Fix opacity peephole bugs

Author: bdero

impeller/aiks/paint_pass_delegate.cc

@@ -7,6 +7,7 @@
 #include "impeller/entity/contents/contents.h"
 #include "impeller/entity/contents/texture_contents.h"
 #include "impeller/entity/entity_pass.h"
+#include "impeller/geometry/color.h"
 #include "impeller/geometry/path_builder.h"
 
 namespace impeller {
@@ -72,7 +73,8 @@ bool OpacityPeepholePassDelegate::CanElide() {
 // |EntityPassDelgate|
 bool OpacityPeepholePassDelegate::CanCollapseIntoParentPass(
     EntityPass* entity_pass) {
-  if (paint_.color.alpha <= 0.0 || paint_.color.alpha >= 1.0 ||
+  if (paint_.blend_mode != BlendMode::kSourceOver ||
+      paint_.color.alpha <= 0.0 || paint_.color.alpha >= 1.0 ||
       paint_.image_filter.has_value() || paint_.color_filter.has_value()) {
     return false;
   }
@@ -97,7 +99,7 @@ bool OpacityPeepholePassDelegate::CanCollapseIntoParentPass(
   auto had_subpass = entity_pass->IterateUntilSubpass(
       [&all_coverages, &all_can_accept](Entity& entity) {
         auto contents = entity.GetContents();
-        if (!contents->CanInheritOpacity(entity)) {
+        if (!entity.CanInheritOpacity()) {
           all_can_accept = false;
           return false;
         }
@@ -119,7 +121,7 @@ bool OpacityPeepholePassDelegate::CanCollapseIntoParentPass(
   }
   auto alpha = paint_.color.alpha;
   entity_pass->IterateUntilSubpass([&alpha](Entity& entity) {
-    entity.GetContents()->SetInheritedOpacity(alpha);
+    entity.SetInheritedOpacity(alpha);
     return true;
   });
   return true;

impeller/entity/entity.cc

@@ -12,6 +12,7 @@
 #include "impeller/entity/contents/filters/filter_contents.h"
 #include "impeller/entity/contents/texture_contents.h"
 #include "impeller/entity/entity_pass.h"
+#include "impeller/geometry/color.h"
 #include "impeller/geometry/vector.h"
 #include "impeller/renderer/render_pass.h"
 
@@ -101,6 +102,28 @@ BlendMode Entity::GetBlendMode() const {
   return blend_mode_;
 }
 
+bool Entity::CanInheritOpacity() const {
+  if (!contents_) {
+    return false;
+  }
+  if (!((blend_mode_ == BlendMode::kSource && contents_->IsOpaque()) ||
+        blend_mode_ == BlendMode::kSourceOver)) {
+    return false;
+  }
+  return contents_->CanInheritOpacity(*this);
+}
+
+bool Entity::SetInheritedOpacity(Scalar alpha) {
+  if (!CanInheritOpacity()) {
+    return false;
+  }
+  if (blend_mode_ == BlendMode::kSource && contents_->IsOpaque()) {
+    blend_mode_ = BlendMode::kSourceOver;
+  }
+  contents_->SetInheritedOpacity(alpha);
+  return true;
+}
+
 /// @brief  Returns true if the blend mode is "destrictive", meaning that even
 ///         fully transparent source colors would result in the destination
 ///         getting changed.

impeller/entity/entity.h

@@ -88,6 +88,10 @@ class Entity {
 
   static bool IsBlendModeDestructive(BlendMode blend_mode);
 
+  bool CanInheritOpacity() const;
+
+  bool SetInheritedOpacity(Scalar alpha);
+
  private:
   Matrix transformation_;
   std::shared_ptr<Contents> contents_;