Merge pull request 'Add GUI scale and glass on every version' (#40) from glass-blur into master

Reviewed-on: #40

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

@@ -0,0 +1,377 @@
+package org.saturnclient.impl.ui;
+
+// Glass: a copy of the game behind the screen, blurred, drawn through each panel's rounded rectangle
+// texture as a mask. There's a copy for each blur strength in use (menus and widgets have their own),
+// blurred with vanilla's blur at that radius, so it holds the world or panorama without the screen's
+// own animated background blur.
+//
+// The GUI rewrites split this into three implementations:
+// - 1.21.6+: the GUI is drawn after the screen builds it, so the copy is taken from the main
+//   framebuffer while the screen builds its GUI, and glass is a GUI element with its own pipeline
+//   (shaders/core/glass.fsh). The blur is vanilla's effect rebuilt with the radius set.
+// - 1.21.5: the screen draws straight into the framebuffer, blurring it first, so the game is saved
+//   before the blur (saveBackground). Glass is a render layer with its own pipeline
+//   (shaders/core/glass_pre_1_21_6.fsh), and the blur takes the radius as it runs.
+// - 1.21.4: as 1.21.5, with GL framebuffers copied by blitting, and a shader program
+//   (shaders/core/glass.json) instead of a pipeline.
+//? if >=1.21.6 {
+import java.io.Reader;
+import java.util.HashMap;
+import java.util.Map;
+
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+import com.mojang.blaze3d.pipeline.RenderPipeline;
+import com.mojang.blaze3d.systems.RenderSystem;
+import com.mojang.blaze3d.textures.FilterMode;
+import com.mojang.blaze3d.textures.GpuTextureView;
+import com.mojang.serialization.JsonOps;
+
+import org.saturnclient.config.Config;
+import org.saturnclient.saturnclient.SaturnClient;
+
+import net.minecraft.client.gl.Framebuffer;
+import net.minecraft.client.gl.PostEffectPipeline;
+import net.minecraft.client.gl.PostEffectProcessor;
+import net.minecraft.client.gl.RenderPipelines;
+import net.minecraft.client.gl.SimpleFramebuffer;
+import net.minecraft.client.render.DefaultFramebufferSet;
+import net.minecraft.client.render.ProjectionMatrix2;
+import net.minecraft.client.texture.AbstractTexture;
+import net.minecraft.client.texture.TextureSetup;
+import net.minecraft.client.util.Pool;
+import net.minecraft.util.Identifier;
+
+public final class GlassRenderer {
+    public static final RenderPipeline PIPELINE = RenderPipeline.builder(RenderPipelines.POSITION_TEX_COLOR_SNIPPET)
+            .withLocation(Identifier.of("saturnclient", "pipeline/glass"))
+            .withFragmentShader(Identifier.of("saturnclient", "core/glass"))
+            .withSampler("Sampler1")
+            .build();
+
+    private static final Identifier BLUR = Identifier.ofVanilla("post_effect/blur.json");
+    private static final ProjectionMatrix2 PROJECTION = new ProjectionMatrix2("saturn glass", 0.1f, 1000f, false);
+    // For the blurs' intermediate targets, freed once unused for a few frames
+    private static final Pool POOL = new Pool(3);
+
+    // By blur strength. A blur that failed to load is kept as null, so it isn't retried every frame.
+    private static final Map<Integer, PostEffectProcessor> BLURS = new HashMap<>();
+    private static final Map<Integer, SimpleFramebuffer> BACKDROPS = new HashMap<>();
+
+    private GlassRenderer() {
+    }
+
+    // Copies the main framebuffer and blurs the copy by blur. Call once a frame for each blur, while
+    // the screen builds its GUI, before drawing glass with it.
+    public static void captureBackdrop(int blur) {
+        Framebuffer main = SaturnClient.client.getFramebuffer();
+        int width = main.textureWidth;
+        int height = main.textureHeight;
+
+        SimpleFramebuffer backdrop = BACKDROPS.get(blur);
+        if (backdrop == null) {
+            backdrop = new SimpleFramebuffer("Saturn glass " + blur, width, height, false);
+            BACKDROPS.put(blur, backdrop);
+        } else if (backdrop.textureWidth != width || backdrop.textureHeight != height) {
+            backdrop.resize(width, height);
+        }
+        //? if <1.21.11
+        //backdrop.getColorAttachment().setTextureFilter(FilterMode.LINEAR, false);
+
+        RenderSystem.getDevice().createCommandEncoder().copyTextureToTexture(
+                main.getColorAttachment(), backdrop.getColorAttachment(), 0, 0, 0, 0, 0, width, height);
+
+        PostEffectProcessor processor = getBlur(blur);
+        if (processor != null) {
+            processor.render(backdrop, POOL);
+        }
+        POOL.decrementLifespan();
+        release(blur);
+    }
+
+    // The mask, then the copy blurred by blur, as the glass pipeline samples them
+    public static TextureSetup textures(AbstractTexture mask, int blur) {
+        GpuTextureView backdrop = BACKDROPS.get(blur).getColorAttachmentView();
+        //? if >=1.21.11
+        return TextureSetup.of(mask.getGlTextureView(), mask.getSampler(), backdrop, RenderSystem.getSamplerCache().get(FilterMode.LINEAR));
+        //? if <1.21.11
+        //return TextureSetup.of(mask.getGlTextureView(), backdrop);
+    }
+
+    // Frees the copies and blurs of strengths that are no longer set, besides kept
+    private static void release(int kept) {
+        BACKDROPS.entrySet().removeIf(entry -> {
+            boolean unused = entry.getKey() != kept && !isSet(entry.getKey());
+            if (unused) {
+                entry.getValue().delete();
+            }
+            return unused;
+        });
+        BLURS.entrySet().removeIf(entry -> {
+            boolean unused = entry.getKey() != kept && !isSet(entry.getKey());
+            if (unused && entry.getValue() != null) {
+                entry.getValue().close();
+            }
+            return unused;
+        });
+    }
+
+    private static boolean isSet(int blur) {
+        return blur == Config.menuBlur.value || blur == Config.widgetBlur.value;
+    }
+
+    private static PostEffectProcessor getBlur(int blur) {
+        if (!BLURS.containsKey(blur)) {
+            BLURS.put(blur, loadBlur(blur));
+        }
+        return BLURS.get(blur);
+    }
+
+    // Vanilla's blur, with its radius set to blur. Vanilla's own leaves it at 0, which makes the shader
+    // read the menu blur setting (Saturn's animated background blur while a Saturn screen is open).
+    private static PostEffectProcessor loadBlur(int blur) {
+        try (Reader reader = SaturnClient.client.getResourceManager().getResourceOrThrow(BLUR).getReader()) {
+            JsonElement json = JsonParser.parseReader(reader);
+            setRadius(json, blur);
+
+            PostEffectPipeline pipeline = PostEffectPipeline.CODEC.parse(JsonOps.INSTANCE, json).getOrThrow();
+            return PostEffectProcessor.parseEffect(pipeline, SaturnClient.client.getTextureManager(),
+                    DefaultFramebufferSet.MAIN_ONLY, Identifier.of("saturnclient", "glass_blur_" + blur), PROJECTION);
+        } catch (Exception e) {
+            SaturnClient.LOGGER.error("Couldn't load the glass blur", e);
+            return null;
+        }
+    }
+
+    // Sets every "Radius" uniform in the effect
+    private static void setRadius(JsonElement json, int radius) {
+        if (json.isJsonArray()) {
+            json.getAsJsonArray().forEach(element -> setRadius(element, radius));
+        } else if (json.isJsonObject()) {
+            JsonObject object = json.getAsJsonObject();
+            if (object.has("name") && object.get("name").getAsString().equals("Radius")) {
+                object.addProperty("value", (float) radius);
+            }
+            object.entrySet().forEach(entry -> setRadius(entry.getValue(), radius));
+        }
+    }
+}
+//?} else if >=1.21.5 {
+/*import java.util.HashMap;
+import java.util.Map;
+
+import com.mojang.blaze3d.pipeline.RenderPipeline;
+import com.mojang.blaze3d.systems.RenderSystem;
+import com.mojang.blaze3d.textures.FilterMode;
+
+import org.saturnclient.config.Config;
+import org.saturnclient.saturnclient.SaturnClient;
+
+import net.minecraft.client.gl.Framebuffer;
+import net.minecraft.client.gl.PostEffectProcessor;
+import net.minecraft.client.gl.RenderPipelines;
+import net.minecraft.client.gl.SimpleFramebuffer;
+import net.minecraft.client.render.DefaultFramebufferSet;
+import net.minecraft.client.render.RenderLayer;
+import net.minecraft.client.render.RenderPhase;
+import net.minecraft.client.util.Pool;
+import net.minecraft.util.Identifier;
+
+public final class GlassRenderer {
+    private static final RenderPipeline PIPELINE = RenderPipeline.builder(RenderPipelines.POSITION_TEX_COLOR_SNIPPET)
+            .withLocation(Identifier.of("saturnclient", "pipeline/glass"))
+            .withFragmentShader(Identifier.of("saturnclient", "core/glass_pre_1_21_6"))
+            .withSampler("Sampler1")
+            .build();
+
+    private static final Identifier BLUR = Identifier.ofVanilla("blur");
+    // For the blur's intermediate target, freed once unused for a few frames
+    private static final Pool POOL = new Pool(3);
+
+    private static final Map<Integer, SimpleFramebuffer> BACKDROPS = new HashMap<>();
+    // By mask and blur
+    private static final Map<String, RenderLayer> LAYERS = new HashMap<>();
+    // The game behind the screen before the screen blurs it, which glass is blurred from
+    private static SimpleFramebuffer background;
+
+    private GlassRenderer() {
+    }
+
+    // Saves the main framebuffer for glass. Call each frame before the screen blurs its background.
+    public static void saveBackground() {
+        background = copy(SaturnClient.client.getFramebuffer(), background, "Saturn glass background");
+    }
+
+    // Copies the saved background and blurs the copy by blur. Call once a frame for each blur, before
+    // drawing glass with it.
+    public static void captureBackdrop(int blur) {
+        Framebuffer from = background != null ? background : SaturnClient.client.getFramebuffer();
+        SimpleFramebuffer backdrop = copy(from, BACKDROPS.get(blur), "Saturn glass " + blur);
+        BACKDROPS.put(blur, backdrop);
+
+        PostEffectProcessor processor = SaturnClient.client.getShaderLoader().loadPostEffect(BLUR,
+                DefaultFramebufferSet.MAIN_ONLY);
+        if (processor != null) {
+            processor.render(backdrop, POOL, pass -> pass.setUniform("Radius", (float) blur));
+        }
+        POOL.decrementLifespan();
+        release(blur);
+    }
+
+    // Draws glass through mask with the copy blurred by blur
+    public static RenderLayer getLayer(Identifier mask, int blur) {
+        return LAYERS.computeIfAbsent(mask + " " + blur, key -> RenderLayer.of("saturn_glass", 786432, PIPELINE,
+                RenderLayer.MultiPhaseParameters.builder()
+                        .texture(new RenderPhase.TextureBase(() -> {
+                            RenderSystem.setShaderTexture(0,
+                                    SaturnClient.client.getTextureManager().getTexture(mask).getGlTexture());
+                            RenderSystem.setShaderTexture(1, BACKDROPS.get(blur).getColorAttachment());
+                        }, () -> {
+                        }))
+                        .build(false)));
+    }
+
+    // Frees the copies of strengths that are no longer set, besides kept
+    private static void release(int kept) {
+        BACKDROPS.entrySet().removeIf(entry -> {
+            boolean unused = entry.getKey() != kept && entry.getKey() != Config.menuBlur.value
+                    && entry.getKey() != Config.widgetBlur.value;
+            if (unused) {
+                entry.getValue().delete();
+            }
+            return unused;
+        });
+    }
+
+    // Copies from into to, made or resized to match
+    private static SimpleFramebuffer copy(Framebuffer from, SimpleFramebuffer to, String name) {
+        int width = from.textureWidth;
+        int height = from.textureHeight;
+
+        if (to == null) {
+            to = new SimpleFramebuffer(name, width, height, false);
+        } else if (to.textureWidth != width || to.textureHeight != height) {
+            to.resize(width, height);
+        }
+        to.getColorAttachment().setTextureFilter(FilterMode.LINEAR, false);
+
+        RenderSystem.getDevice().createCommandEncoder().copyTextureToTexture(
+                from.getColorAttachment(), to.getColorAttachment(), 0, 0, 0, 0, 0, width, height);
+        return to;
+    }
+}
+*///?} else {
+/*import java.util.HashMap;
+import java.util.Map;
+
+import org.lwjgl.opengl.GL11;
+import org.lwjgl.opengl.GL30;
+
+import com.mojang.blaze3d.platform.GlStateManager;
+import com.mojang.blaze3d.systems.RenderSystem;
+
+import org.saturnclient.config.Config;
+import org.saturnclient.saturnclient.SaturnClient;
+
+import net.minecraft.client.gl.Defines;
+import net.minecraft.client.gl.Framebuffer;
+import net.minecraft.client.gl.PostEffectProcessor;
+import net.minecraft.client.gl.ShaderProgramKey;
+import net.minecraft.client.gl.SimpleFramebuffer;
+import net.minecraft.client.render.DefaultFramebufferSet;
+import net.minecraft.client.render.RenderLayer;
+import net.minecraft.client.render.RenderPhase;
+import net.minecraft.client.render.VertexFormat;
+import net.minecraft.client.render.VertexFormats;
+import net.minecraft.client.util.Pool;
+import net.minecraft.util.Identifier;
+
+public final class GlassRenderer {
+    private static final ShaderProgramKey PROGRAM = new ShaderProgramKey(Identifier.of("saturnclient", "core/glass"),
+            VertexFormats.POSITION_TEXTURE_COLOR, Defines.EMPTY);
+
+    private static final Identifier BLUR = Identifier.ofVanilla("blur");
+    // For the blur's intermediate target, freed once unused for a few frames
+    private static final Pool POOL = new Pool(3);
+
+    private static final Map<Integer, SimpleFramebuffer> BACKDROPS = new HashMap<>();
+    // By mask and blur
+    private static final Map<String, RenderLayer> LAYERS = new HashMap<>();
+    // The game behind the screen before the screen blurs it, which glass is blurred from
+    private static SimpleFramebuffer background;
+
+    private GlassRenderer() {
+    }
+
+    // Saves the main framebuffer for glass. Call each frame before the screen blurs its background.
+    public static void saveBackground() {
+        background = copy(SaturnClient.client.getFramebuffer(), background);
+    }
+
+    // Copies the saved background and blurs the copy by blur. Call once a frame for each blur, before
+    // drawing glass with it.
+    public static void captureBackdrop(int blur) {
+        Framebuffer from = background != null ? background : SaturnClient.client.getFramebuffer();
+        SimpleFramebuffer backdrop = copy(from, BACKDROPS.get(blur));
+        BACKDROPS.put(blur, backdrop);
+
+        PostEffectProcessor processor = SaturnClient.client.getShaderLoader().loadPostEffect(BLUR,
+                DefaultFramebufferSet.MAIN_ONLY);
+        if (processor != null) {
+            processor.setUniforms("Radius", blur);
+            processor.render(backdrop, POOL);
+        }
+        POOL.decrementLifespan();
+        release(blur);
+        SaturnClient.client.getFramebuffer().beginWrite(false);
+    }
+
+    // Draws glass through mask with the copy blurred by blur
+    public static RenderLayer getLayer(Identifier mask, int blur) {
+        return LAYERS.computeIfAbsent(mask + " " + blur, key -> RenderLayer.of("saturn_glass",
+                VertexFormats.POSITION_TEXTURE_COLOR, VertexFormat.DrawMode.QUADS, 786432,
+                RenderLayer.MultiPhaseParameters.builder()
+                        .texture(new RenderPhase.TextureBase(() -> {
+                            RenderSystem.setShaderTexture(0, mask);
+                            RenderSystem.setShaderTexture(1, BACKDROPS.get(blur).getColorAttachment());
+                        }, () -> {
+                        }))
+                        .program(new RenderPhase.ShaderProgram(PROGRAM))
+                        .transparency(RenderPhase.TRANSLUCENT_TRANSPARENCY)
+                        .build(false)));
+    }
+
+    // Frees the copies of strengths that are no longer set, besides kept
+    private static void release(int kept) {
+        BACKDROPS.entrySet().removeIf(entry -> {
+            boolean unused = entry.getKey() != kept && entry.getKey() != Config.menuBlur.value
+                    && entry.getKey() != Config.widgetBlur.value;
+            if (unused) {
+                entry.getValue().delete();
+            }
+            return unused;
+        });
+    }
+
+    // Copies from into to, made or resized to match
+    private static SimpleFramebuffer copy(Framebuffer from, SimpleFramebuffer to) {
+        int width = from.textureWidth;
+        int height = from.textureHeight;
+
+        if (to == null) {
+            to = new SimpleFramebuffer(width, height, false);
+        } else if (to.textureWidth != width || to.textureHeight != height) {
+            to.resize(width, height);
+        }
+        to.setTexFilter(GL11.GL_LINEAR);
+
+        GlStateManager._glBindFramebuffer(GL30.GL_READ_FRAMEBUFFER, from.fbo);
+        GlStateManager._glBindFramebuffer(GL30.GL_DRAW_FRAMEBUFFER, to.fbo);
+        GlStateManager._glBlitFrameBuffer(0, 0, width, height, 0, 0, width, height, GL11.GL_COLOR_BUFFER_BIT,
+                GL11.GL_NEAREST);
+        SaturnClient.client.getFramebuffer().beginWrite(false);
+        return to;
+    }
+}
+*///?}

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

@@ -5,7 +5,9 @@ package org.saturnclient.impl.ui;
 //? if >=1.21.6 {
 import java.util.ArrayDeque;
 import java.util.Deque;
+import java.util.HashSet;
 import java.util.Objects;
+import java.util.Set;
 
 import org.jetbrains.annotations.Nullable;
 import org.joml.Matrix3x2f;
@@ -40,7 +42,6 @@ import net.minecraft.client.render.entity.state.EntityRenderState;
 import net.minecraft.client.render.item.KeyedItemRenderState;
 //?} else
 //import net.minecraft.client.render.item.ItemRenderState;
-//? if >=1.21.11
 import net.minecraft.client.texture.AbstractTexture;
 import net.minecraft.client.texture.Sprite;
 import net.minecraft.client.texture.TextureSetup;
@@ -61,6 +62,8 @@ public class RenderScopeImpl implements RenderScope {
 
     private ScissorStack scissorStack;
     private int opacity = 0xFF << 24;
+    // The glass blurs made for this scope's frame
+    private final Set<Integer> capturedBlurs = new HashSet<>();
 
     public RenderScopeImpl(DrawContext context) {
         this(context.getMatrices(), ((DrawContextAccessor) (Object) context).getState());
@@ -230,6 +233,25 @@ public class RenderScopeImpl implements RenderScope {
                 this.scissorStack.peekLast()));
     }
 
+    @Override
+    public void drawGlass(IdentifierRef mask, int x, int y, int width, int height, int blur) {
+        int color = getColor(0xFFFFFFFF);
+        if (mask == null || color >>> 24 == 0)
+            return;
+
+        if (capturedBlurs.add(blur)) {
+            GlassRenderer.captureBackdrop(blur);
+        }
+
+        AbstractTexture maskTexture = SaturnClient.client.getTextureManager().getTexture((Identifier) (Object) mask);
+        this.state.addSimpleElement(new TexturedQuadGuiElementRenderState(
+                GlassRenderer.PIPELINE,
+                GlassRenderer.textures(maskTexture, blur),
+                new Matrix3x2f(this.matrices.stack),
+                x, y, x + width, y + height, 0, 1, 0, 1, color,
+                this.scissorStack.peekLast()));
+    }
+
     // Scissor management
     @Override
     public void enableScissor(int x1, int y1, int x2, int y2) {
@@ -368,7 +390,9 @@ public class RenderScopeImpl implements RenderScope {
 //?} else {
 /*import java.util.ArrayDeque;
 import java.util.Deque;
+import java.util.HashSet;
 import java.util.Objects;
+import java.util.Set;
 import java.util.function.Consumer;
 
 import org.jetbrains.annotations.Nullable;
@@ -421,6 +445,8 @@ public class RenderScopeImpl implements RenderScope {
     public VertexConsumerProvider.Immediate vertexConsumers;
     private ScissorStack scissorStack = new ScissorStack();
     private int opacity = 255 << 24;
+    // The glass blurs made for this scope's frame
+    private final Set<Integer> capturedBlurs = new HashSet<>();
     private final ItemRenderState itemRenderState;
 
     // ----------------------------
@@ -660,6 +686,33 @@ public class RenderScopeImpl implements RenderScope {
         matrices.pop();
     }
 
+    @Override
+    public void drawGlass(IdentifierRef mask, int x, int y, int width, int height, int blur) {
+        int color = getColor(0xFFFFFFFF);
+        if (mask == null || color >>> 24 == 0)
+            return;
+
+        if (capturedBlurs.add(blur)) {
+            GlassRenderer.captureBackdrop(blur);
+        }
+
+        // In quarter units, as drawTexturedQuad draws
+        int x1 = x * 4;
+        int x2 = (x + width) * 4;
+        int y1 = y * 4;
+        int y2 = (y + height) * 4;
+
+        matrices.push();
+        matrices.scale(0.25f, 0.25f, 1.0f);
+        Matrix4f matrix4f = matrices.peek().getPositionMatrix();
+        VertexConsumer vertexConsumer = vertexConsumers.getBuffer(GlassRenderer.getLayer((Identifier) (Object) mask, blur));
+        vertexConsumer.vertex(matrix4f, x1, y1, 0).texture(0, 0).color(color);
+        vertexConsumer.vertex(matrix4f, x1, y2, 0).texture(0, 1).color(color);
+        vertexConsumer.vertex(matrix4f, x2, y2, 0).texture(1, 1).color(color);
+        vertexConsumer.vertex(matrix4f, x2, y1, 0).texture(1, 0).color(color);
+        matrices.pop();
+    }
+
     // ----------------------------
     // Items
     // ----------------------------

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

@@ -3,6 +3,7 @@ package org.saturnclient.impl.ui;
 import java.time.Duration;
 import java.time.Instant;
 
+import org.saturnclient.config.Config;
 import org.saturnclient.ui.RenderScope;
 import org.saturnclient.ui.SaturnScreen;
 import org.saturnclient.ui.SaturnScreen.ScreenProvider;
@@ -86,8 +87,10 @@ public class SaturnScreenFabric extends Screen implements ScreenProvider {
         }
         long elapsed = Duration.between(screen.start, Instant.now()).toMillis();
 
-        mouseX *= 2;
-        mouseY *= 2;
+        screen.updateScale();
+
+        mouseX = (int) (mouseX / screen.scale);
+        mouseY = (int) (mouseY / screen.scale);
 
         // From 1.21.6 the background, blur included, is drawn in renderBackground.
         //? if <1.21.6 {
@@ -95,12 +98,18 @@ public class SaturnScreenFabric extends Screen implements ScreenProvider {
             ROTATING_PANORAMA_RENDERER.render(context, this.width, this.height, screen.backgroundOpacity, delta);
         }
 
-        PostEffectProcessor postEffectProcessor = this.client.getShaderLoader().loadPostEffect(
+        // Glass is blurred from the game as it is before this screen blurs it.
+        if (Config.usesGlass()) {
+            context.draw();
+            GlassRenderer.saveBackground();
+        }
+
+        float radius = screen.getBackgroundBlur();
+        PostEffectProcessor postEffectProcessor = radius < 1 ? null : this.client.getShaderLoader().loadPostEffect(
                 Identifier.ofVanilla("blur"),
                 DefaultFramebufferSet.MAIN_ONLY);
 
         if (postEffectProcessor != null) {
-            float radius = screen.getBackgroundBlur();
             //? if >=1.21.5
             postEffectProcessor.render(this.client.getFramebuffer(), this.pool, pass -> pass.setUniform("Radius", radius));
             //? if <1.21.5
@@ -245,11 +254,11 @@ public class SaturnScreenFabric extends Screen implements ScreenProvider {
 
     @Override
     public int getWidth() {
-        return width * 2;
+        return width;
     }
 
     @Override
     public int getHeight() {
-        return height * 2;
+        return height;
     }
 }

src/main/resources/assets/saturnclient/shaders/core/glass.fsh

@@ -0,0 +1,28 @@
+#version 330
+
+// Saturn's glass: the blurred game behind the screen, cut to a panel's shape. For 1.21.6 and
+// later; glass_pre_1_21_6.fsh (with glass.json, the program 1.21.4 loads) is for older versions.
+
+// Vanilla's own, since its layout changes between versions (1.21.11 dropped LineWidth)
+#moj_import <minecraft:dynamictransforms.glsl>
+
+// The panel's rounded rectangle, the same texture its background is drawn with
+uniform sampler2D Sampler0;
+// The game behind the screen, blurred, the size of the framebuffer
+uniform sampler2D Sampler1;
+
+in vec2 texCoord0;
+in vec4 vertexColor;
+
+out vec4 fragColor;
+
+void main() {
+    float mask = texture(Sampler0, texCoord0).a * vertexColor.a;
+    if (mask == 0.0) {
+        discard;
+    }
+
+    // The blurred copy lines up with the framebuffer being drawn to.
+    vec2 screenUv = gl_FragCoord.xy / vec2(textureSize(Sampler1, 0));
+    fragColor = vec4(texture(Sampler1, screenUv).rgb, mask) * ColorModulator;
+}

src/main/resources/assets/saturnclient/shaders/core/glass.json

@@ -0,0 +1,13 @@
+{
+    "vertex": "minecraft:core/position_tex_color",
+    "fragment": "saturnclient:core/glass_pre_1_21_6",
+    "samplers": [
+        { "name": "Sampler0" },
+        { "name": "Sampler1" }
+    ],
+    "uniforms": [
+        { "name": "ModelViewMat", "type": "matrix4x4", "count": 16, "values": [ 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0 ] },
+        { "name": "ProjMat", "type": "matrix4x4", "count": 16, "values": [ 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0 ] },
+        { "name": "ColorModulator", "type": "float", "count": 4, "values": [ 1.0, 1.0, 1.0, 1.0 ] }
+    ]
+}

src/main/resources/assets/saturnclient/shaders/core/glass_pre_1_21_6.fsh

@@ -0,0 +1,27 @@
+#version 150
+
+// Saturn's glass (see glass.fsh), for 1.21.4 and 1.21.5, which set uniforms one by one instead of in
+// blocks.
+
+uniform vec4 ColorModulator;
+
+// The panel's rounded rectangle, the same texture its background is drawn with
+uniform sampler2D Sampler0;
+// The game behind the screen, blurred, the size of the framebuffer
+uniform sampler2D Sampler1;
+
+in vec2 texCoord0;
+in vec4 vertexColor;
+
+out vec4 fragColor;
+
+void main() {
+    float mask = texture(Sampler0, texCoord0).a * vertexColor.a;
+    if (mask == 0.0) {
+        discard;
+    }
+
+    // The blurred copy lines up with the framebuffer being drawn to.
+    vec2 screenUv = gl_FragCoord.xy / vec2(textureSize(Sampler1, 0));
+    fragColor = vec4(texture(Sampler1, screenUv).rgb, mask) * ColorModulator;
+}