fix: resolve issue when loading a world a second time (#4829)

This contains two major changes:
- wipe all the prefabs and let the engine re-resolve them when the world loads, and
- unload any assets that are not loaded in by core

As gestalt loads a whole new environment for every game, any assets from a previous session are not compatible for another session.

List of changes:
* fix: resolved loading issue when attempting to start a world twice
* chore: add InitialiseRendering
* chore: add rendering to client and only how with a local client
* chore: remove caching from DefaultColorSource

Author: pollend

engine/src/main/java/org/terasology/engine/core/TerasologyEngine.java

@@ -29,7 +29,6 @@
 import org.terasology.engine.core.subsystem.common.ThreadManagerSubsystem;
 import org.terasology.engine.core.subsystem.common.TimeSubsystem;
 import org.terasology.engine.core.subsystem.common.WorldGenerationSubsystem;
-import org.terasology.engine.core.subsystem.rendering.ModuleRenderingSubsystem;
 import org.terasology.engine.entitySystem.prefab.Prefab;
 import org.terasology.engine.entitySystem.prefab.internal.PojoPrefab;
 import org.terasology.engine.i18n.I18nSubsystem;
@@ -175,7 +174,6 @@ public TerasologyEngine(TimeSubsystem timeSubsystem, Collection<EngineSubsystem>
         this.allSubsystems.add(new GameSubsystem());
         this.allSubsystems.add(new I18nSubsystem());
         this.allSubsystems.add(new TelemetrySubSystem());
-        this.allSubsystems.add(new ModuleRenderingSubsystem());
 
         // add all subsystem as engine module part. (needs for ECS classes loaded from external subsystems)
         allSubsystems.stream().map(Object::getClass).forEach(this::addToClassesOnClasspathsToAddToEngine);
@@ -489,7 +487,6 @@ public boolean tick() {
         }
 
         Iterator<Float> updateCycles = timeSubsystem.getEngineTime().tick();
-        CoreRegistry.setContext(currentState.getContext());
         rootContext.get(NetworkSystem.class).setContext(currentState.getContext());
 
         for (EngineSubsystem subsystem : allSubsystems) {
@@ -586,6 +583,7 @@ private void switchState(GameState newState) {
         if (currentState != null) {
             currentState.dispose();
         }
+        CoreRegistry.setContext(newState.getContext());
         currentState = newState;
         LoggingContext.setGameState(newState);
         newState.init(this);

engine/src/main/java/org/terasology/engine/core/bootstrap/EnvironmentSwitchHandler.java

@@ -107,7 +107,6 @@ public void handleSwitchToGameEnvironment(Context context) {
         autoConfigManager.loadConfigsIn(context);
 
         ModuleAwareAssetTypeManager assetTypeManager = context.get(ModuleAwareAssetTypeManager.class);
-
         /*
          * The registering of the prefab formats is done in this method, because it needs to be done before
          * the environment of the asset manager gets changed.
@@ -116,6 +115,7 @@ public void handleSwitchToGameEnvironment(Context context) {
          * existing then yet.
          */
         unregisterPrefabFormats(assetTypeManager);
+
         registeredPrefabFormat = new PrefabFormat(componentLibrary, typeHandlerLibrary);
         assetTypeManager.getAssetFileDataProducer(assetTypeManager
                 .getAssetType(Prefab.class)

engine/src/main/java/org/terasology/engine/core/modes/StateIngame.java

@@ -8,11 +8,13 @@
 import org.terasology.engine.core.ComponentSystemManager;
 import org.terasology.engine.core.GameEngine;
 import org.terasology.engine.core.GameThread;
+import org.terasology.engine.core.TerasologyConstants;
 import org.terasology.engine.core.bootstrap.EnvironmentSwitchHandler;
 import org.terasology.engine.core.module.ModuleManager;
 import org.terasology.engine.core.subsystem.DisplayDevice;
 import org.terasology.engine.entitySystem.entity.internal.EngineEntityManager;
 import org.terasology.engine.entitySystem.event.internal.EventSystem;
+import org.terasology.engine.entitySystem.prefab.Prefab;
 import org.terasology.engine.entitySystem.systems.UpdateSubscriberSystem;
 import org.terasology.engine.game.GameManifest;
 import org.terasology.engine.identity.storageServiceClient.StorageServiceWorker;
@@ -28,7 +30,13 @@
 import org.terasology.engine.rendering.nui.layers.mainMenu.MessagePopup;
 import org.terasology.engine.rendering.world.WorldRenderer;
 import org.terasology.engine.rendering.world.WorldRenderer.RenderingStage;
+import org.terasology.engine.world.block.loader.BlockFamilyDefinition;
 import org.terasology.engine.world.chunks.ChunkProvider;
+import org.terasology.gestalt.assets.Asset;
+import org.terasology.gestalt.assets.AssetType;
+import org.terasology.gestalt.assets.ResourceUrn;
+import org.terasology.gestalt.assets.management.AssetTypeManager;
+import org.terasology.gestalt.assets.module.ModuleAwareAssetTypeManager;
 import org.terasology.gestalt.module.Module;
 import org.terasology.gestalt.module.ModuleEnvironment;
 import org.terasology.nui.databinding.ReadOnlyBinding;
@@ -103,6 +111,19 @@ public void dispose(boolean shuttingDown) {
         ChunkProvider chunkProvider = context.get(ChunkProvider.class);
         chunkProvider.dispose();
 
+        AssetTypeManager assetTypeManager = context.get(ModuleAwareAssetTypeManager.class);
+        // dispose all module assets
+        assetTypeManager.getAssetTypes().forEach(assetType -> {
+            for (ResourceUrn urn : assetType.getLoadedAssetUrns()) {
+                if (!urn.getModuleName().equals(TerasologyConstants.ENGINE_MODULE)) {
+                    assetType.getAsset(urn).ifPresent(Asset::dispose);
+                }
+            }
+        });
+        // dispose engine assets that should not be kept when switching game states
+        assetTypeManager.getAssetType(BlockFamilyDefinition.class).ifPresent(AssetType::disposeAll);
+        assetTypeManager.getAssetType(Prefab.class).ifPresent(AssetType::disposeAll);
+
         boolean save = networkSystem.getMode().isAuthority();
         if (save) {
             storageManager.waitForCompletionOfPreviousSaveAndStartSaving();

engine/src/main/java/org/terasology/engine/core/modes/StateLoading.java

@@ -29,6 +29,7 @@
 import org.terasology.engine.core.modes.loadProcesses.InitialiseSystems;
 import org.terasology.engine.core.modes.loadProcesses.InitialiseWorld;
 import org.terasology.engine.core.modes.loadProcesses.InitialiseWorldGenerator;
+import org.terasology.engine.core.modes.loadProcesses.InitialiseRendering;
 import org.terasology.engine.core.modes.loadProcesses.JoinServer;
 import org.terasology.engine.core.modes.loadProcesses.LoadEntities;
 import org.terasology.engine.core.modes.loadProcesses.LoadExtraBlockData;
@@ -141,6 +142,7 @@ public void init(GameEngine engine) {
 
     private void initClient() {
         loadProcesses.add(new JoinServer(context, gameManifest, joinStatus));
+        loadProcesses.add(new InitialiseRendering(context));
         loadProcesses.add(new InitialiseEntitySystem(context));
         loadProcesses.add(new RegisterBlocks(context, gameManifest));
         loadProcesses.add(new InitialiseGraphics(context));
@@ -165,6 +167,9 @@ private void initClient() {
 
     private void initHost() {
         loadProcesses.add(new RegisterMods(context, gameManifest));
+        if(netMode.hasLocalClient()) {
+            loadProcesses.add(new InitialiseRendering(context));
+        }
         loadProcesses.add(new InitialiseEntitySystem(context));
         loadProcesses.add(new RegisterBlocks(context, gameManifest));
         loadProcesses.add(new InitialiseGraphics(context));

engine/src/main/java/org/terasology/engine/core/modes/loadProcesses/InitialiseRendering.java

@@ -0,0 +1,42 @@
+// Copyright 2021 The Terasology Foundation
+// SPDX-License-Identifier: Apache-2.0
+
+package org.terasology.engine.core.modes.loadProcesses;
+
+import org.terasology.engine.context.Context;
+import org.terasology.engine.core.modes.SingleStepLoadProcess;
+import org.terasology.engine.core.module.rendering.RenderingModuleRegistry;
+
+/**
+ * Add {@link RenderingModuleRegistry} to the game {@link Context}.
+ * 
+ * The rendering system is required whenever a client starts or joins a game. As rendering may fail to re-initialise
+ * correctly when it has previously been constructed, this loading process will populate the {@link Context} with a
+ * freshly created rendering system.
+ * 
+ * When switching the game state, the rendering system can just be disposed with the old state.
+ */
+public class InitialiseRendering extends SingleStepLoadProcess {
+    private final Context context;
+
+    public InitialiseRendering(Context context) {
+        this.context = context;
+    }
+
+
+    @Override
+    public String getMessage() {
+        return "Initialising Rendering System...";
+    }
+
+    @Override
+    public boolean step() {
+        context.put(RenderingModuleRegistry.class, new RenderingModuleRegistry());
+        return true;
+    }
+
+    @Override
+    public int getExpectedCost() {
+        return 1;
+    }
+}

engine/src/main/java/org/terasology/engine/core/subsystem/rendering/ModuleRenderingSubsystem.java

@@ -103,6 +103,7 @@ public void bindTextures() {
         for (int slot : textureMap.keys()) {
             Texture texture = textureMap.get(slot);
             if (texture.isDisposed()) {
+                textureMap.remove(slot);
                 logger.error("Attempted to bind disposed texture {}", texture);
             } else {
                 shaderManager.bindTexture(slot, texture);

engine/src/main/java/org/terasology/engine/rendering/opengl/GLSLMaterial.java

@@ -17,29 +17,23 @@ public Colorc calcColor(int x, int y, int z) {
     COLOR_LUT {
         @Override
         public Colorc calcColor(int x, int y, int z) {
+            ColorProvider colorProvider = CoreRegistry.get(ColorProvider.class);
+            // Return white as default if there aren't any color providers
             if (colorProvider == null) {
-                colorProvider = CoreRegistry.get(ColorProvider.class);
-                // Return white as default if there aren't any color providers
-                if (colorProvider == null) {
-                    return Color.white;
-                }
+                return Color.white;
             }
             return colorProvider.colorLut(x, y, z);
         }
     },
     FOLIAGE_LUT {
         @Override
         public Colorc calcColor(int x, int y, int z) {
+            ColorProvider colorProvider = CoreRegistry.get(ColorProvider.class);
+            // Return white as default if there aren't any color providers
             if (colorProvider == null) {
-                colorProvider = CoreRegistry.get(ColorProvider.class);
-                // Return white as default if there aren't any color providers
-                if (colorProvider == null) {
-                    return Color.white;
-                }
+                return Color.white;
             }
             return colorProvider.foliageLut(x, y, z);
         }
     };
-
-    private static ColorProvider colorProvider;
 }