[CP][Impeller] Create framebuffer blend vertices based on the snapshot's texture size instead of coverage (#52790) (#53235)

The snapshot's transform is provided to the pipeline.  If the vertices are based on the coverage rectangle, then that will apply the snapshot's transform twice.

Fixes flutter/flutter#148213

Author: Jonah Williams

impeller/aiks/aiks_unittests.cc

@@ -3458,6 +3458,21 @@ TEST_P(AiksTest, CanRenderClippedBackdropFilter) {
   ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
 }
 
+TEST_P(AiksTest, FramebufferAdvancedBlendCoverage) {
+  auto texture = CreateTextureForFixture("airplane.jpg",
+                                         /*enable_mipmapping=*/true);
+
+  // Draw with an advanced blend that can use FramebufferBlendContents and
+  // verify that the scale transform is correctly applied to the image.
+  Canvas canvas;
+  canvas.DrawPaint({.color = Color::DarkGray()});
+  canvas.Scale(Vector2(0.4, 0.4));
+  canvas.DrawImage(std::make_shared<Image>(texture), {20, 20},
+                   {.blend_mode = BlendMode::kMultiply});
+
+  ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
+}
+
 }  // namespace testing
 }  // namespace impeller
 

impeller/entity/contents/framebuffer_blend_contents.cc

@@ -52,13 +52,8 @@ bool FramebufferBlendContents::Render(const ContentContext& renderer,
   if (!src_snapshot.has_value()) {
     return true;
   }
-  auto coverage = src_snapshot->GetCoverage();
-  if (!coverage.has_value()) {
-    return true;
-  }
-  Rect src_coverage = coverage.value();
 
-  auto size = src_coverage.GetSize();
+  auto size = src_snapshot->texture->GetSize();
   VertexBufferBuilder<VS::PerVertexData> vtx_builder;
   vtx_builder.AddVertices({
       {Point(0, 0), Point(0, 0)},

testing/impeller_golden_tests_output.txt

@@ -476,6 +476,9 @@ impeller_Play_AiksTest_FilledRoundRectsRenderCorrectly_Vulkan.png
 impeller_Play_AiksTest_ForegroundBlendSubpassCollapseOptimization_Metal.png
 impeller_Play_AiksTest_ForegroundBlendSubpassCollapseOptimization_OpenGLES.png
 impeller_Play_AiksTest_ForegroundBlendSubpassCollapseOptimization_Vulkan.png
+impeller_Play_AiksTest_FramebufferAdvancedBlendCoverage_Metal.png
+impeller_Play_AiksTest_FramebufferAdvancedBlendCoverage_OpenGLES.png
+impeller_Play_AiksTest_FramebufferAdvancedBlendCoverage_Vulkan.png
 impeller_Play_AiksTest_GaussianBlurAnimatedBackdrop_Metal.png
 impeller_Play_AiksTest_GaussianBlurAnimatedBackdrop_OpenGLES.png
 impeller_Play_AiksTest_GaussianBlurAnimatedBackdrop_Vulkan.png