src/main/java/org/saturnclient/impl/features/mixins/render/GameRendererMixin.java

@@ -1,12 +1,20 @@
 package org.saturnclient.impl.features.mixins.render;
 
+//? if >=1.21.6
+import net.minecraft.client.MinecraftClient;
+//? if >=1.21.6
+import net.minecraft.client.option.GameOptions;
 import net.minecraft.client.render.GameRenderer;
 
+//? if >=1.21.6
+import org.saturnclient.impl.ui.SaturnScreenFabric;
 import org.saturnclient.mod.mods.FreelookMod;
 import org.saturnclient.mod.mods.ZoomMod;
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.Inject;
+//? if >=1.21.6
+import org.spongepowered.asm.mixin.injection.Redirect;
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
 
 /**
@@ -38,4 +46,18 @@ public class GameRendererMixin {
             cir.setReturnValue(zoomedFov);
         }
     }
+
+    //? if >=1.21.6 {
+    // From 1.21.6 the menu blur's strength is the vanilla setting, read here every frame. While a
+    // Saturn screen is open, it's Saturn's background blur instead, faded in with the screen.
+    @Redirect(method = "render", at = @At(value = "INVOKE",
+            target = "Lnet/minecraft/client/option/GameOptions;getMenuBackgroundBlurrinessValue()I"))
+    private int useSaturnBlur(GameOptions options) {
+        if (MinecraftClient.getInstance().currentScreen instanceof SaturnScreenFabric saturnScreen) {
+            return saturnScreen.screen.getBackgroundBlur();
+        }
+
+        return options.getMenuBackgroundBlurrinessValue();
+    }
+    //?}
 }

src/main/java/org/saturnclient/impl/ui/SaturnScreenFabric.java

@@ -89,25 +89,18 @@ public class SaturnScreenFabric extends Screen implements ScreenProvider {
         mouseX *= 2;
         mouseY *= 2;
 
-        // From 1.21.6 the panorama renderer has no opacity (and takes no delta), so it's drawn fully
-        // opaque there.
-        if (panoramaReady && client.world == null && client.getCurrentServerEntry() == null) {
-            //? if >=1.21.6 {
-            ROTATING_PANORAMA_RENDERER.render(context, this.width, this.height, true);
-            //?} else
-            //ROTATING_PANORAMA_RENDERER.render(context, this.width, this.height, screen.backgroundOpacity, delta);
+        // From 1.21.6 the background, blur included, is drawn in renderBackground.
+        //? if <1.21.6 {
+        /*if (isShowingPanorama()) {
+            ROTATING_PANORAMA_RENDERER.render(context, this.width, this.height, screen.backgroundOpacity, delta);
         }
 
-        // TODO: the background blur (screen.backgroundBlur) is only drawn before 1.21.6 so far. See
-        // also issue #23.
-
-        //? if <1.21.6 {
-        /*PostEffectProcessor postEffectProcessor = this.client.getShaderLoader().loadPostEffect(
+        PostEffectProcessor postEffectProcessor = this.client.getShaderLoader().loadPostEffect(
                 Identifier.ofVanilla("blur"),
                 DefaultFramebufferSet.MAIN_ONLY);
 
         if (postEffectProcessor != null) {
-            float radius = screen.backgroundBlur * Math.min((float) elapsed / 700, 1.0f);
+            float radius = screen.getBackgroundBlur();
             //? if >=1.21.5
             postEffectProcessor.render(this.client.getFramebuffer(), this.pool, pass -> pass.setUniform("Radius", radius));
             //? if <1.21.5
@@ -122,6 +115,32 @@ public class SaturnScreenFabric extends Screen implements ScreenProvider {
         screen.render(renderScope, mouseX, mouseY, delta, elapsed);
     }
 
+    //? if >=1.21.6 {
+    // Vanilla's background would cover Saturn's panorama, and blurs by the vanilla setting. The
+    // strength of this blur comes from GameRendererMixin, which gives Saturn's setting instead.
+    @Override
+    public void renderBackground(DrawContext context, int mouseX, int mouseY, float delta) {
+        // The panorama renderer has no opacity (and takes no delta) from 1.21.6, so it's drawn fully
+        // opaque.
+        if (isShowingPanorama()) {
+            ROTATING_PANORAMA_RENDERER.render(context, this.width, this.height, true);
+        }
+
+        if (screen.getBackgroundBlur() >= 1) {
+            context.applyBlur();
+        }
+
+        if (client.world != null) {
+            renderDarkening(context);
+        }
+    }
+    //?}
+
+    /** Whether Saturn's panorama is behind the screen: outside a world, once it's loaded. */
+    private boolean isShowingPanorama() {
+        return panoramaReady && client.world == null && client.getCurrentServerEntry() == null;
+    }
+
     // 1.21.9 moved mouse and key events to Click and KeyInput.
     //? if >=1.21.9 {
     @Override