[Impeller] Add ColorBurn, fix SourceOver alpha, make default pipeline initialization robust

ci/licenses_golden/licenses_flutter

@@ -529,6 +529,12 @@ FILE: ../../../flutter/impeller/entity/entity_pass_delegate.h
 FILE: ../../../flutter/impeller/entity/entity_playground.cc
 FILE: ../../../flutter/impeller/entity/entity_playground.h
 FILE: ../../../flutter/impeller/entity/entity_unittests.cc
+FILE: ../../../flutter/impeller/entity/shaders/advanced_blend.vert
+FILE: ../../../flutter/impeller/entity/shaders/advanced_blend_colorburn.frag
+FILE: ../../../flutter/impeller/entity/shaders/advanced_blend_screen.frag
+FILE: ../../../flutter/impeller/entity/shaders/blend.frag
+FILE: ../../../flutter/impeller/entity/shaders/blend.vert
+FILE: ../../../flutter/impeller/entity/shaders/blending.glsl
 FILE: ../../../flutter/impeller/entity/shaders/border_mask_blur.frag
 FILE: ../../../flutter/impeller/entity/shaders/border_mask_blur.vert
 FILE: ../../../flutter/impeller/entity/shaders/gaussian_blur.frag
@@ -541,10 +547,6 @@ FILE: ../../../flutter/impeller/entity/shaders/solid_fill.frag
 FILE: ../../../flutter/impeller/entity/shaders/solid_fill.vert
 FILE: ../../../flutter/impeller/entity/shaders/solid_stroke.frag
 FILE: ../../../flutter/impeller/entity/shaders/solid_stroke.vert
-FILE: ../../../flutter/impeller/entity/shaders/texture_blend.frag
-FILE: ../../../flutter/impeller/entity/shaders/texture_blend.vert
-FILE: ../../../flutter/impeller/entity/shaders/texture_blend_screen.frag
-FILE: ../../../flutter/impeller/entity/shaders/texture_blend_screen.vert
 FILE: ../../../flutter/impeller/entity/shaders/texture_fill.frag
 FILE: ../../../flutter/impeller/entity/shaders/texture_fill.vert
 FILE: ../../../flutter/impeller/fixtures/airplane.jpg

impeller/aiks/aiks_unittests.cc

@@ -493,6 +493,7 @@ TEST_P(AiksTest, CanDrawWithAdvancedBlend) {
         {"Modulate", Entity::BlendMode::kModulate},
         // Advanced blends (non Porter-Duff/color blends)
         {"Screen", Entity::BlendMode::kScreen},
+        {"ColorBurn", Entity::BlendMode::kColorBurn},
     };
     assert(blends.size() ==
            static_cast<size_t>(Entity::BlendMode::kLastAdvancedBlendMode) + 1);
@@ -520,6 +521,7 @@ TEST_P(AiksTest, CanDrawWithAdvancedBlend) {
     };
 
     Paint paint;
+    paint.blend_mode = Entity::BlendMode::kSourceOver;
 
     // Draw a fancy color wheel for the backdrop.
     // https://www.desmos.com/calculator/xw7kafthwd
@@ -546,10 +548,16 @@ TEST_P(AiksTest, CanDrawWithAdvancedBlend) {
       ImGui::SetNextWindowPos({325, 550});
     }
 
-    ImGui::Begin("Controls");
+    // UI state.
     static int current_blend_index = 3;
-    ImGui::ListBox("Blending mode", &current_blend_index,
-                   blend_mode_names.data(), blend_mode_names.size());
+    static float alpha = 1;
+
+    ImGui::Begin("Controls");
+    {
+      ImGui::ListBox("Blending mode", &current_blend_index,
+                     blend_mode_names.data(), blend_mode_names.size());
+      ImGui::SliderFloat("Alpha", &alpha, 0, 1);
+    }
     ImGui::End();
 
     Canvas canvas;
@@ -569,11 +577,11 @@ TEST_P(AiksTest, CanDrawWithAdvancedBlend) {
       paint.blend_mode = Entity::BlendMode::kPlus;
       const Scalar x = std::sin(k2Pi / 3);
       const Scalar y = -std::cos(k2Pi / 3);
-      paint.color = Color::Red();
+      paint.color = Color::Red().WithAlpha(alpha);
       canvas.DrawCircle(Point(-x, y) * 45, 65, paint);
-      paint.color = Color::Green();
+      paint.color = Color::Green().WithAlpha(alpha);
       canvas.DrawCircle(Point(0, -1) * 45, 65, paint);
-      paint.color = Color::Blue();
+      paint.color = Color::Blue().WithAlpha(alpha);
       canvas.DrawCircle(Point(x, y) * 45, 65, paint);
     }
     canvas.Restore();

impeller/blobcat/blob.h

@@ -26,7 +26,7 @@ struct Blob {
     kFragment,
   };
 
-  static constexpr size_t kMaxNameLength = 24u;
+  static constexpr size_t kMaxNameLength = 32u;
 
   ShaderType type = ShaderType::kVertex;
   uint64_t offset = 0;

impeller/display_list/display_list_dispatcher.cc

@@ -214,11 +214,13 @@ static std::optional<Entity::BlendMode> ToBlendMode(flutter::DlBlendMode mode) {
     case flutter::DlBlendMode::kModulate:
       return Entity::BlendMode::kModulate;
     case flutter::DlBlendMode::kScreen:
+      return Entity::BlendMode::kScreen;
+    case flutter::DlBlendMode::kColorBurn:
+      return Entity::BlendMode::kColorBurn;
     case flutter::DlBlendMode::kOverlay:
     case flutter::DlBlendMode::kDarken:
     case flutter::DlBlendMode::kLighten:
     case flutter::DlBlendMode::kColorDodge:
-    case flutter::DlBlendMode::kColorBurn:
     case flutter::DlBlendMode::kHardLight:
     case flutter::DlBlendMode::kSoftLight:
     case flutter::DlBlendMode::kDifference:
@@ -240,6 +242,7 @@ void DisplayListDispatcher::setBlendMode(flutter::DlBlendMode dl_mode) {
     paint_.blend_mode = mode.value();
   } else {
     UNIMPLEMENTED;
+    paint_.blend_mode = Entity::BlendMode::kSourceOver;
   }
 }
 

impeller/entity/BUILD.gn

@@ -8,24 +8,25 @@ impeller_shaders("entity_shaders") {
   name = "entity"
 
   shaders = [
+    "shaders/advanced_blend.vert",
+    "shaders/advanced_blend_colorburn.frag",
+    "shaders/advanced_blend_screen.frag",
+    "shaders/blend.frag",
+    "shaders/blend.vert",
+    "shaders/border_mask_blur.frag",
+    "shaders/border_mask_blur.vert",
+    "shaders/gaussian_blur.frag",
+    "shaders/gaussian_blur.vert",
+    "shaders/glyph_atlas.frag",
+    "shaders/glyph_atlas.vert",
     "shaders/gradient_fill.frag",
     "shaders/gradient_fill.vert",
     "shaders/solid_fill.frag",
     "shaders/solid_fill.vert",
     "shaders/solid_stroke.frag",
     "shaders/solid_stroke.vert",
-    "shaders/texture_blend.frag",
-    "shaders/texture_blend.vert",
-    "shaders/texture_blend_screen.frag",
-    "shaders/texture_blend_screen.vert",
-    "shaders/gaussian_blur.frag",
-    "shaders/gaussian_blur.vert",
-    "shaders/border_mask_blur.frag",
-    "shaders/border_mask_blur.vert",
     "shaders/texture_fill.frag",
     "shaders/texture_fill.vert",
-    "shaders/glyph_atlas.frag",
-    "shaders/glyph_atlas.vert",
   ]
 }
 

impeller/entity/contents/content_context.cc

@@ -13,28 +13,161 @@
 
 namespace impeller {
 
+void ContentContextOptions::ApplyToPipelineDescriptor(
+    PipelineDescriptor& desc) const {
+  auto pipeline_blend = blend_mode;
+  if (blend_mode > Entity::BlendMode::kLastPipelineBlendMode) {
+    VALIDATION_LOG << "Cannot use blend mode " << static_cast<int>(blend_mode)
+                   << " as a pipeline blend.";
+    pipeline_blend = Entity::BlendMode::kSourceOver;
+  }
+
+  desc.SetSampleCount(sample_count);
+
+  ColorAttachmentDescriptor color0 = *desc.GetColorAttachmentDescriptor(0u);
+  color0.alpha_blend_op = BlendOperation::kAdd;
+  color0.color_blend_op = BlendOperation::kAdd;
+
+  static_assert(Entity::BlendMode::kLastPipelineBlendMode ==
+                Entity::BlendMode::kModulate);
+
+  switch (pipeline_blend) {
+    case Entity::BlendMode::kClear:
+      color0.dst_alpha_blend_factor = BlendFactor::kZero;
+      color0.dst_color_blend_factor = BlendFactor::kZero;
+      color0.src_alpha_blend_factor = BlendFactor::kZero;
+      color0.src_color_blend_factor = BlendFactor::kZero;
+      break;
+    case Entity::BlendMode::kSource:
+      color0.dst_alpha_blend_factor = BlendFactor::kZero;
+      color0.dst_color_blend_factor = BlendFactor::kZero;
+      color0.src_alpha_blend_factor = BlendFactor::kSourceAlpha;
+      color0.src_color_blend_factor = BlendFactor::kOne;
+      break;
+    case Entity::BlendMode::kDestination:
+      color0.dst_alpha_blend_factor = BlendFactor::kDestinationAlpha;
+      color0.dst_color_blend_factor = BlendFactor::kOne;
+      color0.src_alpha_blend_factor = BlendFactor::kZero;
+      color0.src_color_blend_factor = BlendFactor::kZero;
+      break;
+    case Entity::BlendMode::kSourceOver:
+      color0.dst_alpha_blend_factor = BlendFactor::kOneMinusSourceAlpha;
+      color0.dst_color_blend_factor = BlendFactor::kOneMinusSourceAlpha;
+      color0.src_alpha_blend_factor = BlendFactor::kOne;
+      color0.src_color_blend_factor = BlendFactor::kOne;
+      break;
+    case Entity::BlendMode::kDestinationOver:
+      color0.dst_alpha_blend_factor = BlendFactor::kDestinationAlpha;
+      color0.dst_color_blend_factor = BlendFactor::kOne;
+      color0.src_alpha_blend_factor = BlendFactor::kOneMinusDestinationAlpha;
+      color0.src_color_blend_factor = BlendFactor::kOneMinusDestinationAlpha;
+      break;
+    case Entity::BlendMode::kSourceIn:
+      color0.dst_alpha_blend_factor = BlendFactor::kZero;
+      color0.dst_color_blend_factor = BlendFactor::kZero;
+      color0.src_alpha_blend_factor = BlendFactor::kDestinationAlpha;
+      color0.src_color_blend_factor = BlendFactor::kDestinationAlpha;
+      break;
+    case Entity::BlendMode::kDestinationIn:
+      color0.dst_alpha_blend_factor = BlendFactor::kSourceAlpha;
+      color0.dst_color_blend_factor = BlendFactor::kSourceAlpha;
+      color0.src_alpha_blend_factor = BlendFactor::kZero;
+      color0.src_color_blend_factor = BlendFactor::kZero;
+      break;
+    case Entity::BlendMode::kSourceOut:
+      color0.dst_alpha_blend_factor = BlendFactor::kZero;
+      color0.dst_color_blend_factor = BlendFactor::kZero;
+      color0.src_alpha_blend_factor = BlendFactor::kOneMinusDestinationAlpha;
+      color0.src_color_blend_factor = BlendFactor::kOneMinusDestinationAlpha;
+      break;
+    case Entity::BlendMode::kDestinationOut:
+      color0.dst_alpha_blend_factor = BlendFactor::kOneMinusSourceAlpha;
+      color0.dst_color_blend_factor = BlendFactor::kOneMinusSourceAlpha;
+      color0.src_alpha_blend_factor = BlendFactor::kZero;
+      color0.src_color_blend_factor = BlendFactor::kZero;
+      break;
+    case Entity::BlendMode::kSourceATop:
+      color0.dst_alpha_blend_factor = BlendFactor::kOneMinusSourceAlpha;
+      color0.dst_color_blend_factor = BlendFactor::kOneMinusSourceAlpha;
+      color0.src_alpha_blend_factor = BlendFactor::kDestinationAlpha;
+      color0.src_color_blend_factor = BlendFactor::kDestinationAlpha;
+      break;
+    case Entity::BlendMode::kDestinationATop:
+      color0.dst_alpha_blend_factor = BlendFactor::kSourceAlpha;
+      color0.dst_color_blend_factor = BlendFactor::kSourceAlpha;
+      color0.src_alpha_blend_factor = BlendFactor::kOneMinusDestinationAlpha;
+      color0.src_color_blend_factor = BlendFactor::kOneMinusDestinationAlpha;
+      break;
+    case Entity::BlendMode::kXor:
+      color0.dst_alpha_blend_factor = BlendFactor::kOneMinusSourceAlpha;
+      color0.dst_color_blend_factor = BlendFactor::kOneMinusSourceAlpha;
+      color0.src_alpha_blend_factor = BlendFactor::kOneMinusDestinationAlpha;
+      color0.src_color_blend_factor = BlendFactor::kOneMinusDestinationAlpha;
+      break;
+    case Entity::BlendMode::kPlus:
+      color0.dst_alpha_blend_factor = BlendFactor::kOne;
+      color0.dst_color_blend_factor = BlendFactor::kOne;
+      color0.src_alpha_blend_factor = BlendFactor::kOne;
+      color0.src_color_blend_factor = BlendFactor::kOne;
+      break;
+    case Entity::BlendMode::kModulate:
+      // kSourceColor and kDestinationColor override the alpha blend factor.
+      color0.dst_alpha_blend_factor = BlendFactor::kZero;
+      color0.dst_color_blend_factor = BlendFactor::kSourceColor;
+      color0.src_alpha_blend_factor = BlendFactor::kZero;
+      color0.src_color_blend_factor = BlendFactor::kZero;
+      break;
+    default:
+      FML_UNREACHABLE();
+  }
+  desc.SetColorAttachmentDescriptor(0u, std::move(color0));
+
+  if (desc.GetFrontStencilAttachmentDescriptor().has_value()) {
+    StencilAttachmentDescriptor stencil =
+        desc.GetFrontStencilAttachmentDescriptor().value();
+    stencil.stencil_compare = stencil_compare;
+    stencil.depth_stencil_pass = stencil_operation;
+    desc.SetStencilAttachmentDescriptors(stencil);
+  }
+}
+
+template <typename PipelineT>
+static std::unique_ptr<PipelineT> CreateDefaultPipeline(
+    const Context& context) {
+  auto desc = PipelineT::Builder::MakeDefaultPipelineDescriptor(context);
+  if (!desc.has_value()) {
+    return nullptr;
+  }
+  // Apply default ContentContextOptions to the descriptor.
+  ContentContextOptions{}.ApplyToPipelineDescriptor(*desc);
+  return std::make_unique<PipelineT>(context, desc);
+}
+
 ContentContext::ContentContext(std::shared_ptr<Context> context)
     : context_(std::move(context)) {
   if (!context_ || !context_->IsValid()) {
     return;
   }
 
-  // Pipelines whose default descriptors work fine for the entity framework.
   gradient_fill_pipelines_[{}] =
-      std::make_unique<GradientFillPipeline>(*context_);
-  solid_fill_pipelines_[{}] = std::make_unique<SolidFillPipeline>(*context_);
+      CreateDefaultPipeline<GradientFillPipeline>(*context_);
+  solid_fill_pipelines_[{}] =
+      CreateDefaultPipeline<SolidFillPipeline>(*context_);
   texture_blend_pipelines_[{}] =
-      std::make_unique<TextureBlendPipeline>(*context_);
-  texture_blend_screen_pipelines_[{}] =
-      std::make_unique<TextureBlendScreenPipeline>(*context_);
-  texture_pipelines_[{}] = std::make_unique<TexturePipeline>(*context_);
+      CreateDefaultPipeline<BlendPipeline>(*context_);
+  blend_screen_pipelines_[{}] =
+      CreateDefaultPipeline<BlendScreenPipeline>(*context_);
+  blend_colorburn_pipelines_[{}] =
+      CreateDefaultPipeline<BlendColorburnPipeline>(*context_);
+  texture_pipelines_[{}] = CreateDefaultPipeline<TexturePipeline>(*context_);
   gaussian_blur_pipelines_[{}] =
-      std::make_unique<GaussianBlurPipeline>(*context_);
+      CreateDefaultPipeline<GaussianBlurPipeline>(*context_);
   border_mask_blur_pipelines_[{}] =
-      std::make_unique<BorderMaskBlurPipeline>(*context_);
+      CreateDefaultPipeline<BorderMaskBlurPipeline>(*context_);
   solid_stroke_pipelines_[{}] =
-      std::make_unique<SolidStrokePipeline>(*context_);
-  glyph_atlas_pipelines_[{}] = std::make_unique<GlyphAtlasPipeline>(*context_);
+      CreateDefaultPipeline<SolidStrokePipeline>(*context_);
+  glyph_atlas_pipelines_[{}] =
+      CreateDefaultPipeline<GlyphAtlasPipeline>(*context_);
 
   // Pipelines that are variants of the base pipelines with custom descriptors.
   // TODO(98684): Rework this API to allow fetching the descriptor without