[Impeller] implements blur styles for gradients (flutter#51264)

fixes flutter#144449

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

Author: gaaclarke

impeller/aiks/aiks_blur_unittests.cc

@@ -755,6 +755,105 @@ TEST_P(AiksTest, GaussianBlurAnimatedBackdrop) {
   ASSERT_TRUE(OpenPlaygroundHere(callback));
 }
 
+TEST_P(AiksTest, GaussianBlurStyleInnerGradient) {
+  Canvas canvas;
+  canvas.Scale(GetContentScale());
+
+  canvas.DrawPaint({.color = Color(0.1, 0.1, 0.1, 1.0)});
+
+  std::vector<Color> colors = {Color{0.9568, 0.2627, 0.2118, 1.0},
+                               Color{0.7568, 0.2627, 0.2118, 1.0}};
+  std::vector<Scalar> stops = {0.0, 1.0};
+
+  Paint paint;
+  paint.color_source = ColorSource::MakeLinearGradient(
+      {0, 0}, {200, 200}, std::move(colors), std::move(stops),
+      Entity::TileMode::kMirror, {});
+  paint.mask_blur_descriptor = Paint::MaskBlurDescriptor{
+      .style = FilterContents::BlurStyle::kInner,
+      .sigma = Sigma(30),
+  };
+  canvas.DrawPath(PathBuilder()
+                      .MoveTo({200, 200})
+                      .LineTo({300, 400})
+                      .LineTo({100, 400})
+                      .Close()
+                      .TakePath(),
+                  paint);
+
+  // Draw another thing to make sure the clip area is reset.
+  Paint red;
+  red.color = Color::Red();
+  canvas.DrawRect(Rect::MakeXYWH(0, 0, 200, 200), red);
+  ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
+}
+
+TEST_P(AiksTest, GaussianBlurStyleSolidGradient) {
+  Canvas canvas;
+  canvas.Scale(GetContentScale());
+
+  canvas.DrawPaint({.color = Color(0.1, 0.1, 0.1, 1.0)});
+
+  std::vector<Color> colors = {Color{0.9568, 0.2627, 0.2118, 1.0},
+                               Color{0.7568, 0.2627, 0.2118, 1.0}};
+  std::vector<Scalar> stops = {0.0, 1.0};
+
+  Paint paint;
+  paint.color_source = ColorSource::MakeLinearGradient(
+      {0, 0}, {200, 200}, std::move(colors), std::move(stops),
+      Entity::TileMode::kMirror, {});
+  paint.mask_blur_descriptor = Paint::MaskBlurDescriptor{
+      .style = FilterContents::BlurStyle::kSolid,
+      .sigma = Sigma(30),
+  };
+  canvas.DrawPath(PathBuilder()
+                      .MoveTo({200, 200})
+                      .LineTo({300, 400})
+                      .LineTo({100, 400})
+                      .Close()
+                      .TakePath(),
+                  paint);
+
+  // Draw another thing to make sure the clip area is reset.
+  Paint red;
+  red.color = Color::Red();
+  canvas.DrawRect(Rect::MakeXYWH(0, 0, 200, 200), red);
+  ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
+}
+
+TEST_P(AiksTest, GaussianBlurStyleOuterGradient) {
+  Canvas canvas;
+  canvas.Scale(GetContentScale());
+
+  canvas.DrawPaint({.color = Color(0.1, 0.1, 0.1, 1.0)});
+
+  std::vector<Color> colors = {Color{0.9568, 0.2627, 0.2118, 1.0},
+                               Color{0.7568, 0.2627, 0.2118, 1.0}};
+  std::vector<Scalar> stops = {0.0, 1.0};
+
+  Paint paint;
+  paint.color_source = ColorSource::MakeLinearGradient(
+      {0, 0}, {200, 200}, std::move(colors), std::move(stops),
+      Entity::TileMode::kMirror, {});
+  paint.mask_blur_descriptor = Paint::MaskBlurDescriptor{
+      .style = FilterContents::BlurStyle::kOuter,
+      .sigma = Sigma(30),
+  };
+  canvas.DrawPath(PathBuilder()
+                      .MoveTo({200, 200})
+                      .LineTo({300, 400})
+                      .LineTo({100, 400})
+                      .Close()
+                      .TakePath(),
+                  paint);
+
+  // Draw another thing to make sure the clip area is reset.
+  Paint red;
+  red.color = Color::Red();
+  canvas.DrawRect(Rect::MakeXYWH(0, 0, 200, 200), red);
+  ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
+}
+
 TEST_P(AiksTest, GaussianBlurStyleInner) {
   Canvas canvas;
   canvas.Scale(GetContentScale());

impeller/aiks/paint.cc

@@ -170,7 +170,8 @@ std::shared_ptr<FilterContents> Paint::MaskBlurDescriptor::CreateMaskBlur(
   /// 2. Blur the mask.
 
   auto blurred_mask = FilterContents::MakeGaussianBlur(
-      FilterInput::Make(mask), sigma, sigma, Entity::TileMode::kDecal, style);
+      FilterInput::Make(mask), sigma, sigma, Entity::TileMode::kDecal, style,
+      color_source_contents->GetGeometry());
 
   /// 3. Replace the geometry of the original color source with a rectangle that
   ///    covers the full region of the blurred mask. Note that geometry is in

impeller/entity/contents/filters/gaussian_blur_filter_contents.cc

@@ -210,30 +210,39 @@ Entity ApplyClippedBlurStyle(Entity::ClipOperation clip_operation,
                              const Snapshot& input_snapshot,
                              Entity blur_entity,
                              const std::shared_ptr<Geometry>& geometry) {
-  auto shared_blur_entity = std::make_shared<Entity>(std::move(blur_entity));
-  shared_blur_entity->SetNewClipDepth(entity.GetNewClipDepth());
-  auto clipper = std::make_unique<ClipContents>();
-  clipper->SetClipOperation(clip_operation);
-  clipper->SetGeometry(geometry);
+  auto clip_contents = std::make_shared<ClipContents>();
+  clip_contents->SetClipOperation(clip_operation);
+  clip_contents->SetGeometry(geometry);
+  Entity clipper;
+  clipper.SetContents(clip_contents);
   auto restore = std::make_unique<ClipRestoreContents>();
-  Entity result;
-  result.SetTransform(entity.GetTransform());
-  result.SetContents(Contents::MakeAnonymous(
-      fml::MakeCopyable([shared_blur_entity, clipper = std::move(clipper),
-                         restore = std::move(restore)](
-                            const ContentContext& renderer,
-                            const Entity& entity, RenderPass& pass) mutable {
+  Matrix entity_transform = entity.GetTransform();
+  Matrix blur_transform = blur_entity.GetTransform();
+  auto renderer = fml::MakeCopyable(
+      [blur_entity = blur_entity.Clone(), clipper = std::move(clipper),
+       restore = std::move(restore), entity_transform,
+       blur_transform](const ContentContext& renderer, const Entity& entity,
+                       RenderPass& pass) mutable {
         bool result = true;
-        result = clipper->Render(renderer, entity, pass) && result;
-        result = shared_blur_entity->Render(renderer, pass) && result;
+        clipper.SetNewClipDepth(entity.GetNewClipDepth());
+        clipper.SetTransform(entity.GetTransform() * entity_transform);
+        result = clipper.Render(renderer, pass) && result;
+        blur_entity.SetNewClipDepth(entity.GetNewClipDepth());
+        blur_entity.SetTransform(entity.GetTransform() * blur_transform);
+        result = blur_entity.Render(renderer, pass) && result;
         if constexpr (!ContentContext::kEnableStencilThenCover) {
           result = restore->Render(renderer, entity, pass) && result;
         }
         return result;
-      }),
-      [shared_blur_entity](const Entity& entity) {
-        return shared_blur_entity->GetCoverage();
-      }));
+      });
+  auto coverage =
+      fml::MakeCopyable([blur_entity = std::move(blur_entity),
+                         blur_transform](const Entity& entity) mutable {
+        blur_entity.SetTransform(entity.GetTransform() * blur_transform);
+        return blur_entity.GetCoverage();
+      });
+  Entity result;
+  result.SetContents(Contents::MakeAnonymous(renderer, coverage));
   return result;
 }
 
@@ -256,24 +265,33 @@ Entity ApplyBlurStyle(FilterContents::BlurStyle blur_style,
                                    input, input_snapshot,
                                    std::move(blur_entity), geometry);
     case FilterContents::BlurStyle::kSolid: {
-      Entity blurred = ApplyClippedBlurStyle(Entity::ClipOperation::kIntersect,
-                                             entity, input, input_snapshot,
-                                             std::move(blur_entity), geometry);
       Entity snapshot_entity = Entity::FromSnapshot(
           input_snapshot, entity.GetBlendMode(), entity.GetClipDepth());
       Entity result;
-      std::optional<Rect> coverage = blurred.GetCoverage();
+      Matrix blurred_transform = blur_entity.GetTransform();
+      Matrix snapshot_transform = snapshot_entity.GetTransform();
       result.SetContents(Contents::MakeAnonymous(
-          fml::MakeCopyable([blurred = std::move(blurred),
+          fml::MakeCopyable([blur_entity = blur_entity.Clone(),
+                             blurred_transform, snapshot_transform,
                              snapshot_entity = std::move(snapshot_entity)](
                                 const ContentContext& renderer,
                                 const Entity& entity,
                                 RenderPass& pass) mutable {
-            return blurred.Render(renderer, pass) &&
-                   snapshot_entity.Render(renderer, pass);
+            bool result = true;
+            blur_entity.SetNewClipDepth(entity.GetNewClipDepth());
+            blur_entity.SetTransform(entity.GetTransform() * blurred_transform);
+            result = result && blur_entity.Render(renderer, pass);
+            snapshot_entity.SetTransform(entity.GetTransform() *
+                                         snapshot_transform);
+            snapshot_entity.SetNewClipDepth(entity.GetNewClipDepth());
+            result = result && snapshot_entity.Render(renderer, pass);
+            return result;
           }),
-          fml::MakeCopyable(
-              [coverage](const Entity& entity) { return coverage; })));
+          fml::MakeCopyable([blur_entity = blur_entity.Clone(),
+                             blurred_transform](const Entity& entity) mutable {
+            blur_entity.SetTransform(entity.GetTransform() * blurred_transform);
+            return blur_entity.GetCoverage();
+          })));
       return result;
     }
   }

testing/impeller_golden_tests_output.txt

@@ -488,12 +488,21 @@ impeller_Play_AiksTest_GaussianBlurRotatedAndClipped_Vulkan.png
 impeller_Play_AiksTest_GaussianBlurScaledAndClipped_Metal.png
 impeller_Play_AiksTest_GaussianBlurScaledAndClipped_OpenGLES.png
 impeller_Play_AiksTest_GaussianBlurScaledAndClipped_Vulkan.png
+impeller_Play_AiksTest_GaussianBlurStyleInnerGradient_Metal.png
+impeller_Play_AiksTest_GaussianBlurStyleInnerGradient_OpenGLES.png
+impeller_Play_AiksTest_GaussianBlurStyleInnerGradient_Vulkan.png
 impeller_Play_AiksTest_GaussianBlurStyleInner_Metal.png
 impeller_Play_AiksTest_GaussianBlurStyleInner_OpenGLES.png
 impeller_Play_AiksTest_GaussianBlurStyleInner_Vulkan.png
+impeller_Play_AiksTest_GaussianBlurStyleOuterGradient_Metal.png
+impeller_Play_AiksTest_GaussianBlurStyleOuterGradient_OpenGLES.png
+impeller_Play_AiksTest_GaussianBlurStyleOuterGradient_Vulkan.png
 impeller_Play_AiksTest_GaussianBlurStyleOuter_Metal.png
 impeller_Play_AiksTest_GaussianBlurStyleOuter_OpenGLES.png
 impeller_Play_AiksTest_GaussianBlurStyleOuter_Vulkan.png
+impeller_Play_AiksTest_GaussianBlurStyleSolidGradient_Metal.png
+impeller_Play_AiksTest_GaussianBlurStyleSolidGradient_OpenGLES.png
+impeller_Play_AiksTest_GaussianBlurStyleSolidGradient_Vulkan.png
 impeller_Play_AiksTest_GaussianBlurStyleSolid_Metal.png
 impeller_Play_AiksTest_GaussianBlurStyleSolid_OpenGLES.png
 impeller_Play_AiksTest_GaussianBlurStyleSolid_Vulkan.png