From 8af165e4f4093a44fb07348967448b59767edeb7 Mon Sep 17 00:00:00 2001
From: Brandon DeRosier <bdero@google.com>
Date: Tue, 24 Sep 2024 22:27:28 -0700
Subject: [PATCH 1/8] [Flutter GPU] Add missing MSAA stuff.

---
 lib/gpu/context.cc                  |   5 ++
 lib/gpu/context.h                   |   4 +
 lib/gpu/lib/src/command_buffer.dart |   8 +-
 lib/gpu/lib/src/context.dart        |  16 ++++
 lib/gpu/lib/src/render_pass.dart    |  87 ++++++++++++++++++--
 lib/gpu/render_pass.cc              |  16 +++-
 lib/gpu/render_pass.h               |   3 +-
 testing/dart/gpu_test.dart          | 120 +++++++++++++++++++++-------
 8 files changed, 221 insertions(+), 38 deletions(-)

diff --git a/lib/gpu/context.cc b/lib/gpu/context.cc
index c0c3345ce8487..b360711e55fc9 100644
--- a/lib/gpu/context.cc
+++ b/lib/gpu/context.cc
@@ -111,3 +111,8 @@ extern int InternalFlutterGpu_Context_GetMinimumUniformByteAlignment(
     flutter::gpu::Context* wrapper) {
   return impeller::DefaultUniformAlignment();
 }
+
+extern bool InternalFlutterGpu_Context_GetSupportsOffscreenMSAA(
+    flutter::gpu::Context* wrapper) {
+  return wrapper->GetContext()->GetCapabilities()->SupportsOffscreenMSAA();
+}
diff --git a/lib/gpu/context.h b/lib/gpu/context.h
index b482ae479938b..852b0d3569f02 100644
--- a/lib/gpu/context.h
+++ b/lib/gpu/context.h
@@ -74,6 +74,10 @@ FLUTTER_GPU_EXPORT
 extern int InternalFlutterGpu_Context_GetMinimumUniformByteAlignment(
     flutter::gpu::Context* wrapper);
 
+FLUTTER_GPU_EXPORT
+extern bool InternalFlutterGpu_Context_GetSupportsOffscreenMSAA(
+    flutter::gpu::Context* wrapper);
+
 }  // extern "C"
 
 #endif  // FLUTTER_LIB_GPU_CONTEXT_H_
diff --git a/lib/gpu/lib/src/command_buffer.dart b/lib/gpu/lib/src/command_buffer.dart
index 09cae10b8fa75..20c0137ce69aa 100644
--- a/lib/gpu/lib/src/command_buffer.dart
+++ b/lib/gpu/lib/src/command_buffer.dart
@@ -9,13 +9,15 @@ part of flutter_gpu;
 typedef CompletionCallback<T> = void Function(bool success);
 
 base class CommandBuffer extends NativeFieldWrapperClass1 {
+  final GpuContext _gpuContext;
+
   /// Creates a new CommandBuffer.
-  CommandBuffer._(GpuContext gpuContext) {
-    _initialize(gpuContext);
+  CommandBuffer._(this._gpuContext) {
+    _initialize(_gpuContext);
   }
 
   RenderPass createRenderPass(RenderTarget renderTarget) {
-    return RenderPass._(this, renderTarget);
+    return RenderPass._(_gpuContext, this, renderTarget);
   }
 
   void submit({CompletionCallback? completionCallback}) {
diff --git a/lib/gpu/lib/src/context.dart b/lib/gpu/lib/src/context.dart
index 217b387314908..a0a0513468afe 100644
--- a/lib/gpu/lib/src/context.dart
+++ b/lib/gpu/lib/src/context.dart
@@ -46,6 +46,18 @@ base class GpuContext extends NativeFieldWrapperClass1 {
     return _getMinimumUniformByteAlignment();
   }
 
+  /// Whether the backend supports multisample anti-aliasing for offscreen
+  /// color and stencil attachments. A subset of OpenGLES-only devices do not
+  /// support this functionality.
+  ///
+  /// Any texture created via [createTexture] is an offscreen texture.
+  /// There is currently no way to render directly against the "onscreen"
+  /// texture that the framework renders to, so all Flutter GPU textures are
+  /// "offscreen".
+  bool get doesSupportOffscreenMSAA {
+    return _getSupportsOffscreenMSAA();
+  }
+
   /// Allocates a new region of GPU-resident memory.
   ///
   /// The [storageMode] must be either [StorageMode.hostVisible] or
@@ -134,6 +146,10 @@ base class GpuContext extends NativeFieldWrapperClass1 {
   @Native<Int Function(Pointer<Void>)>(
       symbol: 'InternalFlutterGpu_Context_GetMinimumUniformByteAlignment')
   external int _getMinimumUniformByteAlignment();
+
+  @Native<Bool Function(Pointer<Void>)>(
+      symbol: 'InternalFlutterGpu_Context_GetSupportsOffscreenMSAA')
+  external bool _getSupportsOffscreenMSAA();
 }
 
 /// The default graphics context.
diff --git a/lib/gpu/lib/src/render_pass.dart b/lib/gpu/lib/src/render_pass.dart
index 95d7b5f317add..f0af57e99486c 100644
--- a/lib/gpu/lib/src/render_pass.dart
+++ b/lib/gpu/lib/src/render_pass.dart
@@ -21,6 +21,32 @@ base class ColorAttachment {
 
   Texture texture;
   Texture? resolveTexture;
+
+  void _assertValid() {
+    if (resolveTexture != null) {
+      assert(resolveTexture!.format == texture.format,
+          "ColorAttachment MSAA resolve texture must have the same format as the texture");
+      assert(
+          resolveTexture!.width == texture.width &&
+              resolveTexture!.height == texture.height,
+          "ColorAttachment MSAA resolve texture must have the same dimensions as the texture");
+      assert(resolveTexture!.sampleCount == 1,
+          "ColorAttachment MSAA resolve texture must have a sample count of 1");
+      assert(texture.sampleCount > 1,
+          "ColorAttachment must have a sample count greater than 1 when a MSAA resolve texture is set");
+      assert(
+          storeAction == StoreAction.multisampleResolve ||
+              storeAction == StoreAction.storeAndMultisampleResolve,
+          "ColorAttachment StoreAction must be multisampleResolve or storeAndMultisampleResolve when a resolve texture is set");
+      assert(resolveTexture!.storageMode != StorageMode.deviceTransient,
+          "ColorAttachment MSAA resolve texture must not have a storage mode of deviceTransient");
+    }
+
+    assert(
+        texture.storageMode != StorageMode.deviceTransient ||
+            loadAction != LoadAction.load,
+        "ColorAttachment loadAction must not be load when the texture has a storage mode of deviceTransient");
+  }
 }
 
 base class DepthStencilAttachment {
@@ -43,6 +69,43 @@ base class DepthStencilAttachment {
   int stencilClearValue;
 
   Texture texture;
+  Texture? resolveTexture;
+
+  void _assertValid() {
+    if (resolveTexture != null) {
+      assert(resolveTexture!.format == texture.format,
+          "DepthStencilAttachment MSAA resolve texture must have the same format as the texture");
+      assert(
+          resolveTexture!.width == texture.width &&
+              resolveTexture!.height == texture.height,
+          "DepthStencilAttachment MSAA resolve texture must have the same dimensions as the texture");
+      assert(resolveTexture!.sampleCount == 1,
+          "DepthStencilAttachment MSAA resolve texture must have a sample count of 1");
+      assert(texture.sampleCount > 1,
+          "DepthStencilAttachment must have a sample count greater than 1 when a MSAA resolve texture is set");
+      assert(
+          depthStoreAction == StoreAction.multisampleResolve ||
+              depthStoreAction == StoreAction.storeAndMultisampleResolve,
+          "DepthStencilAttachment depthStoreAction must be multisampleResolve or storeAndMultisampleResolve when a resolve texture is set");
+      assert(
+          stencilStoreAction == StoreAction.multisampleResolve ||
+              stencilStoreAction == StoreAction.storeAndMultisampleResolve,
+          "DepthStencilAttachment stencilStoreAction must be multisampleResolve or storeAndMultisampleResolve when a resolve texture is set");
+      assert(resolveTexture!.storageMode != StorageMode.deviceTransient,
+          "DepthStencilAttachment MSAA resolve texture must not have a storage mode of deviceTransient");
+    }
+
+    if (texture.storageMode == StorageMode.deviceTransient) {
+      assert(
+          texture.storageMode != StorageMode.deviceTransient ||
+              depthLoadAction != LoadAction.load,
+          "DepthStencilAttachment depthLoadAction must not be load when the texture has a storage mode of deviceTransient");
+      assert(
+          texture.storageMode != StorageMode.deviceTransient ||
+              stencilLoadAction != LoadAction.load,
+          "DepthStencilAttachment stencilLoadAction must not be load when the texture has a storage mode of deviceTransient");
+    }
+  }
 }
 
 base class StencilConfig {
@@ -117,13 +180,25 @@ base class RenderTarget {
             colorAttachments: [colorAttachment],
             depthStencilAttachment: depthStencilAttachment);
 
+  _assertValid() {
+    for (final color in colorAttachments) {
+      color._assertValid();
+    }
+    if (depthStencilAttachment != null) {
+      depthStencilAttachment!._assertValid();
+    }
+  }
+
   final List<ColorAttachment> colorAttachments;
   final DepthStencilAttachment? depthStencilAttachment;
 }
 
 base class RenderPass extends NativeFieldWrapperClass1 {
   /// Creates a new RenderPass.
-  RenderPass._(CommandBuffer commandBuffer, RenderTarget renderTarget) {
+  RenderPass._(GpuContext gpuContext, CommandBuffer commandBuffer,
+      RenderTarget renderTarget) {
+    renderTarget._assertValid();
+
     _initialize();
     String? error;
     for (final (index, color) in renderTarget.colorAttachments.indexed) {
@@ -150,7 +225,8 @@ base class RenderPass extends NativeFieldWrapperClass1 {
           ds.stencilLoadAction.index,
           ds.stencilStoreAction.index,
           ds.stencilClearValue,
-          ds.texture);
+          ds.texture,
+          ds.resolveTexture);
       if (error != null) {
         throw Exception(error);
       }
@@ -309,8 +385,8 @@ base class RenderPass extends NativeFieldWrapperClass1 {
       Texture? resolveTexture);
 
   @Native<
-          Handle Function(
-              Pointer<Void>, Int, Int, Float, Int, Int, Int, Pointer<Void>)>(
+          Handle Function(Pointer<Void>, Int, Int, Float, Int, Int, Int,
+              Pointer<Void>, Handle)>(
       symbol: 'InternalFlutterGpu_RenderPass_SetDepthStencilAttachment')
   external String? _setDepthStencilAttachment(
       int depthLoadAction,
@@ -319,7 +395,8 @@ base class RenderPass extends NativeFieldWrapperClass1 {
       int stencilLoadAction,
       int stencilStoreAction,
       int stencilClearValue,
-      Texture texture);
+      Texture texture,
+      Texture? resolveTexture);
 
   @Native<Handle Function(Pointer<Void>, Pointer<Void>)>(
       symbol: 'InternalFlutterGpu_RenderPass_Begin')
diff --git a/lib/gpu/render_pass.cc b/lib/gpu/render_pass.cc
index 70d68d0e78081..a6a93a8096237 100644
--- a/lib/gpu/render_pass.cc
+++ b/lib/gpu/render_pass.cc
@@ -255,13 +255,24 @@ Dart_Handle InternalFlutterGpu_RenderPass_SetDepthStencilAttachment(
     int stencil_load_action,
     int stencil_store_action,
     int stencil_clear_value,
-    flutter::gpu::Texture* texture) {
+    flutter::gpu::Texture* texture,
+    Dart_Handle resolve_texture_wrapper) {
+  flutter::gpu::Texture* resolve_texture = nullptr;
+
+  if (!Dart_IsNull(resolve_texture_wrapper)) {
+    resolve_texture = tonic::DartConverter<flutter::gpu::Texture*>::FromDart(
+        resolve_texture_wrapper);
+  }
+
   {
     impeller::DepthAttachment desc;
     desc.load_action = flutter::gpu::ToImpellerLoadAction(depth_load_action);
     desc.store_action = flutter::gpu::ToImpellerStoreAction(depth_store_action);
     desc.clear_depth = depth_clear_value;
     desc.texture = texture->GetTexture();
+    if (resolve_texture) {
+      desc.resolve_texture = resolve_texture->GetTexture();
+    }
     wrapper->GetRenderTarget().SetDepthAttachment(desc);
   }
   {
@@ -271,6 +282,9 @@ Dart_Handle InternalFlutterGpu_RenderPass_SetDepthStencilAttachment(
         flutter::gpu::ToImpellerStoreAction(stencil_store_action);
     desc.clear_stencil = stencil_clear_value;
     desc.texture = texture->GetTexture();
+    if (resolve_texture) {
+      desc.resolve_texture = resolve_texture->GetTexture();
+    }
     wrapper->GetRenderTarget().SetStencilAttachment(desc);
   }
 
diff --git a/lib/gpu/render_pass.h b/lib/gpu/render_pass.h
index da9840d62699f..3b1873d73b38b 100644
--- a/lib/gpu/render_pass.h
+++ b/lib/gpu/render_pass.h
@@ -137,7 +137,8 @@ extern Dart_Handle InternalFlutterGpu_RenderPass_SetDepthStencilAttachment(
     int stencil_load_action,
     int stencil_store_action,
     int stencil_clear_value,
-    flutter::gpu::Texture* texture);
+    flutter::gpu::Texture* texture,
+    Dart_Handle resolve_texture_wrapper);
 
 FLUTTER_GPU_EXPORT
 extern Dart_Handle InternalFlutterGpu_RenderPass_Begin(
diff --git a/testing/dart/gpu_test.dart b/testing/dart/gpu_test.dart
index 508e7e08d9e6f..2fee673093eff 100644
--- a/testing/dart/gpu_test.dart
+++ b/testing/dart/gpu_test.dart
@@ -60,6 +60,7 @@ RenderPassState createSimpleRenderPass({Vector4? clearColor}) {
   final gpu.Texture? depthStencilTexture = gpu.gpuContext.createTexture(
       gpu.StorageMode.deviceTransient, 100, 100,
       format: gpu.gpuContext.defaultDepthStencilFormat);
+  assert(depthStencilTexture != null);
 
   final gpu.CommandBuffer commandBuffer = gpu.gpuContext.createCommandBuffer();
 
@@ -74,6 +75,70 @@ RenderPassState createSimpleRenderPass({Vector4? clearColor}) {
   return RenderPassState(renderTexture, commandBuffer, renderPass);
 }
 
+RenderPassState createSimpleRenderPassWithMSAA() {
+  // Create transient MSAA attachments, which will live entirely in tile memory
+  // for most GPUs.
+
+  final gpu.Texture? renderTexture = gpu.gpuContext.createTexture(
+      gpu.StorageMode.deviceTransient, 100, 100,
+      format: gpu.gpuContext.defaultColorFormat, sampleCount: 4);
+  assert(renderTexture != null);
+
+  final gpu.Texture? depthStencilTexture = gpu.gpuContext.createTexture(
+      gpu.StorageMode.deviceTransient, 100, 100,
+      format: gpu.gpuContext.defaultDepthStencilFormat, sampleCount: 4);
+  assert(depthStencilTexture != null);
+
+  // Create the single-sample resolve texture that live in DRAM and will be
+  // drawn to the screen.
+
+  final gpu.Texture? resolveTexture = gpu.gpuContext.createTexture(
+      gpu.StorageMode.devicePrivate, 100, 100,
+      format: gpu.gpuContext.defaultColorFormat);
+  assert(resolveTexture != null);
+
+  final gpu.CommandBuffer commandBuffer = gpu.gpuContext.createCommandBuffer();
+
+  final gpu.RenderTarget renderTarget = gpu.RenderTarget.singleColor(
+      gpu.ColorAttachment(
+          texture: renderTexture!,
+          resolveTexture: resolveTexture,
+          storeAction: gpu.StoreAction.multisampleResolve),
+      depthStencilAttachment:
+          gpu.DepthStencilAttachment(texture: depthStencilTexture!));
+
+  final gpu.RenderPass renderPass =
+      commandBuffer.createRenderPass(renderTarget);
+
+  return RenderPassState(resolveTexture!, commandBuffer, renderPass);
+}
+
+void drawTriangle(RenderPassState state, Vector4 color) {
+  final gpu.RenderPipeline pipeline = createUnlitRenderPipeline();
+
+  state.renderPass.bindPipeline(pipeline);
+
+  final gpu.HostBuffer transients = gpu.gpuContext.createHostBuffer();
+  final gpu.BufferView vertices = transients.emplace(float32(<double>[
+    -0.5, 0.5, //
+    0.0, -0.5, //
+    0.5, 0.5, //
+  ]));
+  final gpu.BufferView vertInfoData =
+      transients.emplace(unlitUBO(Matrix4.identity(), color));
+  state.renderPass.bindVertexBuffer(vertices, 3);
+
+  // TODO(bdero): Overwrite bindings with the same slot so we don't need to clear.
+  //              https://github.com/flutter/flutter/issues/155335
+  state.renderPass.clearBindings();
+
+  final gpu.UniformSlot vertInfo =
+      pipeline.vertexShader.getUniformSlot('VertInfo');
+  state.renderPass.bindUniform(vertInfo, vertInfoData);
+
+  state.renderPass.draw();
+}
+
 void main() async {
   final ImageComparer comparer = await ImageComparer.create();
 
@@ -337,34 +402,7 @@ void main() async {
   // Renders a green triangle pointing downwards.
   test('Can render triangle', () async {
     final state = createSimpleRenderPass();
-
-    final gpu.RenderPipeline pipeline = createUnlitRenderPipeline();
-    state.renderPass.bindPipeline(pipeline);
-
-    // Configure blending with defaults (just to test the bindings).
-    state.renderPass.setColorBlendEnable(true);
-    state.renderPass.setColorBlendEquation(gpu.ColorBlendEquation());
-
-    final gpu.HostBuffer transients = gpu.gpuContext.createHostBuffer();
-    final gpu.BufferView vertices = transients.emplace(float32(<double>[
-      -0.5, 0.5, //
-      0.0, -0.5, //
-      0.5, 0.5, //
-    ]));
-    final gpu.BufferView vertInfoData = transients.emplace(float32(<double>[
-      1, 0, 0, 0, // mvp
-      0, 1, 0, 0, // mvp
-      0, 0, 1, 0, // mvp
-      0, 0, 0, 1, // mvp
-      0, 1, 0, 1, // color
-    ]));
-    state.renderPass.bindVertexBuffer(vertices, 3);
-
-    final gpu.UniformSlot vertInfo =
-        pipeline.vertexShader.getUniformSlot('VertInfo');
-    state.renderPass.bindUniform(vertInfo, vertInfoData);
-    state.renderPass.draw();
-
+    drawTriangle(state, Colors.lime);
     state.commandBuffer.submit();
 
     final ui.Image image = state.renderTexture.asImage();
@@ -411,6 +449,32 @@ void main() async {
     await comparer.addGoldenImage(image, 'flutter_gpu_test_triangle_polygon_mode.png');
   }, skip: !impellerEnabled);
 
+  // Renders a green triangle pointing downwards, with 4xMSAA.
+  test('Can render triangle with MSAA', () async {
+    final state = createSimpleRenderPassWithMSAA();
+    drawTriangle(state, Colors.lime);
+    state.commandBuffer.submit();
+
+    final ui.Image image = state.renderTexture.asImage();
+    await comparer.addGoldenImage(image, 'flutter_gpu_test_triangle_msaa.png');
+  }, skip: !(impellerEnabled && gpu.gpuContext.doesSupportOffscreenMSAA));
+
+  test(
+      'Rendering with MSAA throws exception when offscreen MSAA is not supported',
+      () async {
+    try {
+      final state = createSimpleRenderPassWithMSAA();
+      drawTriangle(state, Colors.lime);
+      state.commandBuffer.submit();
+      fail('Exception not thrown when offscreen MSAA is not supported.');
+    } catch (e) {
+      expect(
+          e.toString(),
+          contains(
+              'The backend does not support multisample anti-aliasing for offscreen color and stencil attachments'));
+    }
+  }, skip: gpu.gpuContext.doesSupportOffscreenMSAA);
+
   // Renders a hollow green triangle pointing downwards.
   test('Can render hollowed out triangle using stencil ops', () async {
     final state = createSimpleRenderPass();

From 4a2974885dce230c81a38c7875d732419c478352 Mon Sep 17 00:00:00 2001
From: Brandon DeRosier <bdero@google.com>
Date: Tue, 8 Oct 2024 15:11:13 -0700
Subject: [PATCH 2/8] Use exceptions for errors

---
 lib/gpu/lib/src/render_pass.dart | 129 ++++++++++++++++++-------------
 1 file changed, 74 insertions(+), 55 deletions(-)

diff --git a/lib/gpu/lib/src/render_pass.dart b/lib/gpu/lib/src/render_pass.dart
index f0af57e99486c..6213f66373347 100644
--- a/lib/gpu/lib/src/render_pass.dart
+++ b/lib/gpu/lib/src/render_pass.dart
@@ -22,30 +22,35 @@ base class ColorAttachment {
   Texture texture;
   Texture? resolveTexture;
 
-  void _assertValid() {
+  void _validate() {
     if (resolveTexture != null) {
-      assert(resolveTexture!.format == texture.format,
-          "ColorAttachment MSAA resolve texture must have the same format as the texture");
-      assert(
-          resolveTexture!.width == texture.width &&
-              resolveTexture!.height == texture.height,
-          "ColorAttachment MSAA resolve texture must have the same dimensions as the texture");
-      assert(resolveTexture!.sampleCount == 1,
-          "ColorAttachment MSAA resolve texture must have a sample count of 1");
-      assert(texture.sampleCount > 1,
-          "ColorAttachment must have a sample count greater than 1 when a MSAA resolve texture is set");
-      assert(
-          storeAction == StoreAction.multisampleResolve ||
-              storeAction == StoreAction.storeAndMultisampleResolve,
-          "ColorAttachment StoreAction must be multisampleResolve or storeAndMultisampleResolve when a resolve texture is set");
-      assert(resolveTexture!.storageMode != StorageMode.deviceTransient,
-          "ColorAttachment MSAA resolve texture must not have a storage mode of deviceTransient");
+      if (resolveTexture!.format != texture.format) {
+        throw Exception(
+            "ColorAttachment MSAA resolve texture must have the same format as the texture");
+      }
+      if (resolveTexture!.width != texture.width ||
+          resolveTexture!.height != texture.height) {
+        throw Exception(
+            "ColorAttachment MSAA resolve texture must have the same dimensions as the texture");
+      }
+      if (resolveTexture!.sampleCount != 1) {
+        throw Exception(
+            "ColorAttachment MSAA resolve texture must have a sample count of 1");
+      }
+      if (texture.sampleCount <= 1) {
+        throw Exception(
+            "ColorAttachment must have a sample count greater than 1 when a MSAA resolve texture is set");
+      }
+      if (storeAction != StoreAction.multisampleResolve &&
+          storeAction != StoreAction.storeAndMultisampleResolve) {
+        throw Exception(
+            "ColorAttachment StoreAction must be multisampleResolve or storeAndMultisampleResolve when a resolve texture is set");
+      }
+      if (resolveTexture!.storageMode == StorageMode.deviceTransient) {
+        throw Exception(
+            "ColorAttachment MSAA resolve texture must not have a storage mode of deviceTransient");
+      }
     }
-
-    assert(
-        texture.storageMode != StorageMode.deviceTransient ||
-            loadAction != LoadAction.load,
-        "ColorAttachment loadAction must not be load when the texture has a storage mode of deviceTransient");
   }
 }
 
@@ -71,39 +76,50 @@ base class DepthStencilAttachment {
   Texture texture;
   Texture? resolveTexture;
 
-  void _assertValid() {
+  void _validate() {
     if (resolveTexture != null) {
-      assert(resolveTexture!.format == texture.format,
-          "DepthStencilAttachment MSAA resolve texture must have the same format as the texture");
-      assert(
-          resolveTexture!.width == texture.width &&
-              resolveTexture!.height == texture.height,
-          "DepthStencilAttachment MSAA resolve texture must have the same dimensions as the texture");
-      assert(resolveTexture!.sampleCount == 1,
-          "DepthStencilAttachment MSAA resolve texture must have a sample count of 1");
-      assert(texture.sampleCount > 1,
-          "DepthStencilAttachment must have a sample count greater than 1 when a MSAA resolve texture is set");
-      assert(
-          depthStoreAction == StoreAction.multisampleResolve ||
-              depthStoreAction == StoreAction.storeAndMultisampleResolve,
-          "DepthStencilAttachment depthStoreAction must be multisampleResolve or storeAndMultisampleResolve when a resolve texture is set");
-      assert(
-          stencilStoreAction == StoreAction.multisampleResolve ||
-              stencilStoreAction == StoreAction.storeAndMultisampleResolve,
-          "DepthStencilAttachment stencilStoreAction must be multisampleResolve or storeAndMultisampleResolve when a resolve texture is set");
-      assert(resolveTexture!.storageMode != StorageMode.deviceTransient,
-          "DepthStencilAttachment MSAA resolve texture must not have a storage mode of deviceTransient");
+      if (resolveTexture!.format != texture.format) {
+        throw Exception(
+            "DepthStencilAttachment MSAA resolve texture must have the same format as the texture");
+      }
+      if (resolveTexture!.width != texture.width ||
+          resolveTexture!.height != texture.height) {
+        throw Exception(
+            "DepthStencilAttachment MSAA resolve texture must have the same dimensions as the texture");
+      }
+      if (resolveTexture!.sampleCount != 1) {
+        throw Exception(
+            "DepthStencilAttachment MSAA resolve texture must have a sample count of 1");
+      }
+      if (texture.sampleCount <= 1) {
+        throw Exception(
+            "DepthStencilAttachment must have a sample count greater than 1 when a MSAA resolve texture is set");
+      }
+      if (depthStoreAction != StoreAction.multisampleResolve &&
+          depthStoreAction != StoreAction.storeAndMultisampleResolve) {
+        throw Exception(
+            "DepthStencilAttachment depthStoreAction must be multisampleResolve or storeAndMultisampleResolve when a resolve texture is set");
+      }
+      if (stencilStoreAction != StoreAction.multisampleResolve &&
+          stencilStoreAction != StoreAction.storeAndMultisampleResolve) {
+        throw Exception(
+            "DepthStencilAttachment stencilStoreAction must be multisampleResolve or storeAndMultisampleResolve when a resolve texture is set");
+      }
+      if (resolveTexture!.storageMode == StorageMode.deviceTransient) {
+        throw Exception(
+            "DepthStencilAttachment MSAA resolve texture must not have a storage mode of deviceTransient");
+      }
     }
 
     if (texture.storageMode == StorageMode.deviceTransient) {
-      assert(
-          texture.storageMode != StorageMode.deviceTransient ||
-              depthLoadAction != LoadAction.load,
-          "DepthStencilAttachment depthLoadAction must not be load when the texture has a storage mode of deviceTransient");
-      assert(
-          texture.storageMode != StorageMode.deviceTransient ||
-              stencilLoadAction != LoadAction.load,
-          "DepthStencilAttachment stencilLoadAction must not be load when the texture has a storage mode of deviceTransient");
+      if (depthLoadAction == LoadAction.load) {
+        throw Exception(
+            "DepthStencilAttachment depthLoadAction must not be load when the texture has a storage mode of deviceTransient");
+      }
+      if (stencilLoadAction == LoadAction.load) {
+        throw Exception(
+            "DepthStencilAttachment stencilLoadAction must not be load when the texture has a storage mode of deviceTransient");
+      }
     }
   }
 }
@@ -180,12 +196,12 @@ base class RenderTarget {
             colorAttachments: [colorAttachment],
             depthStencilAttachment: depthStencilAttachment);
 
-  _assertValid() {
+  _validate() {
     for (final color in colorAttachments) {
-      color._assertValid();
+      color._validate();
     }
     if (depthStencilAttachment != null) {
-      depthStencilAttachment!._assertValid();
+      depthStencilAttachment!._validate();
     }
   }
 
@@ -197,7 +213,10 @@ base class RenderPass extends NativeFieldWrapperClass1 {
   /// Creates a new RenderPass.
   RenderPass._(GpuContext gpuContext, CommandBuffer commandBuffer,
       RenderTarget renderTarget) {
-    renderTarget._assertValid();
+    assert(() {
+      renderTarget._validate();
+      return true;
+    }());
 
     _initialize();
     String? error;

From 10ef5b4ad3a015b6841075d8a47dad030db33f6f Mon Sep 17 00:00:00 2001
From: Brandon DeRosier <bdero@google.com>
Date: Tue, 8 Oct 2024 15:14:07 -0700
Subject: [PATCH 3/8] Remove depthstencil resolve

---
 lib/gpu/lib/src/render_pass.dart | 45 +++-----------------------------
 lib/gpu/render_pass.cc           | 16 +-----------
 lib/gpu/render_pass.h            |  3 +--
 3 files changed, 6 insertions(+), 58 deletions(-)

diff --git a/lib/gpu/lib/src/render_pass.dart b/lib/gpu/lib/src/render_pass.dart
index 6213f66373347..5782271072769 100644
--- a/lib/gpu/lib/src/render_pass.dart
+++ b/lib/gpu/lib/src/render_pass.dart
@@ -74,43 +74,8 @@ base class DepthStencilAttachment {
   int stencilClearValue;
 
   Texture texture;
-  Texture? resolveTexture;
 
   void _validate() {
-    if (resolveTexture != null) {
-      if (resolveTexture!.format != texture.format) {
-        throw Exception(
-            "DepthStencilAttachment MSAA resolve texture must have the same format as the texture");
-      }
-      if (resolveTexture!.width != texture.width ||
-          resolveTexture!.height != texture.height) {
-        throw Exception(
-            "DepthStencilAttachment MSAA resolve texture must have the same dimensions as the texture");
-      }
-      if (resolveTexture!.sampleCount != 1) {
-        throw Exception(
-            "DepthStencilAttachment MSAA resolve texture must have a sample count of 1");
-      }
-      if (texture.sampleCount <= 1) {
-        throw Exception(
-            "DepthStencilAttachment must have a sample count greater than 1 when a MSAA resolve texture is set");
-      }
-      if (depthStoreAction != StoreAction.multisampleResolve &&
-          depthStoreAction != StoreAction.storeAndMultisampleResolve) {
-        throw Exception(
-            "DepthStencilAttachment depthStoreAction must be multisampleResolve or storeAndMultisampleResolve when a resolve texture is set");
-      }
-      if (stencilStoreAction != StoreAction.multisampleResolve &&
-          stencilStoreAction != StoreAction.storeAndMultisampleResolve) {
-        throw Exception(
-            "DepthStencilAttachment stencilStoreAction must be multisampleResolve or storeAndMultisampleResolve when a resolve texture is set");
-      }
-      if (resolveTexture!.storageMode == StorageMode.deviceTransient) {
-        throw Exception(
-            "DepthStencilAttachment MSAA resolve texture must not have a storage mode of deviceTransient");
-      }
-    }
-
     if (texture.storageMode == StorageMode.deviceTransient) {
       if (depthLoadAction == LoadAction.load) {
         throw Exception(
@@ -244,8 +209,7 @@ base class RenderPass extends NativeFieldWrapperClass1 {
           ds.stencilLoadAction.index,
           ds.stencilStoreAction.index,
           ds.stencilClearValue,
-          ds.texture,
-          ds.resolveTexture);
+          ds.texture);
       if (error != null) {
         throw Exception(error);
       }
@@ -404,8 +368,8 @@ base class RenderPass extends NativeFieldWrapperClass1 {
       Texture? resolveTexture);
 
   @Native<
-          Handle Function(Pointer<Void>, Int, Int, Float, Int, Int, Int,
-              Pointer<Void>, Handle)>(
+          Handle Function(
+              Pointer<Void>, Int, Int, Float, Int, Int, Int, Pointer<Void>)>(
       symbol: 'InternalFlutterGpu_RenderPass_SetDepthStencilAttachment')
   external String? _setDepthStencilAttachment(
       int depthLoadAction,
@@ -414,8 +378,7 @@ base class RenderPass extends NativeFieldWrapperClass1 {
       int stencilLoadAction,
       int stencilStoreAction,
       int stencilClearValue,
-      Texture texture,
-      Texture? resolveTexture);
+      Texture texture);
 
   @Native<Handle Function(Pointer<Void>, Pointer<Void>)>(
       symbol: 'InternalFlutterGpu_RenderPass_Begin')
diff --git a/lib/gpu/render_pass.cc b/lib/gpu/render_pass.cc
index a6a93a8096237..70d68d0e78081 100644
--- a/lib/gpu/render_pass.cc
+++ b/lib/gpu/render_pass.cc
@@ -255,24 +255,13 @@ Dart_Handle InternalFlutterGpu_RenderPass_SetDepthStencilAttachment(
     int stencil_load_action,
     int stencil_store_action,
     int stencil_clear_value,
-    flutter::gpu::Texture* texture,
-    Dart_Handle resolve_texture_wrapper) {
-  flutter::gpu::Texture* resolve_texture = nullptr;
-
-  if (!Dart_IsNull(resolve_texture_wrapper)) {
-    resolve_texture = tonic::DartConverter<flutter::gpu::Texture*>::FromDart(
-        resolve_texture_wrapper);
-  }
-
+    flutter::gpu::Texture* texture) {
   {
     impeller::DepthAttachment desc;
     desc.load_action = flutter::gpu::ToImpellerLoadAction(depth_load_action);
     desc.store_action = flutter::gpu::ToImpellerStoreAction(depth_store_action);
     desc.clear_depth = depth_clear_value;
     desc.texture = texture->GetTexture();
-    if (resolve_texture) {
-      desc.resolve_texture = resolve_texture->GetTexture();
-    }
     wrapper->GetRenderTarget().SetDepthAttachment(desc);
   }
   {
@@ -282,9 +271,6 @@ Dart_Handle InternalFlutterGpu_RenderPass_SetDepthStencilAttachment(
         flutter::gpu::ToImpellerStoreAction(stencil_store_action);
     desc.clear_stencil = stencil_clear_value;
     desc.texture = texture->GetTexture();
-    if (resolve_texture) {
-      desc.resolve_texture = resolve_texture->GetTexture();
-    }
     wrapper->GetRenderTarget().SetStencilAttachment(desc);
   }
 
diff --git a/lib/gpu/render_pass.h b/lib/gpu/render_pass.h
index 3b1873d73b38b..da9840d62699f 100644
--- a/lib/gpu/render_pass.h
+++ b/lib/gpu/render_pass.h
@@ -137,8 +137,7 @@ extern Dart_Handle InternalFlutterGpu_RenderPass_SetDepthStencilAttachment(
     int stencil_load_action,
     int stencil_store_action,
     int stencil_clear_value,
-    flutter::gpu::Texture* texture,
-    Dart_Handle resolve_texture_wrapper);
+    flutter::gpu::Texture* texture);
 
 FLUTTER_GPU_EXPORT
 extern Dart_Handle InternalFlutterGpu_RenderPass_Begin(

From f64cd0d5a4a8ecadfb16bf60f826eea5c45f5c38 Mon Sep 17 00:00:00 2001
From: Brandon DeRosier <bdero@google.com>
Date: Fri, 18 Oct 2024 18:23:43 -0700
Subject: [PATCH 4/8] Gracefully fallback to not using MSAA when normal MSAA is
 not supported.

---
 lib/gpu/context.cc     | 9 ++++++++-
 lib/gpu/context.h      | 2 ++
 lib/gpu/render_pass.cc | 9 +++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/lib/gpu/context.cc b/lib/gpu/context.cc
index b360711e55fc9..7204ac443c375 100644
--- a/lib/gpu/context.cc
+++ b/lib/gpu/context.cc
@@ -10,11 +10,18 @@
 #include "flutter/lib/ui/ui_dart_state.h"
 #include "fml/make_copyable.h"
 #include "impeller/core/platform.h"
+#include "impeller/renderer/context.h"
 #include "tonic/converter/dart_converter.h"
 
 namespace flutter {
 namespace gpu {
 
+bool SupportsNormalOffscreenMSAA(const impeller::Context& context) {
+  auto& capabilities = context.GetCapabilities();
+  return capabilities->SupportsOffscreenMSAA() &&
+         !capabilities->SupportsImplicitResolvingMSAA();
+}
+
 IMPLEMENT_WRAPPERTYPEINFO(flutter_gpu, Context);
 
 std::shared_ptr<impeller::Context> Context::default_context_;
@@ -114,5 +121,5 @@ extern int InternalFlutterGpu_Context_GetMinimumUniformByteAlignment(
 
 extern bool InternalFlutterGpu_Context_GetSupportsOffscreenMSAA(
     flutter::gpu::Context* wrapper) {
-  return wrapper->GetContext()->GetCapabilities()->SupportsOffscreenMSAA();
+  return flutter::gpu::SupportsNormalOffscreenMSAA(*wrapper->GetContext());
 }
diff --git a/lib/gpu/context.h b/lib/gpu/context.h
index 852b0d3569f02..4dbabcb5e432d 100644
--- a/lib/gpu/context.h
+++ b/lib/gpu/context.h
@@ -13,6 +13,8 @@
 namespace flutter {
 namespace gpu {
 
+bool SupportsNormalOffscreenMSAA(const impeller::Context& context);
+
 class Context : public RefCountedDartWrappable<Context> {
   DEFINE_WRAPPERTYPEINFO();
   FML_FRIEND_MAKE_REF_COUNTED(Context);
diff --git a/lib/gpu/render_pass.cc b/lib/gpu/render_pass.cc
index 70d68d0e78081..1efc53f09a526 100644
--- a/lib/gpu/render_pass.cc
+++ b/lib/gpu/render_pass.cc
@@ -20,6 +20,7 @@
 #include "impeller/renderer/pipeline.h"
 #include "impeller/renderer/pipeline_descriptor.h"
 #include "impeller/renderer/pipeline_library.h"
+#include "lib/gpu/context.h"
 #include "lib/ui/ui_dart_state.h"
 #include "tonic/converter/dart_converter.h"
 
@@ -242,6 +243,14 @@ Dart_Handle InternalFlutterGpu_RenderPass_SetColorAttachment(
         tonic::DartConverter<flutter::gpu::Texture*>::FromDart(
             resolve_texture_wrapper);
     desc.resolve_texture = resolve_texture->GetTexture();
+
+    // If the backend doesn't support normal MSAA, gracefully fallback to
+    // rendering without MSAA.
+    if (!flutter::gpu::SupportsNormalOffscreenMSAA(*wrapper->GetContext())) {
+      desc.texture = desc.resolve_texture;
+      desc.resolve_texture = nullptr;
+      desc.store_action = impeller::StoreAction::kStore;
+    }
   }
   wrapper->GetRenderTarget().SetColorAttachment(desc, color_attachment_index);
   return Dart_Null();

From 29bd4c4d3fa712d28d0a274e9b68b9c7a94a0e77 Mon Sep 17 00:00:00 2001
From: Brandon DeRosier <bdero@google.com>
Date: Fri, 18 Oct 2024 19:52:39 -0700
Subject: [PATCH 5/8] Remove clearBindings hack

---
 testing/dart/gpu_test.dart | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/testing/dart/gpu_test.dart b/testing/dart/gpu_test.dart
index 2fee673093eff..d26826e917150 100644
--- a/testing/dart/gpu_test.dart
+++ b/testing/dart/gpu_test.dart
@@ -128,10 +128,6 @@ void drawTriangle(RenderPassState state, Vector4 color) {
       transients.emplace(unlitUBO(Matrix4.identity(), color));
   state.renderPass.bindVertexBuffer(vertices, 3);
 
-  // TODO(bdero): Overwrite bindings with the same slot so we don't need to clear.
-  //              https://github.com/flutter/flutter/issues/155335
-  state.renderPass.clearBindings();
-
   final gpu.UniformSlot vertInfo =
       pipeline.vertexShader.getUniformSlot('VertInfo');
   state.renderPass.bindUniform(vertInfo, vertInfoData);

From 930646fe7ce12423dfd3c48022359ecefc569b46 Mon Sep 17 00:00:00 2001
From: Brandon DeRosier <bdero@google.com>
Date: Mon, 21 Oct 2024 16:17:24 -0700
Subject: [PATCH 6/8] The RenderPass isn't initialized yet, so pass the
 gpuContext to SetColorAttachment.

---
 lib/gpu/lib/src/render_pass.dart | 5 ++++-
 lib/gpu/render_pass.cc           | 3 ++-
 lib/gpu/render_pass.h            | 1 +
 3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/lib/gpu/lib/src/render_pass.dart b/lib/gpu/lib/src/render_pass.dart
index 5782271072769..02e373c328f58 100644
--- a/lib/gpu/lib/src/render_pass.dart
+++ b/lib/gpu/lib/src/render_pass.dart
@@ -187,6 +187,7 @@ base class RenderPass extends NativeFieldWrapperClass1 {
     String? error;
     for (final (index, color) in renderTarget.colorAttachments.indexed) {
       error = _setColorAttachment(
+          gpuContext,
           index,
           color.loadAction.index,
           color.storeAction.index,
@@ -346,6 +347,7 @@ base class RenderPass extends NativeFieldWrapperClass1 {
 
   @Native<
       Handle Function(
+          Pointer<Void>,
           Pointer<Void>,
           Int,
           Int,
@@ -357,6 +359,7 @@ base class RenderPass extends NativeFieldWrapperClass1 {
           Pointer<Void>,
           Handle)>(symbol: 'InternalFlutterGpu_RenderPass_SetColorAttachment')
   external String? _setColorAttachment(
+      GpuContext context,
       int colorAttachmentIndex,
       int loadAction,
       int storeAction,
@@ -491,7 +494,7 @@ base class RenderPass extends NativeFieldWrapperClass1 {
       symbol: 'InternalFlutterGpu_RenderPass_SetPrimitiveType')
   external void _setPrimitiveType(int primitiveType);
 
-    @Native<Void Function(Pointer<Void>, Int)>(
+  @Native<Void Function(Pointer<Void>, Int)>(
       symbol: 'InternalFlutterGpu_RenderPass_SetWindingOrder')
   external void _setWindingOrder(int windingOrder);
 
diff --git a/lib/gpu/render_pass.cc b/lib/gpu/render_pass.cc
index 1efc53f09a526..fda1dbbd23852 100644
--- a/lib/gpu/render_pass.cc
+++ b/lib/gpu/render_pass.cc
@@ -223,6 +223,7 @@ void InternalFlutterGpu_RenderPass_Initialize(Dart_Handle wrapper) {
 
 Dart_Handle InternalFlutterGpu_RenderPass_SetColorAttachment(
     flutter::gpu::RenderPass* wrapper,
+    flutter::gpu::Context* context,
     int color_attachment_index,
     int load_action,
     int store_action,
@@ -246,7 +247,7 @@ Dart_Handle InternalFlutterGpu_RenderPass_SetColorAttachment(
 
     // If the backend doesn't support normal MSAA, gracefully fallback to
     // rendering without MSAA.
-    if (!flutter::gpu::SupportsNormalOffscreenMSAA(*wrapper->GetContext())) {
+    if (!flutter::gpu::SupportsNormalOffscreenMSAA(*context->GetContext())) {
       desc.texture = desc.resolve_texture;
       desc.resolve_texture = nullptr;
       desc.store_action = impeller::StoreAction::kStore;
diff --git a/lib/gpu/render_pass.h b/lib/gpu/render_pass.h
index da9840d62699f..865e375ac7955 100644
--- a/lib/gpu/render_pass.h
+++ b/lib/gpu/render_pass.h
@@ -118,6 +118,7 @@ extern void InternalFlutterGpu_RenderPass_Initialize(Dart_Handle wrapper);
 FLUTTER_GPU_EXPORT
 extern Dart_Handle InternalFlutterGpu_RenderPass_SetColorAttachment(
     flutter::gpu::RenderPass* wrapper,
+    flutter::gpu::Context* context,
     int color_attachment_index,
     int load_action,
     int store_action,

From fe133820c531f0e16122cbf5f6a6d0b3f53a9940 Mon Sep 17 00:00:00 2001
From: Brandon DeRosier <bdero@google.com>
Date: Mon, 21 Oct 2024 16:45:38 -0700
Subject: [PATCH 7/8] Correct test skip logic

---
 testing/dart/gpu_test.dart | 29 +++++++++++++++++++----------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/testing/dart/gpu_test.dart b/testing/dart/gpu_test.dart
index d26826e917150..864620b1be7c7 100644
--- a/testing/dart/gpu_test.dart
+++ b/testing/dart/gpu_test.dart
@@ -442,7 +442,8 @@ void main() async {
     state.commandBuffer.submit();
 
     final ui.Image image = state.renderTexture.asImage();
-    await comparer.addGoldenImage(image, 'flutter_gpu_test_triangle_polygon_mode.png');
+    await comparer.addGoldenImage(
+        image, 'flutter_gpu_test_triangle_polygon_mode.png');
   }, skip: !impellerEnabled);
 
   // Renders a green triangle pointing downwards, with 4xMSAA.
@@ -469,7 +470,7 @@ void main() async {
           contains(
               'The backend does not support multisample anti-aliasing for offscreen color and stencil attachments'));
     }
-  }, skip: gpu.gpuContext.doesSupportOffscreenMSAA);
+  }, skip: !(impellerEnabled && gpu.gpuContext.doesSupportOffscreenMSAA));
 
   // Renders a hollow green triangle pointing downwards.
   test('Can render hollowed out triangle using stencil ops', () async {
@@ -608,13 +609,20 @@ void main() async {
 
     final gpu.HostBuffer transients = gpu.gpuContext.createHostBuffer();
     final gpu.BufferView vertices = transients.emplace(float32(<double>[
-     1.0,  0.0,
-     0.5,  0.8,
-    -0.5,  0.8,
-    -1.0,  0.0,
-    -0.5, -0.8,
-     0.5, -0.8,
-     1.0,  0.0
+      1.0,
+      0.0,
+      0.5,
+      0.8,
+      -0.5,
+      0.8,
+      -1.0,
+      0.0,
+      -0.5,
+      -0.8,
+      0.5,
+      -0.8,
+      1.0,
+      0.0
     ]));
     final gpu.BufferView vertInfoData = transients.emplace(float32(<double>[
       1, 0, 0, 0, // mvp
@@ -633,6 +641,7 @@ void main() async {
     state.commandBuffer.submit();
 
     final ui.Image image = state.renderTexture.asImage();
-    await comparer.addGoldenImage(image, 'flutter_gpu_test_hexgon_line_strip.png');
+    await comparer.addGoldenImage(
+        image, 'flutter_gpu_test_hexgon_line_strip.png');
   }, skip: !impellerEnabled);
 }

From 00ee6f575e29efa200a6abcf1e6fa881be8dd31b Mon Sep 17 00:00:00 2001
From: Brandon DeRosier <bdero@google.com>
Date: Mon, 21 Oct 2024 17:21:53 -0700
Subject: [PATCH 8/8] Fix skip logic more

---
 testing/dart/gpu_test.dart | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/testing/dart/gpu_test.dart b/testing/dart/gpu_test.dart
index 864620b1be7c7..47c0c7d1ea838 100644
--- a/testing/dart/gpu_test.dart
+++ b/testing/dart/gpu_test.dart
@@ -470,7 +470,7 @@ void main() async {
           contains(
               'The backend does not support multisample anti-aliasing for offscreen color and stencil attachments'));
     }
-  }, skip: !(impellerEnabled && gpu.gpuContext.doesSupportOffscreenMSAA));
+  }, skip: !(impellerEnabled && !gpu.gpuContext.doesSupportOffscreenMSAA));
 
   // Renders a hollow green triangle pointing downwards.
   test('Can render hollowed out triangle using stencil ops', () async {