Fix: Release monitor buffers on *client* thread

These buffers were being released on the server thread, causing the
logical server in a single player session to crash just before shutting
down. It seems the crash happened late enough to not cause world
corruption issues, and so went unnoticed. It was however causing a
memory leak when quitting/rejoining worlds, and it left the save file
lock in limbo.

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

@@ -20,6 +20,7 @@ import dan200.computercraft.client.render.TileEntityMonitorRenderer;
 import dan200.computercraft.client.render.TileEntityTurtleRenderer;
 import dan200.computercraft.client.render.TurtleModelLoader;
 import dan200.computercraft.client.render.TurtlePlayerRenderer;
+import dan200.computercraft.events.ClientUnloadWorldEvent;
 import dan200.computercraft.shared.ComputerCraftRegistry;
 import dan200.computercraft.shared.common.ContainerHeldItem;
 import dan200.computercraft.shared.common.IColouredItem;
@@ -47,14 +48,13 @@ import net.fabricmc.fabric.api.client.rendereregistry.v1.BlockEntityRendererRegi
 import net.fabricmc.fabric.api.client.rendereregistry.v1.EntityRendererRegistry;
 import net.fabricmc.fabric.api.client.screenhandler.v1.ScreenRegistry;
 import net.fabricmc.fabric.api.event.client.ClientSpriteRegistryCallback;
-import net.fabricmc.fabric.api.event.lifecycle.v1.ServerWorldEvents;
 import net.fabricmc.fabric.mixin.object.builder.ModelPredicateProviderRegistrySpecificAccessor;
 
 @Environment (EnvType.CLIENT)
 public final class ComputerCraftProxyClient implements ClientModInitializer {
 
-    public static void initEvents() {
-
+    private static void initEvents() {
+        ClientUnloadWorldEvent.EVENT.register( () -> ClientMonitor.destroyAll() );
     }
 
     @Override
@@ -96,13 +96,9 @@ public final class ComputerCraftProxyClient implements ClientModInitializer {
                              () -> ComputerCraftRegistry.ModItems.POCKET_COMPUTER_ADVANCED);
         ClientRegistry.onItemColours();
 
-        // TODO Verify this does things properly
-        ServerWorldEvents.UNLOAD.register(((minecraftServer, serverWorld) -> {
-            ClientMonitor.destroyAll();
-        }));
+        initEvents();
     }
 
-
     // My IDE doesn't think so, but we do actually need these generics.
     private static void registerContainers() {
         ScreenRegistry.<ContainerComputer, GuiComputer<ContainerComputer>>register(ComputerCraftRegistry.ModContainers.COMPUTER, GuiComputer::create);
@@ -125,15 +121,4 @@ public final class ComputerCraftProxyClient implements ClientModInitializer {
             ModelPredicateProviderRegistrySpecificAccessor.callRegister(item.get(), id, getter);
         }
     }
-
-    //    @Mod.EventBusSubscriber (modid = ComputerCraft.MOD_ID, value = Dist.CLIENT)
-    //    public static final class ForgeHandlers {
-    //        @SubscribeEvent
-    //        public static void onWorldUnload(WorldEvent.Unload event) {
-    //            if (event.getWorld()
-    //                     .isClient()) {
-    //                ClientMonitor.destroyAll();
-    //            }
-    //        }
-    //    }
 }

src/main/java/dan200/computercraft/events/ClientUnloadWorldEvent.java

@@ -0,0 +1,17 @@
+package dan200.computercraft.events;
+
+import net.fabricmc.fabric.api.event.Event;
+import net.fabricmc.fabric.api.event.EventFactory;
+
+@FunctionalInterface
+public interface ClientUnloadWorldEvent
+{
+    Event<ClientUnloadWorldEvent> EVENT = EventFactory.createArrayBacked( ClientUnloadWorldEvent.class,
+        callbacks -> () -> {
+            for( ClientUnloadWorldEvent callback : callbacks) {
+                callback.onClientUnloadWorld();
+            }
+    });
+
+    void onClientUnloadWorld();
+}

src/main/java/dan200/computercraft/mixin/MixinMinecraftClient.java

@@ -7,6 +7,9 @@
 package dan200.computercraft.mixin;
 
 import dan200.computercraft.client.FrameInfo;
+import dan200.computercraft.events.ClientUnloadWorldEvent;
+import net.minecraft.client.gui.screen.Screen;
+import net.minecraft.client.world.ClientWorld;
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.Inject;
@@ -15,9 +18,20 @@ import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
 import net.minecraft.client.MinecraftClient;
 
 @Mixin (MinecraftClient.class)
-public abstract class MixinMinecraftGame {
+public abstract class MixinMinecraftClient
+{
     @Inject (method = "render", at = @At ("HEAD"))
     private void onRender(CallbackInfo info) {
         FrameInfo.onRenderFrame();
     }
+
+    @Inject(method = "disconnect(Lnet/minecraft/client/gui/screen/Screen;)V", at = @At ("RETURN"))
+    private void disconnectAfter(Screen screen, CallbackInfo info) {
+        ClientUnloadWorldEvent.EVENT.invoker().onClientUnloadWorld();
+    }
+
+    @Inject(method = "joinWorld", at = @At("RETURN"))
+    private void joinWorldAfter(ClientWorld world, CallbackInfo info) {
+        ClientUnloadWorldEvent.EVENT.invoker().onClientUnloadWorld();
+    }
 }

src/main/resources/computercraft.mixins.json

@@ -20,7 +20,7 @@
         "HeldItemRendererAccess",
         "MixinHeldItemRenderer",
         "MixinItemFrameEntityRenderer",
-        "MixinMinecraftGame",
+        "MixinMinecraftClient",
         "MixinScreen",
         "MixinWorldRenderer"
     ],