[Impeller] Limit backdrop blur rendering to the current clip

Author: bdero

impeller/entity/contents/contents.cc

@@ -124,6 +124,14 @@ bool Contents::ShouldRender(const Entity& entity,
   return stencil_coverage->IntersectsWithRect(coverage.value());
 }
 
+void Contents::SetCoverageHint(std::optional<Rect> coverage_hint) {
+  coverage_hint_ = coverage_hint;
+}
+
+const std::optional<Rect>& Contents::GetCoverageHint() const {
+  return coverage_hint_;
+}
+
 std::optional<Size> Contents::GetColorSourceSize() const {
   return color_source_size_;
 };

impeller/entity/contents/contents.h

@@ -56,6 +56,14 @@ class Contents {
   /// @brief Get the screen space bounding rectangle that this contents affects.
   virtual std::optional<Rect> GetCoverage(const Entity& entity) const = 0;
 
+  /// @brief  Hint that specifies the coverage area of this Contents that will
+  ///         actually be used during rendering. This is for optimization
+  ///         purposes only and can not be relied on as a clip. May optionally
+  ///         affect the result of `GetCoverage()`.
+  void SetCoverageHint(std::optional<Rect> coverage_hint);
+
+  const std::optional<Rect>& GetCoverageHint() const;
+
   /// @brief Whether this Contents only emits opaque source colors from the
   ///        fragment stage. This value does not account for any entity
   ///        properties (e.g. the blend mode), clips/visibility culling, or
@@ -110,6 +118,7 @@ class Contents {
   virtual void SetInheritedOpacity(Scalar opacity);
 
  private:
+  std::optional<Rect> coverage_hint_;
   std::optional<Size> color_source_size_;
 
   FML_DISALLOW_COPY_AND_ASSIGN(Contents);

impeller/entity/contents/filters/blend_filter_contents.cc

@@ -649,7 +649,8 @@ std::optional<Entity> BlendFilterContents::RenderFilter(
     const ContentContext& renderer,
     const Entity& entity,
     const Matrix& effect_transform,
-    const Rect& coverage) const {
+    const Rect& coverage,
+    const std::optional<Rect>& coverage_hint) const {
   if (inputs.empty()) {
     return std::nullopt;
   }

impeller/entity/contents/filters/blend_filter_contents.h

@@ -32,11 +32,13 @@ class BlendFilterContents : public ColorFilterContents {
 
  private:
   // |FilterContents|
-  std::optional<Entity> RenderFilter(const FilterInput::Vector& inputs,
-                                     const ContentContext& renderer,
-                                     const Entity& entity,
-                                     const Matrix& effect_transform,
-                                     const Rect& coverage) const override;
+  std::optional<Entity> RenderFilter(
+      const FilterInput::Vector& inputs,
+      const ContentContext& renderer,
+      const Entity& entity,
+      const Matrix& effect_transform,
+      const Rect& coverage,
+      const std::optional<Rect>& coverage_hint) const override;
 
   /// @brief Optimized advanced blend that avoids a second subpass when there is
   ///        only a single input and a foreground color.

impeller/entity/contents/filters/border_mask_blur_filter_contents.cc

@@ -53,7 +53,8 @@ std::optional<Entity> BorderMaskBlurFilterContents::RenderFilter(
     const ContentContext& renderer,
     const Entity& entity,
     const Matrix& effect_transform,
-    const Rect& coverage) const {
+    const Rect& coverage,
+    const std::optional<Rect>& coverage_hint) const {
   using VS = BorderMaskBlurPipeline::VertexShader;
   using FS = BorderMaskBlurPipeline::FragmentShader;
 

impeller/entity/contents/filters/border_mask_blur_filter_contents.h

@@ -29,11 +29,13 @@ class BorderMaskBlurFilterContents final : public FilterContents {
 
  private:
   // |FilterContents|
-  std::optional<Entity> RenderFilter(const FilterInput::Vector& input_textures,
-                                     const ContentContext& renderer,
-                                     const Entity& entity,
-                                     const Matrix& effect_transform,
-                                     const Rect& coverage) const override;
+  std::optional<Entity> RenderFilter(
+      const FilterInput::Vector& input_textures,
+      const ContentContext& renderer,
+      const Entity& entity,
+      const Matrix& effect_transform,
+      const Rect& coverage,
+      const std::optional<Rect>& coverage_hint) const override;
 
   Sigma sigma_x_;
   Sigma sigma_y_;

impeller/entity/contents/filters/color_matrix_filter_contents.cc

@@ -29,7 +29,8 @@ std::optional<Entity> ColorMatrixFilterContents::RenderFilter(
     const ContentContext& renderer,
     const Entity& entity,
     const Matrix& effect_transform,
-    const Rect& coverage) const {
+    const Rect& coverage,
+    const std::optional<Rect>& coverage_hint) const {
   using VS = ColorMatrixColorFilterPipeline::VertexShader;
   using FS = ColorMatrixColorFilterPipeline::FragmentShader;
 

impeller/entity/contents/filters/color_matrix_filter_contents.h

@@ -24,11 +24,13 @@ class ColorMatrixFilterContents final : public ColorFilterContents {
 
  private:
   // |FilterContents|
-  std::optional<Entity> RenderFilter(const FilterInput::Vector& input_textures,
-                                     const ContentContext& renderer,
-                                     const Entity& entity,
-                                     const Matrix& effect_transform,
-                                     const Rect& coverage) const override;
+  std::optional<Entity> RenderFilter(
+      const FilterInput::Vector& input_textures,
+      const ContentContext& renderer,
+      const Entity& entity,
+      const Matrix& effect_transform,
+      const Rect& coverage,
+      const std::optional<Rect>& coverage_hint) const override;
 
   ColorMatrix matrix_;
 

impeller/entity/contents/filters/filter_contents.cc

@@ -153,10 +153,6 @@ void FilterContents::SetInputs(FilterInput::Vector inputs) {
   inputs_ = std::move(inputs);
 }
 
-void FilterContents::SetCoverageCrop(std::optional<Rect> coverage_crop) {
-  coverage_crop_ = coverage_crop;
-}
-
 void FilterContents::SetEffectTransform(Matrix effect_transform) {
   effect_transform_ = effect_transform;
 }
@@ -171,7 +167,7 @@ bool FilterContents::Render(const ContentContext& renderer,
 
   // Run the filter.
 
-  auto maybe_entity = GetEntity(renderer, entity);
+  auto maybe_entity = GetEntity(renderer, entity, GetCoverageHint());
   if (!maybe_entity.has_value()) {
     return true;
   }
@@ -181,8 +177,8 @@ bool FilterContents::Render(const ContentContext& renderer,
 std::optional<Rect> FilterContents::GetLocalCoverage(
     const Entity& local_entity) const {
   auto coverage = GetFilterCoverage(inputs_, local_entity, effect_transform_);
-  if (coverage_crop_.has_value() && coverage.has_value()) {
-    coverage = coverage->Intersection(coverage_crop_.value());
+  if (GetCoverageHint().has_value() && coverage.has_value()) {
+    coverage = coverage->Intersection(*GetCoverageHint());
   }
 
   return coverage;
@@ -223,8 +219,10 @@ std::optional<Rect> FilterContents::GetFilterCoverage(
   return result;
 }
 
-std::optional<Entity> FilterContents::GetEntity(const ContentContext& renderer,
-                                                const Entity& entity) const {
+std::optional<Entity> FilterContents::GetEntity(
+    const ContentContext& renderer,
+    const Entity& entity,
+    const std::optional<Rect>& coverage_hint) const {
   Entity entity_with_local_transform = entity;
   entity_with_local_transform.SetTransformation(
       GetTransform(entity.GetTransformation()));
@@ -235,7 +233,7 @@ std::optional<Entity> FilterContents::GetEntity(const ContentContext& renderer,
   }
 
   return RenderFilter(inputs_, renderer, entity_with_local_transform,
-                      effect_transform_, coverage.value());
+                      effect_transform_, coverage.value(), coverage_hint);
 }
 
 std::optional<Snapshot> FilterContents::RenderToSnapshot(
@@ -247,12 +245,13 @@ std::optional<Snapshot> FilterContents::RenderToSnapshot(
     const std::string& label) const {
   // Resolve the render instruction (entity) from the filter and render it to a
   // snapshot.
-  if (std::optional<Entity> result = GetEntity(renderer, entity);
+  if (std::optional<Entity> result =
+          GetEntity(renderer, entity, coverage_limit);
       result.has_value()) {
     return result->GetContents()->RenderToSnapshot(
         renderer,        // renderer
         result.value(),  // entity
-        std::nullopt,    // coverage_limit
+        coverage_limit,  // coverage_limit
         std::nullopt,    // sampler_descriptor
         true,            // msaa_enabled
         label);          // label

impeller/entity/contents/filters/filter_contents.h

@@ -102,16 +102,15 @@ class FilterContents : public Contents {
   ///         particular filter's implementation.
   void SetInputs(FilterInput::Vector inputs);
 
-  /// @brief  Screen space bounds to use for cropping the filter output.
-  void SetCoverageCrop(std::optional<Rect> coverage_crop);
-
   /// @brief  Sets the transform which gets appended to the effect of this
   ///         filter. Note that this is in addition to the entity's transform.
   void SetEffectTransform(Matrix effect_transform);
 
   /// @brief  Create an Entity that renders this filter's output.
-  std::optional<Entity> GetEntity(const ContentContext& renderer,
-                                  const Entity& entity) const;
+  std::optional<Entity> GetEntity(
+      const ContentContext& renderer,
+      const Entity& entity,
+      const std::optional<Rect>& coverage_hint) const;
 
   // |Contents|
   bool Render(const ContentContext& renderer,
@@ -141,16 +140,17 @@ class FilterContents : public Contents {
       const Matrix& effect_transform) const;
 
   /// @brief  Converts zero or more filter inputs into a render instruction.
-  virtual std::optional<Entity> RenderFilter(const FilterInput::Vector& inputs,
-                                             const ContentContext& renderer,
-                                             const Entity& entity,
-                                             const Matrix& effect_transform,
-                                             const Rect& coverage) const = 0;
+  virtual std::optional<Entity> RenderFilter(
+      const FilterInput::Vector& inputs,
+      const ContentContext& renderer,
+      const Entity& entity,
+      const Matrix& effect_transform,
+      const Rect& coverage,
+      const std::optional<Rect>& coverage_hint) const = 0;
 
   std::optional<Rect> GetLocalCoverage(const Entity& local_entity) const;
 
   FilterInput::Vector inputs_;
-  std::optional<Rect> coverage_crop_;
   Matrix effect_transform_;
 
   FML_DISALLOW_COPY_AND_ASSIGN(FilterContents);