[Impeller] add a generic porter duff blend foreground shader.

ci/licenses_golden/licenses_flutter

@@ -1278,6 +1278,7 @@ ORIGIN: ../../../flutter/impeller/entity/shaders/blending/ios/framebuffer_blend_
 ORIGIN: ../../../flutter/impeller/entity/shaders/blending/ios/framebuffer_blend_saturation.frag + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/shaders/blending/ios/framebuffer_blend_screen.frag + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/shaders/blending/ios/framebuffer_blend_softlight.frag + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/impeller/entity/shaders/blending/porter_duff_blend.frag + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/shaders/border_mask_blur.frag + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/shaders/border_mask_blur.vert + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/shaders/color_matrix_color_filter.frag + ../../../flutter/LICENSE
@@ -3867,6 +3868,7 @@ FILE: ../../../flutter/impeller/entity/shaders/blending/ios/framebuffer_blend_ov
 FILE: ../../../flutter/impeller/entity/shaders/blending/ios/framebuffer_blend_saturation.frag
 FILE: ../../../flutter/impeller/entity/shaders/blending/ios/framebuffer_blend_screen.frag
 FILE: ../../../flutter/impeller/entity/shaders/blending/ios/framebuffer_blend_softlight.frag
+FILE: ../../../flutter/impeller/entity/shaders/blending/porter_duff_blend.frag
 FILE: ../../../flutter/impeller/entity/shaders/border_mask_blur.frag
 FILE: ../../../flutter/impeller/entity/shaders/border_mask_blur.vert
 FILE: ../../../flutter/impeller/entity/shaders/color_matrix_color_filter.frag

impeller/aiks/aiks_unittests.cc

@@ -2035,6 +2035,26 @@ TEST_P(AiksTest, TranslucentSaveLayerWithBlendImageFilterAndDrawsCorrectly) {
   ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
 }
 
+TEST_P(AiksTest, TranslucentSaveLayerWithColorImageFilterAndDrawsCorrectly) {
+  Canvas canvas;
+
+  canvas.DrawRect(Rect::MakeXYWH(100, 100, 300, 300), {.color = Color::Blue()});
+
+  canvas.SaveLayer({
+      .color = Color::Black().WithAlpha(0.5),
+      .color_filter =
+          [](FilterInput::Ref input) {
+            return ColorFilterContents::MakeBlend(
+                BlendMode::kDestinationOver, {std::move(input)}, Color::Red());
+          },
+  });
+
+  canvas.DrawRect(Rect::MakeXYWH(100, 500, 300, 300), {.color = Color::Blue()});
+  canvas.Restore();
+
+  ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
+}
+
 TEST_P(AiksTest, TranslucentSaveLayerImageDrawsCorrectly) {
   Canvas canvas;
 

impeller/aiks/paint.cc

@@ -59,7 +59,7 @@ std::shared_ptr<Contents> Paint::WithFilters(
     std::shared_ptr<Contents> input,
     std::optional<bool> is_solid_color) const {
   bool is_solid_color_val = is_solid_color.value_or(!color_source);
-  input = WithColorFilter(input);
+  input = WithColorFilter(input, /*absorb_opacity=*/true);
   input = WithInvertFilter(input);
   input = WithMaskBlur(input, is_solid_color_val, Matrix());
   input = WithImageFilter(input, Matrix(), /*is_subpass=*/false);

impeller/entity/BUILD.gn

@@ -70,6 +70,7 @@ impeller_shaders("entity_shaders") {
     "shaders/vertices.frag",
     "shaders/yuv_to_rgb_filter.frag",
     "shaders/yuv_to_rgb_filter.vert",
+    "shaders/blending/porter_duff_blend.frag",
   ]
 }
 

impeller/entity/contents/content_context.cc

@@ -287,6 +287,8 @@ ContentContext::ContentContext(std::shared_ptr<Context> context)
       CreateDefaultPipeline<GeometryColorPipeline>(*context_);
   yuv_to_rgb_filter_pipelines_[{}] =
       CreateDefaultPipeline<YUVToRGBFilterPipeline>(*context_);
+  porter_duff_blend_pipelines_[{}] =
+      CreateDefaultPipeline<PorterDuffBlendPipeline>(*context_);
 
   if (solid_fill_pipelines_[{}]->GetDescriptor().has_value()) {
     auto clip_pipeline_descriptor =

impeller/entity/contents/content_context.h

@@ -35,6 +35,7 @@
 #include "impeller/entity/linear_to_srgb_filter.vert.h"
 #include "impeller/entity/morphology_filter.frag.h"
 #include "impeller/entity/morphology_filter.vert.h"
+#include "impeller/entity/porter_duff_blend.frag.h"
 #include "impeller/entity/radial_gradient_fill.frag.h"
 #include "impeller/entity/rrect_blur.frag.h"
 #include "impeller/entity/rrect_blur.vert.h"
@@ -125,7 +126,6 @@ using RadialGradientSSBOFillPipeline =
 using SweepGradientSSBOFillPipeline =
     RenderPipelineT<GradientFillVertexShader,
                     SweepGradientSsboFillFragmentShader>;
-using BlendPipeline = RenderPipelineT<BlendVertexShader, BlendFragmentShader>;
 using RRectBlurPipeline =
     RenderPipelineT<RrectBlurVertexShader, RrectBlurFragmentShader>;
 using BlendPipeline = RenderPipelineT<BlendVertexShader, BlendFragmentShader>;
@@ -165,6 +165,8 @@ using GlyphAtlasPipeline =
     RenderPipelineT<GlyphAtlasVertexShader, GlyphAtlasFragmentShader>;
 using GlyphAtlasSdfPipeline =
     RenderPipelineT<GlyphAtlasSdfVertexShader, GlyphAtlasSdfFragmentShader>;
+using PorterDuffBlendPipeline =
+    RenderPipelineT<BlendVertexShader, PorterDuffBlendFragmentShader>;
 // Instead of requiring new shaders for clips, the solid fill stages are used
 // to redirect writing to the stencil instead of color attachments.
 using ClipPipeline =
@@ -469,6 +471,11 @@ class ContentContext {
     return GetPipeline(yuv_to_rgb_filter_pipelines_, opts);
   }
 
+  std::shared_ptr<Pipeline<PipelineDescriptor>> GetPorterDuffBlendPipeline(
+      ContentContextOptions opts) const {
+    return GetPipeline(porter_duff_blend_pipelines_, opts);
+  }
+
   // Advanced blends.
 
   std::shared_ptr<Pipeline<PipelineDescriptor>> GetBlendColorPipeline(
@@ -705,6 +712,7 @@ class ContentContext {
   mutable Variants<GlyphAtlasSdfPipeline> glyph_atlas_sdf_pipelines_;
   mutable Variants<GeometryColorPipeline> geometry_color_pipelines_;
   mutable Variants<YUVToRGBFilterPipeline> yuv_to_rgb_filter_pipelines_;
+  mutable Variants<PorterDuffBlendPipeline> porter_duff_blend_pipelines_;
   // Advanced blends.
   mutable Variants<BlendColorPipeline> blend_color_pipelines_;
   mutable Variants<BlendColorBurnPipeline> blend_colorburn_pipelines_;

impeller/entity/contents/filters/blend_filter_contents.cc

@@ -179,7 +179,7 @@ static std::optional<Entity> AdvancedBlend(
       entity.GetBlendMode(), entity.GetStencilDepth());
 }
 
-std::optional<Entity> BlendFilterContents::CreateForegroundBlend(
+std::optional<Entity> BlendFilterContents::CreateForegroundAdvancedBlend(
     const std::shared_ptr<FilterInput>& input,
     const ContentContext& renderer,
     const Entity& entity,
@@ -318,21 +318,145 @@ std::optional<Entity> BlendFilterContents::CreateForegroundBlend(
 
   auto contents = AnonymousContents::Make(render_proc, coverage_proc);
 
-  // If there is pending opacity but it was not absorbed by this entity, we have
-  // to convert this back to a snapshot so it can be passed on. This generally
-  // implies that there is another filter about to run, so we'd perform this
-  // operation anyway.
-  auto potential_opacity = alpha.value_or(1.0) * dst_snapshot->opacity;
-  if (!absorb_opacity && potential_opacity < 1.0) {
-    auto result_snapshot = contents->RenderToSnapshot(renderer, entity);
-    if (!result_snapshot.has_value()) {
-      return std::nullopt;
-    }
-    result_snapshot->opacity = potential_opacity;
-    return Entity::FromSnapshot(result_snapshot.value(), entity.GetBlendMode(),
+  Entity sub_entity;
+  sub_entity.SetContents(std::move(contents));
+  sub_entity.SetStencilDepth(entity.GetStencilDepth());
+  sub_entity.SetTransformation(entity.GetTransformation());
+
+  return sub_entity;
+}
+
+constexpr std::array<std::array<Scalar, 5>, 15> kPorterDuffCoefficients = {{
+    {0, 0, 0, 0, 0},    // Clear
+    {1, 0, 0, 0, 0},    // Source
+    {0, 0, 1, 0, 0},    // Destination
+    {1, 0, 1, -1, 0},   // SourceOver
+    {1, -1, 1, 0, 0},   // DestinationOver
+    {0, 1, 0, 0, 0},    // SourceIn
+    {0, 0, 0, 1, 0},    // DestinationIn
+    {1, -1, 0, 0, 0},   // SourceOut
+    {0, 0, 1, -1, 0},   // DestinationOut
+    {0, 1, 1, -1, 0},   // SourceATop
+    {1, -1, 0, 1, 0},   // DestinationATop
+    {1, -1, 1, -1, 0},  // Xor
+    {1, 0, 1, 0, 0},    // Plus
+    {0, 0, 0, 0, 1},    // Modulate
+    {0, 0, 1, 0, -1},   // Screen
+}};
+
+std::optional<Entity> BlendFilterContents::CreateForegroundPorterDuffBlend(
+    const std::shared_ptr<FilterInput>& input,
+    const ContentContext& renderer,
+    const Entity& entity,
+    const Rect& coverage,
+    Color foreground_color,
+    BlendMode blend_mode,
+    std::optional<Scalar> alpha,
+    bool absorb_opacity) const {
+  auto dst_snapshot = input->GetSnapshot(renderer, entity);
+  if (!dst_snapshot.has_value()) {
+    return std::nullopt;
+  }
+
+  if (blend_mode == BlendMode::kClear) {
+    return std::nullopt;
+  }
+
+  if (blend_mode == BlendMode::kDestination) {
+    return Entity::FromSnapshot(dst_snapshot, entity.GetBlendMode(),
                                 entity.GetStencilDepth());
   }
 
+  if (blend_mode == BlendMode::kSource) {
+    auto contents = std::make_shared<SolidColorContents>();
+    contents->SetGeometry(Geometry::MakeRect(coverage));
+    contents->SetColor(foreground_color);
+
+    Entity foreground_entity;
+    foreground_entity.SetBlendMode(entity.GetBlendMode());
+    foreground_entity.SetStencilDepth(entity.GetStencilDepth());
+    foreground_entity.SetContents(std::move(contents));
+    return foreground_entity;
+  }
+
+  RenderProc render_proc = [foreground_color, coverage, dst_snapshot,
+                            blend_mode, absorb_opacity, alpha](
+                               const ContentContext& renderer,
+                               const Entity& entity, RenderPass& pass) -> bool {
+    using VS = PorterDuffBlendPipeline::VertexShader;
+    using FS = PorterDuffBlendPipeline::FragmentShader;
+
+    auto& host_buffer = pass.GetTransientsBuffer();
+
+    auto maybe_dst_uvs = dst_snapshot->GetCoverageUVs(coverage);
+    if (!maybe_dst_uvs.has_value()) {
+      return false;
+    }
+    auto dst_uvs = maybe_dst_uvs.value();
+
+    auto size = coverage.size;
+    auto origin = coverage.origin;
+    VertexBufferBuilder<VS::PerVertexData> vtx_builder;
+    vtx_builder.AddVertices({
+        {origin, dst_uvs[0]},
+        {Point(origin.x + size.width, origin.y), dst_uvs[1]},
+        {Point(origin.x + size.width, origin.y + size.height), dst_uvs[3]},
+        {origin, dst_uvs[0]},
+        {Point(origin.x + size.width, origin.y + size.height), dst_uvs[3]},
+        {Point(origin.x, origin.y + size.height), dst_uvs[2]},
+    });
+    auto vtx_buffer = vtx_builder.CreateVertexBuffer(host_buffer);
+
+    Command cmd;
+    cmd.label = "Foreground PorterDuff Blend Filter";
+    cmd.BindVertices(vtx_buffer);
+    cmd.stencil_reference = entity.GetStencilDepth();
+    auto options = OptionsFromPass(pass);
+    cmd.pipeline = renderer.GetPorterDuffBlendPipeline(options);
+
+    FS::FragInfo frag_info;
+    VS::FrameInfo frame_info;
+
+    auto dst_sampler_descriptor = dst_snapshot->sampler_descriptor;
+    if (renderer.GetDeviceCapabilities().SupportsDecalTileMode()) {
+      dst_sampler_descriptor.width_address_mode = SamplerAddressMode::kDecal;
+      dst_sampler_descriptor.height_address_mode = SamplerAddressMode::kDecal;
+    }
+    auto dst_sampler = renderer.GetContext()->GetSamplerLibrary()->GetSampler(
+        dst_sampler_descriptor);
+    FS::BindTextureSamplerDst(cmd, dst_snapshot->texture, dst_sampler);
+    frame_info.texture_sampler_y_coord_scale =
+        dst_snapshot->texture->GetYCoordScale();
+
+    frag_info.color = foreground_color.Premultiply();
+    frag_info.input_alpha =
+        absorb_opacity ? dst_snapshot->opacity * alpha.value_or(1.0) : 1.0;
+
+    auto blend_coefficients =
+        kPorterDuffCoefficients[static_cast<int>(blend_mode)];
+    frag_info.src_coeff = blend_coefficients[0];
+    frag_info.src_coeff_dst_alpha = blend_coefficients[1];
+    frag_info.dst_coeff = blend_coefficients[2];
+    frag_info.dst_coeff_src_alpha = blend_coefficients[3];
+    frag_info.dst_coeff_src_color = blend_coefficients[4];
+
+    FS::BindFragInfo(cmd, host_buffer.EmplaceUniform(frag_info));
+
+    frame_info.mvp = Matrix::MakeOrthographic(pass.GetRenderTargetSize());
+
+    auto uniform_view = host_buffer.EmplaceUniform(frame_info);
+    VS::BindFrameInfo(cmd, uniform_view);
+
+    return pass.AddCommand(cmd);
+  };
+
+  CoverageProc coverage_proc =
+      [coverage](const Entity& entity) -> std::optional<Rect> {
+    return coverage;
+  };
+
+  auto contents = AnonymousContents::Make(render_proc, coverage_proc);
+
   Entity sub_entity;
   sub_entity.SetContents(std::move(contents));
   sub_entity.SetStencilDepth(entity.GetStencilDepth());
@@ -531,17 +655,23 @@ std::optional<Entity> BlendFilterContents::RenderFilter(
   }
 
   if (blend_mode_ <= Entity::kLastPipelineBlendMode) {
+    if (inputs.size() == 1 && foreground_color_.has_value() &&
+        GetAbsorbOpacity()) {
+      return CreateForegroundPorterDuffBlend(
+          inputs[0], renderer, entity, coverage, foreground_color_.value(),
+          blend_mode_, GetAlpha(), GetAbsorbOpacity());
+    }
     return PipelineBlend(inputs, renderer, entity, coverage, blend_mode_,
                          foreground_color_, GetAbsorbOpacity(), GetAlpha());
   }
 
   if (blend_mode_ <= Entity::kLastAdvancedBlendMode) {
-    if (inputs.size() == 1 && foreground_color_.has_value()) {
-      return CreateForegroundBlend(inputs[0], renderer, entity, coverage,
-                                   foreground_color_.value(), blend_mode_,
-                                   GetAlpha(), GetAbsorbOpacity());
+    if (inputs.size() == 1 && foreground_color_.has_value() &&
+        GetAbsorbOpacity()) {
+      return CreateForegroundAdvancedBlend(
+          inputs[0], renderer, entity, coverage, foreground_color_.value(),
+          blend_mode_, GetAlpha(), GetAbsorbOpacity());
     }
-
     return advanced_blend_proc_(inputs, renderer, entity, coverage,
                                 foreground_color_, GetAbsorbOpacity(),
                                 GetAlpha());

impeller/entity/contents/filters/blend_filter_contents.h

@@ -42,7 +42,21 @@ class BlendFilterContents : public ColorFilterContents {
   ///        only a single input and a foreground color.
   ///
   /// These contents cannot absorb opacity.
-  std::optional<Entity> CreateForegroundBlend(
+  std::optional<Entity> CreateForegroundAdvancedBlend(
+      const std::shared_ptr<FilterInput>& input,
+      const ContentContext& renderer,
+      const Entity& entity,
+      const Rect& coverage,
+      Color foreground_color,
+      BlendMode blend_mode,
+      std::optional<Scalar> alpha,
+      bool absorb_opacity) const;
+
+  /// @brief Optimized porter-duff blend that avoids a second subpass when there
+  ///        is only a single input and a foreground color.
+  ///
+  /// These contents cannot absorb opacity.
+  std::optional<Entity> CreateForegroundPorterDuffBlend(
       const std::shared_ptr<FilterInput>& input,
       const ContentContext& renderer,
       const Entity& entity,

impeller/entity/contents/tiled_texture_contents.cc

@@ -88,8 +88,8 @@ SamplerDescriptor TiledTextureContents::CreateDescriptor(
 
 bool TiledTextureContents::UsesEmulatedTileMode(
     const Capabilities& capabilities) const {
-  return TileModeToAddressMode(x_tile_mode_, capabilities).has_value() &&
-         TileModeToAddressMode(y_tile_mode_, capabilities).has_value();
+  return !TileModeToAddressMode(x_tile_mode_, capabilities).has_value() ||
+         !TileModeToAddressMode(y_tile_mode_, capabilities).has_value();
 }
 
 bool TiledTextureContents::Render(const ContentContext& renderer,
@@ -121,7 +121,7 @@ bool TiledTextureContents::Render(const ContentContext& renderer,
   frame_info.texture_sampler_y_coord_scale = texture_->GetYCoordScale();
 
   Command cmd;
-  cmd.label = "TiledTextureFill";
+  cmd.label = uses_emulated_tile_mode ? "TiledTextureFill" : "TextureFill";
   cmd.stencil_reference = entity.GetStencilDepth();
 
   auto options = OptionsFromPassAndEntity(pass, entity);