Add render sky event

fabric-rendering-v1/src/client/java/net/fabricmc/fabric/api/client/rendering/v1/WorldRenderEvents.java

@@ -223,6 +223,28 @@ private WorldRenderEvents() { }
 		}
 	});
 
+	/**
+	 * Called when rendering the world's skybox.
+	 * This happens right before terrain setup.
+	 *
+	 * <p>Use this for rendering custom sky boxes in existing dimensions,
+	 * such as rendering more stars above a current y value.
+	 *
+	 * <p>Returning false will cancel rendering the skybox.  This has no
+	 * effect on other subscribers to this event - all subscribers will always be called.
+	 */
+	public static final Event<RenderSky> RENDER_SKY = EventFactory.createArrayBacked(RenderSky.class, (context, fogCallback) -> true, callbacks -> (context, fogCallback) -> {
+		boolean shouldRender = true;
+
+		for (final RenderSky callback : callbacks) {
+			if (!callback.renderSky(context, fogCallback)) {
+				shouldRender = false;
+			}
+		}
+
+		return shouldRender;
+	});
+
 	/**
 	 * Called after all framebuffer writes are complete but before all world
 	 * rendering is torn down.
@@ -302,6 +324,11 @@ public interface AfterTranslucent {
 		void afterTranslucent(WorldRenderContext context);
 	}
 
+	@FunctionalInterface
+	public interface RenderSky {
+		boolean renderSky(WorldRenderContext context, Runnable fogCallback);
+	}
+
 	@FunctionalInterface
 	public interface Last {
 		void onLast(WorldRenderContext context);

fabric-rendering-v1/src/client/java/net/fabricmc/fabric/mixin/client/rendering/WorldRendererMixin.java

@@ -212,4 +212,11 @@ private void renderSky(MatrixStack matrices, Matrix4f matrix4f, float tickDelta,
 			}
 		}
 	}
+
+	@Inject(method = "renderSky(Lnet/minecraft/client/util/math/MatrixStack;Lorg/joml/Matrix4f;FLnet/minecraft/client/render/Camera;ZLjava/lang/Runnable;)V", at = @At("HEAD"), cancellable = true)
+	private void onRenderSky(MatrixStack matrices, Matrix4f projectionMatrix, float tickDelta, Camera camera, boolean thickFog, Runnable fogCallback, CallbackInfo info) {
+		if (!WorldRenderEvents.RENDER_SKY.invoker().renderSky(context, fogCallback)) {
+			info.cancel();
+		}
+	}
 }

fabric-rendering-v1/src/testmodClient/java/net/fabricmc/fabric/test/rendering/client/WorldRenderEventsTests.java

@@ -18,7 +18,9 @@
 
 import net.minecraft.block.Blocks;
 import net.minecraft.client.MinecraftClient;
+import net.minecraft.client.network.ClientPlayerEntity;
 import net.minecraft.client.render.OverlayTexture;
+import net.minecraft.item.Items;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.math.Vec3d;
 
@@ -48,9 +50,16 @@ private static boolean onBlockOutline(WorldRenderContext wrc, WorldRenderContext
 		return true;
 	}
 
+	private static boolean onRenderSky(WorldRenderContext wrc, Runnable fogCallback) {
+		ClientPlayerEntity player = MinecraftClient.getInstance().player;
+
+		return !player.isHolding(Items.DEBUG_STICK) || !(player.getY() > 200);
+	}
+
 	// Renders a diamond block above diamond blocks when they are looked at.
 	@Override
 	public void onInitializeClient() {
 		WorldRenderEvents.BLOCK_OUTLINE.register(WorldRenderEventsTests::onBlockOutline);
+		WorldRenderEvents.RENDER_SKY.register(WorldRenderEventsTests::onRenderSky);
 	}
 }