From 6a8d77dccd4d2239ce82e367b91e475f678250c5 Mon Sep 17 00:00:00 2001
From: Jason Simmons <jason-simmons@users.noreply.github.com>
Date: Thu, 23 Jan 2025 07:45:55 -0800
Subject: [PATCH] [Impeller] Implement inherited opacity for
 ColorFilterContents (#161834)

Inherited opacity should be combined with the alpha of the
ColorFilterContents when drawing objects with filters inside an opacity
layer.
---
 .../display_list/aiks_dl_blur_unittests.cc    | 24 +++++++++++++++++++
 .../contents/filters/color_filter_contents.cc |  6 ++++-
 .../contents/filters/color_filter_contents.h  |  4 ++++
 .../testing/impeller_golden_tests_output.txt  |  3 +++
 4 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/engine/src/flutter/impeller/display_list/aiks_dl_blur_unittests.cc b/engine/src/flutter/impeller/display_list/aiks_dl_blur_unittests.cc
index 63a3d5443a..0d235b6142 100644
--- a/engine/src/flutter/impeller/display_list/aiks_dl_blur_unittests.cc
+++ b/engine/src/flutter/impeller/display_list/aiks_dl_blur_unittests.cc
@@ -1376,5 +1376,29 @@ TEST_P(AiksTest,
   ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
 }
 
+TEST_P(AiksTest, BlurGradientWithOpacity) {
+  DisplayListBuilder builder;
+  builder.Scale(GetContentScale().x, GetContentScale().y);
+
+  std::vector<DlColor> colors = {DlColor(0xFFFF0000), DlColor(0xFF00FF00)};
+  std::vector<Scalar> stops = {0.0, 1.0};
+
+  auto gradient = DlColorSource::MakeLinear(
+      {0, 0}, {400, 400}, 2, colors.data(), stops.data(), DlTileMode::kClamp);
+
+  DlPaint save_paint;
+  save_paint.setOpacity(0.5);
+  builder.SaveLayer(nullptr, &save_paint);
+
+  DlPaint paint;
+  paint.setColorSource(gradient);
+  paint.setMaskFilter(DlBlurMaskFilter::Make(DlBlurStyle::kNormal, 1));
+  builder.DrawRect(SkRect::MakeXYWH(100, 100, 200, 200), paint);
+
+  builder.Restore();
+
+  ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
+}
+
 }  // namespace testing
 }  // namespace impeller
diff --git a/engine/src/flutter/impeller/entity/contents/filters/color_filter_contents.cc b/engine/src/flutter/impeller/entity/contents/filters/color_filter_contents.cc
index 489cc4b0cd..6c88925be3 100644
--- a/engine/src/flutter/impeller/entity/contents/filters/color_filter_contents.cc
+++ b/engine/src/flutter/impeller/entity/contents/filters/color_filter_contents.cc
@@ -96,7 +96,11 @@ void ColorFilterContents::SetAlpha(Scalar alpha) {
 }
 
 std::optional<Scalar> ColorFilterContents::GetAlpha() const {
-  return alpha_;
+  return alpha_.value_or(1.0) * inherited_opacity_;
+}
+
+void ColorFilterContents::SetInheritedOpacity(Scalar opacity) {
+  inherited_opacity_ = opacity;
 }
 
 std::optional<Rect> ColorFilterContents::GetFilterSourceCoverage(
diff --git a/engine/src/flutter/impeller/entity/contents/filters/color_filter_contents.h b/engine/src/flutter/impeller/entity/contents/filters/color_filter_contents.h
index 14d9cb8aa5..9acaec6b43 100644
--- a/engine/src/flutter/impeller/entity/contents/filters/color_filter_contents.h
+++ b/engine/src/flutter/impeller/entity/contents/filters/color_filter_contents.h
@@ -45,6 +45,9 @@ class ColorFilterContents : public FilterContents {
 
   std::optional<Scalar> GetAlpha() const;
 
+  // |Contents|
+  void SetInheritedOpacity(Scalar opacity) override;
+
   // |FilterContents|
   std::optional<Rect> GetFilterSourceCoverage(
       const Matrix& effect_transform,
@@ -53,6 +56,7 @@ class ColorFilterContents : public FilterContents {
  private:
   AbsorbOpacity absorb_opacity_ = AbsorbOpacity::kNo;
   std::optional<Scalar> alpha_;
+  Scalar inherited_opacity_ = 1.0;
 
   ColorFilterContents(const ColorFilterContents&) = delete;
 
diff --git a/engine/src/flutter/testing/impeller_golden_tests_output.txt b/engine/src/flutter/testing/impeller_golden_tests_output.txt
index 431408e7c1..875ea2e436 100644
--- a/engine/src/flutter/testing/impeller_golden_tests_output.txt
+++ b/engine/src/flutter/testing/impeller_golden_tests_output.txt
@@ -185,6 +185,9 @@ impeller_Play_AiksTest_BlendModeSrcAlphaXor_Vulkan.png
 impeller_Play_AiksTest_BlendModeXor_Metal.png
 impeller_Play_AiksTest_BlendModeXor_OpenGLES.png
 impeller_Play_AiksTest_BlendModeXor_Vulkan.png
+impeller_Play_AiksTest_BlurGradientWithOpacity_Metal.png
+impeller_Play_AiksTest_BlurGradientWithOpacity_OpenGLES.png
+impeller_Play_AiksTest_BlurGradientWithOpacity_Vulkan.png
 impeller_Play_AiksTest_BlurHasNoEdge_Metal.png
 impeller_Play_AiksTest_BlurHasNoEdge_OpenGLES.png
 impeller_Play_AiksTest_BlurHasNoEdge_Vulkan.png