,9 @@ public abstract class WiredModemPeripheral extends ModemPeripheral implements IW
                     {
                         table.put( i + 1, methodNames[i] );
                     }
-                    return new Object[]{ table };
+                    return MethodResult.of( table );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 4:
             {
@@ -135,6 +141,12 @@ public abstract class WiredModemPeripheral extends ModemPeripheral implements IW
                 System.arraycopy( arguments, 2, methodArgs, 0, arguments.length - 2 );
                 return callMethodRemote( remoteName, context, methodName, methodArgs );
             }
+            case 5:
+            {
+                // getNameLocal
+                String local = getLocalPeripheral().getConnectedName();
+                return local == null ? MethodResult.empty() : MethodResult.of( local );
+            }
             default:
             {
                 // The regular modem methods
@@ -217,7 +229,7 @@ public abstract class WiredModemPeripheral extends ModemPeripheral implements IW
 
     private void attachPeripheralImpl( String periphName, IPeripheral peripheral )
     {
-        if( !peripheralWrappers.containsKey( periphName ) && canSeePeripheral( periphName ) )
+        if( !peripheralWrappers.containsKey( periphName ) && !periphName.equals( getLocalPeripheral().getConnectedName() ) )
         {
             RemotePeripheralWrapper wrapper = new RemotePeripheralWrapper( modem, peripheral, getComputer(), periphName );
             peripheralWrappers.put( periphName, wrapper );
@@ -251,7 +263,7 @@ public abstract class WiredModemPeripheral extends ModemPeripheral implements IW
         return null;
     }
 
-    private Object[] callMethodRemote( String remoteName, ILuaContext context, String method, Object[] arguments ) throws LuaException, InterruptedException
+    private MethodResult callMethodRemote( String remoteName, ICallContext context, String method, Object[] arguments ) throws LuaException
     {
         RemotePeripheralWrapper wrapper;
         synchronized( peripheralWrappers )
@@ -265,7 +277,7 @@ public abstract class WiredModemPeripheral extends ModemPeripheral implements IW
         throw new LuaException( "No peripheral: " + remoteName );
     }
 
-    private static class RemotePeripheralWrapper implements IComputerAccess
+    private static class RemotePeripheralWrapper implements IComputerAccess, IComputerOwned
     {
         private final WiredModemElement m_element;
         private final IPeripheral m_peripheral;
@@ -320,7 +332,7 @@ public abstract class WiredModemPeripheral extends ModemPeripheral implements IW
             return m_methods;
         }
 
-        public Object[] callMethod( ILuaContext context, String methodName, Object[] arguments ) throws LuaException, InterruptedException
+        public MethodResult callMethod( ICallContext context, String methodName, Object[] arguments ) throws LuaException
         {
             if( m_methodMap.containsKey( methodName ) )
             {
@@ -400,5 +412,12 @@ public abstract class WiredModemPeripheral extends ModemPeripheral implements IW
                 return m_element.getRemotePeripherals().get( name );
             }
         }
+
+        @Nullable
+        @Override
+        public Computer getComputer()
+        {
+            return m_computer instanceof IComputerOwned ? ((IComputerOwned) m_computer).getComputer() : null;
+        }
     }
 }

src/main/java/dan200/computercraft/shared/peripheral/monitor/MonitorPeripheral.java

@@ -6,8 +6,10 @@
 
 package dan200.computercraft.shared.peripheral.monitor;
 
+import dan200.computercraft.api.lua.ICallContext;
 import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 import dan200.computercraft.api.peripheral.IComputerAccess;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.core.apis.TermAPI;
@@ -16,6 +18,7 @@ import dan200.computercraft.shared.util.Palette;
 import org.apache.commons.lang3.ArrayUtils;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 
 import static dan200.computercraft.core.apis.ArgumentHelper.*;
 
@@ -70,8 +73,9 @@ public class MonitorPeripheral implements IPeripheral
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull Object args[] ) throws LuaException
+    public MethodResult callMethod( @Nonnull IComputerAccess computer, @Nonnull ICallContext context, int method, @Nonnull Object args[] ) throws LuaException
     {
         ServerMonitor monitor = m_monitor.getCachedServerMonitor();
         if( monitor == null ) throw new LuaException( "Monitor has been detatched" );
@@ -85,21 +89,24 @@ public class MonitorPeripheral implements IPeripheral
             {
                 // write
                 String text;
-                if( args.length > 0 && args[0] != null ) {
-                    text = args[0].toString();
-                } else {
+                if( args.length > 0 && args[ 0 ] != null )
+                {
+                    text = args[ 0 ].toString();
+                }
+                else
+                {
                     text = "";
                 }
                 terminal.write( text );
                 terminal.setCursorPos( terminal.getCursorX() + text.length(), terminal.getCursorY() );
-                return null;
+                return MethodResult.empty();
             }
             case 1:
             {
                 // scroll
                 int value = getInt( args, 0 );
                 terminal.scroll( value );
-                return null;
+                return MethodResult.empty();
             }
             case 2:
             {
@@ -107,42 +114,42 @@ public class MonitorPeripheral implements IPeripheral
                 int x = getInt( args, 0 ) - 1;
                 int y = getInt( args, 1 ) - 1;
                 terminal.setCursorPos( x, y );
-                return null;
+                return MethodResult.empty();
             }
             case 3:
             {
                 // setCursorBlink
                 boolean blink = getBoolean( args, 0 );
                 terminal.setCursorBlink( blink );
-                return null;
+                return MethodResult.empty();
             }
             case 4:
             {
                 // getCursorPos
-                return new Object[] {
+                return MethodResult.of(
                     terminal.getCursorX() + 1,
                     terminal.getCursorY() + 1
-                };
+                );
             }
             case 5:
             {
                 // getSize
-                return new Object[] {
+                return MethodResult.of(
                     terminal.getWidth(),
                     terminal.getHeight()
-                };
+                );
             }
             case 6:
             {
                 // clear
                 terminal.clear();
-                return null;
+                return MethodResult.empty();
             }
             case 7:
             {
                 // clearLine
                 terminal.clearLine();
-                return null;
+                return MethodResult.empty();
             }
             case 8:
             {
@@ -153,7 +160,7 @@ public class MonitorPeripheral implements IPeripheral
                     throw new LuaException( "Expected number in range 0.5-5" );
                 }
                 monitor.setTextScale( scale );
-                return null;
+                return MethodResult.empty();
             }
             case 9:
             case 10:
@@ -161,7 +168,7 @@ public class MonitorPeripheral implements IPeripheral
                 // setTextColour/setTextColor
                 int colour = TermAPI.parseColour( args );
                 terminal.setTextColour( colour );
-                return null;
+                return MethodResult.empty();
             }
             case 11:
             case 12:
@@ -169,15 +176,15 @@ public class MonitorPeripheral implements IPeripheral
                 // setBackgroundColour/setBackgroundColor
                 int colour = TermAPI.parseColour( args );
                 terminal.setBackgroundColour( colour );
-                return null;
+                return MethodResult.empty();
             }
             case 13:
             case 14:
             {
                 // isColour/isColor
-                return new Object[] {
+                return MethodResult.of(
                     monitor.isColour()
-                };
+                );
             }
             case 15:
             case 16:
@@ -204,7 +211,7 @@ public class MonitorPeripheral implements IPeripheral
 
                 terminal.blit( text, textColour, backgroundColour );
                 terminal.setCursorPos( terminal.getCursorX() + text.length(), terminal.getCursorY() );
-                return null;
+                return MethodResult.empty();
             }
             case 20:
             case 21:
@@ -224,7 +231,7 @@ public class MonitorPeripheral implements IPeripheral
                     double b = getReal( args, 3 );
                     TermAPI.setColour( terminal, colour, r, g, b );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 22:
             case 23:
@@ -236,17 +243,25 @@ public class MonitorPeripheral implements IPeripheral
 
                 if( palette != null )
                 {
-                    return ArrayUtils.toObject( palette.getColour( colour ) );
+                    return MethodResult.of( (Object[]) ArrayUtils.toObject( palette.getColour( colour ) ) );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 24:
             {
                 // getTextScale
-                return new Object[] { monitor.getTextScale() / 2.0 };
+                return MethodResult.of( monitor.getTextScale() / 2.0 );
             }
         }
-        return null;
+        return MethodResult.empty();
+    }
+
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull IComputerAccess access, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( access, (ICallContext) context, method, arguments ).evaluate( context );
     }
 
     @Override
@@ -266,7 +281,7 @@ public class MonitorPeripheral implements IPeripheral
     {
         if( other != null && other instanceof MonitorPeripheral )
         {
-            MonitorPeripheral otherMonitor = (MonitorPeripheral)other;
+            MonitorPeripheral otherMonitor = (MonitorPeripheral) other;
             if( otherMonitor.m_monitor == this.m_monitor )
             {
                 return true;

src/main/java/dan200/computercraft/shared/peripheral/monitor/TileMonitor.java

@@ -344,7 +344,7 @@ public class TileMonitor extends TilePeripheralBase
 
     public EnumFacing getFront()
     {
-        return m_dir <= 5 ? EnumFacing.getFront( m_dir ) : (m_dir <= 11 ? EnumFacing.DOWN : EnumFacing.UP);
+        return m_dir <= 5 ? EnumFacing.byIndex( m_dir ) : (m_dir <= 11 ? EnumFacing.DOWN : EnumFacing.UP);
     }
 
     public EnumFacing getRight()

src/main/java/dan200/computercraft/shared/peripheral/printer/PrinterPeripheral.java

@@ -6,13 +6,16 @@
 
 package dan200.computercraft.shared.peripheral.printer;
 
+import dan200.computercraft.api.lua.ICallContext;
 import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 import dan200.computercraft.api.peripheral.IComputerAccess;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.core.terminal.Terminal;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 
 import static dan200.computercraft.core.apis.ArgumentHelper.getInt;
 import static dan200.computercraft.core.apis.ArgumentHelper.optString;
@@ -50,8 +53,9 @@ public class PrinterPeripheral implements IPeripheral
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
+    public MethodResult callMethod( @Nonnull IComputerAccess computer, @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -68,7 +72,7 @@ public class PrinterPeripheral implements IPeripheral
                 Terminal page = getCurrentPage();
                 page.write( text );
                 page.setCursorPos( page.getCursorX() + text.length(), page.getCursorY() );
-                return null;
+                return MethodResult.empty();
             }
             case 1:
             {
@@ -77,7 +81,7 @@ public class PrinterPeripheral implements IPeripheral
                 int y = getInt( args, 1 ) - 1;
                 Terminal page = getCurrentPage();
                 page.setCursorPos( x, y );
-                return null;
+                return MethodResult.empty();
             }
             case 2:
             {
@@ -85,7 +89,7 @@ public class PrinterPeripheral implements IPeripheral
                 Terminal page = getCurrentPage();
                 int x = page.getCursorX();
                 int y = page.getCursorY();
-                return new Object[] { x + 1, y + 1 };
+                return MethodResult.of( x + 1, y + 1 );
             }
             case 3:
             {
@@ -93,23 +97,23 @@ public class PrinterPeripheral implements IPeripheral
                 Terminal page = getCurrentPage();
                 int width = page.getWidth();
                 int height = page.getHeight();
-                return new Object[] { width, height };
+                return MethodResult.of( width, height );
             }
             case 4:
             {
                 // newPage
-                return new Object[] { m_printer.startNewPage() };
+                return MethodResult.of( m_printer.startNewPage() );
             }
             case 5:
             {
                 // endPage
                 getCurrentPage();
-                return new Object[] { m_printer.endCurrentPage() };
+                return MethodResult.of( m_printer.endCurrentPage() );
             }
             case 6:
             {
                 // getInkLevel
-                return new Object[] { m_printer.getInkLevel() };
+                return MethodResult.of( m_printer.getInkLevel() );
             }
             case 7:
             {
@@ -117,20 +121,28 @@ public class PrinterPeripheral implements IPeripheral
                 String title = optString( args, 0, "" );
                 getCurrentPage();
                 m_printer.setPageTitle( title );
-                return null;
+                return MethodResult.empty();
             }
             case 8:
             {
                 // getPaperLevel
-                return new Object[] { m_printer.getPaperLevel() };
+                return MethodResult.of( m_printer.getPaperLevel() );
             }
             default:
             {
-                return null;
+                return MethodResult.empty();
             }
         }
     }
 
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull IComputerAccess access, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( access, (ICallContext) context, method, arguments ).evaluate( context );
+    }
+
     @Override
     public boolean equals( IPeripheral other )
     {

src/main/java/dan200/computercraft/shared/peripheral/printer/TilePrinter.java

@@ -190,10 +190,7 @@ public class TilePrinter extends TilePeripheralBase
     @Override    
     public ItemStack getStackInSlot(int i)
     {
-        synchronized( m_inventory )
-        {
-            return m_inventory.get( i );
-        }
+        return m_inventory.get( i );
     }
 
     @Nonnull

src/main/java/dan200/computercraft/shared/peripheral/speaker/SpeakerPeripheral.java

@@ -7,9 +7,7 @@
 package dan200.computercraft.shared.peripheral.speaker;
 
 import dan200.computercraft.ComputerCraft;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.ILuaTask;
-import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.api.peripheral.IComputerAccess;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import net.minecraft.util.ResourceLocation;
@@ -20,6 +18,7 @@ import net.minecraft.world.World;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
+import java.util.concurrent.atomic.AtomicInteger;
 
 import static dan200.computercraft.core.apis.ArgumentHelper.getString;
 import static dan200.computercraft.core.apis.ArgumentHelper.optReal;
@@ -28,13 +27,13 @@ public class SpeakerPeripheral implements IPeripheral {
     private TileSpeaker m_speaker;
     private long m_clock;
     private long m_lastPlayTime;
-    private int m_notesThisTick;
+    private final AtomicInteger m_notesThisTick;
 
     public SpeakerPeripheral()
     {
         m_clock = 0;
         m_lastPlayTime = 0;
-        m_notesThisTick = 0;
+        m_notesThisTick = new AtomicInteger(  );
     }
 
     SpeakerPeripheral(TileSpeaker speaker)
@@ -43,10 +42,10 @@ public class SpeakerPeripheral implements IPeripheral {
         m_speaker = speaker;
     }
 
-    public synchronized void update()
+    public void update()
     {
         m_clock++;
-        m_notesThisTick = 0;
+        m_notesThisTick.set( 0 );
     }
 
     public World getWorld()
@@ -59,9 +58,9 @@ public class SpeakerPeripheral implements IPeripheral {
         return m_speaker.getPos();
     }
 
-    public synchronized boolean madeSound(long ticks)
+    public boolean madeSound(long ticks)
     {
-        return (m_clock - m_lastPlayTime <= ticks) ;
+        return m_clock - m_lastPlayTime <= ticks;
     }
 
     /* IPeripheral implementation */
@@ -97,21 +96,22 @@ public class SpeakerPeripheral implements IPeripheral {
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull IComputerAccess computerAccess, @Nonnull ILuaContext context, int methodIndex, @Nonnull Object[] args ) throws LuaException
+    public MethodResult callMethod( @Nonnull IComputerAccess computer, @Nonnull ICallContext context, int methodIndex, @Nonnull Object[] args ) throws LuaException
     {
         switch( methodIndex )
         {
             // playSound
             case 0:
             {
-                return playSound(args, context, false);
+                return MethodResult.of( playSound( args, context, false ) );
             }
 
             // playNote
             case 1:
             {
-                return playNote(args, context);
+                return MethodResult.of( playNote( args, context ) );
             }
 
             default:
@@ -122,8 +122,16 @@ public class SpeakerPeripheral implements IPeripheral {
         }
     }
 
-    @Nonnull
-    private synchronized Object[] playNote( Object[] arguments, ILuaContext context ) throws LuaException
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull IComputerAccess access, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( access, (ICallContext) context, method, arguments ).evaluate( context );
+    }
+
+
+    private synchronized boolean playNote( Object[] arguments, ICallContext context ) throws LuaException
     {
         String name = getString(arguments, 0);
         float volume = (float) optReal( arguments, 1, 1.0 );
@@ -136,7 +144,7 @@ public class SpeakerPeripheral implements IPeripheral {
         }
 
         // If the resource location for note block notes changes, this method call will need to be updated
-        Object[] returnValue = playSound(
+        boolean success = playSound(
             new Object[] {
                 "block.note." + name,
                 (double)Math.min( volume, 3f ),
@@ -144,16 +152,15 @@ public class SpeakerPeripheral implements IPeripheral {
             }, context, true
         );
 
-        if( returnValue[0] instanceof Boolean && (Boolean) returnValue[0] )
+        if( success )
         {
-            m_notesThisTick++;
+            m_notesThisTick.incrementAndGet();
         }
 
-        return returnValue;
+        return success;
     }
 
-    @Nonnull
-    private synchronized Object[] playSound( Object[] arguments, ILuaContext context, boolean isNote ) throws LuaException
+    private synchronized boolean playSound( Object[] arguments, ICallContext context, boolean isNote ) throws LuaException
     {
         String name = getString(arguments, 0);
         float volume = (float) optReal( arguments, 1, 1.0 );
@@ -161,7 +168,7 @@ public class SpeakerPeripheral implements IPeripheral {
 
         ResourceLocation resourceName = new ResourceLocation( name );
 
-        if( m_clock - m_lastPlayTime >= TileSpeaker.MIN_TICKS_BETWEEN_SOUNDS || ( ( m_clock - m_lastPlayTime == 0 ) && ( m_notesThisTick < ComputerCraft.maxNotesPerTick ) && isNote ) )
+        if( m_clock - m_lastPlayTime >= TileSpeaker.MIN_TICKS_BETWEEN_SOUNDS || (isNote && m_clock - m_lastPlayTime == 0 && m_notesThisTick.get() < ComputerCraft.maxNotesPerTick) )
         {
             if( SoundEvent.REGISTRY.containsKey(resourceName) )
             {
@@ -183,16 +190,16 @@ public class SpeakerPeripheral implements IPeripheral {
                 });
 
                 m_lastPlayTime = m_clock;
-                return new Object[]{true}; // Success, return true
+                return true; // Success, return true
             }
             else
             {
-                return new Object[]{false}; // Failed - sound not existent, return false
+                return false; // Failed - sound not existent, return false
             }
         }
         else
         {
-            return new Object[]{false}; // Failed - rate limited, return false
+            return false; // Failed - rate limited, return false
         }
     }
 }

src/main/java/dan200/computercraft/shared/peripheral/speaker/TileSpeaker.java

@@ -25,7 +25,7 @@ public class TileSpeaker extends TilePeripheralBase
     }
 
     @Override
-    public synchronized void update()
+    public void update()
     {
         m_peripheral.update();
     }

src/main/java/dan200/computercraft/shared/pocket/apis/PocketAPI.java

@@ -7,9 +7,7 @@
 package dan200.computercraft.shared.pocket.apis;
 
 import dan200.computercraft.ComputerCraft;
-import dan200.computercraft.api.lua.ILuaAPI;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.api.pocket.IPocketUpgrade;
 import dan200.computercraft.shared.pocket.core.PocketServerComputer;
 import dan200.computercraft.shared.util.InventoryUtil;
@@ -21,6 +19,7 @@ import net.minecraft.util.NonNullList;
 import net.minecraftforge.items.wrapper.PlayerMainInvWrapper;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 
 public class PocketAPI implements ILuaAPI
 {
@@ -49,14 +48,15 @@ public class PocketAPI implements ILuaAPI
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] arguments ) throws LuaException
     {
         switch( method )
         {
             case 0:
                 // equipBack
-                return context.executeMainThreadTask( () ->
+                return MethodResult.onMainThread( () ->
                 {
                     if( !(m_computer.getEntity() instanceof EntityPlayer) )
                     {
@@ -94,12 +94,12 @@ public class PocketAPI implements ILuaAPI
                     // Set the new upgrade
                     m_computer.setUpgrade( newUpgrade );
 
-                    return null;
+                    return MethodResult.empty();
                 } );
 
             case 1:
                 // unequipBack
-                return context.executeMainThreadTask( () ->
+                return MethodResult.onMainThread( () ->
                 {
                     if( !(m_computer.getEntity() instanceof EntityPlayer) )
                     {
@@ -125,13 +125,21 @@ public class PocketAPI implements ILuaAPI
                         }
                     }
 
-                    return null;
+                    return MethodResult.empty();
                 } );
             default:
-                return null;
+                return MethodResult.empty();
         }
     }
 
+    @Override
+    @Nullable
+    @Deprecated
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
+
     private static IPocketUpgrade findUpgrade( NonNullList<ItemStack> inv, int start, IPocketUpgrade previous )
     {
         for( int i = 0; i < inv.size(); i++ )

src/main/java/dan200/computercraft/shared/pocket/core/PocketServerComputer.java

@@ -8,6 +8,7 @@ import dan200.computercraft.shared.computer.core.ComputerFamily;
 import dan200.computercraft.shared.computer.core.ServerComputer;
 import net.minecraft.entity.Entity;
 import net.minecraft.entity.player.EntityPlayer;
+import net.minecraft.entity.player.EntityPlayerMP;
 import net.minecraft.entity.player.InventoryPlayer;
 import net.minecraft.item.ItemStack;
 import net.minecraft.nbt.NBTTagCompound;
@@ -138,7 +139,7 @@ public class PocketServerComputer extends ServerComputer implements IPocketAcces
     {
         if( this.m_upgrade == upgrade ) return;
 
-        synchronized (this)
+        synchronized( this )
         {
             ComputerCraft.Items.pocketComputer.setUpgrade( m_stack, upgrade );
             if( m_entity instanceof EntityPlayer ) ((EntityPlayer) m_entity).inventory.markDirty();
@@ -156,6 +157,9 @@ public class PocketServerComputer extends ServerComputer implements IPocketAcces
             setPosition( entity.getPosition() );
         }
 
+        // If a new entity has picked it up then rebroadcast the terminal to them
+        if( entity != m_entity && entity instanceof EntityPlayerMP ) markTerminalChanged();
+
         m_entity = entity;
         m_stack = stack;
 
@@ -165,4 +169,19 @@ public class PocketServerComputer extends ServerComputer implements IPocketAcces
             invalidatePeripheral();
         }
     }
+
+    public void broadcastState( boolean force )
+    {
+        super.broadcastState( force );
+
+        if( (hasTerminalChanged() || force) && m_entity instanceof EntityPlayerMP )
+        {
+            // Broadcast the state to the current entity if they're not already interacting with it.
+            EntityPlayerMP player = (EntityPlayerMP) m_entity;
+            if( player.connection != null && !isInteracting( player ) )
+            {
+                ComputerCraft.sendToPlayer( player, createTerminalPacket() );
+            }
+        }
+    }
 }

src/main/java/dan200/computercraft/shared/pocket/items/ItemPocketComputer.java

@@ -43,7 +43,7 @@ public class ItemPocketComputer extends Item implements IComputerItem, IMedia, I
     {
         setMaxStackSize( 1 );
         setHasSubtypes( true );
-        setUnlocalizedName( "computercraft:pocket_computer" );
+        setTranslationKey( "computercraft:pocket_computer" );
         setCreativeTab( ComputerCraft.mainCreativeTab );
     }
 
@@ -189,7 +189,7 @@ public class ItemPocketComputer extends Item implements IComputerItem, IMedia, I
 
     @Nonnull
     @Override
-    public String getUnlocalizedName( @Nonnull ItemStack stack )
+    public String getTranslationKey( @Nonnull ItemStack stack )
     {
         switch( getFamily( stack ) )
         {
@@ -209,7 +209,7 @@ public class ItemPocketComputer extends Item implements IComputerItem, IMedia, I
     @Override
     public String getItemStackDisplayName( @Nonnull ItemStack stack )
     {
-        String baseString = getUnlocalizedName( stack );
+        String baseString = getTranslationKey( stack );
         IPocketUpgrade upgrade = getUpgrade( stack );
         if( upgrade != null )
         {

src/main/java/dan200/computercraft/shared/proxy/CCTurtleProxyCommon.java

@@ -21,7 +21,6 @@ import dan200.computercraft.shared.turtle.items.ItemTurtleNormal;
 import dan200.computercraft.shared.turtle.items.TurtleItemFactory;
 import dan200.computercraft.shared.turtle.recipes.TurtleUpgradeRecipe;
 import dan200.computercraft.shared.turtle.upgrades.*;
-import dan200.computercraft.shared.util.IEntityDropConsumer;
 import dan200.computercraft.shared.util.ImpostorRecipe;
 import dan200.computercraft.shared.util.InventoryUtil;
 import net.minecraft.block.Block;
@@ -33,33 +32,49 @@ import net.minecraft.item.ItemStack;
 import net.minecraft.item.crafting.IRecipe;
 import net.minecraft.util.NonNullList;
 import net.minecraft.util.ResourceLocation;
+import net.minecraft.util.math.AxisAlignedBB;
+import net.minecraft.util.math.BlockPos;
+import net.minecraft.world.World;
 import net.minecraftforge.common.MinecraftForge;
 import net.minecraftforge.event.RegistryEvent;
+import net.minecraftforge.event.entity.EntityJoinWorldEvent;
 import net.minecraftforge.event.entity.living.LivingDropsEvent;
+import net.minecraftforge.event.world.BlockEvent;
+import net.minecraftforge.fml.common.eventhandler.EventPriority;
 import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;
 import net.minecraftforge.fml.common.registry.EntityRegistry;
 import net.minecraftforge.fml.common.registry.GameRegistry;
 import net.minecraftforge.registries.IForgeRegistry;
 
 import javax.annotation.Nonnull;
-import java.util.*;
+import java.lang.ref.WeakReference;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Function;
 
 public abstract class CCTurtleProxyCommon implements ICCTurtleProxy
-{    
+{
     private Map<Integer, ITurtleUpgrade> m_legacyTurtleUpgrades;
     private Map<String, ITurtleUpgrade> m_turtleUpgrades;
-    private Map<Entity, IEntityDropConsumer> m_dropConsumers;
+
+    private Function<ItemStack, ItemStack> dropConsumer;
+    private List<ItemStack> remainingDrops;
+    private WeakReference<World> dropWorld;
+    private BlockPos dropPos;
+    private AxisAlignedBB dropBounds;
+    private WeakReference<Entity> dropEntity;
 
     public CCTurtleProxyCommon()
     {
         m_legacyTurtleUpgrades = new HashMap<>();
         m_turtleUpgrades = new HashMap<>();
-        m_dropConsumers = new WeakHashMap<>();
     }
-    
+
     // ICCTurtleProxy implementation
-    
-    @Override        
+
+    @Override
     public void preInit()
     {
         MinecraftForge.EVENT_BUS.register( this );
@@ -75,8 +90,8 @@ public abstract class CCTurtleProxyCommon implements ICCTurtleProxy
         // RecipeSorter.register( "computercraft:turtle", TurtleRecipe.class, RecipeSorter.Category.SHAPED, "after:minecraft:shapeless" );
         // RecipeSorter.register( "computercraft:turtle_upgrade", TurtleUpgradeRecipe.class, RecipeSorter.Category.SHAPED, "after:minecraft:shapeless" );
     }
-    
-    @Override        
+
+    @Override
     public void init()
     {
         registerForgeHandlers();
@@ -94,7 +109,7 @@ public abstract class CCTurtleProxyCommon implements ICCTurtleProxy
             ComputerCraft.log.error( message );
             throw new RuntimeException( message );
         }
-        
+
         // Register
         registerTurtleUpgradeInternal( upgrade );
     }
@@ -110,7 +125,7 @@ public abstract class CCTurtleProxyCommon implements ICCTurtleProxy
     {
         return m_legacyTurtleUpgrades.get( legacyId );
     }
-    
+
     @Override
     public ITurtleUpgrade getTurtleUpgrade( @Nonnull ItemStack stack )
     {
@@ -126,7 +141,7 @@ public abstract class CCTurtleProxyCommon implements ICCTurtleProxy
             }
             catch( Exception e )
             {
-                ComputerCraft.log.error("Error getting computer upgrade item", e);
+                ComputerCraft.log.error( "Error getting computer upgrade item", e );
             }
         }
         return null;
@@ -148,7 +163,7 @@ public abstract class CCTurtleProxyCommon implements ICCTurtleProxy
             return true;
         }
     }
-    
+
     private void addAllUpgradedTurtles( ComputerFamily family, NonNullList<ItemStack> list )
     {
         ItemStack basicStack = TurtleItemFactory.create( -1, null, -1, family, null, null, 0, null );
@@ -169,7 +184,7 @@ public abstract class CCTurtleProxyCommon implements ICCTurtleProxy
 
     private void addUpgradedTurtle( ComputerFamily family, ITurtleUpgrade upgrade, List<ItemStack> list )
     {
-        if ( isUpgradeSuitableForFamily( family, upgrade ) )
+        if( isUpgradeSuitableForFamily( family, upgrade ) )
         {
             ItemStack stack = TurtleItemFactory.create( -1, null, -1, family, upgrade, null, 0, null );
             if( !stack.isEmpty() )
@@ -178,54 +193,65 @@ public abstract class CCTurtleProxyCommon implements ICCTurtleProxy
             }
         }
     }
-    
+
     @Override
     public void addAllUpgradedTurtles( NonNullList<ItemStack> list )
     {
         addAllUpgradedTurtles( ComputerFamily.Normal, list );
         addAllUpgradedTurtles( ComputerFamily.Advanced, list );
     }
-    
+
     @Override
-    public void setEntityDropConsumer( Entity entity, IEntityDropConsumer consumer )
+    public void setDropConsumer( Entity entity, Function<ItemStack, ItemStack> consumer )
     {
-        if( !m_dropConsumers.containsKey( entity ) )
-        {
-            boolean captured = entity.captureDrops;
-            
-            if( !captured )
-            {
-                entity.captureDrops = true;
-                ArrayList<EntityItem> items = entity.capturedDrops;
-                
-                if( items == null || items.size() == 0 )
-                {
-                    m_dropConsumers.put( entity, consumer );
-                }
-            }
-        }
-    }    
-    
+        dropConsumer = consumer;
+        remainingDrops = new ArrayList<>();
+        dropEntity = new WeakReference<>( entity );
+        dropWorld = new WeakReference<>( entity.world );
+        dropPos = null;
+        dropBounds = new AxisAlignedBB( entity.getPosition() ).grow( 2, 2, 2 );
+
+        entity.captureDrops = true;
+    }
+
     @Override
-    public void clearEntityDropConsumer( Entity entity )
+    public void setDropConsumer( World world, BlockPos pos, Function<ItemStack, ItemStack> consumer )
     {
-        if( m_dropConsumers.containsKey( entity ) )
+        dropConsumer = consumer;
+        remainingDrops = new ArrayList<>();
+        dropEntity = null;
+        dropWorld = new WeakReference<>( world );
+        dropPos = pos;
+        dropBounds = new AxisAlignedBB( pos ).grow( 2, 2, 2 );
+    }
+
+    @Override
+    public List<ItemStack> clearDropConsumer()
+    {
+        if( dropEntity != null )
         {
-            boolean captured = entity.captureDrops;
-            
-            if( captured )
+            Entity entity = dropEntity.get();
+            if( entity != null )
             {
                 entity.captureDrops = false;
-                ArrayList<EntityItem> items = entity.capturedDrops;
-                
-                if( items != null )
+                if( entity.capturedDrops != null )
                 {
-                    dispatchEntityDrops( entity, items );
-                    items.clear();
+                    for( EntityItem entityItem : entity.capturedDrops ) handleDrops( entityItem.getItem() );
+                    entity.capturedDrops.clear();
                 }
             }
-            m_dropConsumers.remove( entity );
         }
+
+        List<ItemStack> remainingStacks = remainingDrops;
+
+        dropConsumer = null;
+        remainingDrops = null;
+        dropEntity = null;
+        dropWorld = null;
+        dropPos = null;
+        dropBounds = null;
+
+        return remainingStacks;
     }
 
     private void registerTurtleUpgradeInternal( ITurtleUpgrade upgrade )
@@ -289,7 +315,7 @@ public abstract class CCTurtleProxyCommon implements ICCTurtleProxy
     {
         IForgeRegistry<Item> registry = event.getRegistry();
 
-        registry.register( new ItemTurtleLegacy( ComputerCraft.Blocks.turtle).setRegistryName( new ResourceLocation( ComputerCraft.MOD_ID, "turtle" ) ) );
+        registry.register( new ItemTurtleLegacy( ComputerCraft.Blocks.turtle ).setRegistryName( new ResourceLocation( ComputerCraft.MOD_ID, "turtle" ) ) );
         registry.register( new ItemTurtleNormal( ComputerCraft.Blocks.turtleExpanded ).setRegistryName( new ResourceLocation( ComputerCraft.MOD_ID, "turtle_expanded" ) ) );
         registry.register( new ItemTurtleAdvanced( ComputerCraft.Blocks.turtleAdvanced ).setRegistryName( new ResourceLocation( ComputerCraft.MOD_ID, "turtle_advanced" ) ) );
     }
@@ -362,7 +388,7 @@ public abstract class CCTurtleProxyCommon implements ICCTurtleProxy
     private void registerUpgrades()
     {
         // Upgrades
-        ComputerCraft.Upgrades.wirelessModem =  new TurtleModem( false, new ResourceLocation( "computercraft", "wireless_modem" ), 1 );
+        ComputerCraft.Upgrades.wirelessModem = new TurtleModem( false, new ResourceLocation( "computercraft", "wireless_modem" ), 1 );
         registerTurtleUpgradeInternal( ComputerCraft.Upgrades.wirelessModem );
 
         ComputerCraft.Upgrades.craftingTable = new TurtleCraftingTable( 2 );
@@ -396,10 +422,10 @@ public abstract class CCTurtleProxyCommon implements ICCTurtleProxy
         // We have to use mappings.getAllMappings() as the mod ID is upper case but the domain lower.
         for( RegistryEvent.MissingMappings.Mapping<Item> mapping : mappings.getAllMappings() )
         {
-            String domain = mapping.key.getResourceDomain();
+            String domain = mapping.key.getNamespace();
             if( !domain.equalsIgnoreCase( ComputerCraft.MOD_ID ) ) continue;
 
-            String key = mapping.key.getResourcePath();
+            String key = mapping.key.getPath();
             if( key.equalsIgnoreCase( "CC-Turtle" ) )
             {
                 mapping.remap( Item.getItemFromBlock( ComputerCraft.Blocks.turtle ) );
@@ -421,10 +447,10 @@ public abstract class CCTurtleProxyCommon implements ICCTurtleProxy
         // We have to use mappings.getAllMappings() as the mod ID is upper case but the domain lower.
         for( RegistryEvent.MissingMappings.Mapping<Block> mapping : mappings.getAllMappings() )
         {
-            String domain = mapping.key.getResourceDomain();
+            String domain = mapping.key.getNamespace();
             if( !domain.equalsIgnoreCase( ComputerCraft.MOD_ID ) ) continue;
 
-            String key = mapping.key.getResourcePath();
+            String key = mapping.key.getPath();
             if( key.equalsIgnoreCase( "CC-Turtle" ) )
             {
                 mapping.remap( ComputerCraft.Blocks.turtle );
@@ -447,26 +473,60 @@ public abstract class CCTurtleProxyCommon implements ICCTurtleProxy
         GameRegistry.registerTileEntity( TileTurtleExpanded.class, ComputerCraft.LOWER_ID + " : " + "turtleex" );
         GameRegistry.registerTileEntity( TileTurtleAdvanced.class, ComputerCraft.LOWER_ID + " : " + "turtleadv" );
     }
-    
+
     private void registerForgeHandlers()
     {
         ForgeHandlers handlers = new ForgeHandlers();
         MinecraftForge.EVENT_BUS.register( handlers );
     }
-        
-    public class ForgeHandlers
-    {
-        private ForgeHandlers()
-        {
-        }
 
-        // Forge event responses 
-        @SubscribeEvent
+    private void handleDrops(ItemStack stack)
+    {
+        ItemStack remaining = dropConsumer.apply(stack);
+        if (!remaining.isEmpty()) remainingDrops.add(remaining);
+    }
+
+    private class ForgeHandlers
+    {
+        @SubscribeEvent(priority = EventPriority.LOWEST)
         public void onEntityLivingDrops( LivingDropsEvent event )
         {
-            dispatchEntityDrops( event.getEntity(), event.getDrops() );
+            // Capture any mob drops for the current entity
+            if( dropEntity != null && event.getEntity() == dropEntity.get() )
+            {
+                List<EntityItem> drops = event.getDrops();
+                for( EntityItem entityItem : drops ) handleDrops( entityItem.getItem() );
+                drops.clear();
+            }
         }
-        
+
+        @SubscribeEvent(priority = EventPriority.LOWEST)
+        public void onHarvestDrops( BlockEvent.HarvestDropsEvent event )
+        {
+            // Capture block drops for the current entity
+            if( dropWorld != null && dropWorld.get() == event.getWorld()
+                && dropPos != null && dropPos.equals( event.getPos() ) )
+            {
+                for( ItemStack item : event.getDrops() )
+                {
+                    if( event.getWorld().rand.nextFloat() < event.getDropChance() ) handleDrops( item );
+                }
+                event.getDrops().clear();
+            }
+        }
+
+        @SubscribeEvent(priority = EventPriority.LOWEST)
+        public void onEntitySpawn( EntityJoinWorldEvent event )
+        {
+            // Capture any nearby item spawns
+            if( dropWorld != null && dropWorld.get() == event.getWorld() && event.getEntity() instanceof EntityItem
+                && dropBounds.contains( event.getEntity().getPositionVector() ) )
+            {
+                handleDrops( ((EntityItem) event.getEntity()).getItem() );
+                event.setCanceled( true );
+            }
+        }
+
         @SubscribeEvent
         public void onTurtleAction( TurtleActionEvent event) {
             if( ComputerCraft.turtleDisabledActions.contains( event.getAction() ) )
@@ -475,18 +535,5 @@ public abstract class CCTurtleProxyCommon implements ICCTurtleProxy
             }
         }
     }
-    
-    private void dispatchEntityDrops( Entity entity, java.util.List<EntityItem> drops )
-    {
-        IEntityDropConsumer consumer = m_dropConsumers.get( entity );
-        if( consumer != null )
-        {
-            // All checks have passed, lets dispatch the drops
-            for(EntityItem entityItem : drops)
-            {
-                consumer.consumeDrop( entity, entityItem.getItem() );
-            }
-            drops.clear();
-        }
-    }
+
 }

src/main/java/dan200/computercraft/shared/proxy/ComputerCraftProxyCommon.java

@@ -24,6 +24,7 @@ import dan200.computercraft.shared.computer.core.*;
 import dan200.computercraft.shared.computer.inventory.ContainerComputer;
 import dan200.computercraft.shared.computer.items.ItemCommandComputer;
 import dan200.computercraft.shared.computer.items.ItemComputer;
+import dan200.computercraft.shared.integration.charset.IntegrationCharset;
 import dan200.computercraft.shared.media.common.DefaultMediaProvider;
 import dan200.computercraft.shared.media.inventory.ContainerHeldItem;
 import dan200.computercraft.shared.media.items.ItemDiskExpanded;
@@ -76,6 +77,7 @@ import net.minecraftforge.event.RegistryEvent;
 import net.minecraftforge.event.entity.player.PlayerContainerEvent;
 import net.minecraftforge.event.world.WorldEvent;
 import net.minecraftforge.fml.client.event.ConfigChangedEvent;
+import net.minecraftforge.fml.common.Loader;
 import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;
 import net.minecraftforge.fml.common.gameevent.TickEvent;
 import net.minecraftforge.fml.common.network.FMLNetworkEvent;
@@ -83,6 +85,7 @@ import net.minecraftforge.fml.common.network.IGuiHandler;
 import net.minecraftforge.fml.common.network.NetworkRegistry;
 import net.minecraftforge.fml.common.registry.GameRegistry;
 import net.minecraftforge.registries.IForgeRegistry;
+import pl.asie.charset.ModCharset;
 
 import javax.annotation.Nonnull;
 import java.io.File;
@@ -117,6 +120,8 @@ public abstract class ComputerCraftProxyCommon implements IComputerCraftProxy
     {
         registerTileEntities();
         registerForgeHandlers();
+
+        if( Loader.isModLoaded( ModCharset.MODID ) ) IntegrationCharset.register();
     }
 
     @Override
@@ -414,10 +419,10 @@ public abstract class ComputerCraftProxyCommon implements IComputerCraftProxy
         // We have to use mappings.getAllMappings() as the mod ID is upper case but the domain lower.
         for( RegistryEvent.MissingMappings.Mapping<Item> mapping : mappings.getAllMappings() )
         {
-            String domain = mapping.key.getResourceDomain();
+            String domain = mapping.key.getNamespace();
             if( !domain.equalsIgnoreCase( ComputerCraft.MOD_ID ) ) continue;
 
-            String key = mapping.key.getResourcePath();
+            String key = mapping.key.getPath();
             if( key.equalsIgnoreCase( "CC-Computer" ) )
             {
                 mapping.remap( Item.getItemFromBlock( ComputerCraft.Blocks.computer ) );
@@ -451,10 +456,10 @@ public abstract class ComputerCraftProxyCommon implements IComputerCraftProxy
         // We have to use mappings.getAllMappings() as the mod ID is upper case but the domain lower.
         for( RegistryEvent.MissingMappings.Mapping<Block> mapping : mappings.getAllMappings() )
         {
-            String domain = mapping.key.getResourceDomain();
+            String domain = mapping.key.getNamespace();
             if( !domain.equalsIgnoreCase( ComputerCraft.MOD_ID ) ) continue;
 
-            String key = mapping.key.getResourcePath();
+            String key = mapping.key.getPath();
             if( key.equalsIgnoreCase( "CC-Computer" ) )
             {
                 mapping.remap( ComputerCraft.Blocks.computer );

src/main/java/dan200/computercraft/shared/proxy/ICCTurtleProxy.java

@@ -7,12 +7,16 @@
 package dan200.computercraft.shared.proxy;
 
 import dan200.computercraft.api.turtle.ITurtleUpgrade;
-import dan200.computercraft.shared.util.IEntityDropConsumer;
 import net.minecraft.entity.Entity;
 import net.minecraft.item.ItemStack;
 import net.minecraft.util.NonNullList;
+import net.minecraft.util.math.BlockPos;
+import net.minecraft.world.World;
 
 import javax.annotation.Nonnull;
+import java.util.List;
+import java.util.function.Consumer;
+import java.util.function.Function;
 
 public interface ICCTurtleProxy
 {
@@ -25,6 +29,7 @@ public interface ICCTurtleProxy
     ITurtleUpgrade getTurtleUpgrade( @Nonnull ItemStack item );
     void addAllUpgradedTurtles( NonNullList<ItemStack> list );
 
-    void setEntityDropConsumer( Entity entity, IEntityDropConsumer consumer );
-    void clearEntityDropConsumer( Entity entity );
+    void setDropConsumer( Entity entity, Function<ItemStack, ItemStack> consumer );
+    void setDropConsumer( World world, BlockPos pos, Function<ItemStack, ItemStack> consumer );
+    List<ItemStack> clearDropConsumer();
 }

src/main/java/dan200/computercraft/shared/turtle/apis/TurtleAPI.java

@@ -6,9 +6,7 @@
 
 package dan200.computercraft.shared.turtle.apis;
 
-import dan200.computercraft.api.lua.ILuaAPI;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.api.turtle.ITurtleAccess;
 import dan200.computercraft.api.turtle.ITurtleCommand;
 import dan200.computercraft.api.turtle.TurtleSide;
@@ -22,6 +20,7 @@ import net.minecraft.item.ItemStack;
 import net.minecraftforge.common.MinecraftForge;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Optional;
@@ -99,9 +98,9 @@ public class TurtleAPI implements ILuaAPI
         };
     }
     
-    private Object[] tryCommand( ILuaContext context, ITurtleCommand command ) throws LuaException, InterruptedException
+    private MethodResult tryCommand( ITurtleCommand command ) throws LuaException
     {
-        return m_turtle.executeCommand( context, command );
+        return m_turtle.executeCommand( command );
     }
 
     private int parseSlotNumber( Object[] arguments, int index ) throws LuaException
@@ -155,7 +154,8 @@ public class TurtleAPI implements ILuaAPI
     }
 
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException, InterruptedException
+    @Nonnull
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -163,89 +163,89 @@ public class TurtleAPI implements ILuaAPI
             {
                 // forward
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtleMoveCommand( MoveDirection.Forward ) );
+                return tryCommand( new TurtleMoveCommand( MoveDirection.Forward ) );
             }
             case 1:
             {
                 // back
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtleMoveCommand( MoveDirection.Back ) );
+                return tryCommand( new TurtleMoveCommand( MoveDirection.Back ) );
             }
             case 2:
             {
                 // up
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtleMoveCommand( MoveDirection.Up ) );
+                return tryCommand( new TurtleMoveCommand( MoveDirection.Up ) );
             }
             case 3:
             {
                 // down
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtleMoveCommand( MoveDirection.Down ) );
+                return tryCommand( new TurtleMoveCommand( MoveDirection.Down ) );
             }
             case 4:
             {
                 // turnLeft
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtleTurnCommand( TurnDirection.Left ) );
+                return tryCommand( new TurtleTurnCommand( TurnDirection.Left ) );
             }
             case 5:
             {
                 // turnRight
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtleTurnCommand( TurnDirection.Right ) );
+                return tryCommand( new TurtleTurnCommand( TurnDirection.Right ) );
             }
             case 6:
             {
                 // dig
                 Optional<TurtleSide> side = parseSide( args, 0 );
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtleDigCommand( InteractDirection.Forward, side ) );
+                return tryCommand( new TurtleDigCommand( InteractDirection.Forward, side ) );
             }
             case 7:
             {
                 // digUp
                 Optional<TurtleSide> side = parseSide( args, 0 );
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtleDigCommand( InteractDirection.Up, side ) );
+                return tryCommand( new TurtleDigCommand( InteractDirection.Up, side ) );
             }
             case 8:
             {
                 // digDown
                 Optional<TurtleSide> side = parseSide( args, 0 );
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtleDigCommand( InteractDirection.Down, side ) );
+                return tryCommand( new TurtleDigCommand( InteractDirection.Down, side ) );
             }
             case 9:
             {
                 // place
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtlePlaceCommand( InteractDirection.Forward, args ) );
+                return tryCommand( new TurtlePlaceCommand( InteractDirection.Forward, args ) );
             }
             case 10:
             {
                 // placeUp
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtlePlaceCommand( InteractDirection.Up, args ) );
+                return tryCommand( new TurtlePlaceCommand( InteractDirection.Up, args ) );
             }
             case 11:
             {
                 // placeDown
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtlePlaceCommand( InteractDirection.Down, args ) );
+                return tryCommand( new TurtlePlaceCommand( InteractDirection.Down, args ) );
             }
             case 12:
             {
                 // drop
                 int count = parseCount( args, 0 );
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtleDropCommand( InteractDirection.Forward, count ) );
+                return tryCommand( new TurtleDropCommand( InteractDirection.Forward, count ) );
             }
             case 13:
             {
                 // select
                 int slot = parseSlotNumber( args, 0 );
-                return tryCommand( context, new TurtleSelectCommand( slot ) );
+                return tryCommand( new TurtleSelectCommand( slot ) );
             }
             case 14:
             {
@@ -254,11 +254,11 @@ public class TurtleAPI implements ILuaAPI
                 ItemStack stack = m_turtle.getInventory().getStackInSlot( slot );
                 if( !stack.isEmpty() )
                 {
-                    return new Object[] { stack.getCount() };
+                    return MethodResult.of( stack.getCount() );
                 }
                 else
                 {
-                    return new Object[] { 0 };
+                    return MethodResult.of( 0 );
                 }
             }
             case 15:
@@ -268,172 +268,172 @@ public class TurtleAPI implements ILuaAPI
                 ItemStack stack = m_turtle.getInventory().getStackInSlot( slot );
                 if( !stack.isEmpty() )
                 {
-                    return new Object[] {
+                    return MethodResult.of(
                         Math.min( stack.getMaxStackSize(), 64 ) - stack.getCount()
-                    };
+                    );
                 }
-                return new Object[] { 64 };
+                return MethodResult.of( 64 );
             }
             case 16:
             {
                 // detect
-                return tryCommand( context, new TurtleDetectCommand( InteractDirection.Forward ) );
+                return tryCommand( new TurtleDetectCommand( InteractDirection.Forward ) );
             }
             case 17:
             {
                 // detectUp
-                return tryCommand( context, new TurtleDetectCommand( InteractDirection.Up ) );
+                return tryCommand( new TurtleDetectCommand( InteractDirection.Up ) );
             }
             case 18:
             {
                 // detectDown
-                return tryCommand( context, new TurtleDetectCommand( InteractDirection.Down ) );
+                return tryCommand( new TurtleDetectCommand( InteractDirection.Down ) );
             }
             case 19:
             {
                 // compare
-                return tryCommand( context, new TurtleCompareCommand( InteractDirection.Forward ) );
+                return tryCommand( new TurtleCompareCommand( InteractDirection.Forward ) );
             }
             case 20:
             {
                 // compareUp
-                return tryCommand( context, new TurtleCompareCommand( InteractDirection.Up ) );
+                return tryCommand( new TurtleCompareCommand( InteractDirection.Up ) );
             }
             case 21:
             {
                 // compareDown
-                return tryCommand( context, new TurtleCompareCommand( InteractDirection.Down ) );
+                return tryCommand( new TurtleCompareCommand( InteractDirection.Down ) );
             }
             case 22:
             {
                 // attack
                 Optional<TurtleSide> side = parseSide( args, 0 );
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtleAttackCommand( InteractDirection.Forward, side ) );
+                return tryCommand( new TurtleAttackCommand( InteractDirection.Forward, side ) );
             }
             case 23:
             {
                 // attackUp
                 Optional<TurtleSide> side = parseSide( args, 0 );
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtleAttackCommand( InteractDirection.Up, side ) );
+                return tryCommand( new TurtleAttackCommand( InteractDirection.Up, side ) );
             }
             case 24:
             {
                 // attackDown
                 Optional<TurtleSide> side = parseSide( args, 0 );
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtleAttackCommand( InteractDirection.Down, side ) );
+                return tryCommand( new TurtleAttackCommand( InteractDirection.Down, side ) );
             }
             case 25:
             {
                 // dropUp
                 int count = parseCount( args, 0 );
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtleDropCommand( InteractDirection.Up, count ) );
+                return tryCommand( new TurtleDropCommand( InteractDirection.Up, count ) );
             }
             case 26:
             {
                 // dropDown
                 int count = parseCount( args, 0 );
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtleDropCommand( InteractDirection.Down, count ) );
+                return tryCommand( new TurtleDropCommand( InteractDirection.Down, count ) );
             }
             case 27:
             {
                 // suck
                 int count = parseCount( args, 0 );
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtleSuckCommand( InteractDirection.Forward, count ) );
+                return tryCommand( new TurtleSuckCommand( InteractDirection.Forward, count ) );
             }
             case 28:
             {
                 // suckUp
                 int count = parseCount( args, 0 );
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtleSuckCommand( InteractDirection.Up, count ) );
+                return tryCommand( new TurtleSuckCommand( InteractDirection.Up, count ) );
             }
             case 29:
             {
                 // suckDown
                 int count = parseCount( args, 0 );
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtleSuckCommand( InteractDirection.Down, count ) );
+                return tryCommand( new TurtleSuckCommand( InteractDirection.Down, count ) );
             }
             case 30:
             {
                 // getFuelLevel
                 if( m_turtle.isFuelNeeded() )
                 {
-                    return new Object[] { m_turtle.getFuelLevel() };
+                    return MethodResult.of( m_turtle.getFuelLevel() );
                 }
                 else
                 {
-                    return new Object[] { "unlimited" };
+                    return MethodResult.of( "unlimited" );
                 }
             }
             case 31:
             {
                 // refuel
                 int count = parseCount( args, 0 );
-                return tryCommand( context, new TurtleRefuelCommand( count ) );
+                return tryCommand( new TurtleRefuelCommand( count ) );
             }
             case 32:
             {
                 // compareTo
                 int slot = parseSlotNumber( args, 0 );
-                return tryCommand( context, new TurtleCompareToCommand( slot ) );
+                return tryCommand( new TurtleCompareToCommand( slot ) );
             }
             case 33:
             {
                 // transferTo
                 int slot = parseSlotNumber( args, 0 );
                 int count = parseCount( args, 1 );
-                return tryCommand( context, new TurtleTransferToCommand( slot, count ) );
+                return tryCommand( new TurtleTransferToCommand( slot, count ) );
             }
             case 34:
             {
                 // getSelectedSlot
-                return new Object[] { m_turtle.getSelectedSlot() + 1 };
+                return MethodResult.of( m_turtle.getSelectedSlot() + 1 );
             }
             case 35:
             {
                 // getFuelLimit
                 if( m_turtle.isFuelNeeded() )
                 {
-                    return new Object[] { m_turtle.getFuelLimit() };
+                    return MethodResult.of( m_turtle.getFuelLimit() );
                 }
                 else
                 {
-                    return new Object[] { "unlimited" };
+                    return MethodResult.of( "unlimited" );
                 }
             }
             case 36:
             {
                 // equipLeft
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtleEquipCommand( TurtleSide.Left ) );
+                return tryCommand( new TurtleEquipCommand( TurtleSide.Left ) );
             }
             case 37:
             {
                 // equipRight
                 m_environment.addTrackingChange( TrackingField.TURTLE_OPS );
-                return tryCommand( context, new TurtleEquipCommand( TurtleSide.Right ) );
+                return tryCommand( new TurtleEquipCommand( TurtleSide.Right ) );
             }
             case 38:
             {
                 // inspect
-                return tryCommand( context, new TurtleInspectCommand( InteractDirection.Forward ) );
+                return tryCommand( new TurtleInspectCommand( InteractDirection.Forward ) );
             }
             case 39:
             {
                 // inspectUp
-                return tryCommand( context, new TurtleInspectCommand( InteractDirection.Up ) );
+                return tryCommand( new TurtleInspectCommand( InteractDirection.Up ) );
             }
             case 40:
             {
                 // inspectDown
-                return tryCommand( context, new TurtleInspectCommand( InteractDirection.Down ) );
+                return tryCommand( new TurtleInspectCommand( InteractDirection.Down ) );
             }
             case 41:
             {
@@ -455,20 +455,28 @@ public class TurtleAPI implements ILuaAPI
                     TurtleActionEvent event = new TurtleActionEvent( m_turtle, TurtleAction.INSPECT_ITEM );
                     if( MinecraftForge.EVENT_BUS.post( event ) )
                     {
-                        return new Object[] { false, event.getFailureMessage() };
+                        return MethodResult.of( false, event.getFailureMessage() );
                     }
 
-                    return new Object[] { table };
+                    return MethodResult.of( table );
                 }
                 else
                 {
-                    return new Object[] { null };
+                    return MethodResult.of( new Object[] { null } );
                 }
             }
             default:
             {
-                return null;
+                return MethodResult.empty();
             }
         }
     }
+
+    @Override
+    @Nullable
+    @Deprecated
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
 }

src/main/java/dan200/computercraft/shared/turtle/blocks/BlockTurtle.java

@@ -48,7 +48,7 @@ public class BlockTurtle extends BlockComputerBase
     {
         super( Material.IRON );
         setHardness( 2.5f );
-        setUnlocalizedName( "computercraft:turtle" );
+        setTranslationKey( "computercraft:turtle" );
         setCreativeTab( ComputerCraft.mainCreativeTab );
         setDefaultState( this.blockState.getBaseState()
             .withProperty( Properties.FACING, EnumFacing.NORTH )

src/main/java/dan200/computercraft/shared/turtle/core/TurtleBrain.java

@@ -10,7 +10,9 @@ import com.google.common.base.Objects;
 import com.mojang.authlib.GameProfile;
 import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.api.lua.ILuaContext;
+import dan200.computercraft.api.lua.ILuaFunction;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.api.turtle.*;
 import dan200.computercraft.shared.computer.blocks.ComputerProxy;
@@ -127,6 +129,8 @@ public class TurtleBrain implements ITurtleAccess
     private TurtleAnimation m_animation;
     private int m_animationProgress;
     private int m_lastAnimationProgress;
+    
+    TurtlePlayer m_cachedPlayer;
 
     public TurtleBrain( TileTurtle turtle )
     {
@@ -224,7 +228,7 @@ public class TurtleBrain implements ITurtleAccess
     public void readFromNBT( NBTTagCompound nbttagcompound )
     {
         // Read state
-        m_direction = EnumFacing.getFront( nbttagcompound.getInteger( "dir" ) );
+        m_direction = EnumFacing.byIndex( nbttagcompound.getInteger( "dir" ) );
         m_selectedSlot = nbttagcompound.getInteger( "selectedSlot" );
         if( nbttagcompound.hasKey( "fuelLevel" ) )
         {
@@ -368,8 +372,8 @@ public class TurtleBrain implements ITurtleAccess
         // Write overlay
         if( m_overlay != null )
         {
-            nbttagcompound.setString( "overlay_mod", m_overlay.getResourceDomain() );
-            nbttagcompound.setString( "overlay_path", m_overlay.getResourcePath() );
+            nbttagcompound.setString( "overlay_mod", m_overlay.getNamespace() );
+            nbttagcompound.setString( "overlay_path", m_overlay.getPath() );
         }
 
         // Write NBT
@@ -427,8 +431,8 @@ public class TurtleBrain implements ITurtleAccess
         // Overlay
         if( m_overlay != null )
         {
-            nbttagcompound.setString( "overlay_mod", m_overlay.getResourceDomain() );
-            nbttagcompound.setString( "overlay_path", m_overlay.getResourcePath() );
+            nbttagcompound.setString( "overlay_mod", m_overlay.getNamespace() );
+            nbttagcompound.setString( "overlay_path", m_overlay.getPath() );
         }
 
         // Animation
@@ -503,7 +507,7 @@ public class TurtleBrain implements ITurtleAccess
             m_lastAnimationProgress = 0;
         }
 
-        m_direction = EnumFacing.getFront( nbttagcompound.getInteger( "direction" ) );
+        m_direction = EnumFacing.byIndex( nbttagcompound.getInteger( "direction" ) );
         m_fuelLevel = nbttagcompound.getInteger( "fuelLevel" );
     }
 
@@ -759,6 +763,7 @@ public class TurtleBrain implements ITurtleAccess
 
     @Nonnull
     @Override
+    @Deprecated
     public Object[] executeCommand( @Nonnull ILuaContext context, @Nonnull ITurtleCommand command ) throws LuaException, InterruptedException
     {
         if( getWorld().isRemote )
@@ -785,6 +790,38 @@ public class TurtleBrain implements ITurtleAccess
         }
     }
 
+    @Nonnull
+    @Override
+    public MethodResult executeCommand( @Nonnull ITurtleCommand command )
+    {
+        if( getWorld().isRemote )
+        {
+            throw new UnsupportedOperationException();
+        }
+
+        // Issue command
+        int commandID = issueCommand( command );
+
+        // Wait for response
+        return MethodResult.pullEvent( "turtle_response", new ILuaFunction()
+        {
+            @Nonnull
+            @Override
+            public MethodResult call( Object[] response )
+            {
+                if( response.length >= 3 && response[ 1 ] instanceof Number && ((Number) response[ 1 ]).intValue() == commandID
+                    && response[ 2 ] instanceof Boolean )
+                {
+                    Object[] returnValues = new Object[ response.length - 2 ];
+                    System.arraycopy( response, 2, returnValues, 0, returnValues.length );
+                    return MethodResult.of( returnValues );
+                }
+
+                return MethodResult.pullEvent( "turtle_response", this );
+            }
+        } );
+    }
+
     @Override
     public void playAnimation( @Nonnull TurtleAnimation animation )
     {
@@ -996,9 +1033,9 @@ public class TurtleBrain implements ITurtleAccess
 
                 double distance = -1.0 + getAnimationFraction( f );
                 return new Vec3d(
-                    distance * dir.getFrontOffsetX(),
-                    distance * dir.getFrontOffsetY(),
-                    distance * dir.getFrontOffsetZ()
+                    distance * dir.getXOffset(),
+                    distance * dir.getYOffset(),
+                    distance * dir.getZOffset()
                 );
             }
             default:
@@ -1182,31 +1219,31 @@ public class TurtleBrain implements ITurtleAccess
 
                     float pushFrac = 1.0f - ((float)(m_animationProgress + 1) / (float)ANIM_DURATION);
                     float push = Math.max( pushFrac + 0.0125f, 0.0f );
-                    if (moveDir.getFrontOffsetX() < 0)
+                    if (moveDir.getXOffset() < 0)
                     {
-                        minX += moveDir.getFrontOffsetX() * push;
+                        minX += moveDir.getXOffset() * push;
                     }
                     else
                     {
-                        maxX -= moveDir.getFrontOffsetX() * push;
+                        maxX -= moveDir.getXOffset() * push;
                     }
 
-                    if (moveDir.getFrontOffsetY() < 0)
+                    if (moveDir.getYOffset() < 0)
                     {
-                        minY += moveDir.getFrontOffsetY() * push;
+                        minY += moveDir.getYOffset() * push;
                     }
                     else
                     {
-                        maxY -= moveDir.getFrontOffsetY() * push;
+                        maxY -= moveDir.getYOffset() * push;
                     }
 
-                    if (moveDir.getFrontOffsetZ() < 0)
+                    if (moveDir.getZOffset() < 0)
                     {
-                        minZ += moveDir.getFrontOffsetZ() * push;
+                        minZ += moveDir.getZOffset() * push;
                     }
                     else
                     {
-                        maxZ -= moveDir.getFrontOffsetZ() * push;
+                        maxZ -= moveDir.getZOffset() * push;
                     }
 
                     AxisAlignedBB aabb = new AxisAlignedBB( minX, minY, minZ, maxX, maxY, maxZ );
@@ -1214,9 +1251,9 @@ public class TurtleBrain implements ITurtleAccess
                     if( !list.isEmpty() )
                     {
                         double pushStep = 1.0f / ANIM_DURATION;
-                        double pushStepX = moveDir.getFrontOffsetX() * pushStep;
-                        double pushStepY = moveDir.getFrontOffsetY() * pushStep;
-                        double pushStepZ = moveDir.getFrontOffsetZ() * pushStep;
+                        double pushStepX = moveDir.getXOffset() * pushStep;
+                        double pushStepY = moveDir.getYOffset() * pushStep;
+                        double pushStepZ = moveDir.getZOffset() * pushStep;
                         for (Entity entity : list)
                         {
                             entity.move( MoverType.PISTON, pushStepX, pushStepY, pushStepZ );

src/main/java/dan200/computercraft/shared/turtle/core/TurtleCompareCommand.java

@@ -126,7 +126,7 @@ public class TurtleCompareCommand implements ITurtleCommand
                 {
                     return TurtleCommandResult.success();
                 }
-                else if( selectedStack.getUnlocalizedName().equals( lookAtStack.getUnlocalizedName() ) )
+                else if( selectedStack.getTranslationKey().equals( lookAtStack.getTranslationKey() ) )
                 {
                     return TurtleCommandResult.success();
                 }

src/main/java/dan200/computercraft/shared/turtle/core/TurtleMoveCommand.java

@@ -87,9 +87,9 @@ public class TurtleMoveCommand implements ITurtleCommand
                         if( entityBB != null )
                         {
                             AxisAlignedBB pushedBB = entityBB.offset(
-                                direction.getFrontOffsetX(),
-                                direction.getFrontOffsetY(),
-                                direction.getFrontOffsetZ()
+                                direction.getXOffset(),
+                                direction.getYOffset(),
+                                direction.getZOffset()
                             );
                             if( !oldWorld.getCollisionBoxes( null, pushedBB ).isEmpty() )
                             {

src/main/java/dan200/computercraft/shared/turtle/core/TurtlePlaceCommand.java

@@ -30,7 +30,6 @@ import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.math.Vec3d;
 import net.minecraft.util.text.TextComponentString;
 import net.minecraft.world.World;
-import net.minecraft.world.WorldServer;
 import net.minecraftforge.common.ForgeHooks;
 import net.minecraftforge.common.MinecraftForge;
 import net.minecraftforge.event.entity.player.PlayerInteractEvent;
@@ -38,6 +37,7 @@ import net.minecraftforge.fml.common.eventhandler.Event;
 import org.apache.commons.lang3.tuple.Pair;
 
 import javax.annotation.Nonnull;
+import java.util.List;
 
 public class TurtlePlaceCommand implements ITurtleCommand
 {
@@ -180,12 +180,12 @@ public class TurtlePlaceCommand implements ITurtleCommand
 
     public static TurtlePlayer createPlayer( ITurtleAccess turtle, BlockPos position, EnumFacing direction )
     {
-        TurtlePlayer turtlePlayer = new TurtlePlayer( turtle );
+        TurtlePlayer turtlePlayer = TurtlePlayer.get( turtle );
         orientPlayer( turtle, turtlePlayer, position, direction );
         return turtlePlayer;
     }
 
-    public static void orientPlayer( ITurtleAccess turtle, TurtlePlayer turtlePlayer, BlockPos position, EnumFacing direction )
+    private static void orientPlayer( ITurtleAccess turtle, TurtlePlayer turtlePlayer, BlockPos position, EnumFacing direction )
     {
         turtlePlayer.posX = position.getX() + 0.5;
         turtlePlayer.posY = position.getY() + 0.5;
@@ -194,9 +194,9 @@ public class TurtlePlaceCommand implements ITurtleCommand
         // Stop intersection with the turtle itself
         if( turtle.getPosition().equals( position ) )
         {
-            turtlePlayer.posX += 0.48 * direction.getFrontOffsetX();
-            turtlePlayer.posY += 0.48 * direction.getFrontOffsetY();
-            turtlePlayer.posZ += 0.48 * direction.getFrontOffsetZ();
+            turtlePlayer.posX += 0.48 * direction.getXOffset();
+            turtlePlayer.posY += 0.48 * direction.getYOffset();
+            turtlePlayer.posZ += 0.48 * direction.getZOffset();
         }
 
         if( direction.getAxis() != EnumFacing.Axis.Y )
@@ -241,14 +241,10 @@ public class TurtlePlaceCommand implements ITurtleCommand
         // Start claiming entity drops
         Entity hitEntity = hit.getKey();
         Vec3d hitPos = hit.getValue();
-        ComputerCraft.setEntityDropConsumer( hitEntity, ( entity, drop ) ->
-        {
-            ItemStack remainder = InventoryUtil.storeItems( drop, turtle.getItemHandler(), turtle.getSelectedSlot() );
-            if( !remainder.isEmpty() )
-            {
-                WorldUtil.dropItemStack( remainder, world, position, turtle.getDirection().getOpposite() );
-            }
-        } );
+        ComputerCraft.setDropConsumer(
+            hitEntity,
+            drop -> InventoryUtil.storeItems( drop, turtle.getItemHandler(), turtle.getSelectedSlot() )
+        );
 
         // Place on the entity
         boolean placed = false;
@@ -285,7 +281,11 @@ public class TurtlePlaceCommand implements ITurtleCommand
         }
 
         // Stop claiming drops
-        ComputerCraft.clearEntityDropConsumer( hitEntity );
+        List<ItemStack> remainingDrops = ComputerCraft.clearDropConsumer();
+        for( ItemStack remaining : remainingDrops )
+        {
+            WorldUtil.dropItemStack( remaining, world, position, turtle.getDirection().getOpposite() );
+        }
 
         // Put everything we collected into the turtles inventory, then return
         ItemStack remainder = turtlePlayer.unloadInventory( turtle );
@@ -367,9 +367,9 @@ public class TurtlePlaceCommand implements ITurtleCommand
         orientPlayer( turtle, turtlePlayer, playerPosition, playerDir );
 
         // Calculate where the turtle would hit the block
-        float hitX = 0.5f + side.getFrontOffsetX() * 0.5f;
-        float hitY = 0.5f + side.getFrontOffsetY() * 0.5f;
-        float hitZ = 0.5f + side.getFrontOffsetZ() * 0.5f;
+        float hitX = 0.5f + side.getXOffset() * 0.5f;
+        float hitY = 0.5f + side.getYOffset() * 0.5f;
+        float hitZ = 0.5f + side.getZOffset() * 0.5f;
         if( Math.abs( hitY - 0.5f ) < 0.01f )
         {
             hitY = 0.45f;
@@ -382,7 +382,7 @@ public class TurtlePlaceCommand implements ITurtleCommand
 
         // Do the deploying (put everything in the players inventory)
         boolean placed = false;
-
+        TileEntity existingTile = turtle.getWorld().getTileEntity( position );
 
         // See PlayerInteractionManager.processRightClickBlock
         PlayerInteractEvent.RightClickBlock event = ForgeHooks.onRightClickBlock( turtlePlayer, EnumHand.MAIN_HAND, position, side, new Vec3d( hitX, hitY, hitZ ) );
@@ -426,12 +426,11 @@ public class TurtlePlaceCommand implements ITurtleCommand
             {
                 World world = turtle.getWorld();
                 TileEntity tile = world.getTileEntity( position );
-                if( tile == null )
+                if( tile == null || tile == existingTile )
                 {
-                    BlockPos newPosition = WorldUtil.moveCoords( position, side );
-                    tile = world.getTileEntity( newPosition );
+                    tile = world.getTileEntity( WorldUtil.moveCoords( position, side ) );
                 }
-                if( tile != null && tile instanceof TileEntitySign )
+                if( tile instanceof TileEntitySign )
                 {
                     TileEntitySign signTile = (TileEntitySign) tile;
                     String s = (String)extraArguments[0];

src/main/java/dan200/computercraft/shared/turtle/core/TurtlePlayer.java

@@ -36,16 +36,31 @@ public class TurtlePlayer extends FakePlayer
         "[ComputerCraft]"
     );
 
+    /**
+     * Construct a TurtlePlayer which exists in the world
+     *
+     * @param world The world the player exists in
+     * @deprecated This is required by {@link Entity}.
+     */
     @Deprecated
     public TurtlePlayer( World world )
     {
         super( (WorldServer) world, DEFAULT_PROFILE );
     }
-    
-    public TurtlePlayer( ITurtleAccess turtle )
-    {
-        super( (WorldServer) turtle.getWorld(), getProfile( turtle.getOwningPlayer() ));
 
+    private TurtlePlayer( ITurtleAccess turtle )
+    {
+        super( (WorldServer) turtle.getWorld(), getProfile( turtle.getOwningPlayer() ) );
+        setState( turtle );
+    }
+
+    private static GameProfile getProfile( @Nullable GameProfile profile )
+    {
+        return profile != null && profile.isComplete() ? profile : DEFAULT_PROFILE;
+    }
+
+    private void setState( ITurtleAccess turtle )
+    {
         BlockPos position = turtle.getPosition();
         posX = position.getX() + 0.5;
         posY = position.getY() + 0.5;
@@ -53,11 +68,27 @@ public class TurtlePlayer extends FakePlayer
 
         rotationYaw = turtle.getDirection().getHorizontalAngle();
         rotationPitch = 0.0f;
+
+        inventory.clear();
     }
 
-    private static GameProfile getProfile( @Nullable GameProfile profile )
+    public static TurtlePlayer get( ITurtleAccess access )
     {
-        return profile != null && profile.isComplete() ? profile : DEFAULT_PROFILE;
+        if( !(access instanceof TurtleBrain) ) return new TurtlePlayer( access );
+
+        TurtleBrain brain = (TurtleBrain) access;
+        TurtlePlayer player = brain.m_cachedPlayer;
+        if( player == null || player.getGameProfile() != getProfile( access.getOwningPlayer() )
+            || player.getEntityWorld() != access.getWorld() )
+        {
+            player = brain.m_cachedPlayer = new TurtlePlayer( brain );
+        }
+        else
+        {
+            player.setState( access );
+        }
+
+        return player;
     }
 
     public void loadInventory( @Nonnull ItemStack currentStack )
@@ -76,7 +107,7 @@ public class TurtlePlayer extends FakePlayer
         // Store (or drop) anything else we found
         BlockPos dropPosition = turtle.getPosition();
         EnumFacing dropDirection = turtle.getDirection().getOpposite();
-        for( int i=0; i<inventory.getSizeInventory(); ++i )
+        for( int i = 0; i < inventory.getSizeInventory(); ++i )
         {
             ItemStack stack = inventory.getStackInSlot( i );
             if( !stack.isEmpty() )