[Impeller] ensure that srcOver to src conversion takes stroke coverag…

…e into account. (#54817) When computing whether or not an entity can be coerced into src blend from srcOver, take into account that stroke geometries may modulate with alpha to emulate stroke widths less than 1.0. While we're at it, update several computations to use max basis XY (from flutter/flutter#153451 ) since that can lead to incorrect stroke width computations in the presence of canvas scaling. Most of the changes update the APIs that used to take a ` const Entity& entity` to instead use the `const Matrix& transform`, since that is all we used the entity for. See screeenshots in flutter/flutter#154178 (comment) Fixes flutter/flutter#154178
flutter · Aug 28, 2024 · 19ef4a9 · 19ef4a9
1 parent bbb85cf
commit 19ef4a9
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Showing 29 changed files with 228 additions and 105 deletions.
diff --git a/impeller/aiks/aiks_unittests.cc b/impeller/aiks/aiks_unittests.cc
@@ -314,7 +314,7 @@ TEST_P(AiksTest, OpaqueEntitiesGetCoercedToSource) {
   });
 
   ASSERT_TRUE(entity.size() >= 1);
-  ASSERT_TRUE(contents->IsOpaque());
+  ASSERT_TRUE(contents->IsOpaque({}));
   ASSERT_EQ(entity[0].GetBlendMode(), BlendMode::kSource);
 }
 

diff --git a/impeller/aiks/experimental_canvas.cc b/impeller/aiks/experimental_canvas.cc
@@ -673,7 +673,7 @@ void ExperimentalCanvas::AddRenderEntityToCurrentPass(Entity entity,
       entity.GetTransform());
   entity.SetInheritedOpacity(transform_stack_.back().distributed_opacity);
   if (entity.GetBlendMode() == BlendMode::kSourceOver &&
-      entity.GetContents()->IsOpaque()) {
+      entity.GetContents()->IsOpaque(entity.GetTransform())) {
     entity.SetBlendMode(BlendMode::kSource);
   }
 

diff --git a/impeller/entity/contents/color_source_contents.cc b/impeller/entity/contents/color_source_contents.cc
@@ -54,4 +54,9 @@ void ColorSourceContents::SetInheritedOpacity(Scalar opacity) {
   inherited_opacity_ = opacity;
 }
 
+bool ColorSourceContents::AppliesAlphaForStrokeCoverage(
+    const Matrix& transform) const {
+  return GetGeometry() && GetGeometry()->ComputeAlphaCoverage(transform) < 1.0;
+}
+
 }  // namespace impeller
diff --git a/impeller/entity/contents/color_source_contents.h b/impeller/entity/contents/color_source_contents.h
@@ -126,6 +126,10 @@ class ColorSourceContents : public Contents {
     return geom.GetPositionBuffer(renderer, entity, pass);
   }
 
+  /// @brief Whether the entity should be treated as non-opaque due to stroke
+  ///        geometry requiring alpha for coverage.
+  bool AppliesAlphaForStrokeCoverage(const Matrix& transform) const;
+
   template <typename VertexShaderT>
   bool DrawGeometry(const ContentContext& renderer,
                     const Entity& entity,

diff --git a/impeller/entity/contents/conical_gradient_contents.cc b/impeller/entity/contents/conical_gradient_contents.cc
@@ -80,7 +80,8 @@ bool ConicalGradientContents::RenderSSBO(const ContentContext& renderer,
         frag_info.tile_mode = static_cast<Scalar>(tile_mode_);
         frag_info.decal_border_color = decal_border_color_;
         frag_info.alpha =
-            GetOpacityFactor() * GetGeometry()->ComputeAlphaCoverage(entity);
+            GetOpacityFactor() *
+            GetGeometry()->ComputeAlphaCoverage(entity.GetTransform());
         if (focus_) {
           frag_info.focus = focus_.value();
           frag_info.focus_radius = focus_radius_;
@@ -137,7 +138,8 @@ bool ConicalGradientContents::RenderTexture(const ContentContext& renderer,
         frag_info.texture_sampler_y_coord_scale =
             gradient_texture->GetYCoordScale();
         frag_info.alpha =
-            GetOpacityFactor() * GetGeometry()->ComputeAlphaCoverage(entity);
+            GetOpacityFactor() *
+            GetGeometry()->ComputeAlphaCoverage(entity.GetTransform());
         frag_info.half_texel =
             Vector2(0.5 / gradient_texture->GetSize().width,
                     0.5 / gradient_texture->GetSize().height);

diff --git a/impeller/entity/contents/contents.cc b/impeller/entity/contents/contents.cc
@@ -49,7 +49,7 @@ Contents::Contents() = default;
 
 Contents::~Contents() = default;
 
-bool Contents::IsOpaque() const {
+bool Contents::IsOpaque(const Matrix& transform) const {
   return false;
 }
 

diff --git a/impeller/entity/contents/contents.h b/impeller/entity/contents/contents.h
@@ -91,7 +91,9 @@ class Contents {
   ///        properties (e.g. the blend mode), clips/visibility culling, or
   ///        inherited opacity.
   ///
-  virtual bool IsOpaque() const;
+  /// @param transform The current transform matrix of the entity that will
+  /// render this contents.
+  virtual bool IsOpaque(const Matrix& transform) const;
 
   //----------------------------------------------------------------------------
   /// @brief Given the current pass space bounding rectangle of the clip

diff --git a/impeller/entity/contents/linear_gradient_contents.cc b/impeller/entity/contents/linear_gradient_contents.cc
@@ -44,7 +44,7 @@ void LinearGradientContents::SetTileMode(Entity::TileMode tile_mode) {
   tile_mode_ = tile_mode;
 }
 
-bool LinearGradientContents::IsOpaque() const {
+bool LinearGradientContents::IsOpaque(const Matrix& transform) const {
   if (GetOpacityFactor() < 1 || tile_mode_ == Entity::TileMode::kDecal) {
     return false;
   }
@@ -53,7 +53,7 @@ bool LinearGradientContents::IsOpaque() const {
       return false;
     }
   }
-  return true;
+  return !AppliesAlphaForStrokeCoverage(transform);
 }
 
 bool LinearGradientContents::CanApplyFastGradient() const {
@@ -176,7 +176,8 @@ bool LinearGradientContents::FastLinearGradient(const ContentContext& renderer,
 
         FS::FragInfo frag_info;
         frag_info.alpha =
-            GetOpacityFactor() * GetGeometry()->ComputeAlphaCoverage(entity);
+            GetOpacityFactor() *
+            GetGeometry()->ComputeAlphaCoverage(entity.GetTransform());
 
         FS::BindFragInfo(pass, host_buffer.EmplaceUniform(frag_info));
 
@@ -231,7 +232,8 @@ bool LinearGradientContents::RenderTexture(const ContentContext& renderer,
         frag_info.texture_sampler_y_coord_scale =
             gradient_texture->GetYCoordScale();
         frag_info.alpha =
-            GetOpacityFactor() * GetGeometry()->ComputeAlphaCoverage(entity);
+            GetOpacityFactor() *
+            GetGeometry()->ComputeAlphaCoverage(entity.GetTransform());
         ;
         frag_info.half_texel =
             Vector2(0.5 / gradient_texture->GetSize().width,
@@ -284,7 +286,8 @@ bool LinearGradientContents::RenderSSBO(const ContentContext& renderer,
         frag_info.tile_mode = static_cast<Scalar>(tile_mode_);
         frag_info.decal_border_color = decal_border_color_;
         frag_info.alpha =
-            GetOpacityFactor() * GetGeometry()->ComputeAlphaCoverage(entity);
+            GetOpacityFactor() *
+            GetGeometry()->ComputeAlphaCoverage(entity.GetTransform());
         frag_info.start_to_end = end_point_ - start_point_;
         frag_info.inverse_dot_start_to_end =
             CalculateInverseDotStartToEnd(start_point_, end_point_);

diff --git a/impeller/entity/contents/linear_gradient_contents.h b/impeller/entity/contents/linear_gradient_contents.h
@@ -21,7 +21,7 @@ class LinearGradientContents final : public ColorSourceContents {
   ~LinearGradientContents() override;
 
   // |Contents|
-  bool IsOpaque() const override;
+  bool IsOpaque(const Matrix& transform) const override;
 
   // |Contents|
   bool Render(const ContentContext& renderer,

diff --git a/impeller/entity/contents/radial_gradient_contents.cc b/impeller/entity/contents/radial_gradient_contents.cc
@@ -43,7 +43,7 @@ const std::vector<Scalar>& RadialGradientContents::GetStops() const {
   return stops_;
 }
 
-bool RadialGradientContents::IsOpaque() const {
+bool RadialGradientContents::IsOpaque(const Matrix& transform) const {
   if (GetOpacityFactor() < 1 || tile_mode_ == Entity::TileMode::kDecal) {
     return false;
   }
@@ -52,7 +52,7 @@ bool RadialGradientContents::IsOpaque() const {
       return false;
     }
   }
-  return true;
+  return !AppliesAlphaForStrokeCoverage(transform);
 }
 
 bool RadialGradientContents::Render(const ContentContext& renderer,
@@ -86,7 +86,8 @@ bool RadialGradientContents::RenderSSBO(const ContentContext& renderer,
         frag_info.tile_mode = static_cast<Scalar>(tile_mode_);
         frag_info.decal_border_color = decal_border_color_;
         frag_info.alpha =
-            GetOpacityFactor() * GetGeometry()->ComputeAlphaCoverage(entity);
+            GetOpacityFactor() *
+            GetGeometry()->ComputeAlphaCoverage(entity.GetTransform());
 
         auto& host_buffer = renderer.GetTransientsBuffer();
         auto colors = CreateGradientColors(colors_, stops_);
@@ -136,7 +137,8 @@ bool RadialGradientContents::RenderTexture(const ContentContext& renderer,
         frag_info.texture_sampler_y_coord_scale =
             gradient_texture->GetYCoordScale();
         frag_info.alpha =
-            GetOpacityFactor() * GetGeometry()->ComputeAlphaCoverage(entity);
+            GetOpacityFactor() *
+            GetGeometry()->ComputeAlphaCoverage(entity.GetTransform());
         frag_info.half_texel =
             Vector2(0.5 / gradient_texture->GetSize().width,
                     0.5 / gradient_texture->GetSize().height);

diff --git a/impeller/entity/contents/radial_gradient_contents.h b/impeller/entity/contents/radial_gradient_contents.h
@@ -21,7 +21,7 @@ class RadialGradientContents final : public ColorSourceContents {
   ~RadialGradientContents() override;
 
   // |Contents|
-  bool IsOpaque() const override;
+  bool IsOpaque(const Matrix& transform) const override;
 
   // |Contents|
   bool Render(const ContentContext& renderer,

diff --git a/impeller/entity/contents/solid_color_contents.cc b/impeller/entity/contents/solid_color_contents.cc
@@ -28,8 +28,8 @@ bool SolidColorContents::IsSolidColor() const {
   return true;
 }
 
-bool SolidColorContents::IsOpaque() const {
-  return GetColor().IsOpaque();
+bool SolidColorContents::IsOpaque(const Matrix& transform) const {
+  return GetColor().IsOpaque() && !AppliesAlphaForStrokeCoverage(transform);
 }
 
 std::optional<Rect> SolidColorContents::GetCoverage(
@@ -54,8 +54,8 @@ bool SolidColorContents::Render(const ContentContext& renderer,
 
   VS::FrameInfo frame_info;
   FS::FragInfo frag_info;
-  frag_info.color =
-      GetColor().Premultiply() * GetGeometry()->ComputeAlphaCoverage(entity);
+  frag_info.color = GetColor().Premultiply() *
+                    GetGeometry()->ComputeAlphaCoverage(entity.GetTransform());
 
   PipelineBuilderCallback pipeline_callback =
       [&renderer](ContentContextOptions options) {

diff --git a/impeller/entity/contents/solid_color_contents.h b/impeller/entity/contents/solid_color_contents.h
@@ -31,7 +31,7 @@ class SolidColorContents final : public ColorSourceContents {
   bool IsSolidColor() const override;
 
   // |Contents|
-  bool IsOpaque() const override;
+  bool IsOpaque(const Matrix& transform) const override;
 
   // |Contents|
   std::optional<Rect> GetCoverage(const Entity& entity) const override;

diff --git a/impeller/entity/contents/sweep_gradient_contents.cc b/impeller/entity/contents/sweep_gradient_contents.cc
@@ -49,7 +49,7 @@ const std::vector<Scalar>& SweepGradientContents::GetStops() const {
   return stops_;
 }
 
-bool SweepGradientContents::IsOpaque() const {
+bool SweepGradientContents::IsOpaque(const Matrix& transform) const {
   if (GetOpacityFactor() < 1 || tile_mode_ == Entity::TileMode::kDecal) {
     return false;
   }
@@ -58,7 +58,7 @@ bool SweepGradientContents::IsOpaque() const {
       return false;
     }
   }
-  return true;
+  return !AppliesAlphaForStrokeCoverage(transform);
 }
 
 bool SweepGradientContents::Render(const ContentContext& renderer,
@@ -95,7 +95,8 @@ bool SweepGradientContents::RenderSSBO(const ContentContext& renderer,
         frag_info.tile_mode = static_cast<Scalar>(tile_mode_);
         frag_info.decal_border_color = decal_border_color_;
         frag_info.alpha =
-            GetOpacityFactor() * GetGeometry()->ComputeAlphaCoverage(entity);
+            GetOpacityFactor() *
+            GetGeometry()->ComputeAlphaCoverage(entity.GetTransform());
 
         auto& host_buffer = renderer.GetTransientsBuffer();
         auto colors = CreateGradientColors(colors_, stops_);
@@ -147,7 +148,8 @@ bool SweepGradientContents::RenderTexture(const ContentContext& renderer,
         frag_info.tile_mode = static_cast<Scalar>(tile_mode_);
         frag_info.decal_border_color = decal_border_color_;
         frag_info.alpha =
-            GetOpacityFactor() * GetGeometry()->ComputeAlphaCoverage(entity);
+            GetOpacityFactor() *
+            GetGeometry()->ComputeAlphaCoverage(entity.GetTransform());
         frag_info.half_texel =
             Vector2(0.5 / gradient_texture->GetSize().width,
                     0.5 / gradient_texture->GetSize().height);

diff --git a/impeller/entity/contents/sweep_gradient_contents.h b/impeller/entity/contents/sweep_gradient_contents.h
@@ -22,7 +22,7 @@ class SweepGradientContents final : public ColorSourceContents {
   ~SweepGradientContents() override;
 
   // |Contents|
-  bool IsOpaque() const override;
+  bool IsOpaque(const Matrix& transform) const override;
 
   // |Contents|
   bool Render(const ContentContext& renderer,

diff --git a/impeller/entity/contents/tiled_texture_contents.cc b/impeller/entity/contents/tiled_texture_contents.cc
@@ -96,15 +96,15 @@ bool TiledTextureContents::UsesEmulatedTileMode(
 }
 
 // |Contents|
-bool TiledTextureContents::IsOpaque() const {
+bool TiledTextureContents::IsOpaque(const Matrix& transform) const {
   if (GetOpacityFactor() < 1 || x_tile_mode_ == Entity::TileMode::kDecal ||
       y_tile_mode_ == Entity::TileMode::kDecal) {
     return false;
   }
   if (color_filter_) {
     return false;
   }
-  return texture_->IsOpaque();
+  return texture_->IsOpaque() && !AppliesAlphaForStrokeCoverage(transform);
 }
 
 bool TiledTextureContents::Render(const ContentContext& renderer,
@@ -160,14 +160,16 @@ bool TiledTextureContents::Render(const ContentContext& renderer,
           frag_info.x_tile_mode = static_cast<Scalar>(x_tile_mode_);
           frag_info.y_tile_mode = static_cast<Scalar>(y_tile_mode_);
           frag_info.alpha =
-              GetOpacityFactor() * GetGeometry()->ComputeAlphaCoverage(entity);
+              GetOpacityFactor() *
+              GetGeometry()->ComputeAlphaCoverage(entity.GetTransform());
           FSExternal::BindFragInfo(pass, host_buffer.EmplaceUniform(frag_info));
         } else {
           FS::FragInfo frag_info;
           frag_info.x_tile_mode = static_cast<Scalar>(x_tile_mode_);
           frag_info.y_tile_mode = static_cast<Scalar>(y_tile_mode_);
           frag_info.alpha =
-              GetOpacityFactor() * GetGeometry()->ComputeAlphaCoverage(entity);
+              GetOpacityFactor() *
+              GetGeometry()->ComputeAlphaCoverage(entity.GetTransform());
           FS::BindFragInfo(pass, host_buffer.EmplaceUniform(frag_info));
         }
 

diff --git a/impeller/entity/contents/tiled_texture_contents.h b/impeller/entity/contents/tiled_texture_contents.h
@@ -28,7 +28,7 @@ class TiledTextureContents final : public ColorSourceContents {
       std::function<std::shared_ptr<ColorFilterContents>(FilterInput::Ref)>;
 
   // |Contents|
-  bool IsOpaque() const override;
+  bool IsOpaque(const Matrix& transform) const override;
 
   // |Contents|
   bool Render(const ContentContext& renderer,

diff --git a/impeller/entity/entity.cc b/impeller/entity/entity.cc
@@ -126,7 +126,8 @@ bool Entity::CanInheritOpacity() const {
   if (!contents_) {
     return false;
   }
-  if (!((blend_mode_ == BlendMode::kSource && contents_->IsOpaque()) ||
+  if (!((blend_mode_ == BlendMode::kSource &&
+         contents_->IsOpaque(GetTransform())) ||
         blend_mode_ == BlendMode::kSourceOver)) {
     return false;
   }
@@ -137,7 +138,8 @@ bool Entity::SetInheritedOpacity(Scalar alpha) {
   if (!CanInheritOpacity()) {
     return false;
   }
-  if (blend_mode_ == BlendMode::kSource && contents_->IsOpaque()) {
+  if (blend_mode_ == BlendMode::kSource &&
+      contents_->IsOpaque(GetTransform())) {
     blend_mode_ = BlendMode::kSourceOver;
   }
   contents_->SetInheritedOpacity(alpha);

diff --git a/impeller/entity/entity_pass.cc b/impeller/entity/entity_pass.cc
@@ -104,7 +104,7 @@ bool EntityPass::GetBoundsLimitIsSnug() const {
 
 void EntityPass::AddEntity(Entity entity) {
   if (entity.GetBlendMode() == BlendMode::kSourceOver &&
-      entity.GetContents()->IsOpaque()) {
+      entity.GetContents()->IsOpaque(entity.GetTransform())) {
     entity.SetBlendMode(BlendMode::kSource);
   }