Bug 1210560 - Part 1: Add an API specifically intended for users that just Push and Pop-Mask/Pop-Paint. r=jrmuizel

gfx/thebes/gfxContext.cpp

@@ -881,6 +881,16 @@ gfxContext::PushGroup(gfxContentType content)
   mDT->SetTransform(GetDTTransform());
 }
 
+void
+gfxContext::PushGroupForBlendBack(gfxContentType content, Float aOpacity, SourceSurface* aMask, const Matrix& aMaskTransform)
+{
+  PushGroup(content);
+  CurrentState().mBlendOpacity = aOpacity;
+  CurrentState().mBlendMask = aMask;
+  CurrentState().mWasPushedForBlendBack = true;
+  CurrentState().mBlendMaskTransform = aMaskTransform;
+}
+
 static gfxRect
 GetRoundOutDeviceClipExtents(gfxContext* aCtx)
 {
@@ -1004,6 +1014,33 @@ gfxContext::PopGroupToSource()
   CurrentState().surfTransform = mat;
 }
 
+void
+gfxContext::PopGroupAndBlend()
+{
+  MOZ_ASSERT(CurrentState().mWasPushedForBlendBack);
+  Float opacity = CurrentState().mBlendOpacity;
+  RefPtr<SourceSurface> mask = CurrentState().mBlendMask;
+  Matrix maskTransform = CurrentState().mBlendMaskTransform;
+
+  PopGroupToSource();
+
+  CompositionOp oldOp = GetOp();
+  SetOp(CompositionOp::OP_OVER);
+
+  if (mask) {
+    if (!maskTransform.HasNonTranslation()) {
+      Mask(mask, opacity, Point(maskTransform._31, maskTransform._32));
+    } else {
+      MOZ_ASSERT(opacity == 1.0f);
+      Mask(mask, maskTransform);
+    }
+  } else {
+    Paint(opacity);
+  }
+
+  SetOp(oldOp);
+}
+
 #ifdef MOZ_DUMP_PAINTING
 void
 gfxContext::WriteAsPNG(const char* aFile)

gfx/thebes/gfxContext.h

@@ -431,6 +431,11 @@ public:
      * Groups
      */
     void PushGroup(gfxContentType content = gfxContentType::COLOR);
+
+    void PushGroupForBlendBack(gfxContentType content, mozilla::gfx::Float aOpacity = 1.0f,
+                               mozilla::gfx::SourceSurface* aMask = nullptr,
+                               const mozilla::gfx::Matrix& aMaskTransform = mozilla::gfx::Matrix());
+
     /**
      * Like PushGroup, but if the current surface is gfxContentType::COLOR and
      * content is gfxContentType::COLOR_ALPHA, makes the pushed surface gfxContentType::COLOR
@@ -445,6 +450,7 @@ public:
     void PushGroupAndCopyBackground(gfxContentType content = gfxContentType::COLOR);
     already_AddRefed<gfxPattern> PopGroup();
     void PopGroupToSource();
+    void PopGroupAndBlend();
 
     already_AddRefed<mozilla::gfx::SourceSurface>
     PopGroupToSurface(mozilla::gfx::Matrix* aMatrix);
@@ -527,6 +533,11 @@ private:
     Color fontSmoothingBackgroundColor;
     // This is used solely for using minimal intermediate surface size.
     mozilla::gfx::Point deviceOffset;
+    // Support groups
+    mozilla::gfx::Float mBlendOpacity;
+    RefPtr<SourceSurface> mBlendMask;
+    Matrix mBlendMaskTransform;
+    mozilla::DebugOnly<bool> mWasPushedForBlendBack;
   };
 
   // This ensures mPath contains a valid path (in user space!)