Merge branch 'mc-1.20.x' into mc-1.21.x

While Item.inventoryTick is passed a slot number, apparently that slot
corresponds to the offset within a particular inventory compartment
(such as the main inventory or armour)[^1], rather than the inventory as
a whole.

In the case of the off-hand, this means the pocket computer is set to be
in slot 0. When we next tick the computer (to send terminal updates), we
then assume the item has gone missing, and so skip sending updates.

Fixes #1945.

[^1]: A fun side effect of this is that the "selected" flag is true for
  the off-hand iff the player has slot 0 active. This whole thing feels
  like a vanilla bug, but who knows!

.github/ISSUE_TEMPLATE/bug_report.yaml

@@ -8,10 +8,8 @@ body:
     label: Minecraft Version
     description: What version of Minecraft are you using?
     options:
-      - 1.16.x
-      - 1.18.x
-      - 1.19.x
-      - 1.20.x
+      - 1.20.1
+      - 1.21.x
   validations:
     required: true
 - type: input

.pre-commit-config.yaml

@@ -27,7 +27,7 @@ repos:
     exclude: "^(.*\\.(bat)|LICENSE)$"
 
 - repo: https://github.com/fsfe/reuse-tool
-  rev: v2.1.0
+  rev: v4.0.3
   hooks:
   - id: reuse
 

.reuse/dep5

@@ -1,100 +0,0 @@
-Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
-Source: https://github.com/cc-tweaked/cc-tweaked
-Upstream-Name: CC: Tweaked
-Upstream-Contact: Jonathan Coates <git@squiddev.cc>
-
-Files:
-  projects/common/src/main/resources/assets/computercraft/sounds.json
-  projects/common/src/main/resources/assets/computercraft/sounds/empty.ogg
-  projects/common/src/testMod/resources/data/cctest/computercraft/turtle_upgrade/*
-  projects/common/src/testMod/resources/data/cctest/structures/*
-  projects/*/src/generated/*
-  projects/web/src/htmlTransform/export/index.json
-  projects/web/src/htmlTransform/export/items/minecraft/*
-Comment: Generated/data files are CC0.
-Copyright: The CC: Tweaked Developers
-License: CC0-1.0
-
-Files:
-  doc/images/*
-  package.json
-  package-lock.json
-  projects/common/src/client/resources/computercraft-client.mixins.json
-  projects/common/src/main/resources/assets/minecraft/shaders/core/computercraft/monitor_tbo.json
-  projects/common/src/main/resources/computercraft.mixins.json
-  projects/common/src/testMod/resources/computercraft-gametest.mixins.json
-  projects/common/src/testMod/resources/data/computercraft/loot_tables/treasure_disk.json
-  projects/common/src/testMod/resources/pack.mcmeta
-  projects/core/src/main/resources/data/computercraft/lua/rom/modules/command/.ignoreme
-  projects/core/src/main/resources/data/computercraft/lua/rom/modules/main/.ignoreme
-  projects/core/src/main/resources/data/computercraft/lua/rom/modules/turtle/.ignoreme
-  projects/core/src/main/resources/data/computercraft/lua/rom/motd.txt
-  projects/fabric-api/src/main/modJson/fabric.mod.json
-  projects/fabric/src/client/resources/computercraft-client.fabric.mixins.json
-  projects/fabric/src/main/resources/computercraft.fabric.mixins.json
-  projects/fabric/src/main/resources/fabric.mod.json
-  projects/fabric/src/testMod/resources/computercraft-gametest.fabric.mixins.json
-  projects/fabric/src/testMod/resources/fabric.mod.json
-  projects/forge/src/client/resources/computercraft-client.forge.mixins.json
-  projects/forge/src/main/resources/computercraft.forge.mixins.json
-  projects/web/src/frontend/mount/.settings
-  projects/web/src/frontend/mount/example.nfp
-  projects/web/src/frontend/mount/example.nft
-  projects/web/src/frontend/mount/expr_template.lua
-  projects/web/tsconfig.json
-Comment: Several assets where it's inconvenient to create a .license file.
-Copyright: The CC: Tweaked Developers
-License: MPL-2.0
-
-Files:
-  doc/logo.png
-  doc/logo-darkmode.png
-  projects/common/src/main/resources/assets/computercraft/models/*
-  projects/common/src/main/resources/assets/computercraft/textures/*
-  projects/common/src/main/resources/pack.mcmeta
-  projects/common/src/main/resources/pack.png
-  projects/core/src/main/resources/assets/computercraft/textures/gui/term_font.png
-  projects/core/src/main/resources/data/computercraft/lua/rom/autorun/.ignoreme
-  projects/core/src/main/resources/data/computercraft/lua/rom/help/*
-  projects/core/src/main/resources/data/computercraft/lua/rom/programs/fun/advanced/levels/*
-  projects/web/src/htmlTransform/export/items/computercraft/*
-Comment: Bulk-license original assets as CCPL.
-Copyright: 2011 Daniel Ratcliffe
-License: LicenseRef-CCPL
-
-Files:
-  projects/common/src/main/resources/assets/computercraft/lang/cs_cz.json
-  projects/common/src/main/resources/assets/computercraft/lang/ko_kr.json
-  projects/common/src/main/resources/assets/computercraft/lang/pl_pl.json
-  projects/common/src/main/resources/assets/computercraft/lang/pt_br.json
-  projects/common/src/main/resources/assets/computercraft/lang/ru_ru.json
-  projects/common/src/main/resources/assets/computercraft/lang/uk_ua.json
-  projects/common/src/main/resources/assets/computercraft/lang/zh_cn.json
-Comment: Community-contributed license files
-Copyright: 2017 The CC: Tweaked Developers
-License: LicenseRef-CCPL
-
-Files:
-  projects/common/src/main/resources/assets/computercraft/lang/*
-Comment: Community-contributed license files
-Copyright: 2017 The CC: Tweaked Developers
-License: MPL-2.0
-
-Files:
-  .github/*
-Comment:
-  GitHub build scripts are CC0. While we could add a header to each file,
-  it's unclear if it will break actions or issue templates in some way.
-Copyright: Jonathan Coates <git@squiddev.cc>
-License: CC0-1.0
-
-Files:
-  gradle/wrapper/*
-  gradlew
-  gradlew.bat
-Copyright: Gradle Inc
-License: Apache-2.0
-
-Files: projects/core/src/test/resources/test-rom/data/json-parsing/*
-Copyright: 2016 Nicolas Seriot
-License: MIT

CONTRIBUTING.md

@@ -12,7 +12,6 @@ If you've any other questions, [just ask the community][community] or [open an i
 
 ## Table of Contents
  - [Reporting issues](#reporting-issues)
- - [Translations](#translations)
  - [Setting up a development environment](#setting-up-a-development-environment)
  - [Developing CC: Tweaked](#developing-cc-tweaked)
  - [Writing documentation](#writing-documentation)
@@ -21,17 +20,13 @@ If you've any other questions, [just ask the community][community] or [open an i
 If you have a bug, suggestion, or other feedback, the best thing to do is [file an issue][new-issue]. When doing so, do
 use the issue templates - they provide a useful hint on what information to provide.
 
-## Translations
-Translations are managed through [Weblate], an online interface for managing language strings. This is synced
-automatically with GitHub, so please don't submit PRs adding/changing translations!
-
 ## Setting up a development environment
 In order to develop CC: Tweaked, you'll need to download the source code and then run it.
 
  - Make sure you've got the following software installed:
-   - Java Development Kit (JDK). This can be downloaded from [Adoptium].
+   - Java Development Kit 21 (JDK). This can be downloaded from [Adoptium].
    - [Git](https://git-scm.com/).
-   - [NodeJS][node].
+   - [NodeJS 20 or later][node].
 
  - Download CC: Tweaked's source code:
    ```
@@ -101,7 +96,6 @@ about how you can build on that until you've covered everything!
 [community]: README.md#community "Get in touch with the community."
 [Adoptium]: https://adoptium.net/temurin/releases?version=17 "Download OpenJDK 17"
 [illuaminate]: https://github.com/SquidDev/illuaminate/ "Illuaminate on GitHub"
-[weblate]: https://i18n.tweaked.cc/projects/cc-tweaked/minecraft/ "CC: Tweaked weblate instance"
 [docs]: https://tweaked.cc/ "CC: Tweaked documentation"
 [ldoc]: http://stevedonovan.github.io/ldoc/ "ldoc, a Lua documentation generator."
 [mc-test]: https://www.youtube.com/watch?v=vXaWOJTCYNg

README.md

@@ -26,8 +26,9 @@ developing the mod, [check out the instructions here](CONTRIBUTING.md#developing
 
 ## Community
 If you need help getting started with CC: Tweaked, want to show off your latest project, or just want to chat about
-ComputerCraft, do check out our [forum] and [GitHub discussions page][GitHub discussions]! There's also a fairly
-populated, albeit quiet [IRC channel][irc], if that's more your cup of tea.
+ComputerCraft, do check out our [GitHub discussions page][GitHub discussions]! There's also a fairly populated,
+albeit quiet IRC channel on [EsperNet], if that's more your cup of tea. You can join `#computercraft` through your
+desktop client, or online using [KiwiIRC].
 
 We also host fairly comprehensive documentation at [tweaked.cc](https://tweaked.cc/ "The CC: Tweaked website").
 
@@ -39,7 +40,7 @@ on is present.
 ```groovy
 repositories {
   maven {
-    url "https://squiddev.cc/maven/"
+    url "https://maven.squiddev.cc"
     content {
       includeGroup("cc.tweaked")
     }
@@ -85,6 +86,6 @@ the generated documentation [can be browsed online](https://tweaked.cc/javadoc/)
 [modrinth]: https://modrinth.com/mod/gu7yAYhd "Download CC: Tweaked from Modrinth"
 [Minecraft Forge]: https://files.minecraftforge.net/ "Download Minecraft Forge."
 [Fabric]: https://fabricmc.net/use/installer/ "Download Fabric."
-[forum]: https://forums.computercraft.cc/
 [GitHub Discussions]: https://github.com/cc-tweaked/CC-Tweaked/discussions
-[IRC]: https://webchat.esper.net/?channels=computercraft "#computercraft on EsperNet"
+[EsperNet]: https://www.esper.net/
+[KiwiIRC]: https://kiwiirc.com/nextclient/#irc://irc.esper.net:+6697/#computercraft "#computercraft on EsperNet"

REUSE.toml

@@ -0,0 +1,111 @@
+# SPDX-FileCopyrightText: 2017 The CC: Tweaked Developers
+#
+# SPDX-License-Identifier: MPL-2.0
+
+version = 1
+SPDX-PackageName = "CC: Tweaked"
+SPDX-PackageSupplier = "Jonathan Coates <git@squiddev.cc>"
+SPDX-PackageDownloadLocation = "https://github.com/cc-tweaked/cc-tweaked"
+
+[[annotations]]
+# Generated/data files are CC0.
+SPDX-FileCopyrightText = "The CC: Tweaked Developers"
+SPDX-License-Identifier = "CC0-1.0"
+path = [
+    "gradle/gradle-daemon-jvm.properties",
+    "projects/common/src/main/resources/assets/computercraft/sounds.json",
+    "projects/common/src/main/resources/assets/computercraft/sounds/empty.ogg",
+    "projects/common/src/testMod/resources/data/cctest/computercraft/turtle_upgrade/**",
+    "projects/common/src/testMod/resources/data/cctest/structures/**",
+    "projects/**/src/generated/**",
+    "projects/web/src/htmlTransform/export/index.json",
+    "projects/web/src/htmlTransform/export/items/minecraft/**",
+]
+
+[[annotations]]
+# Several assets where it's inconvenient to create a .license file.
+SPDX-FileCopyrightText = "The CC: Tweaked Developers"
+SPDX-License-Identifier = "MPL-2.0"
+path = [
+    "doc/images/**",
+    "package.json",
+    "package-lock.json",
+    "projects/common/src/client/resources/computercraft-client.mixins.json",
+    "projects/common/src/main/resources/assets/minecraft/shaders/core/computercraft/monitor_tbo.json",
+    "projects/common/src/main/resources/computercraft.mixins.json",
+    "projects/common/src/testMod/resources/computercraft-gametest.mixins.json",
+    "projects/common/src/testMod/resources/data/computercraft/loot_tables/treasure_disk.json",
+    "projects/common/src/testMod/resources/pack.mcmeta",
+    "projects/core/src/main/resources/data/computercraft/lua/rom/modules/command/.ignoreme",
+    "projects/core/src/main/resources/data/computercraft/lua/rom/modules/main/.ignoreme",
+    "projects/core/src/main/resources/data/computercraft/lua/rom/modules/turtle/.ignoreme",
+    "projects/core/src/main/resources/data/computercraft/lua/rom/motd.txt",
+    "projects/fabric-api/src/main/modJson/fabric.mod.json",
+    "projects/fabric/src/client/resources/computercraft-client.fabric.mixins.json",
+    "projects/fabric/src/main/resources/computercraft.fabric.mixins.json",
+    "projects/fabric/src/main/resources/fabric.mod.json",
+    "projects/fabric/src/testMod/resources/computercraft-gametest.fabric.mixins.json",
+    "projects/fabric/src/testMod/resources/fabric.mod.json",
+    "projects/forge/src/client/resources/computercraft-client.forge.mixins.json",
+    "projects/forge/src/main/resources/computercraft.forge.mixins.json",
+    "projects/web/src/frontend/mount/.settings",
+    "projects/web/src/frontend/mount/example.nfp",
+    "projects/web/src/frontend/mount/example.nft",
+    "projects/web/src/frontend/mount/expr_template.lua",
+    "projects/web/tsconfig.json",
+]
+
+[[annotations]]
+# Bulk-license original assets as CCPL.
+SPDX-FileCopyrightText = "2011 Daniel Ratcliffe"
+SPDX-License-Identifier = "LicenseRef-CCPL"
+path = [
+    "doc/logo.png",
+    "doc/logo-darkmode.png",
+    "projects/common/src/main/resources/assets/computercraft/models/**",
+    "projects/common/src/main/resources/assets/computercraft/textures/**",
+    "projects/common/src/main/resources/pack.mcmeta",
+    "projects/common/src/main/resources/pack.png",
+    "projects/core/src/main/resources/assets/computercraft/textures/gui/term_font.png",
+    "projects/core/src/main/resources/data/computercraft/lua/rom/autorun/.ignoreme",
+    "projects/core/src/main/resources/data/computercraft/lua/rom/help/**",
+    "projects/core/src/main/resources/data/computercraft/lua/rom/programs/fun/advanced/levels/**",
+    "projects/web/src/htmlTransform/export/items/computercraft/**",
+]
+
+[[annotations]]
+# Community-contributed license files
+SPDX-FileCopyrightText = "2017 The CC: Tweaked Developers"
+SPDX-License-Identifier = "LicenseRef-CCPL"
+path = [
+    "projects/common/src/main/resources/assets/computercraft/lang/cs_cz.json",
+    "projects/common/src/main/resources/assets/computercraft/lang/ko_kr.json",
+    "projects/common/src/main/resources/assets/computercraft/lang/pl_pl.json",
+    "projects/common/src/main/resources/assets/computercraft/lang/pt_br.json",
+    "projects/common/src/main/resources/assets/computercraft/lang/ru_ru.json",
+    "projects/common/src/main/resources/assets/computercraft/lang/uk_ua.json",
+    "projects/common/src/main/resources/assets/computercraft/lang/zh_cn.json",
+]
+
+[[annotations]]
+# Community-contributed license files
+SPDX-FileCopyrightText = "2017 The CC: Tweaked Developers"
+SPDX-License-Identifier = "MPL-2.0"
+path = "projects/common/src/main/resources/assets/computercraft/lang/**"
+
+[[annotations]]
+# GitHub build scripts are CC0. While we could add a header to each file,
+# it's unclear if it will break actions or issue templates in some way.
+SPDX-FileCopyrightText = "Jonathan Coates <git@squiddev.cc>"
+SPDX-License-Identifier = "CC0-1.0"
+path = ".github/**"
+
+[[annotations]]
+path = ["gradle/wrapper/**"]
+SPDX-FileCopyrightText = "Gradle Inc"
+SPDX-License-Identifier = "Apache-2.0"
+
+[[annotations]]
+path = "projects/core/src/test/resources/test-rom/data/json-parsing/**"
+SPDX-FileCopyrightText = "2016 Nicolas Seriot"
+SPDX-License-Identifier = "MIT"

buildSrc/build.gradle.kts

@@ -32,7 +32,7 @@ repositories {
         }
     }
 
-    maven("https://squiddev.cc/maven") {
+    maven("https://maven.squiddev.cc") {
         name = "SquidDev"
         content {
             includeGroup("cc.tweaked.vanilla-extract")

buildSrc/src/main/kotlin/cc-tweaked.java-convention.gradle.kts

@@ -38,7 +38,7 @@ java {
 repositories {
     mavenCentral()
 
-    val mainMaven = maven("https://squiddev.cc/maven") {
+    val mainMaven = maven("https://maven.squiddev.cc/mirror") {
         name = "SquidDev"
     }
 
@@ -47,6 +47,7 @@ repositories {
         filter {
             includeGroup("cc.tweaked")
             // Things we mirror
+            includeGroup("com.simibubi.create")
             includeGroup("commoble.morered")
             includeGroup("dev.architectury")
             includeGroup("dev.emi")
@@ -133,8 +134,8 @@ tasks.processResources {
 tasks.withType(AbstractArchiveTask::class.java).configureEach {
     isPreserveFileTimestamps = false
     isReproducibleFileOrder = true
-    dirMode = Integer.valueOf("755", 8)
-    fileMode = Integer.valueOf("664", 8)
+    filePermissions {}
+    dirPermissions {}
 }
 
 tasks.jar {

buildSrc/src/main/kotlin/cc-tweaked.publishing.gradle.kts

@@ -38,7 +38,7 @@ publishing {
     }
 
     repositories {
-        maven("https://squiddev.cc/maven") {
+        maven("https://maven.squiddev.cc") {
             name = "SquidDev"
 
             credentials(PasswordCredentials::class)

buildSrc/src/main/kotlin/cc/tweaked/gradle/CCTweakedExtension.kt

@@ -22,7 +22,6 @@ import org.gradle.api.tasks.SourceSet
 import org.gradle.api.tasks.bundling.Jar
 import org.gradle.api.tasks.compile.JavaCompile
 import org.gradle.api.tasks.javadoc.Javadoc
-import org.gradle.configurationcache.extensions.capitalized
 import org.gradle.language.base.plugins.LifecycleBasePlugin
 import org.gradle.language.jvm.tasks.ProcessResources
 import org.gradle.process.JavaForkOptions
@@ -181,7 +180,7 @@ abstract class CCTweakedExtension(
 
     fun <T> jacoco(task: NamedDomainObjectProvider<T>) where T : Task, T : JavaForkOptions {
         val classDump = project.layout.buildDirectory.dir("jacocoClassDump/${task.name}")
-        val reportTaskName = "jacoco${task.name.capitalized()}Report"
+        val reportTaskName = "jacoco${task.name.capitalise()}Report"
 
         val jacoco = project.extensions.getByType(JacocoPluginExtension::class.java)
         task.configure {

buildSrc/src/main/kotlin/cc/tweaked/gradle/Extensions.kt

@@ -9,6 +9,7 @@ import org.gradle.api.file.FileSystemLocation
 import org.gradle.api.provider.Property
 import org.gradle.api.provider.Provider
 import org.gradle.api.tasks.JavaExec
+import org.gradle.kotlin.dsl.getByName
 import org.gradle.process.BaseExecSpec
 import org.gradle.process.JavaExecSpec
 import org.gradle.process.ProcessForkOptions
@@ -46,6 +47,21 @@ fun JavaExec.copyToFull(spec: JavaExec) {
     copyToExec(spec)
 }
 
+/**
+ * Base this [JavaExec] task on an existing task.
+ */
+fun JavaExec.copyFromTask(task: JavaExec) {
+    for (dep in task.dependsOn) dependsOn(dep)
+    task.copyToFull(this)
+}
+
+/**
+ * Base this [JavaExec] task on an existing task.
+ */
+fun JavaExec.copyFromTask(task: String) {
+    copyFromTask(project.tasks.getByName<JavaExec>(task))
+}
+
 /**
  * Copy additional [BaseExecSpec] options which aren't handled by [ProcessForkOptions.copyTo].
  */
@@ -143,7 +159,7 @@ fun getNextVersion(version: String): String {
     val lastIndex = mainVersion.lastIndexOf('.')
     if (lastIndex < 0) throw IllegalArgumentException("Cannot parse version format \"$version\"")
     val lastVersion = try {
-        version.substring(lastIndex + 1).toInt()
+        mainVersion.substring(lastIndex + 1).toInt()
     } catch (e: NumberFormatException) {
         throw IllegalArgumentException("Cannot parse version format \"$version\"", e)
     }
@@ -155,3 +171,15 @@ fun getNextVersion(version: String): String {
     if (dashIndex >= 0) out.append(version, dashIndex, version.length)
     return out.toString()
 }
+
+/**
+ * Capitalise the first letter of the string.
+ *
+ * This is a replacement for the now deprecated [String.capitalize].
+ */
+fun String.capitalise(): String {
+    if (isEmpty()) return this
+    val first = this[0]
+    val firstTitle = first.titlecaseChar()
+    return if (first == firstTitle) this else firstTitle + substring(1)
+}

buildSrc/src/main/kotlin/cc/tweaked/gradle/ForgeExtensions.kt

@@ -1,62 +0,0 @@
-// SPDX-FileCopyrightText: 2023 The CC: Tweaked Developers
-//
-// SPDX-License-Identifier: MPL-2.0
-
-package cc.tweaked.gradle
-
-import net.neoforged.gradle.common.runs.run.RunImpl
-import net.neoforged.gradle.common.runs.tasks.RunExec
-import net.neoforged.gradle.dsl.common.extensions.RunnableSourceSet
-import net.neoforged.gradle.dsl.common.runs.run.Run
-import org.gradle.api.plugins.JavaPluginExtension
-import org.gradle.api.tasks.JavaExec
-import org.gradle.api.tasks.SourceSet
-import org.gradle.jvm.toolchain.JavaToolchainService
-import org.gradle.kotlin.dsl.assign
-import org.gradle.kotlin.dsl.create
-import org.gradle.kotlin.dsl.findByType
-import java.nio.file.Files
-
-/**
- * Set [JavaExec] task to run a given [RunConfig].
- *
- * See also [RunExec].
- */
-fun JavaExec.setRunConfig(config: Run) {
-    mainClass.set(config.mainClass)
-    workingDir = config.workingDirectory.get().asFile
-    argumentProviders.add { config.programArguments.get() }
-    jvmArgumentProviders.add { config.jvmArguments.get() }
-
-    environment(config.environmentVariables.get())
-    systemProperties(config.systemProperties.get())
-
-    config.modSources.all().get().values().forEach { classpath(it.runtimeClasspath) }
-    classpath(config.classpath)
-    classpath(config.dependencies.get().runtimeConfiguration)
-
-    (config as RunImpl).taskDependencies.forEach { dependsOn(it) }
-
-    javaLauncher.set(
-        project.extensions.getByType(JavaToolchainService::class.java)
-            .launcherFor(project.extensions.getByType(JavaPluginExtension::class.java).toolchain),
-    )
-
-    doFirst("Create working directory") { Files.createDirectories(workingDir.toPath()) }
-}
-
-/**
- * Add a new [Run.modSource] with a specific mod id.
- */
-fun Run.modSourceAs(sourceSet: SourceSet, mod: String) {
-    // NeoGradle requires a RunnableSourceSet to be present, so we inject it into other project's source sets.
-    val runnable = sourceSet.extensions.findByType<RunnableSourceSet>() ?: run {
-        val extension = sourceSet.extensions.create<RunnableSourceSet>(RunnableSourceSet.NAME, project)
-        extension.modIdentifier = mod
-        extension.modIdentifier.finalizeValueOnRead()
-        extension
-    }
-    if (runnable.modIdentifier.get() != mod) throw IllegalArgumentException("Multiple mod identifiers")
-
-    modSource(sourceSet)
-}

doc/guides/speaker_audio.md

@@ -191,7 +191,7 @@ end
 
 > [Confused?][!NOTE]
 > Don't worry if you don't understand this example. It's quite advanced, and does use some ideas that this guide doesn't
-> cover. That said, don't be afraid to ask on [GitHub Discussions] or [IRC] either!
+> cover. That said, don't be afraid to ask [the community for help][community].
 
 It's worth noting that the examples of audio processing we've mentioned here are about manipulating the _amplitude_ of
 the wave. If you wanted to modify the _frequency_ (for instance, shifting the pitch), things get rather more complex.
@@ -205,5 +205,4 @@ This is, I'm afraid, left as an exercise to the reader.
 [PCM]: https://en.wikipedia.org/wiki/Pulse-code_modulation "Pulse-code Modulation - Wikipedia"
 [Ring Buffer]: https://en.wikipedia.org/wiki/Circular_buffer "Circular buffer - Wikipedia"
 [Sine Wave]: https://en.wikipedia.org/wiki/Sine_wave "Sine wave - Wikipedia"
-[GitHub Discussions]: https://github.com/cc-tweaked/CC-Tweaked/discussions
-[IRC]: https://webchat.esper.net/?channels=computercraft "#computercraft on EsperNet"
+[Community]: /#community

doc/index.md

@@ -50,7 +50,11 @@ little daunting getting started. Thankfully, there's several fantastic tutorials
 Once you're a little more familiar with the mod, the sidebar and links below provide more detailed documentation on the
 various APIs and peripherals provided by the mod.
 
-If you get stuck, do [ask a question on GitHub][GitHub Discussions] or pop in to the ComputerCraft's [IRC channel][IRC].
+<h2 id="community">Community</h2>
+If you need help getting started with CC: Tweaked, want to show off your latest project, or just want to chat about
+ComputerCraft, do check out our [GitHub discussions page][GitHub discussions]! There's also a fairly populated,
+albeit quiet IRC channel on [EsperNet], if that's more your cup of tea. You can join `#computercraft` through your
+desktop client, or online using [KiwiIRC].
 
 ## Get Involved
 CC: Tweaked lives on [GitHub]. If you've got any ideas, feedback or bugs please do [create an issue][bug].
@@ -65,4 +69,5 @@ CC: Tweaked lives on [GitHub]. If you've got any ideas, feedback or bugs please
 [Fabric]: https://fabricmc.net/use/installer/ "Download Fabric."
 [lua]: https://www.lua.org/ "Lua's main website"
 [GitHub Discussions]: https://github.com/cc-tweaked/CC-Tweaked/discussions
-[IRC]: https://webchat.esper.net/?channels=computercraft "#computercraft on EsperNet"
+[EsperNet]: https://www.esper.net/
+[KiwiIRC]: https://kiwiirc.com/nextclient/#irc://irc.esper.net:+6697/#computercraft "#computercraft on EsperNet"

doc/mod-page.md

@@ -50,7 +50,11 @@ little daunting getting started. Thankfully, there's several fantastic tutorials
 Once you're a little more familiar with the mod, the [wiki](https://tweaked.cc/) provides more detailed documentation on the
 various APIs and peripherals provided by the mod.
 
-If you get stuck, do [ask a question on GitHub][GitHub Discussions] or pop in to the ComputerCraft's [IRC channel][IRC].
+## Community
+If you need help getting started with CC: Tweaked, want to show off your latest project, or just want to chat about
+ComputerCraft, do check out our [GitHub discussions page][GitHub discussions]! There's also a fairly populated,
+albeit quiet IRC channel on [EsperNet], if that's more your cup of tea. You can join `#computercraft` through your
+desktop client, or online using [KiwiIRC].
 
 ## Get Involved
 CC: Tweaked lives on [GitHub]. If you've got any ideas, feedback or bugs please do [create an issue][bug].
@@ -60,4 +64,5 @@ CC: Tweaked lives on [GitHub]. If you've got any ideas, feedback or bugs please
 [computercraft]: https://github.com/dan200/ComputerCraft "ComputerCraft on GitHub"
 [lua]: https://www.lua.org/ "Lua's main website"
 [GitHub Discussions]: https://github.com/cc-tweaked/CC-Tweaked/discussions
-[IRC]: http://webchat.esper.net/?channels=computercraft "#computercraft on EsperNet"
+[EsperNet]: https://www.esper.net/
+[KiwiIRC]: https://kiwiirc.com/nextclient/#irc://irc.esper.net:+6697/#computercraft "#computercraft on EsperNet"

doc/reference/breaking_changes.md

@@ -25,13 +25,13 @@ as documentation for breaking changes and "gotchas" one should look out for betw
 
  - Update to Lua 5.2:
    - Support for Lua 5.0's pseudo-argument `arg` has been removed. You should always use `...` for varargs.
-   - Environments are no longer baked into the runtime, and instead use the `_ENV` local or upvalue. `getfenv`/`setfenv`
-     now only work on Lua functions with an `_ENV` upvalue. `getfenv` will return the global environment when called
-     with other functions, and `setfenv` will have no effect.
-   - `load`/`loadstring` defaults to using the global environment (`_G`) rather than the current coroutine's
+   - Environments are no longer baked into the runtime, and instead use the `_ENV` local or upvalue. [`getfenv`]/[`setfenv`]
+     now only work on Lua functions with an `_ENV` upvalue. [`getfenv`] will return the global environment when called
+     with other functions, and [`setfenv`] will have no effect.
+   - [`load`]/[`loadstring`] defaults to using the global environment (`_G`) rather than the current coroutine's
      environment.
-   - Support for dumping functions (`string.dump`) and loading binary chunks has been removed.
-   - `math.random` now uses Lua 5.4's random number generator.
+   - Support for dumping functions ([`string.dump`]) and loading binary chunks has been removed.
+   - [`math.random`] now uses Lua 5.4's random number generator.
 
  - File handles, HTTP requests and websockets now always use the original bytes rather than encoding/decoding to UTF-8.
 
@@ -44,7 +44,7 @@ as documentation for breaking changes and "gotchas" one should look out for betw
    `keys.enter` constant was queued when the key was pressed)
 
  - Minecraft 1.13 removed the concept of item damage and block metadata (see ["The Flattening"][flattening]). As a
-   result `turtle.inspect` no longer provides block metadata, and `turtle.getItemDetail` no longer provides damage.
+   result [`turtle.inspect`] no longer provides block metadata, and [`turtle.getItemDetail`] no longer provides damage.
 
    - Block states (`turtle.inspect().state`) should provide all the same information as block metadata, but in a much
      more understandable format.
@@ -70,7 +70,7 @@ as documentation for breaking changes and "gotchas" one should look out for betw
  - Unlabelled computers and turtles now keep their ID when broken, meaning that unlabelled computers/items do not stack.
 
 ## ComputerCraft 1.80pr1 {#cc-1.80}
- - Programs run via `shell.run` are now started in their own isolated environment. This means globals set by programs
+ - Programs run via [`shell.run`] are now started in their own isolated environment. This means globals set by programs
    will not be accessible outside of this program.
 
  - Programs containing `/` are looked up in the current directory and are no longer looked up on the path. For instance,

gradle.properties

@@ -12,7 +12,7 @@ neogradle.subsystems.conventions.runs.enabled=false
 
 # Mod properties
 isUnstable=true
-modVersion=1.111.0
+modVersion=1.113.0
 
 # Minecraft properties: We want to configure this here so we can read it in settings.gradle
-mcVersion=1.21
+mcVersion=1.21.1

gradle/gradle-daemon-jvm.properties

@@ -0,0 +1,2 @@
+#This file is generated by updateDaemonJvm
+toolchainVersion=21

gradle/libs.versions.toml

@@ -7,14 +7,14 @@
 # Minecraft
 # MC version is specified in gradle.properties, as we need that in settings.gradle.
 # Remember to update corresponding versions in fabric.mod.json/neoforge.mods.toml
-fabric-api = "0.100.3+1.21"
+fabric-api = "0.102.1+1.21.1"
 fabric-loader = "0.15.11"
-neoForge = "21.0.21-beta"
+neoForge = "21.1.9"
 neoForgeSpi = "8.0.1"
 mixin = "0.8.5"
-parchment = "2024.06.16"
-parchmentMc = "1.20.6"
-yarn = "1.21+build.1"
+parchment = "2024.07.28"
+parchmentMc = "1.21"
+yarn = "1.21.1+build.1"
 
 # Core dependencies (these versions are tied to the version Minecraft uses)
 fastutil = "8.5.12"
@@ -39,7 +39,7 @@ nightConfig = "3.6.7"
 emi = "1.1.7+1.21"
 fabricPermissions = "0.3.1"
 iris = "1.6.14+1.20.4"
-jei = "19.0.0.1"
+jei = "19.8.2.99"
 modmenu = "11.0.0-rc.4"
 moreRed = "4.0.0.4"
 oculus = "1.2.5"
@@ -47,6 +47,8 @@ rei = "16.0.729"
 rubidium = "0.6.1"
 sodium = "mc1.20-0.4.10"
 mixinExtra = "0.3.5"
+create-forge = "0.5.1.f-33"
+create-fabric = "0.5.1-f-build.1467+mc1.20.1"
 
 # Testing
 hamcrest = "2.2"
@@ -60,18 +62,18 @@ checkstyle = "10.14.1"
 curseForgeGradle = "1.1.18"
 errorProne-core = "2.27.0"
 errorProne-plugin = "3.1.0"
-fabric-loom = "1.6.7"
+fabric-loom = "1.7.1"
 githubRelease = "2.5.2"
 gradleVersions = "0.50.0"
 ideaExt = "1.1.7"
 illuaminate = "0.1.0-73-g43ee16c"
 lwjgl = "3.3.3"
 minotaur = "2.8.7"
-neoGradle = "7.0.145"
+neoGradle = "7.0.152"
 nullAway = "0.10.25"
 spotless = "6.23.3"
 taskTree = "2.1.1"
-teavm = "0.10.0-SQUID.4"
+teavm = "0.11.0-SQUID.1"
 vanillaExtract = "0.1.3"
 versionCatalogUpdate = "0.8.1"
 
@@ -100,11 +102,13 @@ nightConfig-toml = { module = "com.electronwill.night-config:toml", version.ref
 slf4j = { module = "org.slf4j:slf4j-api", version.ref = "slf4j" }
 
 # Minecraft mods
-fabric-api = { module = "net.fabricmc.fabric-api:fabric-api", version.ref = "fabric-api" }
-fabric-loader = { module = "net.fabricmc:fabric-loader", version.ref = "fabric-loader" }
-fabric-junit = { module = "net.fabricmc:fabric-loader-junit", version.ref = "fabric-loader" }
-fabricPermissions = { module = "me.lucko:fabric-permissions-api", version.ref = "fabricPermissions" }
+create-fabric = { module = "com.simibubi.create:create-fabric-1.20.1", version.ref = "create-fabric" }
+create-forge = { module = "com.simibubi.create:create-1.20.1", version.ref = "create-forge" }
 emi = { module = "dev.emi:emi-xplat-mojmap", version.ref = "emi" }
+fabric-api = { module = "net.fabricmc.fabric-api:fabric-api", version.ref = "fabric-api" }
+fabric-junit = { module = "net.fabricmc:fabric-loader-junit", version.ref = "fabric-loader" }
+fabric-loader = { module = "net.fabricmc:fabric-loader", version.ref = "fabric-loader" }
+fabricPermissions = { module = "me.lucko:fabric-permissions-api", version.ref = "fabricPermissions" }
 iris = { module = "maven.modrinth:iris", version.ref = "iris" }
 jei-api = { module = "mezz.jei:jei-1.21-common-api", version.ref = "jei" }
 jei-fabric = { module = "mezz.jei:jei-1.21-fabric", version.ref = "jei" }

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.7-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.10-bin.zip
 networkTimeout=10000
 validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME

gradlew

@@ -15,6 +15,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
+# SPDX-License-Identifier: Apache-2.0
+#
 
 ##############################################################################
 #
@@ -55,7 +57,7 @@
 #       Darwin, MinGW, and NonStop.
 #
 #   (3) This script is generated from the Groovy template
-#       https://github.com/gradle/gradle/blob/HEAD/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       https://github.com/gradle/gradle/blob/HEAD/platforms/jvm/plugins-application/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
 #       within the Gradle project.
 #
 #       You can find Gradle at https://github.com/gradle/gradle/.
@@ -84,7 +86,8 @@ done
 # shellcheck disable=SC2034
 APP_BASE_NAME=${0##*/}
 # Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
-APP_HOME=$( cd "${APP_HOME:-./}" > /dev/null && pwd -P ) || exit
+APP_HOME=$( cd -P "${APP_HOME:-./}" > /dev/null && printf '%s
+' "$PWD" ) || exit
 
 # Use the maximum available, or set MAX_FD != -1 to use that value.
 MAX_FD=maximum

gradlew.bat

@@ -13,6 +13,8 @@
 @rem See the License for the specific language governing permissions and
 @rem limitations under the License.
 @rem
+@rem SPDX-License-Identifier: Apache-2.0
+@rem
 
 @if "%DEBUG%"=="" @echo off
 @rem ##########################################################################

projects/common-api/src/main/java/dan200/computercraft/api/ComputerCraftAPI.java

@@ -4,9 +4,11 @@
 
 package dan200.computercraft.api;
 
+import dan200.computercraft.api.component.ComputerComponent;
 import dan200.computercraft.api.filesystem.Mount;
 import dan200.computercraft.api.filesystem.WritableMount;
 import dan200.computercraft.api.lua.GenericSource;
+import dan200.computercraft.api.lua.IComputerSystem;
 import dan200.computercraft.api.lua.ILuaAPI;
 import dan200.computercraft.api.lua.ILuaAPIFactory;
 import dan200.computercraft.api.media.IMedia;
@@ -165,7 +167,20 @@ public final class ComputerCraftAPI {
      * Register a custom {@link ILuaAPI}, which may be added onto all computers without requiring a peripheral.
      * <p>
      * Before implementing this interface, consider alternative methods of providing methods. It is generally preferred
-     * to use peripherals to provide functionality to users.
+     * to use peripherals to provide functionality to users. If an API is <em>required</em>, you may want to consider
+     * using {@link ILuaAPI#getModuleName()} to expose this library as a module instead of as a global.
+     * <p>
+     * This may be used with {@link IComputerSystem#getComponent(ComputerComponent)} to only attach APIs to specific
+     * computers. For example, one can add an additional API just to turtles with the following code:
+     *
+     * <pre>{@code
+     * ComputerCraftAPI.registerAPIFactory(computer -> {
+     *   // Read the turtle component.
+     *   var turtle = computer.getComponent(ComputerComponents.TURTLE);
+     *   // If present then add our API.
+     *   return turtle == null ? null : new MyCustomTurtleApi(turtle);
+     * });
+     * }</pre>
      *
      * @param factory The factory for your API subclass.
      * @see ILuaAPIFactory

projects/common-api/src/main/java/dan200/computercraft/api/component/AdminComputer.java

@@ -0,0 +1,24 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.api.component;
+
+import net.minecraft.commands.CommandSourceStack;
+import org.jetbrains.annotations.ApiStatus;
+
+/**
+ * A computer which has permission to perform administrative/op commands, such as the command computer.
+ */
+@ApiStatus.NonExtendable
+public interface AdminComputer {
+    /**
+     * The permission level that this computer can operate at.
+     *
+     * @return The permission level for this computer.
+     * @see CommandSourceStack#hasPermission(int)
+     */
+    default int permissionLevel() {
+        return 2;
+    }
+}

projects/common-api/src/main/java/dan200/computercraft/api/component/ComputerComponent.java

@@ -0,0 +1,48 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.api.component;
+
+import dan200.computercraft.api.lua.IComputerSystem;
+import dan200.computercraft.api.lua.ILuaAPIFactory;
+
+/**
+ * A component attached to a computer.
+ * <p>
+ * Components provide a mechanism to attach additional data to a computer, that can then be queried with
+ * {@link IComputerSystem#getComponent(ComputerComponent)}.
+ * <p>
+ * This is largely designed for {@linkplain ILuaAPIFactory custom APIs}, allowing APIs to read additional properties
+ * of the computer, such as its position.
+ *
+ * @param <T> The type of this component.
+ * @see ComputerComponents The built-in components.
+ */
+@SuppressWarnings("UnusedTypeParameter")
+public final class ComputerComponent<T> {
+    private final String id;
+
+    private ComputerComponent(String id) {
+        this.id = id;
+    }
+
+    /**
+     * Create a new computer component.
+     * <p>
+     * Mods typically will not need to create their own components.
+     *
+     * @param namespace The namespace of this component. This should be the mod id.
+     * @param id        The unique id of this component.
+     * @param <T>       The component
+     * @return The newly created component.
+     */
+    public static <T> ComputerComponent<T> create(String namespace, String id) {
+        return new ComputerComponent<>(namespace + ":" + id);
+    }
+
+    @Override
+    public String toString() {
+        return "ComputerComponent(" + id + ")";
+    }
+}

projects/common-api/src/main/java/dan200/computercraft/api/component/ComputerComponents.java

@@ -0,0 +1,29 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.api.component;
+
+import dan200.computercraft.api.ComputerCraftAPI;
+import dan200.computercraft.api.pocket.IPocketAccess;
+import dan200.computercraft.api.turtle.ITurtleAccess;
+
+/**
+ * The {@link ComputerComponent}s provided by ComputerCraft.
+ */
+public class ComputerComponents {
+    /**
+     * The {@link ITurtleAccess} associated with a turtle.
+     */
+    public static final ComputerComponent<ITurtleAccess> TURTLE = ComputerComponent.create(ComputerCraftAPI.MOD_ID, "turtle");
+
+    /**
+     * The {@link IPocketAccess} associated with a pocket computer.
+     */
+    public static final ComputerComponent<IPocketAccess> POCKET = ComputerComponent.create(ComputerCraftAPI.MOD_ID, "pocket");
+
+    /**
+     * This component is only present on "command computers", and other computers with admin capabilities.
+     */
+    public static final ComputerComponent<AdminComputer> ADMIN_COMPUTER = ComputerComponent.create(ComputerCraftAPI.MOD_ID, "admin_computer");
+}

projects/common-api/src/main/java/dan200/computercraft/api/detail/BasicItemDetailProvider.java

@@ -13,7 +13,7 @@ import java.util.Map;
 import java.util.Objects;
 
 /**
- * An item detail provider for {@link ItemStack}'s whose {@link Item} has a specific type.
+ * An item detail provider for {@link ItemStack}s whose {@link Item} has a specific type.
  *
  * @param <T> The type the stack's item must have.
  */
@@ -22,7 +22,7 @@ public abstract class BasicItemDetailProvider<T> implements DetailProvider<ItemS
     private final @Nullable String namespace;
 
     /**
-     * Create a new item detail provider. Meta will be inserted into a new sub-map named as per {@code namespace}.
+     * Create a new item detail provider. Details will be inserted into a new sub-map named as per {@code namespace}.
      *
      * @param itemType  The type the stack's item must have.
      * @param namespace The namespace to use for this provider.
@@ -34,7 +34,7 @@ public abstract class BasicItemDetailProvider<T> implements DetailProvider<ItemS
     }
 
     /**
-     * Create a new item detail provider. Meta will be inserted directly into the results.
+     * Create a new item detail provider. Details will be inserted directly into the results.
      *
      * @param itemType The type the stack's item must have.
      */
@@ -53,21 +53,18 @@ public abstract class BasicItemDetailProvider<T> implements DetailProvider<ItemS
      * @param stack The item stack to provide details for.
      * @param item  The item to provide details for.
      */
-    public abstract void provideDetails(
-        Map<? super String, Object> data, ItemStack stack, T item
-    );
+    public abstract void provideDetails(Map<? super String, Object> data, ItemStack stack, T item);
 
     @Override
-    public void provideDetails(Map<? super String, Object> data, ItemStack stack) {
+    public final void provideDetails(Map<? super String, Object> data, ItemStack stack) {
         var item = stack.getItem();
         if (!itemType.isInstance(item)) return;
 
-        // If `namespace` is specified, insert into a new data map instead of the existing one.
-        Map<? super String, Object> child = namespace == null ? data : new HashMap<>();
-
-        provideDetails(child, stack, itemType.cast(item));
-
-        if (namespace != null) {
+        if (namespace == null) {
+            provideDetails(data, stack, itemType.cast(item));
+        } else {
+            Map<? super String, Object> child = new HashMap<>();
+            provideDetails(child, stack, itemType.cast(item));
             data.put(namespace, child);
         }
     }

projects/common-api/src/main/java/dan200/computercraft/api/detail/ComponentDetailProvider.java

@@ -0,0 +1,72 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.api.detail;
+
+import net.minecraft.core.component.DataComponentHolder;
+import net.minecraft.core.component.DataComponentType;
+import net.minecraft.world.item.ItemStack;
+
+import javax.annotation.Nullable;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+
+/**
+ * An item detail provider for a specific {@linkplain DataComponentType data component} on {@link ItemStack}s or
+ * other {@link DataComponentHolder}.
+ *
+ * @param <T> The type of the component's contents.
+ */
+public abstract class ComponentDetailProvider<T> implements DetailProvider<DataComponentHolder> {
+    private final DataComponentType<T> component;
+    private final @Nullable String namespace;
+
+    /**
+     * Create a new component detail provider. Details will be inserted into a new sub-map named as per {@code namespace}.
+     *
+     * @param component The data component to provide details for.
+     * @param namespace The namespace to use for this provider.
+     */
+    public ComponentDetailProvider(@Nullable String namespace, DataComponentType<T> component) {
+        Objects.requireNonNull(component);
+        this.component = component;
+        this.namespace = namespace;
+    }
+
+    /**
+     * Create a new component detail provider. Details will be inserted directly into the results.
+     *
+     * @param component The data component to provide details for.
+     */
+    public ComponentDetailProvider(DataComponentType<T> component) {
+        this(null, component);
+    }
+
+    /**
+     * Provide additional details for the given data component. This method is called by {@code turtle.getItemDetail()}.
+     * New properties should be added to the given {@link Map}, {@code data}.
+     * <p>
+     * This method is always called on the server thread, so it is safe to interact with the world here, but you should
+     * take care to avoid long blocking operations as this will stall the server and other computers.
+     *
+     * @param data The full details to be returned for this item stack. New properties should be added to this map.
+     * @param item The component to provide details for.
+     */
+    public abstract void provideComponentDetails(Map<? super String, Object> data, T item);
+
+    @Override
+    public final void provideDetails(Map<? super String, Object> data, DataComponentHolder holder) {
+        var value = holder.get(component);
+        if (value == null) return;
+
+        if (namespace == null) {
+            provideComponentDetails(data, value);
+        } else {
+            Map<? super String, Object> child = new HashMap<>();
+            provideComponentDetails(child, value);
+            data.put(namespace, child);
+        }
+    }
+}

projects/common-api/src/main/java/dan200/computercraft/api/detail/DetailRegistry.java

@@ -26,7 +26,7 @@ public interface DetailRegistry<T> {
      * @param provider The detail provider to register.
      * @see DetailProvider
      */
-    void addProvider(DetailProvider<T> provider);
+    void addProvider(DetailProvider<? super T> provider);
 
     /**
      * Compute basic details about an object. This is cheaper than computing all details operation, and so is suitable

projects/common-api/src/main/java/dan200/computercraft/api/lua/IComputerSystem.java

@@ -0,0 +1,59 @@
+// SPDX-FileCopyrightText: 2017 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.api.lua;
+
+import dan200.computercraft.api.component.ComputerComponent;
+import dan200.computercraft.api.peripheral.IComputerAccess;
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.level.ServerLevel;
+import org.jetbrains.annotations.ApiStatus;
+
+import javax.annotation.Nullable;
+
+/**
+ * An interface passed to {@link ILuaAPIFactory} in order to provide additional information
+ * about a computer.
+ */
+@ApiStatus.NonExtendable
+public interface IComputerSystem extends IComputerAccess {
+    /**
+     * Get the level this computer is currently in.
+     * <p>
+     * This method is not guaranteed to remain the same (even for stationary computers).
+     *
+     * @return The computer's current level.
+     */
+    ServerLevel getLevel();
+
+    /**
+     * Get the position this computer is currently at.
+     * <p>
+     * This method is not guaranteed to remain the same (even for stationary computers).
+     *
+     * @return The computer's current position.
+     */
+    BlockPos getPosition();
+
+    /**
+     * Get the label for this computer.
+     *
+     * @return This computer's label, or {@code null} if it is not set.
+     */
+    @Nullable
+    String getLabel();
+
+    /**
+     * Get a component attached to this computer.
+     * <p>
+     * No component is guaranteed to be on a computer, and so this method should always be guarded with a null check.
+     * <p>
+     * This method will always return the same value for a given component, and so may be cached.
+     *
+     * @param component The component to query.
+     * @param <T>       The type of the component.
+     * @return The component, if present.
+     */
+    <T> @Nullable T getComponent(ComputerComponent<T> component);
+}

projects/common-api/src/main/java/dan200/computercraft/api/lua/ILuaAPIFactory.java

@@ -4,13 +4,15 @@
 
 package dan200.computercraft.api.lua;
 
+import dan200.computercraft.api.ComputerCraftAPI;
+
 import javax.annotation.Nullable;
 
 /**
- * Construct an {@link ILuaAPI} for a specific computer.
+ * Construct an {@link ILuaAPI} for a computer.
  *
  * @see ILuaAPI
- * @see dan200.computercraft.api.ComputerCraftAPI#registerAPIFactory(ILuaAPIFactory)
+ * @see ComputerCraftAPI#registerAPIFactory(ILuaAPIFactory)
  */
 @FunctionalInterface
 public interface ILuaAPIFactory {

projects/common-api/src/main/java/dan200/computercraft/api/pocket/IPocketAccess.java

@@ -5,16 +5,35 @@
 package dan200.computercraft.api.pocket;
 
 import dan200.computercraft.api.upgrades.UpgradeBase;
+import dan200.computercraft.api.upgrades.UpgradeData;
 import net.minecraft.core.component.DataComponentPatch;
+import net.minecraft.server.level.ServerLevel;
 import net.minecraft.world.entity.Entity;
 import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.phys.Vec3;
+import org.jetbrains.annotations.ApiStatus;
 
 import javax.annotation.Nullable;
 
 /**
  * Wrapper class for pocket computers.
  */
+@ApiStatus.NonExtendable
 public interface IPocketAccess {
+    /**
+     * Get the level in which the pocket computer exists.
+     *
+     * @return The pocket computer's level.
+     */
+    ServerLevel getLevel();
+
+    /**
+     * Get the position of the pocket computer.
+     *
+     * @return The pocket computer's position.
+     */
+    Vec3 getPosition();
+
     /**
      * Gets the entity holding this item.
      * <p>
@@ -61,6 +80,26 @@ public interface IPocketAccess {
      */
     void setLight(int colour);
 
+    /**
+     * Get the currently equipped upgrade.
+     *
+     * @return The currently equipped upgrade.
+     * @see #getUpgradeData()
+     * @see #setUpgrade(UpgradeData)
+     */
+    @Nullable
+    UpgradeData<IPocketUpgrade> getUpgrade();
+
+    /**
+     * Set the upgrade for this pocket computer, also updating the item stack.
+     * <p>
+     * Note this method is not thread safe - it must be called from the server thread.
+     *
+     * @param upgrade The new upgrade to set it to, may be {@code null}.
+     * @see #getUpgrade()
+     */
+    void setUpgrade(@Nullable UpgradeData<IPocketUpgrade> upgrade);
+
     /**
      * Get the upgrade-specific NBT.
      * <p>
@@ -70,6 +109,7 @@ public interface IPocketAccess {
      * @see #setUpgradeData(DataComponentPatch)
      * @see UpgradeBase#getUpgradeItem(DataComponentPatch)
      * @see UpgradeBase#getUpgradeData(ItemStack)
+     * @see #getUpgrade()
      */
     DataComponentPatch getUpgradeData();
 

projects/common-api/src/main/java/dan200/computercraft/api/turtle/TurtleSide.java

@@ -5,7 +5,7 @@
 package dan200.computercraft.api.turtle;
 
 /**
- * An enum representing the two sides of the turtle that a turtle turtle might reside.
+ * An enum representing the two sides of the turtle that a turtle upgrade might reside.
  */
 public enum TurtleSide {
     /**

projects/common/build.gradle.kts

@@ -45,6 +45,7 @@ dependencies {
     compileOnly(libs.mixin)
     compileOnly(libs.mixinExtra)
     compileOnly(libs.bundles.externalMods.common)
+    compileOnly(variantOf(libs.create.forge) { classifier("slim") }) { isTransitive = false }
     clientCompileOnly(variantOf(libs.emi) { classifier("api") })
 
     annotationProcessorEverywhere(libs.autoService)

projects/common/src/client/java/dan200/computercraft/client/ClientRegistry.java

@@ -13,6 +13,7 @@ import dan200.computercraft.api.client.turtle.RegisterTurtleUpgradeModeller;
 import dan200.computercraft.api.client.turtle.TurtleUpgradeModeller;
 import dan200.computercraft.client.gui.*;
 import dan200.computercraft.client.pocket.ClientPocketComputers;
+import dan200.computercraft.client.render.CustomLecternRenderer;
 import dan200.computercraft.client.render.RenderTypes;
 import dan200.computercraft.client.render.TurtleBlockEntityRenderer;
 import dan200.computercraft.client.render.monitor.MonitorBlockEntityRenderer;
@@ -25,6 +26,7 @@ import dan200.computercraft.shared.computer.core.ComputerState;
 import dan200.computercraft.shared.computer.core.ServerContext;
 import dan200.computercraft.shared.computer.inventory.AbstractComputerMenu;
 import dan200.computercraft.shared.media.items.DiskItem;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
 import net.minecraft.Util;
 import net.minecraft.client.Minecraft;
 import net.minecraft.client.color.item.ItemColor;
@@ -53,6 +55,7 @@ import net.minecraft.world.level.ItemLike;
 import javax.annotation.Nullable;
 import java.io.File;
 import java.io.IOException;
+import java.util.Collection;
 import java.util.function.BiConsumer;
 import java.util.function.Consumer;
 import java.util.function.Supplier;
@@ -77,6 +80,7 @@ public final class ClientRegistry {
         BlockEntityRenderers.register(ModRegistry.BlockEntities.MONITOR_ADVANCED.get(), MonitorBlockEntityRenderer::new);
         BlockEntityRenderers.register(ModRegistry.BlockEntities.TURTLE_NORMAL.get(), TurtleBlockEntityRenderer::new);
         BlockEntityRenderers.register(ModRegistry.BlockEntities.TURTLE_ADVANCED.get(), TurtleBlockEntityRenderer::new);
+        BlockEntityRenderers.register(ModRegistry.BlockEntities.LECTERN.get(), CustomLecternRenderer::new);
     }
 
     /**
@@ -143,15 +147,14 @@ public final class ClientRegistry {
         register.accept(GuiSprites.initialise(minecraft.getTextureManager()));
     }
 
-    private static final String[] EXTRA_MODELS = new String[]{
-        "block/turtle_colour",
-        "block/turtle_elf_overlay",
-        "block/turtle_rainbow_overlay",
-        "block/turtle_trans_overlay",
+    private static final ResourceLocation[] EXTRA_MODELS = {
+        TurtleOverlay.ELF_MODEL,
+        TurtleBlockEntityRenderer.COLOUR_TURTLE_MODEL,
     };
 
-    public static void registerExtraModels(Consumer<ResourceLocation> register) {
-        for (var model : EXTRA_MODELS) register.accept(ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, model));
+    public static void registerExtraModels(Consumer<ResourceLocation> register, Collection<ResourceLocation> extraModels) {
+        for (var model : EXTRA_MODELS) register.accept(model);
+        extraModels.forEach(register);
         TurtleUpgradeModellers.getDependencies().forEach(register);
     }
 

projects/common/src/client/java/dan200/computercraft/client/gui/PrintoutScreen.java

@@ -6,15 +6,19 @@ package dan200.computercraft.client.gui;
 
 import dan200.computercraft.core.terminal.TextBuffer;
 import dan200.computercraft.shared.ModRegistry;
-import dan200.computercraft.shared.common.HeldItemMenu;
+import dan200.computercraft.shared.media.PrintoutMenu;
 import dan200.computercraft.shared.media.items.PrintoutData;
-import dan200.computercraft.shared.media.items.PrintoutItem;
 import net.minecraft.client.gui.GuiGraphics;
 import net.minecraft.client.gui.screens.inventory.AbstractContainerScreen;
 import net.minecraft.network.chat.Component;
 import net.minecraft.world.entity.player.Inventory;
+import net.minecraft.world.inventory.AbstractContainerMenu;
+import net.minecraft.world.inventory.ContainerListener;
+import net.minecraft.world.item.ItemStack;
 import org.lwjgl.glfw.GLFW;
 
+import java.util.Objects;
+
 import static dan200.computercraft.client.render.PrintoutRenderer.*;
 import static dan200.computercraft.client.render.RenderTypes.FULL_BRIGHT_LIGHTMAP;
 
@@ -23,41 +27,65 @@ import static dan200.computercraft.client.render.RenderTypes.FULL_BRIGHT_LIGHTMA
  *
  * @see dan200.computercraft.client.render.PrintoutRenderer
  */
-public class PrintoutScreen extends AbstractContainerScreen<HeldItemMenu> {
-    private final boolean book;
-    private final int pages;
-    private final TextBuffer[] text;
-    private final TextBuffer[] colours;
-    private int page;
+public final class PrintoutScreen extends AbstractContainerScreen<PrintoutMenu> implements ContainerListener {
+    private PrintoutInfo printout = PrintoutInfo.DEFAULT;
+    private int page = 0;
 
-    public PrintoutScreen(HeldItemMenu container, Inventory player, Component title) {
+    public PrintoutScreen(PrintoutMenu container, Inventory player, Component title) {
         super(container, player, title);
-
         imageHeight = Y_SIZE;
+    }
 
-        var printout = container.getStack().getOrDefault(ModRegistry.DataComponents.PRINTOUT.get(), PrintoutData.EMPTY);
-        this.text = new TextBuffer[printout.lines().size()];
-        this.colours = new TextBuffer[printout.lines().size()];
-        for (var i = 0; i < this.text.length; i++) {
-            var line = printout.lines().get(i);
-            this.text[i] = new TextBuffer(line.text());
-            this.colours[i] = new TextBuffer(line.foreground());
-        }
-
+    private void setPrintout(ItemStack stack) {
         page = 0;
-        pages = Math.max(this.text.length / PrintoutData.LINES_PER_PAGE, 1);
-        book = ((PrintoutItem) container.getStack().getItem()).getType() == PrintoutItem.Type.BOOK;
+        printout = PrintoutInfo.of(PrintoutData.getOrEmpty(stack), stack.is(ModRegistry.Items.PRINTED_BOOK.get()));
+    }
+
+    @Override
+    protected void init() {
+        super.init();
+        menu.addSlotListener(this);
+    }
+
+    @Override
+    public void removed() {
+        menu.removeSlotListener(this);
+    }
+
+    @Override
+    public void slotChanged(AbstractContainerMenu menu, int slot, ItemStack stack) {
+        if (slot == 0) setPrintout(stack);
+    }
+
+    @Override
+    public void dataChanged(AbstractContainerMenu menu, int slot, int data) {
+        if (slot == PrintoutMenu.DATA_CURRENT_PAGE) page = data;
+    }
+
+    private void setPage(int page) {
+        this.page = page;
+
+        var gameMode = Objects.requireNonNull(Objects.requireNonNull(minecraft).gameMode);
+        gameMode.handleInventoryButtonClick(menu.containerId, PrintoutMenu.PAGE_BUTTON_OFFSET + page);
+    }
+
+    private void previousPage() {
+        if (page > 0) setPage(page - 1);
+    }
+
+    private void nextPage() {
+        if (page < printout.pages() - 1) setPage(page + 1);
     }
 
     @Override
     public boolean keyPressed(int key, int scancode, int modifiers) {
         if (key == GLFW.GLFW_KEY_RIGHT) {
-            if (page < pages - 1) page++;
+            nextPage();
             return true;
         }
 
         if (key == GLFW.GLFW_KEY_LEFT) {
-            if (page > 0) page--;
+            previousPage();
             return true;
         }
 
@@ -69,13 +97,13 @@ public class PrintoutScreen extends AbstractContainerScreen<HeldItemMenu> {
         if (super.mouseScrolled(x, y, deltaX, deltaY)) return true;
         if (deltaY < 0) {
             // Scroll up goes to the next page
-            if (page < pages - 1) page++;
+            nextPage();
             return true;
         }
 
         if (deltaY > 0) {
             // Scroll down goes to the previous page
-            if (page > 0) page--;
+            previousPage();
             return true;
         }
 
@@ -88,8 +116,8 @@ public class PrintoutScreen extends AbstractContainerScreen<HeldItemMenu> {
         graphics.pose().pushPose();
         graphics.pose().translate(0, 0, 1);
 
-        drawBorder(graphics.pose(), graphics.bufferSource(), leftPos, topPos, 0, page, pages, book, FULL_BRIGHT_LIGHTMAP);
-        drawText(graphics.pose(), graphics.bufferSource(), leftPos + X_TEXT_MARGIN, topPos + Y_TEXT_MARGIN, PrintoutData.LINES_PER_PAGE * page, FULL_BRIGHT_LIGHTMAP, text, colours);
+        drawBorder(graphics.pose(), graphics.bufferSource(), leftPos, topPos, 0, page, printout.pages(), printout.book(), FULL_BRIGHT_LIGHTMAP);
+        drawText(graphics.pose(), graphics.bufferSource(), leftPos + X_TEXT_MARGIN, topPos + Y_TEXT_MARGIN, PrintoutData.LINES_PER_PAGE * page, FULL_BRIGHT_LIGHTMAP, printout.text(), printout.colour());
 
         graphics.pose().popPose();
     }
@@ -98,4 +126,21 @@ public class PrintoutScreen extends AbstractContainerScreen<HeldItemMenu> {
     protected void renderLabels(GuiGraphics graphics, int mouseX, int mouseY) {
         // Skip rendering labels.
     }
+
+    record PrintoutInfo(int pages, boolean book, TextBuffer[] text, TextBuffer[] colour) {
+        public static final PrintoutInfo DEFAULT = of(PrintoutData.EMPTY, false);
+
+        public static PrintoutInfo of(PrintoutData printout, boolean book) {
+            var text = new TextBuffer[printout.lines().size()];
+            var colours = new TextBuffer[printout.lines().size()];
+            for (var i = 0; i < text.length; i++) {
+                var line = printout.lines().get(i);
+                text[i] = new TextBuffer(line.text());
+                colours[i] = new TextBuffer(line.foreground());
+            }
+
+            var pages = Math.max(text.length / PrintoutData.LINES_PER_PAGE, 1);
+            return new PrintoutInfo(pages, book, text, colours);
+        }
+    }
 }

projects/common/src/client/java/dan200/computercraft/client/model/ExtraModels.java

@@ -0,0 +1,68 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.client.model;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonParseException;
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.JsonOps;
+import dan200.computercraft.api.ComputerCraftAPI;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.server.packs.resources.ResourceManager;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.*;
+
+/**
+ * A list of extra models to load on the client.
+ * <p>
+ * This is largely intended for use with {@linkplain TurtleOverlay turtle overlays}. As overlays are stored in a dynamic
+ * registry, they are not available when resources are loaded, and so we need a way to request the overlays' models be
+ * loaded.
+ *
+ * @param models The models to load.
+ */
+public record ExtraModels(List<ResourceLocation> models) {
+    private static final Logger LOG = LoggerFactory.getLogger(ExtraModels.class);
+    private static final Gson GSON = new Gson();
+
+    /**
+     * The path where the extra models are listed.
+     */
+    public static final ResourceLocation PATH = ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, "extra_models.json");
+
+    /**
+     * The coded used to store the extra model file.
+     */
+    public static final Codec<ExtraModels> CODEC = ResourceLocation.CODEC.listOf().xmap(ExtraModels::new, ExtraModels::models);
+
+    /**
+     * Get the list of all extra models to load.
+     *
+     * @param resources The current resource manager.
+     * @return A set of all resources to load.
+     */
+    public static Collection<ResourceLocation> loadAll(ResourceManager resources) {
+        Set<ResourceLocation> out = new HashSet<>();
+
+        for (var path : resources.getResourceStack(PATH)) {
+            ExtraModels models;
+            try (var stream = path.openAsReader()) {
+                models = ExtraModels.CODEC.parse(JsonOps.INSTANCE, GSON.fromJson(stream, JsonElement.class)).getOrThrow(JsonParseException::new);
+            } catch (IOException | RuntimeException e) {
+                LOG.error("Failed to load extra models from {}", path.sourcePackId());
+                continue;
+            }
+
+            out.addAll(models.models());
+        }
+
+        return Collections.unmodifiableCollection(out);
+    }
+}

projects/common/src/client/java/dan200/computercraft/client/model/LecternPrintoutModel.java

@@ -0,0 +1,117 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.client.model;
+
+import com.mojang.blaze3d.vertex.PoseStack;
+import com.mojang.blaze3d.vertex.VertexConsumer;
+import dan200.computercraft.api.ComputerCraftAPI;
+import dan200.computercraft.client.render.CustomLecternRenderer;
+import dan200.computercraft.shared.media.items.PrintoutItem;
+import net.minecraft.client.model.geom.ModelPart;
+import net.minecraft.client.model.geom.PartPose;
+import net.minecraft.client.model.geom.builders.CubeListBuilder;
+import net.minecraft.client.model.geom.builders.MeshDefinition;
+import net.minecraft.client.resources.model.Material;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.inventory.InventoryMenu;
+
+import java.util.List;
+
+/**
+ * A model for {@linkplain PrintoutItem printouts} placed on a lectern.
+ * <p>
+ * This provides two models, {@linkplain #renderPages(PoseStack, VertexConsumer, int, int, int) one for a variable
+ * number of pages}, and {@linkplain #renderBook(PoseStack, VertexConsumer, int, int) one for books}.
+ *
+ * @see CustomLecternRenderer
+ */
+public class LecternPrintoutModel {
+    public static final ResourceLocation TEXTURE = ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, "entity/printout");
+    public static final Material MATERIAL = new Material(InventoryMenu.BLOCK_ATLAS, TEXTURE);
+
+    private static final int TEXTURE_WIDTH = 32;
+    private static final int TEXTURE_HEIGHT = 32;
+
+    private static final String PAGE_1 = "page_1";
+    private static final String PAGE_2 = "page_2";
+    private static final String PAGE_3 = "page_3";
+    private static final List<String> PAGES = List.of(PAGE_1, PAGE_2, PAGE_3);
+
+    private final ModelPart pagesRoot;
+    private final ModelPart bookRoot;
+    private final ModelPart[] pages;
+
+    public LecternPrintoutModel() {
+        pagesRoot = buildPages();
+        bookRoot = buildBook();
+        pages = PAGES.stream().map(pagesRoot::getChild).toArray(ModelPart[]::new);
+    }
+
+    private static ModelPart buildPages() {
+        var mesh = new MeshDefinition();
+        var parts = mesh.getRoot();
+        parts.addOrReplaceChild(
+            PAGE_1,
+            CubeListBuilder.create().texOffs(0, 0).addBox(-0.005f, -4.0f, -2.5f, 1f, 8.0f, 5.0f),
+            PartPose.ZERO
+        );
+
+        parts.addOrReplaceChild(
+            PAGE_2,
+            CubeListBuilder.create().texOffs(12, 0).addBox(-0.005f, -4.0f, -2.5f, 1f, 8.0f, 5.0f),
+            PartPose.offsetAndRotation(-0.125f, 0, 1.5f, (float) Math.PI * (1f / 16), 0, 0)
+        );
+        parts.addOrReplaceChild(
+            PAGE_3,
+            CubeListBuilder.create().texOffs(12, 0).addBox(-0.005f, -4.0f, -2.5f, 1f, 8.0f, 5.0f),
+            PartPose.offsetAndRotation(-0.25f, 0, -1.5f, (float) -Math.PI * (2f / 16), 0, 0)
+        );
+
+        return mesh.getRoot().bake(TEXTURE_WIDTH, TEXTURE_HEIGHT);
+    }
+
+    private static ModelPart buildBook() {
+        var mesh = new MeshDefinition();
+        var parts = mesh.getRoot();
+
+        parts.addOrReplaceChild(
+            "spine",
+            CubeListBuilder.create().texOffs(12, 15).addBox(-0.005f, -5.0f, -0.5f, 0, 10, 1.0f),
+            PartPose.ZERO
+        );
+
+        var angle = (float) Math.toRadians(5);
+        parts.addOrReplaceChild(
+            "left",
+            CubeListBuilder.create()
+                .texOffs(0, 10).addBox(0, -5.0f, -6.0f, 0, 10, 6.0f)
+                .texOffs(0, 0).addBox(0.005f, -4.0f, -5.0f, 1.0f, 8.0f, 5.0f),
+            PartPose.offsetAndRotation(-0.005f, 0, -0.5f, 0, -angle, 0)
+        );
+
+        parts.addOrReplaceChild(
+            "right",
+            CubeListBuilder.create()
+                .texOffs(14, 10).addBox(0, -5.0f, 0, 0, 10, 6.0f)
+                .texOffs(0, 0).addBox(0.005f, -4.0f, 0, 1.0f, 8.0f, 5.0f),
+            PartPose.offsetAndRotation(-0.005f, 0, 0.5f, 0, angle, 0)
+        );
+
+        return mesh.getRoot().bake(TEXTURE_WIDTH, TEXTURE_HEIGHT);
+    }
+
+    public void renderBook(PoseStack poseStack, VertexConsumer buffer, int packedLight, int packedOverlay) {
+        bookRoot.render(poseStack, buffer, packedLight, packedOverlay);
+    }
+
+    public void renderPages(PoseStack poseStack, VertexConsumer buffer, int packedLight, int packedOverlay, int pageCount) {
+        if (pageCount > pages.length) pageCount = pages.length;
+        var i = 0;
+        for (; i < pageCount; i++) pages[i].visible = true;
+        for (; i < pages.length; i++) pages[i].visible = false;
+
+        pagesRoot.render(poseStack, buffer, packedLight, packedOverlay);
+    }
+}

projects/common/src/client/java/dan200/computercraft/client/model/turtle/TurtleModelParts.java

@@ -12,13 +12,14 @@ import dan200.computercraft.api.turtle.ITurtleUpgrade;
 import dan200.computercraft.api.turtle.TurtleSide;
 import dan200.computercraft.api.upgrades.UpgradeData;
 import dan200.computercraft.client.platform.ClientPlatformHelper;
-import dan200.computercraft.client.render.TurtleBlockEntityRenderer;
 import dan200.computercraft.client.turtle.TurtleUpgradeModellers;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
 import dan200.computercraft.shared.turtle.items.TurtleItem;
 import dan200.computercraft.shared.util.DataComponentUtil;
 import dan200.computercraft.shared.util.Holiday;
 import net.minecraft.client.Minecraft;
 import net.minecraft.client.resources.model.BakedModel;
+import net.minecraft.client.resources.model.ModelManager;
 import net.minecraft.core.component.DataComponents;
 import net.minecraft.resources.ResourceLocation;
 import net.minecraft.world.item.ItemStack;
@@ -52,7 +53,7 @@ public final class TurtleModelParts<T> {
         boolean colour,
         @Nullable UpgradeData<ITurtleUpgrade> leftUpgrade,
         @Nullable UpgradeData<ITurtleUpgrade> rightUpgrade,
-        @Nullable ResourceLocation overlay,
+        @Nullable TurtleOverlay overlay,
         boolean christmas,
         boolean flip
     ) {
@@ -113,10 +114,10 @@ public final class TurtleModelParts<T> {
         var parts = new ArrayList<BakedModel>(4);
         parts.add(transform(combo.colour() ? colourModel : familyModel, transformation));
 
-        var overlayModelLocation = TurtleBlockEntityRenderer.getTurtleOverlayModel(combo.overlay(), combo.christmas());
-        if (overlayModelLocation != null) {
-            parts.add(transform(ClientPlatformHelper.get().getModel(modelManager, overlayModelLocation), transformation));
-        }
+        if (combo.overlay() != null) addPart(parts, modelManager, transformation, combo.overlay().model());
+
+        var showChristmas = TurtleOverlay.showElfOverlay(combo.overlay(), combo.christmas());
+        if (showChristmas) addPart(parts, modelManager, transformation, TurtleOverlay.ELF_MODEL);
 
         addUpgrade(parts, transformation, TurtleSide.LEFT, combo.leftUpgrade());
         addUpgrade(parts, transformation, TurtleSide.RIGHT, combo.rightUpgrade());
@@ -124,6 +125,10 @@ public final class TurtleModelParts<T> {
         return parts;
     }
 
+    private void addPart(List<BakedModel> parts, ModelManager modelManager, Transformation transformation, ResourceLocation model) {
+        parts.add(transform(ClientPlatformHelper.get().getModel(modelManager, model), transformation));
+    }
+
     private void addUpgrade(List<BakedModel> parts, Transformation transformation, TurtleSide side, @Nullable UpgradeData<ITurtleUpgrade> upgrade) {
         if (upgrade == null) return;
         var model = TurtleUpgradeModellers.getModel(upgrade.upgrade(), upgrade.data(), side);

projects/common/src/client/java/dan200/computercraft/client/render/CustomLecternRenderer.java

@@ -0,0 +1,52 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.client.render;
+
+import com.mojang.blaze3d.vertex.PoseStack;
+import com.mojang.math.Axis;
+import dan200.computercraft.client.model.LecternPrintoutModel;
+import dan200.computercraft.shared.lectern.CustomLecternBlockEntity;
+import dan200.computercraft.shared.media.items.PrintoutData;
+import dan200.computercraft.shared.media.items.PrintoutItem;
+import net.minecraft.client.renderer.MultiBufferSource;
+import net.minecraft.client.renderer.RenderType;
+import net.minecraft.client.renderer.blockentity.BlockEntityRenderer;
+import net.minecraft.client.renderer.blockentity.BlockEntityRendererProvider;
+import net.minecraft.client.renderer.blockentity.LecternRenderer;
+import net.minecraft.world.level.block.LecternBlock;
+
+/**
+ * A block entity renderer for our {@linkplain CustomLecternBlockEntity lectern}.
+ * <p>
+ * This largely follows {@link LecternRenderer}, but with support for multiple types of item.
+ */
+public class CustomLecternRenderer implements BlockEntityRenderer<CustomLecternBlockEntity> {
+    private final LecternPrintoutModel printoutModel;
+
+    public CustomLecternRenderer(BlockEntityRendererProvider.Context context) {
+        printoutModel = new LecternPrintoutModel();
+    }
+
+    @Override
+    public void render(CustomLecternBlockEntity lectern, float partialTick, PoseStack poseStack, MultiBufferSource buffer, int packedLight, int packedOverlay) {
+        poseStack.pushPose();
+        poseStack.translate(0.5f, 1.0625f, 0.5f);
+        poseStack.mulPose(Axis.YP.rotationDegrees(-lectern.getBlockState().getValue(LecternBlock.FACING).getClockWise().toYRot()));
+        poseStack.mulPose(Axis.ZP.rotationDegrees(67.5f));
+        poseStack.translate(0, -0.125f, 0);
+
+        var item = lectern.getItem();
+        if (item.getItem() instanceof PrintoutItem printout) {
+            var vertexConsumer = LecternPrintoutModel.MATERIAL.buffer(buffer, RenderType::entitySolid);
+            if (printout.getType() == PrintoutItem.Type.BOOK) {
+                printoutModel.renderBook(poseStack, vertexConsumer, packedLight, packedOverlay);
+            } else {
+                printoutModel.renderPages(poseStack, vertexConsumer, packedLight, packedOverlay, PrintoutData.getOrEmpty(item).pages());
+            }
+        }
+
+        poseStack.popPose();
+    }
+}

projects/common/src/client/java/dan200/computercraft/client/render/TurtleBlockEntityRenderer.java

@@ -11,6 +11,7 @@ import dan200.computercraft.api.ComputerCraftAPI;
 import dan200.computercraft.api.turtle.TurtleSide;
 import dan200.computercraft.client.platform.ClientPlatformHelper;
 import dan200.computercraft.client.turtle.TurtleUpgradeModellers;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
 import dan200.computercraft.shared.turtle.blocks.TurtleBlockEntity;
 import dan200.computercraft.shared.util.Holiday;
 import net.minecraft.client.Minecraft;
@@ -21,14 +22,15 @@ import net.minecraft.client.renderer.blockentity.BlockEntityRenderer;
 import net.minecraft.client.renderer.blockentity.BlockEntityRendererProvider;
 import net.minecraft.client.resources.model.BakedModel;
 import net.minecraft.resources.ResourceLocation;
+import net.minecraft.util.CommonColors;
+import net.minecraft.util.FastColor;
 import net.minecraft.world.phys.BlockHitResult;
 import net.minecraft.world.phys.HitResult;
 
 import javax.annotation.Nullable;
 
 public class TurtleBlockEntityRenderer implements BlockEntityRenderer<TurtleBlockEntity> {
-    private static final ResourceLocation COLOUR_TURTLE_MODEL = ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, "block/turtle_colour");
-    private static final ResourceLocation ELF_OVERLAY_MODEL = ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, "block/turtle_elf_overlay");
+    public static final ResourceLocation COLOUR_TURTLE_MODEL = ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, "block/turtle_colour");
 
     private final BlockEntityRenderDispatcher renderer;
     private final Font font;
@@ -38,12 +40,6 @@ public class TurtleBlockEntityRenderer implements BlockEntityRenderer<TurtleBloc
         font = context.getFont();
     }
 
-    public static @Nullable ResourceLocation getTurtleOverlayModel(@Nullable ResourceLocation overlay, boolean christmas) {
-        if (overlay != null) return overlay;
-        if (christmas) return ELF_OVERLAY_MODEL;
-        return null;
-    }
-
     @Override
     public void render(TurtleBlockEntity turtle, float partialTicks, PoseStack transform, MultiBufferSource buffers, int lightmapCoord, int overlayLight) {
         transform.pushPose();
@@ -62,13 +58,13 @@ public class TurtleBlockEntityRenderer implements BlockEntityRenderer<TurtleBloc
             transform.pushPose();
             transform.translate(0.5, 1.2, 0.5);
             transform.mulPose(mc.getEntityRenderDispatcher().cameraOrientation());
-            transform.scale(-0.025f, -0.025f, 0.025f);
+            transform.scale(0.025f, -0.025f, 0.025f);
 
             var matrix = transform.last().pose();
             var opacity = (int) (mc.options.getBackgroundOpacity(0.25f) * 255) << 24;
             var width = -font.width(label) / 2.0f;
             font.drawInBatch(label, width, (float) 0, 0x20ffffff, false, matrix, buffers, Font.DisplayMode.SEE_THROUGH, opacity, lightmapCoord);
-            font.drawInBatch(label, width, (float) 0, 0xffffffff, false, matrix, buffers, Font.DisplayMode.NORMAL, 0, lightmapCoord);
+            font.drawInBatch(label, width, (float) 0, CommonColors.WHITE, false, matrix, buffers, Font.DisplayMode.NORMAL, 0, lightmapCoord);
 
             transform.popPose();
         }
@@ -94,14 +90,15 @@ public class TurtleBlockEntityRenderer implements BlockEntityRenderer<TurtleBloc
             renderModel(transform, buffers, lightmapCoord, overlayLight, model, null);
         } else {
             // Otherwise render it using the colour item.
-            renderModel(transform, buffers, lightmapCoord, overlayLight, COLOUR_TURTLE_MODEL, new int[]{ colour });
+            renderModel(transform, buffers, lightmapCoord, overlayLight, COLOUR_TURTLE_MODEL, new int[]{ FastColor.ARGB32.opaque(colour) });
         }
 
         // Render the overlay
-        var overlayModel = getTurtleOverlayModel(overlay, Holiday.getCurrent() == Holiday.CHRISTMAS);
-        if (overlayModel != null) {
-            renderModel(transform, buffers, lightmapCoord, overlayLight, overlayModel, null);
-        }
+        if (overlay != null) renderModel(transform, buffers, lightmapCoord, overlayLight, overlay.model(), null);
+
+        // And the Christmas overlay.
+        var showChristmas = TurtleOverlay.showElfOverlay(overlay, Holiday.getCurrent() == Holiday.CHRISTMAS);
+        if (showChristmas) renderModel(transform, buffers, lightmapCoord, overlayLight, TurtleOverlay.ELF_MODEL, null);
 
         // Render the upgrades
         renderUpgrade(transform, buffers, lightmapCoord, overlayLight, turtle, TurtleSide.LEFT, partialTicks);

projects/common/src/client/java/dan200/computercraft/data/client/ClientDataProviders.java

@@ -5,16 +5,20 @@
 package dan200.computercraft.data.client;
 
 import dan200.computercraft.client.gui.GuiSprites;
+import dan200.computercraft.client.model.LecternPrintoutModel;
 import dan200.computercraft.data.DataProviders;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
 import dan200.computercraft.shared.turtle.inventory.UpgradeSlot;
 import net.minecraft.client.renderer.texture.atlas.SpriteSource;
 import net.minecraft.client.renderer.texture.atlas.SpriteSources;
 import net.minecraft.client.renderer.texture.atlas.sources.SingleFile;
+import net.minecraft.core.HolderLookup;
 import net.minecraft.resources.ResourceLocation;
 import net.minecraft.server.packs.PackType;
 
 import java.util.List;
 import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
 import java.util.stream.Stream;
 
 /**
@@ -26,11 +30,12 @@ public final class ClientDataProviders {
     private ClientDataProviders() {
     }
 
-    public static void add(DataProviders.GeneratorSink generator) {
+    public static void add(DataProviders.GeneratorSink generator, CompletableFuture<HolderLookup.Provider> registries) {
         generator.addFromCodec("Block atlases", PackType.CLIENT_RESOURCES, "atlases", SpriteSources.FILE_CODEC, out -> {
             out.accept(ResourceLocation.withDefaultNamespace("blocks"), List.of(
                 new SingleFile(UpgradeSlot.LEFT_UPGRADE, Optional.empty()),
-                new SingleFile(UpgradeSlot.RIGHT_UPGRADE, Optional.empty())
+                new SingleFile(UpgradeSlot.RIGHT_UPGRADE, Optional.empty()),
+                new SingleFile(LecternPrintoutModel.TEXTURE, Optional.empty())
             ));
             out.accept(GuiSprites.SPRITE_SHEET, Stream.of(
                 // Buttons
@@ -44,5 +49,12 @@ public final class ClientDataProviders {
                 GuiSprites.COMPUTER_COLOUR.textures()
             ).flatMap(x -> x).<SpriteSource>map(x -> new SingleFile(x, Optional.empty())).toList());
         });
+
+        generator.add(pack -> new ExtraModelsProvider(pack, registries) {
+            @Override
+            public Stream<ResourceLocation> getModels(HolderLookup.Provider registries) {
+                return registries.lookupOrThrow(TurtleOverlay.REGISTRY).listElements().map(x -> x.value().model());
+            }
+        });
     }
 }

projects/common/src/client/java/dan200/computercraft/data/client/ExtraModelsProvider.java

@@ -0,0 +1,52 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.data.client;
+
+import com.mojang.serialization.JsonOps;
+import dan200.computercraft.client.model.ExtraModels;
+import net.minecraft.core.HolderLookup;
+import net.minecraft.data.CachedOutput;
+import net.minecraft.data.DataProvider;
+import net.minecraft.data.PackOutput;
+import net.minecraft.resources.ResourceLocation;
+
+import java.nio.file.Path;
+import java.util.concurrent.CompletableFuture;
+import java.util.stream.Stream;
+
+/**
+ * A data provider to generate {@link ExtraModels}.
+ */
+abstract class ExtraModelsProvider implements DataProvider {
+    private final Path path;
+    private final CompletableFuture<HolderLookup.Provider> registries;
+
+    ExtraModelsProvider(PackOutput output, CompletableFuture<HolderLookup.Provider> registries) {
+        path = output.getOutputFolder(PackOutput.Target.RESOURCE_PACK).resolve(ExtraModels.PATH.getNamespace()).resolve(ExtraModels.PATH.getPath());
+        this.registries = registries;
+    }
+
+    /**
+     * Return a stream of models to load.
+     *
+     * @param registries The current registries.
+     * @return The collection of extra models to load.
+     */
+    public abstract Stream<ResourceLocation> getModels(HolderLookup.Provider registries);
+
+    @Override
+    public final CompletableFuture<?> run(CachedOutput output) {
+        return registries.thenCompose(registries -> {
+            var models = new ExtraModels(getModels(registries).sorted().toList());
+            var json = ExtraModels.CODEC.encodeStart(JsonOps.INSTANCE, models).getOrThrow(IllegalStateException::new);
+            return DataProvider.saveStable(output, json, path);
+        });
+    }
+
+    @Override
+    public final String getName() {
+        return "Extra Models";
+    }
+}

projects/common/src/generated/resources/assets/computercraft/blockstates/lectern.json

@@ -0,0 +1,8 @@
+{
+  "variants": {
+    "facing=east": {"model": "minecraft:block/lectern", "y": 90},
+    "facing=north": {"model": "minecraft:block/lectern", "y": 0},
+    "facing=south": {"model": "minecraft:block/lectern", "y": 180},
+    "facing=west": {"model": "minecraft:block/lectern", "y": 270}
+  }
+}

projects/common/src/generated/resources/assets/computercraft/extra_models.json

@@ -0,0 +1 @@
+["computercraft:block/turtle_rainbow_overlay", "computercraft:block/turtle_trans_overlay"]

projects/common/src/generated/resources/assets/minecraft/atlases/blocks.json

@@ -1,6 +1,7 @@
 {
   "sources": [
     {"type": "minecraft:single", "resource": "computercraft:gui/turtle_upgrade_left"},
-    {"type": "minecraft:single", "resource": "computercraft:gui/turtle_upgrade_right"}
+    {"type": "minecraft:single", "resource": "computercraft:gui/turtle_upgrade_right"},
+    {"type": "minecraft:single", "resource": "computercraft:entity/printout"}
   ]
 }

projects/common/src/generated/resources/data/computercraft/advancement/recipes/redstone/turtle_advanced_overlays/rainbow_flag.json

@@ -3,7 +3,7 @@
   "criteria": {
     "has_dye": {"conditions": {"items": [{"items": "#c:dyes"}]}, "trigger": "minecraft:inventory_changed"},
     "has_the_recipe": {
-      "conditions": {"recipe": "computercraft:turtle_advanced_overlays/turtle_trans_overlay"},
+      "conditions": {"recipe": "computercraft:turtle_advanced_overlays/rainbow_flag"},
       "trigger": "minecraft:recipe_unlocked"
     },
     "has_turtle": {
@@ -12,5 +12,5 @@
     }
   },
   "requirements": [["has_the_recipe", "has_turtle", "has_dye"]],
-  "rewards": {"recipes": ["computercraft:turtle_advanced_overlays/turtle_trans_overlay"]}
+  "rewards": {"recipes": ["computercraft:turtle_advanced_overlays/rainbow_flag"]}
 }

projects/common/src/generated/resources/data/computercraft/advancement/recipes/redstone/turtle_advanced_overlays/trans_flag.json

@@ -3,7 +3,7 @@
   "criteria": {
     "has_dye": {"conditions": {"items": [{"items": "#c:dyes"}]}, "trigger": "minecraft:inventory_changed"},
     "has_the_recipe": {
-      "conditions": {"recipe": "computercraft:turtle_advanced_overlays/turtle_rainbow_overlay"},
+      "conditions": {"recipe": "computercraft:turtle_advanced_overlays/trans_flag"},
       "trigger": "minecraft:recipe_unlocked"
     },
     "has_turtle": {
@@ -12,5 +12,5 @@
     }
   },
   "requirements": [["has_the_recipe", "has_turtle", "has_dye"]],
-  "rewards": {"recipes": ["computercraft:turtle_advanced_overlays/turtle_rainbow_overlay"]}
+  "rewards": {"recipes": ["computercraft:turtle_advanced_overlays/trans_flag"]}
 }

projects/common/src/generated/resources/data/computercraft/advancement/recipes/redstone/turtle_normal_overlays/rainbow_flag.json

@@ -3,7 +3,7 @@
   "criteria": {
     "has_dye": {"conditions": {"items": [{"items": "#c:dyes"}]}, "trigger": "minecraft:inventory_changed"},
     "has_the_recipe": {
-      "conditions": {"recipe": "computercraft:turtle_normal_overlays/turtle_trans_overlay"},
+      "conditions": {"recipe": "computercraft:turtle_normal_overlays/rainbow_flag"},
       "trigger": "minecraft:recipe_unlocked"
     },
     "has_turtle": {
@@ -12,5 +12,5 @@
     }
   },
   "requirements": [["has_the_recipe", "has_turtle", "has_dye"]],
-  "rewards": {"recipes": ["computercraft:turtle_normal_overlays/turtle_trans_overlay"]}
+  "rewards": {"recipes": ["computercraft:turtle_normal_overlays/rainbow_flag"]}
 }

projects/common/src/generated/resources/data/computercraft/advancement/recipes/redstone/turtle_normal_overlays/trans_flag.json

@@ -3,7 +3,7 @@
   "criteria": {
     "has_dye": {"conditions": {"items": [{"items": "#c:dyes"}]}, "trigger": "minecraft:inventory_changed"},
     "has_the_recipe": {
-      "conditions": {"recipe": "computercraft:turtle_normal_overlays/turtle_rainbow_overlay"},
+      "conditions": {"recipe": "computercraft:turtle_normal_overlays/trans_flag"},
       "trigger": "minecraft:recipe_unlocked"
     },
     "has_turtle": {
@@ -12,5 +12,5 @@
     }
   },
   "requirements": [["has_the_recipe", "has_turtle", "has_dye"]],
-  "rewards": {"recipes": ["computercraft:turtle_normal_overlays/turtle_rainbow_overlay"]}
+  "rewards": {"recipes": ["computercraft:turtle_normal_overlays/trans_flag"]}
 }

projects/common/src/generated/resources/data/computercraft/computercraft/turtle_overlay/rainbow_flag.json

@@ -0,0 +1 @@
+{"model": "computercraft:block/turtle_rainbow_overlay", "show_elf_overlay": true}

projects/common/src/generated/resources/data/computercraft/computercraft/turtle_overlay/trans_flag.json

@@ -0,0 +1 @@
+{"model": "computercraft:block/turtle_trans_overlay", "show_elf_overlay": true}

projects/common/src/generated/resources/data/computercraft/loot_table/blocks/lectern.json

@@ -0,0 +1,12 @@
+{
+  "type": "minecraft:block",
+  "pools": [
+    {
+      "bonus_rolls": 0.0,
+      "conditions": [{"condition": "minecraft:survives_explosion"}],
+      "entries": [{"type": "minecraft:item", "name": "minecraft:lectern"}],
+      "rolls": 1.0
+    }
+  ],
+  "random_sequence": "computercraft:blocks/lectern"
+}

projects/common/src/generated/resources/data/computercraft/recipe/turtle_advanced_overlays/rainbow_flag.json

@@ -20,7 +20,7 @@
     {"item": "computercraft:turtle_advanced"}
   ],
   "result": {
-    "components": {"computercraft:overlay": "computercraft:block/turtle_rainbow_overlay"},
+    "components": {"computercraft:overlay": "computercraft:rainbow_flag"},
     "count": 1,
     "id": "computercraft:turtle_advanced"
   }

projects/common/src/generated/resources/data/computercraft/recipe/turtle_advanced_overlays/trans_flag.json

@@ -17,7 +17,7 @@
     {"item": "computercraft:turtle_advanced"}
   ],
   "result": {
-    "components": {"computercraft:overlay": "computercraft:block/turtle_trans_overlay"},
+    "components": {"computercraft:overlay": "computercraft:trans_flag"},
     "count": 1,
     "id": "computercraft:turtle_advanced"
   }

projects/common/src/generated/resources/data/computercraft/recipe/turtle_normal_overlays/rainbow_flag.json

@@ -20,7 +20,7 @@
     {"item": "computercraft:turtle_normal"}
   ],
   "result": {
-    "components": {"computercraft:overlay": "computercraft:block/turtle_rainbow_overlay"},
+    "components": {"computercraft:overlay": "computercraft:rainbow_flag"},
     "count": 1,
     "id": "computercraft:turtle_normal"
   }

projects/common/src/generated/resources/data/computercraft/recipe/turtle_normal_overlays/trans_flag.json

@@ -17,7 +17,7 @@
     {"item": "computercraft:turtle_normal"}
   ],
   "result": {
-    "components": {"computercraft:overlay": "computercraft:block/turtle_trans_overlay"},
+    "components": {"computercraft:overlay": "computercraft:trans_flag"},
     "count": 1,
     "id": "computercraft:turtle_normal"
   }

projects/common/src/main/java/dan200/computercraft/data/BlockModelProvider.java

@@ -23,6 +23,7 @@ import net.minecraft.data.models.BlockModelGenerators;
 import net.minecraft.data.models.blockstates.*;
 import net.minecraft.data.models.model.*;
 import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.level.block.state.properties.BlockStateProperties;
 import net.minecraft.world.level.block.state.properties.BooleanProperty;
 import net.minecraft.world.level.block.state.properties.Property;
@@ -100,6 +101,11 @@ class BlockModelProvider {
         registerTurtleUpgrade(generators, "block/turtle_speaker", "block/turtle_speaker_face");
         registerTurtleModem(generators, "block/turtle_modem_normal", "block/wireless_modem_normal_face");
         registerTurtleModem(generators, "block/turtle_modem_advanced", "block/wireless_modem_advanced_face");
+
+        generators.blockStateOutput.accept(MultiVariantGenerator.multiVariant(
+            ModRegistry.Blocks.LECTERN.get(),
+            Variant.variant().with(VariantProperties.MODEL, ModelLocationUtils.getModelLocation(Blocks.LECTERN))
+        ).with(createHorizontalFacingDispatch()));
     }
 
     private static void registerDiskDrive(BlockModelGenerators generators) {

projects/common/src/main/java/dan200/computercraft/data/DataProviders.java

@@ -7,6 +7,7 @@ package dan200.computercraft.data;
 import com.mojang.serialization.Codec;
 import dan200.computercraft.api.pocket.IPocketUpgrade;
 import dan200.computercraft.api.turtle.ITurtleUpgrade;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
 import net.minecraft.Util;
 import net.minecraft.core.HolderLookup;
 import net.minecraft.core.RegistrySetBuilder;
@@ -38,6 +39,7 @@ public final class DataProviders {
             Util.make(new RegistrySetBuilder(), builder -> {
                 builder.add(ITurtleUpgrade.REGISTRY, TurtleUpgradeProvider::addUpgrades);
                 builder.add(IPocketUpgrade.REGISTRY, PocketUpgradeProvider::addUpgrades);
+                builder.add(TurtleOverlay.REGISTRY, TurtleOverlays::register);
             }));
         var fullRegistries = fullRegistryPatch.thenApply(RegistrySetBuilder.PatchedRegistries::full);
 
@@ -57,7 +59,8 @@ public final class DataProviders {
         // and invoke that.
         try {
             Class.forName("dan200.computercraft.data.client.ClientDataProviders")
-                .getMethod("add", GeneratorSink.class).invoke(null, generator);
+                .getMethod("add", GeneratorSink.class, CompletableFuture.class)
+                .invoke(null, generator, fullRegistries);
         } catch (ReflectiveOperationException e) {
             throw new RuntimeException(e);
         }

projects/common/src/main/java/dan200/computercraft/data/LanguageProvider.java

@@ -288,7 +288,9 @@ public final class LanguageProvider implements DataProvider {
         return Stream.of(
             BuiltInRegistries.BLOCK.holders()
                 .filter(x -> x.key().location().getNamespace().equals(ComputerCraftAPI.MOD_ID))
-                .map(x -> x.value().getDescriptionId()),
+                .map(x -> x.value().getDescriptionId())
+                // Exclude blocks that just reuse vanilla translations, such as the lectern.
+                .filter(x -> !x.startsWith("block.minecraft.")),
             BuiltInRegistries.ITEM.holders()
                 .filter(x -> x.key().location().getNamespace().equals(ComputerCraftAPI.MOD_ID))
                 .map(x -> x.value().getDescriptionId()),

projects/common/src/main/java/dan200/computercraft/data/LootTableProvider.java

@@ -14,6 +14,7 @@ import dan200.computercraft.shared.peripheral.modem.wired.CableModemVariant;
 import net.minecraft.advancements.critereon.StatePropertiesPredicate;
 import net.minecraft.data.loot.LootTableProvider.SubProviderEntry;
 import net.minecraft.resources.ResourceKey;
+import net.minecraft.world.item.Items;
 import net.minecraft.world.level.block.Block;
 import net.minecraft.world.level.storage.loot.LootPool;
 import net.minecraft.world.level.storage.loot.LootTable;
@@ -56,6 +57,8 @@ class LootTableProvider {
         computerDrop(add, ModRegistry.Blocks.TURTLE_NORMAL);
         computerDrop(add, ModRegistry.Blocks.TURTLE_ADVANCED);
 
+        blockDrop(add, ModRegistry.Blocks.LECTERN, LootItem.lootTableItem(Items.LECTERN), ExplosionCondition.survivesExplosion());
+
         add.accept(ModRegistry.Blocks.CABLE.get().getLootTable(), LootTable
             .lootTable()
             .withPool(LootPool.lootPool()

projects/common/src/main/java/dan200/computercraft/data/RecipeProvider.java

@@ -28,6 +28,7 @@ import dan200.computercraft.shared.recipe.ImpostorShapelessRecipe;
 import dan200.computercraft.shared.recipe.TransformShapedRecipe;
 import dan200.computercraft.shared.recipe.TransformShapelessRecipe;
 import dan200.computercraft.shared.recipe.function.CopyComponents;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
 import dan200.computercraft.shared.turtle.items.TurtleItem;
 import dan200.computercraft.shared.turtle.recipes.TurtleUpgradeRecipe;
 import dan200.computercraft.shared.util.ColourUtils;
@@ -45,6 +46,7 @@ import net.minecraft.data.recipes.RecipeCategory;
 import net.minecraft.data.recipes.RecipeOutput;
 import net.minecraft.data.recipes.ShapedRecipeBuilder;
 import net.minecraft.data.recipes.ShapelessRecipeBuilder;
+import net.minecraft.resources.ResourceKey;
 import net.minecraft.resources.ResourceLocation;
 import net.minecraft.tags.ItemTags;
 import net.minecraft.tags.TagKey;
@@ -96,7 +98,7 @@ final class RecipeProvider extends net.minecraft.data.recipes.RecipeProvider {
         diskColours(add);
         pocketUpgrades(add, registries);
         turtleUpgrades(add, registries);
-        turtleOverlays(add);
+        turtleOverlays(add, registries);
 
         addSpecial(add, new DiskRecipe(CraftingBookCategory.MISC));
         addSpecial(add, new ColourableRecipe(CraftingBookCategory.MISC));
@@ -189,8 +191,8 @@ final class RecipeProvider extends net.minecraft.data.recipes.RecipeProvider {
         }
     }
 
-    private void turtleOverlays(RecipeOutput add) {
-        turtleOverlay(add, "turtle_trans_overlay", x -> x
+    private void turtleOverlays(RecipeOutput add, HolderLookup.Provider registries) {
+        turtleOverlay(add, registries, TurtleOverlays.TRANS_FLAG, x -> x
             .unlockedBy("has_dye", inventoryChange(itemPredicate(ingredients.dye())))
             .requires(ColourUtils.getDyeTag(DyeColor.LIGHT_BLUE))
             .requires(ColourUtils.getDyeTag(DyeColor.PINK))
@@ -198,7 +200,7 @@ final class RecipeProvider extends net.minecraft.data.recipes.RecipeProvider {
             .requires(Items.STICK)
         );
 
-        turtleOverlay(add, "turtle_rainbow_overlay", x -> x
+        turtleOverlay(add, registries, TurtleOverlays.RAINBOW_FLAG, x -> x
             .unlockedBy("has_dye", inventoryChange(itemPredicate(ingredients.dye())))
             .requires(ColourUtils.getDyeTag(DyeColor.RED))
             .requires(ColourUtils.getDyeTag(DyeColor.ORANGE))
@@ -210,14 +212,14 @@ final class RecipeProvider extends net.minecraft.data.recipes.RecipeProvider {
         );
     }
 
-    private void turtleOverlay(RecipeOutput add, String overlay, Consumer<ShapelessSpecBuilder> build) {
-        var overlayId = ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, "block/" + overlay);
+    private void turtleOverlay(RecipeOutput add, HolderLookup.Provider registries, ResourceKey<TurtleOverlay> overlay, Consumer<ShapelessSpecBuilder> build) {
+        var holder = registries.lookupOrThrow(overlay.registryKey()).getOrThrow(overlay);
 
         for (var turtleItem : turtleItems()) {
             var name = RegistryHelper.getKeyOrThrow(BuiltInRegistries.ITEM, turtleItem);
 
             var builder = ShapelessSpecBuilder
-                .shapeless(RecipeCategory.REDSTONE, DataComponentUtil.createStack(turtleItem, ModRegistry.DataComponents.OVERLAY.get(), overlayId))
+                .shapeless(RecipeCategory.REDSTONE, DataComponentUtil.createStack(turtleItem, ModRegistry.DataComponents.OVERLAY.get(), holder))
                 .group(name.withSuffix("_overlay").toString())
                 .unlockedBy("has_turtle", inventoryChange(turtleItem));
             build.accept(builder);
@@ -226,7 +228,7 @@ final class RecipeProvider extends net.minecraft.data.recipes.RecipeProvider {
                 .build(s -> new TransformShapelessRecipe(s, List.of(
                     CopyComponents.builder(turtleItem).exclude(ModRegistry.DataComponents.OVERLAY.get()).build()
                 )))
-                .save(add, name.withSuffix("_overlays/" + overlay));
+                .save(add, name.withSuffix("_overlays/" + overlay.location().getPath()));
         }
     }
 

projects/common/src/main/java/dan200/computercraft/data/TagProvider.java

@@ -5,9 +5,9 @@
 package dan200.computercraft.data;
 
 import dan200.computercraft.api.ComputerCraftTags;
-import dan200.computercraft.shared.util.RegistryHelper;
 import dan200.computercraft.shared.ModRegistry;
 import dan200.computercraft.shared.integration.ExternalModTags;
+import dan200.computercraft.shared.util.RegistryHelper;
 import net.minecraft.core.Registry;
 import net.minecraft.data.tags.ItemTagsProvider;
 import net.minecraft.data.tags.TagsProvider;
@@ -107,6 +107,7 @@ class TagProvider {
             ModRegistry.Items.MONITOR_ADVANCED.get()
         );
 
+        // Allow printed books to be placed in bookshelves.
         tags.tag(ItemTags.BOOKSHELF_BOOKS).add(ModRegistry.Items.PRINTED_BOOK.get());
 
         tags.tag(ComputerCraftTags.Items.TURTLE_CAN_PLACE)

projects/common/src/main/java/dan200/computercraft/data/TurtleOverlays.java

@@ -0,0 +1,38 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.data;
+
+import dan200.computercraft.api.ComputerCraftAPI;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
+import net.minecraft.data.worldgen.BootstrapContext;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.resources.ResourceLocation;
+
+/**
+ * Built-in turtle overlays.
+ */
+final class TurtleOverlays {
+    public static final ResourceKey<TurtleOverlay> RAINBOW_FLAG = create("rainbow_flag");
+    public static final ResourceKey<TurtleOverlay> TRANS_FLAG = create("trans_flag");
+
+    private static ResourceKey<TurtleOverlay> create(String name) {
+        return ResourceKey.create(TurtleOverlay.REGISTRY, ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, name));
+    }
+
+    private TurtleOverlays() {
+    }
+
+    public static void register(BootstrapContext<TurtleOverlay> registry) {
+        registry.register(RAINBOW_FLAG, new TurtleOverlay(
+            ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, "block/turtle_rainbow_overlay"),
+            true
+        ));
+
+        registry.register(TRANS_FLAG, new TurtleOverlay(
+            ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, "block/turtle_trans_overlay"),
+            true
+        ));
+    }
+}

projects/common/src/main/java/dan200/computercraft/impl/ApiFactories.java

@@ -14,7 +14,6 @@ import java.util.Objects;
 /**
  * The global factory for {@link ILuaAPIFactory}s.
  *
- * @see dan200.computercraft.core.ComputerContext.Builder#apiFactories(Collection)
  * @see dan200.computercraft.api.ComputerCraftAPI#registerAPIFactory(ILuaAPIFactory)
  */
 public final class ApiFactories {

projects/common/src/main/java/dan200/computercraft/impl/detail/DetailRegistryImpl.java

@@ -15,7 +15,7 @@ import java.util.*;
  * @param <T> The type of object that this registry provides details for.
  */
 public class DetailRegistryImpl<T> implements DetailRegistry<T> {
-    private final Collection<DetailProvider<T>> providers = new ArrayList<>();
+    private final Collection<DetailProvider<? super T>> providers = new ArrayList<>();
     private final DetailProvider<T> basic;
 
     public DetailRegistryImpl(DetailProvider<T> basic) {
@@ -24,7 +24,7 @@ public class DetailRegistryImpl<T> implements DetailRegistry<T> {
     }
 
     @Override
-    public synchronized void addProvider(DetailProvider<T> provider) {
+    public synchronized void addProvider(DetailProvider<? super T> provider) {
         Objects.requireNonNull(provider, "provider cannot be null");
         if (!providers.contains(provider)) providers.add(provider);
     }

projects/common/src/main/java/dan200/computercraft/mixin/ItemStackComponentizationFixMixin.java

@@ -31,7 +31,7 @@ abstract class ItemStackComponentizationFixMixin extends DataFix {
     }
 
     @Inject(method = "fixItemStack", at = @At("TAIL"))
-    @SuppressWarnings("UnusedMethod")
+    @SuppressWarnings("unused")
     private static void fixItemStack(ItemStackComponentizationFix.ItemStackData data, Dynamic<?> ops, CallbackInfo ci) {
         ComponentizationFixers.fixItemComponents(data, ops);
     }

projects/common/src/main/java/dan200/computercraft/shared/CommonHooks.java

@@ -9,6 +9,7 @@ import dan200.computercraft.core.apis.http.NetworkUtils;
 import dan200.computercraft.shared.computer.core.ResourceMount;
 import dan200.computercraft.shared.computer.core.ServerContext;
 import dan200.computercraft.shared.computer.metrics.ComputerMBean;
+import dan200.computercraft.shared.lectern.CustomLecternBlock;
 import dan200.computercraft.shared.peripheral.monitor.MonitorWatcher;
 import dan200.computercraft.shared.util.DropConsumer;
 import dan200.computercraft.shared.util.TickScheduler;
@@ -20,16 +21,23 @@ import net.minecraft.server.dedicated.DedicatedServer;
 import net.minecraft.server.level.ServerLevel;
 import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.server.packs.resources.PreparableReloadListener;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.InteractionResult;
 import net.minecraft.world.entity.Entity;
+import net.minecraft.world.entity.player.Player;
 import net.minecraft.world.item.CreativeModeTab;
 import net.minecraft.world.item.CreativeModeTabs;
 import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.LecternBlock;
 import net.minecraft.world.level.chunk.LevelChunk;
 import net.minecraft.world.level.storage.loot.BuiltInLootTables;
 import net.minecraft.world.level.storage.loot.LootPool;
 import net.minecraft.world.level.storage.loot.LootTable;
 import net.minecraft.world.level.storage.loot.entries.NestedLootTable;
 import net.minecraft.world.level.storage.loot.providers.number.ConstantValue;
+import net.minecraft.world.phys.BlockHitResult;
 
 import javax.annotation.Nullable;
 import java.util.Set;
@@ -92,6 +100,20 @@ public final class CommonHooks {
         TickScheduler.onChunkTicketChanged(level, chunkPos, oldLevel, newLevel);
     }
 
+    public static InteractionResult onUseBlock(Player player, Level level, InteractionHand hand, BlockHitResult hitResult) {
+        if (player.isSpectator()) return InteractionResult.PASS;
+
+        var pos = hitResult.getBlockPos();
+        var heldItem = player.getItemInHand(hand);
+        var blockState = level.getBlockState(pos);
+
+        if (blockState.is(Blocks.LECTERN) && !blockState.getValue(LecternBlock.HAS_BOOK)) {
+            return CustomLecternBlock.tryPlaceItem(player, level, pos, blockState, heldItem);
+        }
+
+        return InteractionResult.PASS;
+    }
+
     public static final ResourceKey<LootTable> TREASURE_DISK_LOOT = ResourceKey.create(Registries.LOOT_TABLE, ResourceLocation.fromNamespaceAndPath(ComputerCraftAPI.MOD_ID, "treasure_disk"));
 
     private static final Set<ResourceKey<LootTable>> TREASURE_DISK_LOOT_TABLES = Set.of(

projects/common/src/main/java/dan200/computercraft/shared/ModRegistry.java

@@ -8,6 +8,7 @@ import com.mojang.brigadier.arguments.ArgumentType;
 import com.mojang.serialization.Codec;
 import com.mojang.serialization.MapCodec;
 import dan200.computercraft.api.ComputerCraftAPI;
+import dan200.computercraft.api.component.ComputerComponents;
 import dan200.computercraft.api.detail.DetailProvider;
 import dan200.computercraft.api.detail.VanillaDetailRegistries;
 import dan200.computercraft.api.media.IMedia;
@@ -25,7 +26,7 @@ import dan200.computercraft.shared.command.arguments.TrackingFieldArgumentType;
 import dan200.computercraft.shared.common.ClearColourRecipe;
 import dan200.computercraft.shared.common.ColourableRecipe;
 import dan200.computercraft.shared.common.DefaultBundledRedstoneProvider;
-import dan200.computercraft.shared.common.HeldItemMenu;
+import dan200.computercraft.shared.computer.apis.CommandAPI;
 import dan200.computercraft.shared.computer.blocks.CommandComputerBlock;
 import dan200.computercraft.shared.computer.blocks.ComputerBlock;
 import dan200.computercraft.shared.computer.blocks.ComputerBlockEntity;
@@ -42,12 +43,14 @@ import dan200.computercraft.shared.data.PlayerCreativeLootCondition;
 import dan200.computercraft.shared.details.BlockDetails;
 import dan200.computercraft.shared.details.ItemDetails;
 import dan200.computercraft.shared.integration.PermissionRegistry;
+import dan200.computercraft.shared.lectern.CustomLecternBlock;
+import dan200.computercraft.shared.lectern.CustomLecternBlockEntity;
+import dan200.computercraft.shared.media.PrintoutMenu;
 import dan200.computercraft.shared.media.items.*;
 import dan200.computercraft.shared.media.recipes.DiskRecipe;
 import dan200.computercraft.shared.media.recipes.PrintoutRecipe;
 import dan200.computercraft.shared.network.container.ComputerContainerData;
 import dan200.computercraft.shared.network.container.ContainerData;
-import dan200.computercraft.shared.network.container.HeldItemContainerData;
 import dan200.computercraft.shared.peripheral.diskdrive.DiskDriveBlock;
 import dan200.computercraft.shared.peripheral.diskdrive.DiskDriveBlockEntity;
 import dan200.computercraft.shared.peripheral.diskdrive.DiskDriveMenu;
@@ -64,6 +67,7 @@ import dan200.computercraft.shared.peripheral.speaker.SpeakerBlockEntity;
 import dan200.computercraft.shared.platform.PlatformHelper;
 import dan200.computercraft.shared.platform.RegistrationHelper;
 import dan200.computercraft.shared.platform.RegistryEntry;
+import dan200.computercraft.shared.pocket.apis.PocketAPI;
 import dan200.computercraft.shared.pocket.items.PocketComputerItem;
 import dan200.computercraft.shared.pocket.peripherals.PocketModem;
 import dan200.computercraft.shared.pocket.peripherals.PocketSpeaker;
@@ -72,8 +76,11 @@ import dan200.computercraft.shared.recipe.*;
 import dan200.computercraft.shared.recipe.function.CopyComponents;
 import dan200.computercraft.shared.recipe.function.RecipeFunction;
 import dan200.computercraft.shared.turtle.FurnaceRefuelHandler;
+import dan200.computercraft.shared.turtle.TurtleOverlay;
+import dan200.computercraft.shared.turtle.apis.TurtleAPI;
 import dan200.computercraft.shared.turtle.blocks.TurtleBlock;
 import dan200.computercraft.shared.turtle.blocks.TurtleBlockEntity;
+import dan200.computercraft.shared.turtle.core.TurtleAccessInternal;
 import dan200.computercraft.shared.turtle.inventory.TurtleMenu;
 import dan200.computercraft.shared.turtle.items.TurtleItem;
 import dan200.computercraft.shared.turtle.recipes.TurtleUpgradeRecipe;
@@ -81,6 +88,7 @@ import dan200.computercraft.shared.turtle.upgrades.TurtleCraftingTable;
 import dan200.computercraft.shared.turtle.upgrades.TurtleModem;
 import dan200.computercraft.shared.turtle.upgrades.TurtleSpeaker;
 import dan200.computercraft.shared.turtle.upgrades.TurtleTool;
+import dan200.computercraft.shared.util.ComponentMap;
 import dan200.computercraft.shared.util.DataComponentUtil;
 import dan200.computercraft.shared.util.NonNegativeId;
 import net.minecraft.commands.CommandSourceStack;
@@ -95,7 +103,6 @@ import net.minecraft.network.RegistryFriendlyByteBuf;
 import net.minecraft.network.chat.Component;
 import net.minecraft.network.codec.ByteBufCodecs;
 import net.minecraft.network.codec.StreamCodec;
-import net.minecraft.resources.ResourceLocation;
 import net.minecraft.world.flag.FeatureFlags;
 import net.minecraft.world.inventory.MenuType;
 import net.minecraft.world.item.BlockItem;
@@ -108,12 +115,15 @@ import net.minecraft.world.item.crafting.Recipe;
 import net.minecraft.world.item.crafting.RecipeSerializer;
 import net.minecraft.world.item.crafting.SimpleCraftingRecipeSerializer;
 import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.SoundType;
 import net.minecraft.world.level.block.entity.BlockEntity;
 import net.minecraft.world.level.block.entity.BlockEntityType;
 import net.minecraft.world.level.block.state.BlockBehaviour;
+import net.minecraft.world.level.block.state.properties.NoteBlockInstrument;
 import net.minecraft.world.level.material.MapColor;
 import net.minecraft.world.level.storage.loot.predicates.LootItemConditionType;
 
+import java.util.Objects;
 import java.util.function.BiFunction;
 import java.util.function.Predicate;
 import java.util.function.UnaryOperator;
@@ -178,6 +188,10 @@ public final class ModRegistry {
         public static final RegistryEntry<WiredModemFullBlock> WIRED_MODEM_FULL = REGISTRY.register("wired_modem_full",
             () -> new WiredModemFullBlock(modemProperties().mapColor(MapColor.STONE)));
         public static final RegistryEntry<CableBlock> CABLE = REGISTRY.register("cable", () -> new CableBlock(modemProperties().mapColor(MapColor.STONE)));
+
+        public static final RegistryEntry<CustomLecternBlock> LECTERN = REGISTRY.register("lectern", () -> new CustomLecternBlock(
+            BlockBehaviour.Properties.of().mapColor(MapColor.WOOD).instrument(NoteBlockInstrument.BASS).strength(2.5F).sound(SoundType.WOOD).ignitedByLava()
+        ));
     }
 
     public static class BlockEntities {
@@ -219,6 +233,8 @@ public final class ModRegistry {
             ofBlock(Blocks.WIRELESS_MODEM_NORMAL, (p, s) -> new WirelessModemBlockEntity(BlockEntities.WIRELESS_MODEM_NORMAL.get(), p, s, false));
         public static final RegistryEntry<BlockEntityType<WirelessModemBlockEntity>> WIRELESS_MODEM_ADVANCED =
             ofBlock(Blocks.WIRELESS_MODEM_ADVANCED, (p, s) -> new WirelessModemBlockEntity(BlockEntities.WIRELESS_MODEM_ADVANCED.get(), p, s, true));
+
+        public static final RegistryEntry<BlockEntityType<CustomLecternBlockEntity>> LECTERN = ofBlock(Blocks.LECTERN, CustomLecternBlockEntity::new);
     }
 
     public static final class Items {
@@ -320,8 +336,8 @@ public final class ModRegistry {
         /**
          * The overlay on a turtle.
          */
-        public static final RegistryEntry<DataComponentType<ResourceLocation>> OVERLAY = register("overlay", b -> b
-            .persistent(ResourceLocation.CODEC).networkSynchronized(ResourceLocation.STREAM_CODEC)
+        public static final RegistryEntry<DataComponentType<Holder<TurtleOverlay>>> OVERLAY = register("overlay", b -> b
+            .persistent(TurtleOverlay.CODEC).networkSynchronized(TurtleOverlay.STREAM_CODEC)
         );
 
         /**
@@ -422,11 +438,8 @@ public final class ModRegistry {
         public static final RegistryEntry<MenuType<PrinterMenu>> PRINTER = REGISTRY.register("printer",
             () -> new MenuType<>(PrinterMenu::new, FeatureFlags.VANILLA_SET));
 
-        public static final RegistryEntry<MenuType<HeldItemMenu>> PRINTOUT = REGISTRY.register("printout",
-            () -> ContainerData.toType(
-                HeldItemContainerData.STREAM_CODEC,
-                (id, inventory, data) -> new HeldItemMenu(Menus.PRINTOUT.get(), id, inventory.player, data.hand())
-            ));
+        public static final RegistryEntry<MenuType<PrintoutMenu>> PRINTOUT = REGISTRY.register("printout",
+            () -> new MenuType<>((i, c) -> PrintoutMenu.createRemote(i), FeatureFlags.VANILLA_SET));
     }
 
     static class ArgumentTypes {
@@ -579,6 +592,22 @@ public final class ModRegistry {
             return null;
         });
 
+        ComputerCraftAPI.registerAPIFactory(computer -> {
+            var turtle = computer.getComponent(ComputerComponents.TURTLE);
+            var metrics = Objects.requireNonNull(computer.getComponent(ComponentMap.METRICS));
+            return turtle == null ? null : new TurtleAPI(metrics, (TurtleAccessInternal) turtle);
+        });
+
+        ComputerCraftAPI.registerAPIFactory(computer -> {
+            var pocket = computer.getComponent(ComputerComponents.POCKET);
+            return pocket == null ? null : new PocketAPI(pocket);
+        });
+
+        ComputerCraftAPI.registerAPIFactory(computer -> {
+            var admin = computer.getComponent(ComputerComponents.ADMIN_COMPUTER);
+            return admin == null ? null : new CommandAPI(computer, admin);
+        });
+
         VanillaDetailRegistries.ITEM_STACK.addProvider(ItemDetails::fill);
         VanillaDetailRegistries.BLOCK_IN_WORLD.addProvider(BlockDetails::fill);
     }

projects/common/src/main/java/dan200/computercraft/shared/command/text/TableBuilder.java

@@ -63,7 +63,7 @@ public class TableBuilder {
     /**
      * Get the number of columns for this table.
      * <p>
-     * This will be the same as {@link #getHeaders()}'s length if it is is non-{@code null},
+     * This will be the same as {@link #getHeaders()}'s length if it is non-{@code null},
      * otherwise the length of the first column.
      *
      * @return The number of columns.

projects/common/src/main/java/dan200/computercraft/shared/common/HeldItemMenu.java

@@ -1,68 +0,0 @@
-// Copyright Daniel Ratcliffe, 2011-2022. Do not distribute without permission.
-//
-// SPDX-License-Identifier: LicenseRef-CCPL
-
-package dan200.computercraft.shared.common;
-
-import net.minecraft.network.chat.Component;
-import net.minecraft.world.InteractionHand;
-import net.minecraft.world.MenuProvider;
-import net.minecraft.world.entity.player.Inventory;
-import net.minecraft.world.entity.player.Player;
-import net.minecraft.world.inventory.AbstractContainerMenu;
-import net.minecraft.world.inventory.MenuType;
-import net.minecraft.world.item.ItemStack;
-
-import javax.annotation.Nullable;
-
-public class HeldItemMenu extends AbstractContainerMenu {
-    private final ItemStack stack;
-    private final InteractionHand hand;
-
-    public HeldItemMenu(MenuType<? extends HeldItemMenu> type, int id, Player player, InteractionHand hand) {
-        super(type, id);
-
-        this.hand = hand;
-        stack = player.getItemInHand(hand).copy();
-    }
-
-    public ItemStack getStack() {
-        return stack;
-    }
-
-    @Override
-    public ItemStack quickMoveStack(Player player, int slot) {
-        return ItemStack.EMPTY;
-    }
-
-    @Override
-    public boolean stillValid(Player player) {
-        if (!player.isAlive()) return false;
-
-        var stack = player.getItemInHand(hand);
-        return stack == this.stack || !stack.isEmpty() && !this.stack.isEmpty() && stack.getItem() == this.stack.getItem();
-    }
-
-    public static class Factory implements MenuProvider {
-        private final MenuType<HeldItemMenu> type;
-        private final Component name;
-        private final InteractionHand hand;
-
-        public Factory(MenuType<HeldItemMenu> type, ItemStack stack, InteractionHand hand) {
-            this.type = type;
-            name = stack.getHoverName();
-            this.hand = hand;
-        }
-
-        @Override
-        public Component getDisplayName() {
-            return name;
-        }
-
-        @Nullable
-        @Override
-        public AbstractContainerMenu createMenu(int id, Inventory inventory, Player player) {
-            return new HeldItemMenu(type, id, player, hand);
-        }
-    }
-}

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

@@ -6,11 +6,11 @@ package dan200.computercraft.shared.computer.apis;
 
 import com.mojang.brigadier.tree.CommandNode;
 import com.mojang.brigadier.tree.LiteralCommandNode;
+import dan200.computercraft.api.component.AdminComputer;
 import dan200.computercraft.api.detail.BlockReference;
 import dan200.computercraft.api.detail.VanillaDetailRegistries;
 import dan200.computercraft.api.lua.*;
 import dan200.computercraft.core.Logging;
-import dan200.computercraft.shared.computer.core.ServerComputer;
 import dan200.computercraft.shared.util.NBTUtil;
 import net.minecraft.commands.CommandSource;
 import net.minecraft.commands.CommandSourceStack;
@@ -35,11 +35,13 @@ import java.util.*;
 public class CommandAPI implements ILuaAPI {
     private static final Logger LOG = LoggerFactory.getLogger(CommandAPI.class);
 
-    private final ServerComputer computer;
+    private final IComputerSystem computer;
+    private final AdminComputer admin;
     private final OutputReceiver receiver = new OutputReceiver();
 
-    public CommandAPI(ServerComputer computer) {
+    public CommandAPI(IComputerSystem computer, AdminComputer admin) {
         this.computer = computer;
+        this.admin = admin;
     }
 
     @Override
@@ -295,7 +297,7 @@ public class CommandAPI implements ILuaAPI {
 
         return new CommandSourceStack(receiver,
             Vec3.atCenterOf(computer.getPosition()), Vec2.ZERO,
-            computer.getLevel(), 2,
+            computer.getLevel(), admin.permissionLevel(),
             name, Component.literal(name),
             computer.getLevel().getServer(), null
         );

projects/common/src/main/java/dan200/computercraft/shared/computer/blocks/AbstractComputerBlockEntity.java

@@ -39,7 +39,7 @@ import javax.annotation.Nullable;
 import java.util.Objects;
 import java.util.UUID;
 
-public abstract class AbstractComputerBlockEntity extends BlockEntity implements IComputerBlockEntity, Nameable, MenuProvider {
+public abstract class AbstractComputerBlockEntity extends BlockEntity implements Nameable, MenuProvider {
     private static final String NBT_ID = "ComputerId";
     private static final String NBT_LABEL = "Label";
     private static final String NBT_ON = "On";
@@ -111,7 +111,7 @@ public abstract class AbstractComputerBlockEntity extends BlockEntity implements
         fresh = false;
         computerID = computer.getID();
 
-        // If the on state has changed, mark as as dirty.
+        // If the on state has changed, mark as dirty.
         var newOn = computer.isOn();
         if (on != newOn) {
             on = newOn;
@@ -326,17 +326,14 @@ public abstract class AbstractComputerBlockEntity extends BlockEntity implements
         for (var dir : DirectionUtil.FACINGS) updateRedstoneTo(dir);
     }
 
-    @Override
     public final int getComputerID() {
         return computerID;
     }
 
-    @Override
     public final @Nullable String getLabel() {
         return label;
     }
 
-    @Override
     public final void setComputerID(int id) {
         if (getLevel().isClientSide || computerID == id) return;
 
@@ -344,7 +341,6 @@ public abstract class AbstractComputerBlockEntity extends BlockEntity implements
         BlockEntityHelpers.updateBlock(this);
     }
 
-    @Override
     public final void setLabel(@Nullable String label) {
         if (getLevel().isClientSide || Objects.equals(this.label, label)) return;
 
@@ -354,7 +350,6 @@ public abstract class AbstractComputerBlockEntity extends BlockEntity implements
         BlockEntityHelpers.updateBlock(this);
     }
 
-    @Override
     public ComputerFamily getFamily() {
         return family;
     }

projects/common/src/main/java/dan200/computercraft/shared/computer/blocks/ComputerBlockEntity.java

@@ -12,6 +12,7 @@ import dan200.computercraft.shared.computer.core.ComputerState;
 import dan200.computercraft.shared.computer.core.ServerComputer;
 import dan200.computercraft.shared.computer.inventory.ComputerMenuWithoutInventory;
 import dan200.computercraft.shared.config.Config;
+import dan200.computercraft.shared.util.ComponentMap;
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.Direction;
 import net.minecraft.server.level.ServerLevel;
@@ -34,7 +35,8 @@ public class ComputerBlockEntity extends AbstractComputerBlockEntity {
     protected ServerComputer createComputer(int id) {
         return new ServerComputer(
             (ServerLevel) getLevel(), getBlockPos(), id, label,
-            getFamily(), Config.computerTermWidth, Config.computerTermHeight
+            getFamily(), Config.computerTermWidth, Config.computerTermHeight,
+            ComponentMap.empty()
         );
     }
 

projects/common/src/main/java/dan200/computercraft/shared/computer/blocks/IComputerBlockEntity.java

@@ -1,22 +0,0 @@
-// Copyright Daniel Ratcliffe, 2011-2022. Do not distribute without permission.
-//
-// SPDX-License-Identifier: LicenseRef-CCPL
-
-package dan200.computercraft.shared.computer.blocks;
-
-import dan200.computercraft.shared.computer.core.ComputerFamily;
-
-import javax.annotation.Nullable;
-
-public interface IComputerBlockEntity {
-    int getComputerID();
-
-    void setComputerID(int id);
-
-    @Nullable
-    String getLabel();
-
-    void setLabel(@Nullable String label);
-
-    ComputerFamily getFamily();
-}

projects/common/src/main/java/dan200/computercraft/shared/computer/core/ComputerSystem.java

@@ -0,0 +1,101 @@
+// SPDX-FileCopyrightText: 2019 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.shared.computer.core;
+
+import dan200.computercraft.api.component.ComputerComponent;
+import dan200.computercraft.api.lua.IComputerSystem;
+import dan200.computercraft.api.lua.ILuaAPIFactory;
+import dan200.computercraft.api.peripheral.IPeripheral;
+import dan200.computercraft.core.apis.ComputerAccess;
+import dan200.computercraft.core.apis.IAPIEnvironment;
+import dan200.computercraft.core.computer.ApiLifecycle;
+import dan200.computercraft.shared.util.ComponentMap;
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.level.ServerLevel;
+
+import javax.annotation.Nullable;
+import java.util.Map;
+
+/**
+ * Implementation of {@link IComputerSystem} for usage by externally registered APIs.
+ *
+ * @see ILuaAPIFactory
+ */
+final class ComputerSystem extends ComputerAccess implements IComputerSystem, ApiLifecycle {
+    private final ServerComputer computer;
+    private final IAPIEnvironment environment;
+    private final ComponentMap components;
+
+    private boolean active;
+
+    ComputerSystem(ServerComputer computer, IAPIEnvironment environment, ComponentMap components) {
+        super(environment);
+        this.computer = computer;
+        this.environment = environment;
+        this.components = components;
+    }
+
+    void activate() {
+        active = true;
+    }
+
+    @Override
+    public void shutdown() {
+        unmountAll();
+    }
+
+    @Override
+    public String getAttachmentName() {
+        return "computer";
+    }
+
+    @Override
+    public ServerLevel getLevel() {
+        if (!active) {
+            throw new IllegalStateException("""
+                Cannot access level when constructing the API. Computers are not guaranteed to stay in one place and
+                APIs should not rely on the level remaining constant. Instead, call this method when needed.
+                """.replace('\n', ' ').strip()
+            );
+        }
+        return computer.getLevel();
+    }
+
+    @Override
+    public BlockPos getPosition() {
+        if (!active) {
+            throw new IllegalStateException("""
+                Cannot access computer position when constructing the API. Computers are not guaranteed to stay in one
+                place and APIs should not rely on the position remaining constant. Instead, call this method when
+                needed.
+                """.replace('\n', ' ').strip()
+            );
+        }
+        return computer.getPosition();
+    }
+
+    @Nullable
+    @Override
+    public String getLabel() {
+        return environment.getLabel();
+    }
+
+    @Override
+    public Map<String, IPeripheral> getAvailablePeripherals() {
+        // TODO: Should this return peripherals on the current computer?
+        return Map.of();
+    }
+
+    @Nullable
+    @Override
+    public IPeripheral getAvailablePeripheral(String name) {
+        return null;
+    }
+
+    @Override
+    public <T> @Nullable T getComponent(ComputerComponent<T> component) {
+        return components.get(component);
+    }
+}

projects/common/src/main/java/dan200/computercraft/shared/computer/core/ResourceMount.java

@@ -7,7 +7,6 @@ package dan200.computercraft.shared.computer.core;
 import com.google.common.annotations.VisibleForTesting;
 import dan200.computercraft.api.filesystem.FileOperationException;
 import dan200.computercraft.core.filesystem.ArchiveMount;
-import dan200.computercraft.core.filesystem.FileSystem;
 import net.minecraft.ResourceLocationException;
 import net.minecraft.resources.ResourceLocation;
 import net.minecraft.server.MinecraftServer;
@@ -65,9 +64,10 @@ public final class ResourceMount extends ArchiveMount<ResourceMount.FileEntry> {
             existingNamespace = file.getNamespace();
 
             if (!file.getNamespace().equals(namespace)) continue;
-            if (!FileSystem.contains(subPath, file.getPath())) continue; // Some packs seem to include the parent?
 
-            var localPath = FileSystem.toLocal(file.getPath(), subPath);
+            var localPath = getLocalPath(file.getPath(), subPath);
+            if (localPath == null) continue;
+
             try {
                 getOrCreateChild(newRoot, localPath, this::createEntry);
             } catch (ResourceLocationException e) {

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

@@ -5,15 +5,16 @@
 package dan200.computercraft.shared.computer.core;
 
 import dan200.computercraft.api.ComputerCraftAPI;
+import dan200.computercraft.api.component.AdminComputer;
+import dan200.computercraft.api.component.ComputerComponents;
 import dan200.computercraft.api.filesystem.WritableMount;
-import dan200.computercraft.api.lua.ILuaAPI;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.api.peripheral.WorkMonitor;
 import dan200.computercraft.core.computer.Computer;
 import dan200.computercraft.core.computer.ComputerEnvironment;
 import dan200.computercraft.core.computer.ComputerSide;
 import dan200.computercraft.core.metrics.MetricsObserver;
-import dan200.computercraft.shared.computer.apis.CommandAPI;
+import dan200.computercraft.impl.ApiFactories;
 import dan200.computercraft.shared.computer.menu.ComputerMenu;
 import dan200.computercraft.shared.computer.terminal.NetworkedTerminal;
 import dan200.computercraft.shared.computer.terminal.TerminalState;
@@ -22,6 +23,7 @@ import dan200.computercraft.shared.network.NetworkMessage;
 import dan200.computercraft.shared.network.client.ClientNetworkContext;
 import dan200.computercraft.shared.network.client.ComputerTerminalClientMessage;
 import dan200.computercraft.shared.network.server.ServerNetworking;
+import dan200.computercraft.shared.util.ComponentMap;
 import net.minecraft.core.BlockPos;
 import net.minecraft.server.level.ServerLevel;
 import net.minecraft.world.entity.player.Player;
@@ -48,7 +50,8 @@ public class ServerComputer implements InputHandler, ComputerEnvironment {
     private int ticksSincePing;
 
     public ServerComputer(
-        ServerLevel level, BlockPos position, int computerID, @Nullable String label, ComputerFamily family, int terminalWidth, int terminalHeight
+        ServerLevel level, BlockPos position, int computerID, @Nullable String label, ComputerFamily family, int terminalWidth, int terminalHeight,
+        ComponentMap baseComponents
     ) {
         this.level = level;
         this.position = position;
@@ -58,10 +61,27 @@ public class ServerComputer implements InputHandler, ComputerEnvironment {
         terminal = new NetworkedTerminal(terminalWidth, terminalHeight, family != ComputerFamily.NORMAL, this::markTerminalChanged);
         metrics = context.metrics().createMetricObserver(this);
 
+        var componentBuilder = ComponentMap.builder();
+        componentBuilder.add(ComponentMap.METRICS, metrics);
+        if (family == ComputerFamily.COMMAND) {
+            componentBuilder.add(ComputerComponents.ADMIN_COMPUTER, new AdminComputer() {
+            });
+        }
+        componentBuilder.add(baseComponents);
+        var components = componentBuilder.build();
+
         computer = new Computer(context.computerContext(), this, terminal, computerID);
         computer.setLabel(label);
 
-        if (family == ComputerFamily.COMMAND) addAPI(new CommandAPI(this));
+        // Load in the externally registered APIs.
+        for (var factory : ApiFactories.getAll()) {
+            var system = new ComputerSystem(this, computer.getAPIEnvironment(), components);
+            var api = factory.create(system);
+            if (api == null) continue;
+
+            system.activate();
+            computer.addApi(api, system);
+        }
     }
 
     public ComputerFamily getFamily() {
@@ -211,10 +231,6 @@ public class ServerComputer implements InputHandler, ComputerEnvironment {
         computer.getEnvironment().setBundledRedstoneInput(side, combination);
     }
 
-    public void addAPI(ILuaAPI api) {
-        computer.addApi(api);
-    }
-
     public void setPeripheral(ComputerSide side, @Nullable IPeripheral peripheral) {
         computer.getEnvironment().setPeripheral(side, peripheral);
     }

projects/common/src/main/java/dan200/computercraft/shared/computer/core/ServerContext.java

@@ -17,7 +17,6 @@ import dan200.computercraft.core.lua.ILuaMachine;
 import dan200.computercraft.core.methods.MethodSupplier;
 import dan200.computercraft.core.methods.PeripheralMethod;
 import dan200.computercraft.impl.AbstractComputerCraftAPI;
-import dan200.computercraft.impl.ApiFactories;
 import dan200.computercraft.impl.GenericSources;
 import dan200.computercraft.shared.CommonHooks;
 import dan200.computercraft.shared.computer.metrics.GlobalMetrics;
@@ -74,7 +73,6 @@ public final class ServerContext {
             .computerThreads(ConfigSpec.computerThreads.get())
             .mainThreadScheduler(mainThread)
             .luaFactory(luaMachine)
-            .apiFactories(ApiFactories.getAll())
             .genericMethods(GenericSources.getAllMethods())
             .build();
         idAssigner = new IDAssigner(storageDir.resolve("ids.json"));

projects/common/src/main/java/dan200/computercraft/shared/config/AddressRuleConfig.java

@@ -69,6 +69,13 @@ class AddressRuleConfig {
         );
     }
 
+    public static UnmodifiableConfig newRule() {
+        return makeRule(config -> {
+            config.add("host", "example.com");
+            config.add("action", Action.DENY.name().toLowerCase(Locale.ROOT));
+        });
+    }
+
     private static UnmodifiableConfig makeRule(Consumer<CommentedConfig> setup) {
         var config = InMemoryCommentedFormat.defaultInstance().createConfig(LinkedHashMap::new);
         setup.accept(config);

projects/common/src/main/java/dan200/computercraft/shared/config/ConfigFile.java

@@ -126,7 +126,7 @@ public interface ConfigFile {
 
         public abstract ConfigFile.Value<Integer> defineInRange(String path, int defaultValue, int min, int max);
 
-        public abstract <T> ConfigFile.Value<List<? extends T>> defineList(String path, List<? extends T> defaultValue, Predicate<Object> elementValidator);
+        public abstract <T> ConfigFile.Value<List<? extends T>> defineList(String path, List<? extends T> defaultValue, Supplier<T> newValue, Predicate<Object> elementValidator);
 
         public abstract <V extends Enum<V>> ConfigFile.Value<V> defineEnum(String path, V defaultValue);
 

projects/common/src/main/java/dan200/computercraft/shared/config/ConfigSpec.java

@@ -145,7 +145,7 @@ public final class ConfigSpec {
                     or a single method (computercraft:inventory#pushItems).
                     """)
                 .worldRestart()
-                .defineList("disabled_generic_methods", List.of(), x -> x instanceof String);
+                .defineList("disabled_generic_methods", List.of(), () -> "", x -> x instanceof String);
         }
 
         {
@@ -214,7 +214,7 @@ public final class ConfigSpec {
                      - "max_websocket_message" (optional): The maximum size (in bytes) that a computer can send or
                        receive in one websocket packet.
                      - "use_proxy" (optional): Enable use of the HTTP/SOCKS proxy if it is configured.""")
-                .defineList("rules", AddressRuleConfig.defaultRules(), x -> x instanceof UnmodifiableConfig);
+                .defineList("rules", AddressRuleConfig.defaultRules(), AddressRuleConfig::newRule, x -> x instanceof UnmodifiableConfig);
 
             httpMaxRequests = builder
                 .comment("""

projects/common/src/main/java/dan200/computercraft/shared/data/HasComputerIdLootCondition.java

@@ -5,7 +5,7 @@
 package dan200.computercraft.shared.data;
 
 import dan200.computercraft.shared.ModRegistry;
-import dan200.computercraft.shared.computer.blocks.IComputerBlockEntity;
+import dan200.computercraft.shared.computer.blocks.AbstractComputerBlockEntity;
 import net.minecraft.world.level.storage.loot.LootContext;
 import net.minecraft.world.level.storage.loot.parameters.LootContextParam;
 import net.minecraft.world.level.storage.loot.parameters.LootContextParams;
@@ -27,7 +27,7 @@ public final class HasComputerIdLootCondition implements LootItemCondition {
     @Override
     public boolean test(LootContext lootContext) {
         var tile = lootContext.getParamOrNull(LootContextParams.BLOCK_ENTITY);
-        return tile instanceof IComputerBlockEntity computer && computer.getComputerID() >= 0;
+        return tile instanceof AbstractComputerBlockEntity computer && computer.getComputerID() >= 0;
     }
 
     @Override

projects/common/src/main/java/dan200/computercraft/shared/details/ItemDetails.java

@@ -53,7 +53,9 @@ public class ItemDetails {
         data.put("itemGroups", getItemGroups(stack));
 
         var lore = stack.get(DataComponents.LORE);
-        if (lore != null) data.put("lore", lore.lines().stream().map(Component::getString).toList());
+        if (lore != null && !lore.lines().isEmpty()) {
+            data.put("lore", lore.lines().stream().map(Component::getString).toList());
+        }
 
         var enchants = getAllEnchants(stack);
         if (!enchants.isEmpty()) data.put("enchantments", enchants);

projects/common/src/main/java/dan200/computercraft/shared/integration/CreateIntegration.java

@@ -0,0 +1,34 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.shared.integration;
+
+import com.simibubi.create.content.contraptions.BlockMovementChecks;
+import com.simibubi.create.content.contraptions.BlockMovementChecks.CheckResult;
+import dan200.computercraft.shared.peripheral.modem.wired.CableBlock;
+import dan200.computercraft.shared.peripheral.modem.wireless.WirelessModemBlock;
+
+/**
+ * Integration with Create.
+ */
+public final class CreateIntegration {
+    public static final String ID = "create";
+
+    private CreateIntegration() {
+    }
+
+    public static void setup() {
+        // Allow modems to be treated as "attached" to their adjacent block.
+        BlockMovementChecks.registerAttachedCheck((state, world, pos, direction) -> {
+            var block = state.getBlock();
+            if (block instanceof WirelessModemBlock) {
+                return CheckResult.of(state.getValue(WirelessModemBlock.FACING) == direction);
+            } else if (block instanceof CableBlock) {
+                return CheckResult.of(state.getValue(CableBlock.MODEM).getFacing() == direction);
+            } else {
+                return CheckResult.PASS;
+            }
+        });
+    }
+}

projects/common/src/main/java/dan200/computercraft/shared/integration/ExternalModTags.java

@@ -8,6 +8,7 @@ import net.minecraft.core.registries.Registries;
 import net.minecraft.resources.ResourceLocation;
 import net.minecraft.tags.TagKey;
 import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.state.BlockState;
 
 /**
  * Tags defined by external mods.
@@ -26,9 +27,9 @@ public final class ExternalModTags {
         /**
          * Create's "brittle" tag, used to determine if this block needs to be moved before its neighbours.
          *
-         * @see <a href="https://github.com/Creators-of-Create/Create/blob/mc1.20.1/dev/src/main/java/com/simibubi/create/content/contraptions/BlockMovementChecks.java">{@code BlockMovementChecks}</a>
+         * @see com.simibubi.create.content.contraptions.BlockMovementChecks#isBrittle(BlockState)
          */
-        public static final TagKey<Block> CREATE_BRITTLE = make("create", "brittle");
+        public static final TagKey<Block> CREATE_BRITTLE = make(CreateIntegration.ID, "brittle");
 
         private static TagKey<Block> make(String mod, String name) {
             return TagKey.create(Registries.BLOCK, ResourceLocation.fromNamespaceAndPath(mod, name));

projects/common/src/main/java/dan200/computercraft/shared/lectern/CustomLecternBlock.java

@@ -0,0 +1,163 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.shared.lectern;
+
+import dan200.computercraft.shared.ModRegistry;
+import dan200.computercraft.shared.media.items.PrintoutItem;
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.stats.Stats;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.InteractionResult;
+import net.minecraft.world.entity.item.ItemEntity;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+import net.minecraft.world.item.context.UseOnContext;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.LevelReader;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.LecternBlock;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.phys.BlockHitResult;
+
+/**
+ * Extends {@link LecternBlock} with support for {@linkplain PrintoutItem printouts}.
+ * <p>
+ * Unlike the vanilla lectern, this block is never empty. If the book is removed from the lectern, it converts back to
+ * its vanilla version (see {@link #clearLectern(Level, BlockPos, BlockState)}).
+ *
+ * @see PrintoutItem#useOn(UseOnContext) Placing books into a lectern.
+ */
+public class CustomLecternBlock extends LecternBlock {
+    public CustomLecternBlock(Properties properties) {
+        super(properties);
+        registerDefaultState(defaultBlockState().setValue(HAS_BOOK, true));
+    }
+
+    /**
+     * Attempt to place an item onto an (empty) lectern.
+     *
+     * @param player     The player placing the item.
+     * @param level      The current level.
+     * @param pos        The position of the lectern.
+     * @param blockState The current state of the lectern.
+     * @param item       The item to place in the custom lectern.
+     * @return Whether the item was placed or not.
+     */
+    public static InteractionResult tryPlaceItem(Player player, Level level, BlockPos pos, BlockState blockState, ItemStack item) {
+        if (item.getItem() instanceof PrintoutItem) {
+            if (!level.isClientSide) replaceLectern(player, level, pos, blockState, item);
+            return InteractionResult.sidedSuccess(level.isClientSide);
+        }
+
+        return InteractionResult.PASS;
+    }
+
+    /**
+     * Replace a vanilla lectern with a custom one.
+     *
+     * @param player     The player placing the item.
+     * @param level      The current level.
+     * @param pos        The position of the lectern.
+     * @param blockState The current state of the lectern.
+     * @param item       The item to place in the custom lectern.
+     */
+    private static void replaceLectern(Player player, Level level, BlockPos pos, BlockState blockState, ItemStack item) {
+        level.setBlockAndUpdate(pos, ModRegistry.Blocks.LECTERN.get().defaultBlockState()
+            .setValue(HAS_BOOK, true)
+            .setValue(FACING, blockState.getValue(FACING))
+            .setValue(POWERED, blockState.getValue(POWERED)));
+
+        if (level.getBlockEntity(pos) instanceof CustomLecternBlockEntity be) {
+            be.setItem(item.consumeAndReturn(1, player));
+        }
+    }
+
+    /**
+     * Remove a custom lectern and replace it with an empty vanilla one.
+     *
+     * @param level      The current level.
+     * @param pos        The position of the lectern.
+     * @param blockState The current state of the lectern.
+     */
+    static void clearLectern(Level level, BlockPos pos, BlockState blockState) {
+        level.setBlockAndUpdate(pos, Blocks.LECTERN.defaultBlockState()
+            .setValue(HAS_BOOK, false)
+            .setValue(FACING, blockState.getValue(FACING))
+            .setValue(POWERED, blockState.getValue(POWERED)));
+    }
+
+    @Override
+    @Deprecated
+    public ItemStack getCloneItemStack(LevelReader level, BlockPos pos, BlockState state) {
+        return new ItemStack(Items.LECTERN);
+    }
+
+    @Override
+    public void tick(BlockState state, ServerLevel level, BlockPos pos, RandomSource random) {
+        // If we've no lectern, remove it.
+        if (level.getBlockEntity(pos) instanceof CustomLecternBlockEntity lectern && lectern.getItem().isEmpty()) {
+            clearLectern(level, pos, state);
+            return;
+        }
+
+        super.tick(state, level, pos, random);
+    }
+
+    @Override
+    public void onRemove(BlockState state, Level level, BlockPos pos, BlockState newState, boolean isMoving) {
+        if (state.is(newState.getBlock())) return;
+
+        if (level.getBlockEntity(pos) instanceof CustomLecternBlockEntity lectern) {
+            dropItem(level, pos, state, lectern.getItem().copy());
+        }
+
+        super.onRemove(state, level, pos, newState, isMoving);
+    }
+
+    private static void dropItem(Level level, BlockPos pos, BlockState state, ItemStack stack) {
+        if (stack.isEmpty()) return;
+
+        var direction = state.getValue(FACING);
+        var dx = 0.25 * direction.getStepX();
+        var dz = 0.25 * direction.getStepZ();
+        var entity = new ItemEntity(level, pos.getX() + 0.5 + dx, pos.getY() + 1, pos.getZ() + 0.5 + dz, stack);
+        entity.setDefaultPickUpDelay();
+        level.addFreshEntity(entity);
+    }
+
+    @Override
+    public String getDescriptionId() {
+        return Blocks.LECTERN.getDescriptionId();
+    }
+
+    @Override
+    public CustomLecternBlockEntity newBlockEntity(BlockPos pos, BlockState state) {
+        return new CustomLecternBlockEntity(pos, state);
+    }
+
+    @Override
+    public int getAnalogOutputSignal(BlockState blockState, Level level, BlockPos pos) {
+        return level.getBlockEntity(pos) instanceof CustomLecternBlockEntity lectern ? lectern.getRedstoneSignal() : 0;
+    }
+
+    @Override
+    public InteractionResult useWithoutItem(BlockState state, Level level, BlockPos pos, Player player, BlockHitResult hit) {
+        if (!level.isClientSide && level.getBlockEntity(pos) instanceof CustomLecternBlockEntity lectern) {
+            if (player.isSecondaryUseActive()) {
+                // When shift+clicked with an empty hand, drop the item and replace with the normal lectern.
+                clearLectern(level, pos, state);
+            } else {
+                // Otherwise open the screen.
+                player.openMenu(lectern);
+            }
+
+            player.awardStat(Stats.INTERACT_WITH_LECTERN);
+        }
+
+        return InteractionResult.sidedSuccess(level.isClientSide);
+    }
+}

projects/common/src/main/java/dan200/computercraft/shared/lectern/CustomLecternBlockEntity.java

@@ -0,0 +1,195 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.shared.lectern;
+
+import dan200.computercraft.shared.ModRegistry;
+import dan200.computercraft.shared.container.BasicContainer;
+import dan200.computercraft.shared.container.SingleContainerData;
+import dan200.computercraft.shared.media.PrintoutMenu;
+import dan200.computercraft.shared.media.items.PrintoutData;
+import dan200.computercraft.shared.media.items.PrintoutItem;
+import dan200.computercraft.shared.util.BlockEntityHelpers;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.HolderLookup;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.Tag;
+import net.minecraft.network.chat.Component;
+import net.minecraft.network.protocol.Packet;
+import net.minecraft.network.protocol.game.ClientGamePacketListener;
+import net.minecraft.network.protocol.game.ClientboundBlockEntityDataPacket;
+import net.minecraft.util.Mth;
+import net.minecraft.world.Container;
+import net.minecraft.world.MenuProvider;
+import net.minecraft.world.entity.player.Inventory;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.inventory.AbstractContainerMenu;
+import net.minecraft.world.inventory.ContainerData;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.block.LecternBlock;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.entity.LecternBlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.AbstractList;
+import java.util.List;
+
+/**
+ * The block entity for our {@link CustomLecternBlock}.
+ *
+ * @see LecternBlockEntity
+ */
+public final class CustomLecternBlockEntity extends BlockEntity implements MenuProvider {
+    private static final String NBT_ITEM = "Item";
+    private static final String NBT_PAGE = "Page";
+
+    private ItemStack item = ItemStack.EMPTY;
+    private int page, pageCount;
+
+    public CustomLecternBlockEntity(BlockPos pos, BlockState blockState) {
+        super(ModRegistry.BlockEntities.LECTERN.get(), pos, blockState);
+    }
+
+    public ItemStack getItem() {
+        return item;
+    }
+
+    void setItem(ItemStack item) {
+        this.item = item;
+        itemChanged();
+        BlockEntityHelpers.updateBlock(this);
+    }
+
+    int getRedstoneSignal() {
+        if (item.getItem() instanceof PrintoutItem) {
+            var progress = pageCount > 1 ? (float) page / (pageCount - 1) : 1F;
+            return Mth.floor(progress * 14f) + 1;
+        }
+
+        return 15;
+    }
+
+    /**
+     * Called after the item has changed. This sets up the state for the new item.
+     */
+    private void itemChanged() {
+        if (item.getItem() instanceof PrintoutItem) {
+            pageCount = PrintoutData.getOrEmpty(item).pages();
+            page = Mth.clamp(page, 0, pageCount - 1);
+        } else {
+            pageCount = page = 0;
+        }
+    }
+
+    /**
+     * Set the current page, emitting a redstone pulse if needed.
+     *
+     * @param page The new page.
+     */
+    private void setPage(int page) {
+        if (this.page == page) return;
+
+        this.page = page;
+        setChanged();
+        if (getLevel() != null) LecternBlock.signalPageChange(getLevel(), getBlockPos(), getBlockState());
+    }
+
+    @Override
+    public void loadAdditional(CompoundTag tag, HolderLookup.Provider registries) {
+        super.loadAdditional(tag, registries);
+
+        item = tag.contains(NBT_ITEM, Tag.TAG_COMPOUND) ? ItemStack.parseOptional(registries, tag.getCompound(NBT_ITEM)) : ItemStack.EMPTY;
+        page = tag.getInt(NBT_PAGE);
+        itemChanged();
+    }
+
+    @Override
+    protected void saveAdditional(CompoundTag tag, HolderLookup.Provider registries) {
+        super.saveAdditional(tag, registries);
+
+        if (!item.isEmpty()) tag.put(NBT_ITEM, item.save(registries));
+        if (item.getItem() instanceof PrintoutItem) tag.putInt(NBT_PAGE, page);
+    }
+
+    @Override
+    public Packet<ClientGamePacketListener> getUpdatePacket() {
+        return ClientboundBlockEntityDataPacket.create(this);
+    }
+
+    @Override
+    public CompoundTag getUpdateTag(HolderLookup.Provider registries) {
+        var tag = super.getUpdateTag(registries);
+        tag.put(NBT_ITEM, item.save(registries));
+        return tag;
+    }
+
+    @Nullable
+    @Override
+    public AbstractContainerMenu createMenu(int containerId, Inventory playerInventory, Player player) {
+        var item = getItem();
+        if (item.getItem() instanceof PrintoutItem) {
+            return new PrintoutMenu(
+                containerId, new LecternContainer(), 0,
+                p -> Container.stillValidBlockEntity(this, player, Container.DEFAULT_DISTANCE_BUFFER),
+                new PrintoutContainerData()
+            );
+        }
+
+        return null;
+    }
+
+    @Override
+    public Component getDisplayName() {
+        return getItem().getDisplayName();
+    }
+
+    /**
+     * A read-only container storing the lectern's contents.
+     */
+    private final class LecternContainer implements BasicContainer {
+        private final List<ItemStack> itemView = new AbstractList<>() {
+            @Override
+            public ItemStack get(int index) {
+                if (index != 0) throw new IndexOutOfBoundsException("Inventory only has one slot");
+                return item;
+            }
+
+            @Override
+            public int size() {
+                return 1;
+            }
+        };
+
+        @Override
+        public List<ItemStack> getItems() {
+            return itemView;
+        }
+
+        @Override
+        public void setChanged() {
+            // Should never happen, so a no-op.
+        }
+
+        @Override
+        public boolean stillValid(Player player) {
+            return !isRemoved();
+        }
+    }
+
+    /**
+     * {@link ContainerData} for a {@link PrintoutMenu}. This provides a read/write view of the current page.
+     */
+    private final class PrintoutContainerData implements SingleContainerData {
+        @Override
+        public int get() {
+            return page;
+        }
+
+        @Override
+        public void set(int index, int value) {
+            if (index == 0) setPage(value);
+        }
+    }
+}

projects/common/src/main/java/dan200/computercraft/shared/media/PrintoutMenu.java

@@ -0,0 +1,137 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.shared.media;
+
+import dan200.computercraft.shared.ModRegistry;
+import dan200.computercraft.shared.container.InvisibleSlot;
+import dan200.computercraft.shared.media.items.PrintoutData;
+import dan200.computercraft.shared.media.items.PrintoutItem;
+import net.minecraft.util.Mth;
+import net.minecraft.world.Container;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.SimpleContainer;
+import net.minecraft.world.entity.player.Inventory;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.inventory.*;
+import net.minecraft.world.item.ItemStack;
+
+import java.util.function.Predicate;
+
+/**
+ * The menus for {@linkplain PrintoutItem printouts}.
+ * <p>
+ * This is a somewhat similar design to {@link LecternMenu}, which is used to read written books.
+ * <p>
+ * This holds a single slot (containing the printout), and a single data slot ({@linkplain #DATA_CURRENT_PAGE holding
+ * the current page}). The page is set by the client by sending a {@linkplain #clickMenuButton(Player, int) button
+ * press} with an index of {@link #PAGE_BUTTON_OFFSET} plus the current page.
+ * <p>
+ * The client-side screen uses {@linkplain ContainerListener container listeners} to subscribe to item and page changes.
+ * However, listeners aren't fired on the client, so we copy {@link LecternMenu}'s hack and call
+ * {@link #broadcastChanges()} whenever an item or data value are changed.
+ */
+public class PrintoutMenu extends AbstractContainerMenu {
+    public static final int DATA_CURRENT_PAGE = 0;
+    private static final int DATA_SIZE = 1;
+
+    public static final int PAGE_BUTTON_OFFSET = 100;
+
+    private final Predicate<Player> valid;
+    private final ContainerData currentPage;
+
+    public PrintoutMenu(
+        int containerId, Container container, int slotIdx, Predicate<Player> valid, ContainerData currentPage
+    ) {
+        super(ModRegistry.Menus.PRINTOUT.get(), containerId);
+        this.valid = valid;
+        this.currentPage = currentPage;
+
+        addSlot(new InvisibleSlot(container, slotIdx) {
+            @Override
+            public void setChanged() {
+                super.setChanged();
+                slotsChanged(container); // Trigger listeners on the client.
+            }
+        });
+        addDataSlots(currentPage);
+    }
+
+    /**
+     * Create {@link PrintoutMenu} for use a remote (client).
+     *
+     * @param containerId The current container id.
+     * @return The constructed container.
+     */
+    public static PrintoutMenu createRemote(int containerId) {
+        return new PrintoutMenu(containerId, new SimpleContainer(1), 0, p -> true, new SimpleContainerData(DATA_SIZE));
+    }
+
+    /**
+     * Create a {@link PrintoutMenu} for the printout in the current player's hand.
+     *
+     * @param containerId The current container id.
+     * @param player      The player to open the container.
+     * @param hand        The hand containing the item.
+     * @return The constructed container.
+     */
+    public static PrintoutMenu createInHand(int containerId, Player player, InteractionHand hand) {
+        var currentStack = player.getItemInHand(hand);
+        var currentItem = currentStack.getItem();
+
+        var slot = switch (hand) {
+            case MAIN_HAND -> player.getInventory().selected;
+            case OFF_HAND -> Inventory.SLOT_OFFHAND;
+        };
+        return new PrintoutMenu(
+            containerId, player.getInventory(), slot,
+            p -> player.getItemInHand(hand).getItem() == currentItem, new SimpleContainerData(DATA_SIZE)
+        );
+    }
+
+    @Override
+    public ItemStack quickMoveStack(Player player, int index) {
+        return ItemStack.EMPTY;
+    }
+
+    @Override
+    public boolean stillValid(Player player) {
+        return valid.test(player);
+    }
+
+    @Override
+    public boolean clickMenuButton(Player player, int id) {
+        if (id >= PAGE_BUTTON_OFFSET) {
+            var page = Mth.clamp(id - PAGE_BUTTON_OFFSET, 0, PrintoutData.getOrEmpty(getPrintout()).pages() - 1);
+            setData(DATA_CURRENT_PAGE, page);
+            return true;
+        }
+
+        return super.clickMenuButton(player, id);
+    }
+
+    /**
+     * Get the current printout.
+     *
+     * @return The current printout.
+     */
+    public ItemStack getPrintout() {
+        return getSlot(0).getItem();
+    }
+
+    /**
+     * Get the current page.
+     *
+     * @return The current page.
+     */
+    public int getPage() {
+        return currentPage.get(DATA_CURRENT_PAGE);
+    }
+
+    @Override
+    public void setData(int id, int data) {
+        super.setData(id, data);
+        broadcastChanges(); // Trigger listeners on the client.
+    }
+}

projects/common/src/main/java/dan200/computercraft/shared/media/items/PrintoutItem.java

@@ -4,13 +4,13 @@
 
 package dan200.computercraft.shared.media.items;
 
-import dan200.computercraft.shared.ModRegistry;
-import dan200.computercraft.shared.common.HeldItemMenu;
-import dan200.computercraft.shared.network.container.HeldItemContainerData;
+import com.google.common.base.Strings;
+import dan200.computercraft.shared.media.PrintoutMenu;
 import net.minecraft.network.chat.Component;
 import net.minecraft.world.InteractionHand;
 import net.minecraft.world.InteractionResult;
 import net.minecraft.world.InteractionResultHolder;
+import net.minecraft.world.SimpleMenuProvider;
 import net.minecraft.world.entity.player.Player;
 import net.minecraft.world.item.Item;
 import net.minecraft.world.item.ItemStack;
@@ -41,11 +41,13 @@ public class PrintoutItem extends Item {
 
     @Override
     public InteractionResultHolder<ItemStack> use(Level world, Player player, InteractionHand hand) {
+        var stack = player.getItemInHand(hand);
         if (!world.isClientSide) {
-            new HeldItemContainerData(hand)
-                .open(player, new HeldItemMenu.Factory(ModRegistry.Menus.PRINTOUT.get(), player.getItemInHand(hand), hand));
+            var title = PrintoutData.getOrEmpty(stack).title();
+            var displayTitle = Strings.isNullOrEmpty(title) ? stack.getDisplayName() : Component.literal(title);
+            player.openMenu(new SimpleMenuProvider((id, playerInventory, p) -> PrintoutMenu.createInHand(id, p, hand), displayTitle));
         }
-        return new InteractionResultHolder<>(InteractionResult.sidedSuccess(world.isClientSide), player.getItemInHand(hand));
+        return new InteractionResultHolder<>(InteractionResult.sidedSuccess(world.isClientSide), stack);
     }
 
     public Type getType() {

projects/common/src/main/java/dan200/computercraft/shared/network/client/PocketComputerDataMessage.java

@@ -43,7 +43,7 @@ public record PocketComputerDataMessage(
         this(
             computer.getInstanceUUID(),
             computer.getState(),
-            computer.getLight(),
+            computer.getBrain().getLight(),
             sendTerminal ? Optional.of(computer.getTerminalState()) : Optional.empty()
         );
     }

projects/common/src/main/java/dan200/computercraft/shared/network/container/HeldItemContainerData.java

@@ -1,31 +0,0 @@
-// SPDX-FileCopyrightText: 2019 The CC: Tweaked Developers
-//
-// SPDX-License-Identifier: MPL-2.0
-
-package dan200.computercraft.shared.network.container;
-
-import dan200.computercraft.shared.common.HeldItemMenu;
-import dan200.computercraft.shared.media.items.PrintoutItem;
-import dan200.computercraft.shared.network.codec.MoreStreamCodecs;
-import net.minecraft.network.RegistryFriendlyByteBuf;
-import net.minecraft.network.codec.StreamCodec;
-import net.minecraft.world.InteractionHand;
-
-/**
- * Opens a printout GUI based on the currently held item.
- *
- * @param hand The hand holding this item.
- * @see HeldItemMenu
- * @see PrintoutItem
- */
-public record HeldItemContainerData(InteractionHand hand) implements ContainerData {
-    public static final StreamCodec<RegistryFriendlyByteBuf, HeldItemContainerData> STREAM_CODEC = StreamCodec.composite(
-        MoreStreamCodecs.ofEnum(InteractionHand.class), HeldItemContainerData::hand,
-        HeldItemContainerData::new
-    );
-
-    @Override
-    public void toBytes(RegistryFriendlyByteBuf buf) {
-        STREAM_CODEC.encode(buf, this);
-    }
-}

projects/common/src/main/java/dan200/computercraft/shared/peripheral/diskdrive/DiskDriveBlockEntity.java

@@ -99,11 +99,13 @@ public final class DiskDriveBlockEntity extends AbstractContainerBlockEntity imp
 
     @Override
     public void clearRemoved() {
+        super.clearRemoved();
         updateMedia();
     }
 
     @Override
     public void setRemoved() {
+        super.setRemoved();
         if (recordPlaying) stopRecord();
     }
 

projects/common/src/main/java/dan200/computercraft/shared/peripheral/generic/methods/AbstractFluidMethods.java

@@ -70,10 +70,10 @@ public abstract class AbstractFluidMethods<T> implements GenericPeripheral {
     ) throws LuaException;
 
     /**
-     * Move a fluid from a connected fluid container into this oneone.
+     * Move a fluid from a connected fluid container into this one.
      * <p>
      * This allows you to pull fluid in the current fluid container from another container <em>on the same wired
-     * network</em>. Both containers must attached to wired modems which are connected via a cable.
+     * network</em>. Both containers must be attached to wired modems which are connected via a cable.
      *
      * @param to        Container to move fluid to.
      * @param computer  The current computer.

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

@@ -276,16 +276,18 @@ public abstract class SpeakerPeripheral implements IPeripheral {
      * Attempt to stream some audio data to the speaker.
      * <p>
      * This accepts a list of audio samples as amplitudes between -128 and 127. These are stored in an internal buffer
-     * and played back at 48kHz. If this buffer is full, this function will return {@literal false}. You should wait for
-     * a [`speaker_audio_empty`] event before trying again.
+     * and played back at 48kHz. If this buffer is full, this function will return {@literal false}. Programs should
+     * wait for a [`speaker_audio_empty`] event before trying to play audio again.
      * <p>
-     * > [!NOTE]
-     * > The speaker only buffers a single call to {@link #playAudio} at once. This means if you try to play a small
-     * > number of samples, you'll have a lot of stutter. You should try to play as many samples in one call as possible
-     * > (up to 128×1024), as this reduces the chances of audio stuttering or halting, especially when the server or
-     * > computer is lagging.
+     * The speaker only buffers a single call to {@link #playAudio} at once. This means if you try to play a small
+     * number of samples, you'll have a lot of stutter. You should try to play as many samples in one call as possible
+     * (up to 128×1024), as this reduces the chances of audio stuttering or halting, especially when the server or
+     * computer is lagging.
      * <p>
-     * [`speaker_audio`] provides a more complete guide to using speakers
+     * While the speaker accepts 8-bit PCM audio, the audio stream is re-encoded before being played. This means that
+     * the supplied samples may not be played out exactly.
+     * <p>
+     * [`speaker_audio`] provides a more complete guide to using speakers.
      *
      * @param context The Lua context.
      * @param audio   The audio data to play.

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

@@ -6,10 +6,10 @@ package dan200.computercraft.shared.pocket.apis;
 
 import dan200.computercraft.api.lua.ILuaAPI;
 import dan200.computercraft.api.lua.LuaFunction;
+import dan200.computercraft.api.pocket.IPocketAccess;
 import dan200.computercraft.api.pocket.IPocketUpgrade;
 import dan200.computercraft.api.upgrades.UpgradeData;
 import dan200.computercraft.impl.PocketUpgrades;
-import dan200.computercraft.shared.pocket.core.PocketServerComputer;
 import net.minecraft.core.NonNullList;
 import net.minecraft.world.entity.player.Player;
 import net.minecraft.world.item.ItemStack;
@@ -30,14 +30,20 @@ import java.util.Objects;
  *   print("On something else")
  * end
  * }</pre>
+ * <p>
+ * ## Recipes
+ * <div class="recipe-container">
+ *  <mc-recipe recipe="computercraft:pocket_computer_normal"></mc-recipe>
+ *  <mc-recipe recipe="computercraft:pocket_computer_advanced"></mc-recipe>
+ * </div>
  *
  * @cc.module pocket
  */
 public class PocketAPI implements ILuaAPI {
-    private final PocketServerComputer computer;
+    private final IPocketAccess pocket;
 
-    public PocketAPI(PocketServerComputer computer) {
-        this.computer = computer;
+    public PocketAPI(IPocketAccess pocket) {
+        this.pocket = pocket;
     }
 
     @Override
@@ -56,10 +62,10 @@ public class PocketAPI implements ILuaAPI {
      */
     @LuaFunction(mainThread = true)
     public final Object[] equipBack() {
-        var entity = computer.getEntity();
+        var entity = pocket.getEntity();
         if (!(entity instanceof Player player)) return new Object[]{ false, "Cannot find player" };
         var inventory = player.getInventory();
-        var previousUpgrade = computer.getUpgrade();
+        var previousUpgrade = pocket.getUpgrade();
 
         // Attempt to find the upgrade, starting in the main segment, and then looking in the opposite
         // one. We start from the position the item is currently in and loop round to the start.
@@ -73,7 +79,7 @@ public class PocketAPI implements ILuaAPI {
         if (previousUpgrade != null) storeItem(player, previousUpgrade.getUpgradeItem());
 
         // Set the new upgrade
-        computer.setUpgrade(newUpgrade);
+        pocket.setUpgrade(newUpgrade);
 
         return new Object[]{ true };
     }
@@ -87,13 +93,13 @@ public class PocketAPI implements ILuaAPI {
      */
     @LuaFunction(mainThread = true)
     public final Object[] unequipBack() {
-        var entity = computer.getEntity();
+        var entity = pocket.getEntity();
         if (!(entity instanceof Player player)) return new Object[]{ false, "Cannot find player" };
-        var previousUpgrade = computer.getUpgrade();
+        var previousUpgrade = pocket.getUpgrade();
 
         if (previousUpgrade == null) return new Object[]{ false, "Nothing to unequip" };
 
-        computer.setUpgrade(null);
+        pocket.setUpgrade(null);
 
         storeItem(player, previousUpgrade.getUpgradeItem());
 
@@ -111,7 +117,7 @@ public class PocketAPI implements ILuaAPI {
         for (var i = 0; i < inv.size(); i++) {
             var invStack = inv.get((i + start) % inv.size());
             if (!invStack.isEmpty()) {
-                var newUpgrade = PocketUpgrades.instance().get(computer.getLevel().registryAccess(), invStack);
+                var newUpgrade = PocketUpgrades.instance().get(pocket.getLevel().registryAccess(), invStack);
 
                 if (newUpgrade != null && !Objects.equals(newUpgrade, previous)) {
                     // Consume an item from this stack and exit the loop

projects/common/src/main/java/dan200/computercraft/shared/pocket/core/PocketBrain.java

@@ -0,0 +1,176 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.shared.pocket.core;
+
+import dan200.computercraft.api.pocket.IPocketAccess;
+import dan200.computercraft.api.pocket.IPocketUpgrade;
+import dan200.computercraft.api.upgrades.UpgradeData;
+import dan200.computercraft.core.computer.ComputerSide;
+import dan200.computercraft.shared.computer.core.ComputerFamily;
+import dan200.computercraft.shared.network.client.PocketComputerDataMessage;
+import dan200.computercraft.shared.network.server.ServerNetworking;
+import dan200.computercraft.shared.pocket.items.PocketComputerItem;
+import net.minecraft.core.component.DataComponentPatch;
+import net.minecraft.core.component.DataComponents;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.component.DyedItemColor;
+import net.minecraft.world.phys.Vec3;
+
+import javax.annotation.Nullable;
+
+/**
+ * Holds additional state for a pocket computer. This includes pocket computer upgrade,
+ * {@linkplain IPocketAccess#getLight() light colour} and {@linkplain IPocketAccess#getColour() colour}.
+ * <p>
+ * This state is read when the brain is created, and written back to the holding item stack when the holding entity is
+ * ticked (see {@link #updateItem(ItemStack)}).
+ */
+public final class PocketBrain implements IPocketAccess {
+    private final PocketServerComputer computer;
+
+    private PocketHolder holder;
+    private Vec3 position;
+
+    private boolean dirty = false;
+    private @Nullable UpgradeData<IPocketUpgrade> upgrade;
+    private int colour = -1;
+    private int lightColour = -1;
+
+    public PocketBrain(PocketHolder holder, int computerID, @Nullable String label, ComputerFamily family, @Nullable UpgradeData<IPocketUpgrade> upgrade) {
+        this.computer = new PocketServerComputer(this, holder, computerID, label, family);
+        this.holder = holder;
+        this.position = holder.pos();
+        this.upgrade = upgrade;
+        invalidatePeripheral();
+    }
+
+    /**
+     * Get the corresponding pocket computer for this brain.
+     *
+     * @return The pocket computer.
+     */
+    public PocketServerComputer computer() {
+        return computer;
+    }
+
+    PocketHolder holder() {
+        return holder;
+    }
+
+    /**
+     * Update the position and holder for this computer.
+     *
+     * @param newHolder The new holder
+     */
+    public void updateHolder(PocketHolder newHolder) {
+        position = newHolder.pos();
+        computer.setPosition(newHolder.level(), newHolder.blockPos());
+
+        var oldHolder = this.holder;
+        if (holder.equals(newHolder)) return;
+        holder = newHolder;
+
+        // If a new player has picked it up then rebroadcast the terminal to them
+        var oldPlayer = oldHolder instanceof PocketHolder.PlayerHolder p ? p.entity() : null;
+        if (newHolder instanceof PocketHolder.PlayerHolder player && player.entity() != oldPlayer) {
+            ServerNetworking.sendToPlayer(new PocketComputerDataMessage(computer, true), player.entity());
+        }
+    }
+
+    /**
+     * Write back properties of the pocket brain to the item.
+     *
+     * @param stack The pocket computer stack to update.
+     * @return Whether the item was changed.
+     */
+    public boolean updateItem(ItemStack stack) {
+        if (!dirty) return false;
+        this.dirty = false;
+
+        stack.set(DataComponents.DYED_COLOR, colour == -1 ? null : new DyedItemColor(colour, false));
+        PocketComputerItem.setUpgrade(stack, upgrade);
+        return true;
+    }
+
+    @Override
+    public ServerLevel getLevel() {
+        return computer.getLevel();
+    }
+
+    @Override
+    public Vec3 getPosition() {
+        // This method can be called from off-thread, and so we must use the cached position rather than rereading
+        // from the holder.
+        return position;
+    }
+
+    @Override
+    public @Nullable Entity getEntity() {
+        return holder instanceof PocketHolder.EntityHolder entity && holder.isValid(computer) ? entity.entity() : null;
+    }
+
+    @Override
+    public int getColour() {
+        return colour;
+    }
+
+    @Override
+    public void setColour(int colour) {
+        if (this.colour == colour) return;
+        dirty = true;
+        this.colour = colour;
+    }
+
+    @Override
+    public int getLight() {
+        return lightColour;
+    }
+
+    @Override
+    public void setLight(int colour) {
+        if (colour < 0 || colour > 0xFFFFFF) colour = -1;
+        lightColour = colour;
+    }
+
+    @Override
+    public DataComponentPatch getUpgradeData() {
+        var upgrade = this.upgrade;
+        return upgrade == null ? DataComponentPatch.EMPTY : upgrade.data();
+    }
+
+    @Override
+    public void setUpgradeData(DataComponentPatch data) {
+        var upgrade = this.upgrade;
+        if (upgrade == null) return;
+        this.upgrade = UpgradeData.of(upgrade.holder(), data);
+    }
+
+    @Override
+    public void invalidatePeripheral() {
+        var peripheral = upgrade == null ? null : upgrade.upgrade().createPeripheral(this);
+        computer.setPeripheral(ComputerSide.BACK, peripheral);
+    }
+
+    @Override
+    public @Nullable UpgradeData<IPocketUpgrade> getUpgrade() {
+        return upgrade;
+    }
+
+    /**
+     * Set the upgrade for this pocket computer, also updating the item stack.
+     * <p>
+     * Note this method is not thread safe - it must be called from the server thread.
+     *
+     * @param upgrade The new upgrade to set it to, may be {@code null}.
+     */
+    @Override
+    public void setUpgrade(@Nullable UpgradeData<IPocketUpgrade> upgrade) {
+        this.upgrade = upgrade;
+        dirty = true;
+        invalidatePeripheral();
+    }
+}

projects/common/src/main/java/dan200/computercraft/shared/pocket/core/PocketHolder.java

@@ -0,0 +1,115 @@
+// SPDX-FileCopyrightText: 2024 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.shared.pocket.core;
+
+import dan200.computercraft.shared.computer.core.ServerComputer;
+import dan200.computercraft.shared.pocket.items.PocketComputerItem;
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.entity.item.ItemEntity;
+import net.minecraft.world.phys.Vec3;
+
+/**
+ * An object that holds a pocket computer item.
+ */
+public sealed interface PocketHolder permits PocketHolder.EntityHolder {
+    /**
+     * The level this holder is in.
+     *
+     * @return The holder's level.
+     */
+    ServerLevel level();
+
+    /**
+     * The position of this holder.
+     *
+     * @return The position of this holder.
+     */
+    Vec3 pos();
+
+    /**
+     * The block position of this holder.
+     *
+     * @return The position of this holder.
+     */
+    BlockPos blockPos();
+
+    /**
+     * Determine if this holder is still valid for a particular computer.
+     *
+     * @param computer The current computer.
+     * @return Whether this holder is valid.
+     */
+    boolean isValid(ServerComputer computer);
+
+    /**
+     * Mark the pocket computer item as having changed.
+     */
+    void setChanged();
+
+    /**
+     * An {@link Entity} holding a pocket computer.
+     */
+    sealed interface EntityHolder extends PocketHolder permits PocketHolder.PlayerHolder, PocketHolder.ItemEntityHolder {
+        /**
+         * Get the entity holding this pocket computer.
+         *
+         * @return The holding entity.
+         */
+        Entity entity();
+
+        @Override
+        default ServerLevel level() {
+            return (ServerLevel) entity().level();
+        }
+
+        @Override
+        default Vec3 pos() {
+            return entity().getEyePosition();
+        }
+
+        @Override
+        default BlockPos blockPos() {
+            return entity().blockPosition();
+        }
+    }
+
+    /**
+     * A pocket computer in a player's slot.
+     *
+     * @param entity The current player.
+     * @param slot   The slot the pocket computer is in.
+     */
+    record PlayerHolder(ServerPlayer entity, int slot) implements EntityHolder {
+        @Override
+        public boolean isValid(ServerComputer computer) {
+            return entity().isAlive() && PocketComputerItem.isServerComputer(computer, entity().getInventory().getItem(this.slot()));
+        }
+
+        @Override
+        public void setChanged() {
+            entity.getInventory().setChanged();
+        }
+    }
+
+    /**
+     * A pocket computer in an {@link ItemEntity}.
+     *
+     * @param entity The item entity.
+     */
+    record ItemEntityHolder(ItemEntity entity) implements EntityHolder {
+        @Override
+        public boolean isValid(ServerComputer computer) {
+            return entity().isAlive() && PocketComputerItem.isServerComputer(computer, this.entity().getItem());
+        }
+
+        @Override
+        public void setChanged() {
+            entity.setItem(entity.getItem().copy());
+        }
+    }
+}