Revert "Revert "[impeller] convert src over to src for solid color" (#41466)"

This reverts commit 8fe8e94.

Author: Jonah Williams

impeller/entity/contents/solid_color_contents.cc

@@ -46,6 +46,11 @@ bool SolidColorContents::ShouldRender(
   return Contents::ShouldRender(entity, stencil_coverage);
 }
 
+bool SolidColorContents::ConvertToSrc(const Entity& entity) const {
+  return entity.GetBlendMode() == BlendMode::kSourceOver &&
+         GetColor().alpha >= 1.0;
+}
+
 bool SolidColorContents::Render(const ContentContext& renderer,
                                 const Entity& entity,
                                 RenderPass& pass) const {
@@ -60,6 +65,9 @@ bool SolidColorContents::Render(const ContentContext& renderer,
       GetGeometry()->GetPositionBuffer(renderer, entity, pass);
 
   auto options = OptionsFromPassAndEntity(pass, entity);
+  if (ConvertToSrc(entity)) {
+    options.blend_mode = BlendMode::kSource;
+  }
   if (geometry_result.prevent_overdraw) {
     options.stencil_compare = CompareFunction::kEqual;
     options.stencil_operation = StencilOperation::kIncrementClamp;

impeller/entity/contents/solid_color_contents.h

@@ -46,6 +46,10 @@ class SolidColorContents final : public ColorSourceContents {
               const Entity& entity,
               RenderPass& pass) const override;
 
+  /// @brief Convert SrcOver blend modes into Src blend modes if the color has
+  ///        no opacity.
+  bool ConvertToSrc(const Entity& entity) const;
+
  private:
   Color color_;
 

impeller/entity/entity_unittests.cc

@@ -2547,5 +2547,25 @@ TEST_P(EntityTest, CoverageForStrokePathWithNegativeValuesInTransform) {
   ASSERT_RECT_NEAR(coverage.value(), Rect::MakeXYWH(102.5, 342.5, 85, 155));
 }
 
+TEST_P(EntityTest, ConvertToSrcBlend) {
+  Entity entity;
+  entity.SetBlendMode(BlendMode::kSourceOver);
+
+  auto contents = SolidColorContents::Make(
+      PathBuilder{}.AddRect(Rect::MakeSize(Size(100, 100))).TakePath(),
+      Color::Red());
+
+  ASSERT_TRUE(contents->ConvertToSrc(entity));
+
+  // Color with alpha, should return false.
+  contents->SetInheritedOpacity(0.5);
+  ASSERT_FALSE(contents->ConvertToSrc(entity));
+
+  // Non source over blend mode, should return false.
+  contents->SetInheritedOpacity(1.0);
+  entity.SetBlendMode(BlendMode::kDestination);
+  ASSERT_FALSE(contents->ConvertToSrc(entity));
+}
+
 }  // namespace testing
 }  // namespace impeller