Add remaining additive blends (flutter#76)

Author: bdero

impeller/entity/contents/content_context.h

@@ -159,12 +159,61 @@ class ContentContext {
         color0.src_alpha_blend_factor = BlendFactor::kOneMinusDestinationAlpha;
         color0.src_color_blend_factor = BlendFactor::kOneMinusDestinationAlpha;
         break;
-      case Entity::BlendMode::kPlus:
+      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::kSourceAlpha;
+        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;
     }
     desc.SetColorAttachmentDescriptor(0u, std::move(color0));
   }

impeller/entity/entity.h

@@ -27,7 +27,15 @@ class Entity {
     kDestination,
     kSourceOver,
     kDestinationOver,
+    kSourceIn,
+    kDestinationIn,
+    kSourceOut,
+    kDestinationOut,
+    kSourceATop,
+    kDestinationATop,
+    kXor,
     kPlus,
+    kModulate,
   };
 
   Entity();

impeller/entity/entity_unittests.cc

@@ -522,9 +522,33 @@ TEST_F(EntityTest, BlendingModeOptions) {
       case Entity::BlendMode::kDestinationOver:
         blend_mode_names.push_back("DestinationOver");
         blend_mode_values.push_back(Entity::BlendMode::kDestinationOver);
+      case Entity::BlendMode::kSourceIn:
+        blend_mode_names.push_back("SourceIn");
+        blend_mode_values.push_back(Entity::BlendMode::kSourceIn);
+      case Entity::BlendMode::kDestinationIn:
+        blend_mode_names.push_back("DestinationIn");
+        blend_mode_values.push_back(Entity::BlendMode::kDestinationIn);
+      case Entity::BlendMode::kSourceOut:
+        blend_mode_names.push_back("SourceOut");
+        blend_mode_values.push_back(Entity::BlendMode::kSourceOut);
+      case Entity::BlendMode::kDestinationOut:
+        blend_mode_names.push_back("DestinationOut");
+        blend_mode_values.push_back(Entity::BlendMode::kDestinationOut);
+      case Entity::BlendMode::kSourceATop:
+        blend_mode_names.push_back("SourceATop");
+        blend_mode_values.push_back(Entity::BlendMode::kSourceATop);
+      case Entity::BlendMode::kDestinationATop:
+        blend_mode_names.push_back("DestinationATop");
+        blend_mode_values.push_back(Entity::BlendMode::kDestinationATop);
+      case Entity::BlendMode::kXor:
+        blend_mode_names.push_back("Xor");
+        blend_mode_values.push_back(Entity::BlendMode::kXor);
       case Entity::BlendMode::kPlus:
         blend_mode_names.push_back("Plus");
         blend_mode_values.push_back(Entity::BlendMode::kPlus);
+      case Entity::BlendMode::kModulate:
+        blend_mode_names.push_back("Modulate");
+        blend_mode_values.push_back(Entity::BlendMode::kModulate);
     };
   }