Add the cposteffect command

src/main/java/net/earthcomputer/clientcommands/ClientCommands.java

@@ -168,6 +168,7 @@ public static void registerCommands(CommandDispatcher<FabricClientCommandSource>
         // PlayerInfoCommand.register(dispatcher);
         PluginsCommand.register(dispatcher);
         PosCommand.register(dispatcher);
+        PostEffectCommand.register(dispatcher);
         RelogCommand.register(dispatcher);
         RenderCommand.register(dispatcher);
         ReplyCommand.register(dispatcher);

src/main/java/net/earthcomputer/clientcommands/command/PostEffectCommand.java

@@ -0,0 +1,32 @@
+package net.earthcomputer.clientcommands.command;
+
+import com.mojang.brigadier.Command;
+import com.mojang.brigadier.CommandDispatcher;
+import net.fabricmc.fabric.api.client.command.v2.FabricClientCommandSource;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.ResourceLocation;
+import org.jetbrains.annotations.Nullable;
+
+import static net.earthcomputer.clientcommands.command.arguments.PostChainArgument.*;
+import static net.fabricmc.fabric.api.client.command.v2.ClientCommandManager.*;
+
+public class PostEffectCommand {
+    public static void register(CommandDispatcher<FabricClientCommandSource> dispatcher) {
+        dispatcher.register(literal("cposteffect")
+            .then(argument("posteffect", postChain())
+                .executes(ctx -> applyPostEffect(ctx.getSource(), getPostChain(ctx, "posteffect"))))
+            .then(literal("reset")
+                .executes(ctx -> applyPostEffect(ctx.getSource(), null))));
+    }
+
+    private static int applyPostEffect(FabricClientCommandSource source, @Nullable ResourceLocation postEffect) {
+        if (postEffect == null) {
+            source.getClient().gameRenderer.clearPostEffect();
+            source.sendFeedback(Component.translatable("commands.cposteffect.reset.success"));
+            return Command.SINGLE_SUCCESS;
+        }
+        source.getClient().gameRenderer.setPostEffect(postEffect);
+        source.sendFeedback(Component.translatable("commands.cposteffect.apply.success", postEffect));
+        return Command.SINGLE_SUCCESS;
+    }
+}

src/main/java/net/earthcomputer/clientcommands/command/arguments/PostChainArgument.java

@@ -0,0 +1,60 @@
+package net.earthcomputer.clientcommands.command.arguments;
+
+import com.mojang.brigadier.StringReader;
+import com.mojang.brigadier.arguments.ArgumentType;
+import com.mojang.brigadier.context.CommandContext;
+import com.mojang.brigadier.exceptions.CommandSyntaxException;
+import com.mojang.brigadier.exceptions.DynamicCommandExceptionType;
+import com.mojang.brigadier.suggestion.Suggestions;
+import com.mojang.brigadier.suggestion.SuggestionsBuilder;
+import net.fabricmc.fabric.api.client.command.v2.FabricClientCommandSource;
+import net.minecraft.client.renderer.GameRenderer;
+import net.minecraft.commands.SharedSuggestionProvider;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.ResourceLocation;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+
+public class PostChainArgument implements ArgumentType<ResourceLocation> {
+
+    private static final Collection<String> EXAMPLES = Arrays.asList("invert", "minecraft:spider", "minecraft:creeper");
+
+    private static final DynamicCommandExceptionType UNKNOWN_POST_CHAIN_EXCEPTION = new DynamicCommandExceptionType(postChain -> Component.translatable("commands.cposteffect.unknownPostEffect", postChain));
+
+    // known working post chains, "minecraft:entity_outline" and "minecraft:transparency" also exist but do not work directly
+    // see assets/minecraft/post_effect for all post chains
+    // perhaps this can be extracted from Minecraft.getInstance().getShaderManager().compilationCache.configs.postChains()
+    private static final Set<ResourceLocation> SUPPORTED_POST_CHAINS = Set.of(GameRenderer.BLUR_POST_CHAIN_ID, ResourceLocation.withDefaultNamespace("creeper"), ResourceLocation.withDefaultNamespace("invert"), ResourceLocation.withDefaultNamespace("spider"));
+
+    public static PostChainArgument postChain() {
+        return new PostChainArgument();
+    }
+
+    public static ResourceLocation getPostChain(final CommandContext<FabricClientCommandSource> context, final String name) {
+        return context.getArgument(name, ResourceLocation.class);
+    }
+
+    @Override
+    public ResourceLocation parse(StringReader reader) throws CommandSyntaxException {
+        int start = reader.getCursor();
+        ResourceLocation postChainId = ResourceLocation.read(reader);
+        if (!SUPPORTED_POST_CHAINS.contains(postChainId)) {
+            reader.setCursor(start);
+            throw UNKNOWN_POST_CHAIN_EXCEPTION.createWithContext(reader, postChainId);
+        }
+        return postChainId;
+    }
+
+    @Override
+    public <S> CompletableFuture<Suggestions> listSuggestions(CommandContext<S> context, SuggestionsBuilder builder) {
+        return SharedSuggestionProvider.suggestResource(SUPPORTED_POST_CHAINS, builder);
+    }
+
+    @Override
+    public Collection<String> getExamples() {
+        return EXAMPLES;
+    }
+}

src/main/resources/assets/clientcommands/lang/en_us.json

@@ -226,6 +226,10 @@
   "commands.cpos.level.the_end": "the End",
   "commands.cpos.level.the_nether": "the Nether",
 
+  "commands.cposteffect.apply.success": "Successfully applied post effect %s",
+  "commands.cposteffect.reset.success": "Successfully reset post effect",
+  "commands.cposteffect.unknownPostEffect": "Unknown post effect %s",
+
   "commands.crelog.failed": "Failed to relog",
 
   "commands.crender.entities.success": "Entity rendering rules have been updated",

src/main/resources/clientcommands.aw

@@ -41,6 +41,10 @@ accessible field net/minecraft/network/codec/IdDispatchCodec toId Lit/unimi/dsi/
 # cpermissionlevel
 accessible method net/minecraft/client/player/LocalPlayer getPermissionLevel ()I
 
+# cposteffect
+accessible field net/minecraft/client/renderer/GameRenderer BLUR_POST_CHAIN_ID Lnet/minecraft/resources/ResourceLocation;
+accessible method net/minecraft/client/renderer/GameRenderer setPostEffect (Lnet/minecraft/resources/ResourceLocation;)V
+
 # cwaypoint
 accessible field net/minecraft/server/MinecraftServer storageSource Lnet/minecraft/world/level/storage/LevelStorageSource$LevelStorageAccess;
 accessible method net/minecraft/client/renderer/GameRenderer getFov (Lnet/minecraft/client/Camera;FZ)F