diff -r 000000000000 -r 6474c204b198 gfx/2d/DrawTargetDual.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gfx/2d/DrawTargetDual.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,164 @@
+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+  * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+     
+#ifndef MOZILLA_GFX_DRAWTARGETDUAL_H_
+#define MOZILLA_GFX_DRAWTARGETDUAL_H_
+     
+#include <vector>
+#include <sstream>
+
+#include "SourceSurfaceDual.h"
+     
+#include "2D.h"
+#include "Filters.h"
+     
+namespace mozilla {
+namespace gfx {
+     
+#define FORWARD_FUNCTION(funcName) \
+  virtual void funcName() { mA->funcName(); mB->funcName(); }
+#define FORWARD_FUNCTION1(funcName, var1Type, var1Name) \
+  virtual void funcName(var1Type var1Name) { mA->funcName(var1Name); mB->funcName(var1Name); }
+
+/* This is a special type of DrawTarget. It duplicates all drawing calls
+ * accross two drawtargets. An exception to this is when a snapshot of another
+ * dual DrawTarget is used as the source for any surface data. In this case
+ * the snapshot of the first source DrawTarget is used as a source for the call
+ * to the first destination DrawTarget (mA) and the snapshot of the second
+ * source DrawTarget is used at the source for the second destination
+ * DrawTarget (mB). This class facilitates black-background/white-background
+ * drawing for per-component alpha extraction for backends which do not support
+ * native component alpha.
+ */
+class DrawTargetDual : public DrawTarget
+{
+public:
+  MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(DrawTargetDual)
+  DrawTargetDual(DrawTarget *aA, DrawTarget *aB)
+    : mA(aA)
+    , mB(aB)
+  { 
+    mFormat = aA->GetFormat();
+  }
+     
+  virtual BackendType GetType() const { return mA->GetType(); }
+  virtual TemporaryRef<SourceSurface> Snapshot() { return new SourceSurfaceDual(mA, mB); }
+  virtual IntSize GetSize() { return mA->GetSize(); }
+     
+  FORWARD_FUNCTION(Flush)
+  FORWARD_FUNCTION1(PushClip, const Path *, aPath)
+  FORWARD_FUNCTION1(PushClipRect, const Rect &, aRect)
+  FORWARD_FUNCTION(PopClip)
+  FORWARD_FUNCTION1(ClearRect, const Rect &, aRect)
+
+  virtual void SetTransform(const Matrix &aTransform) {
+    mTransform = aTransform;
+    mA->SetTransform(aTransform);
+    mB->SetTransform(aTransform);
+  }
+
+  virtual void DrawSurface(SourceSurface *aSurface, const Rect &aDest, const Rect & aSource,
+                           const DrawSurfaceOptions &aSurfOptions, const DrawOptions &aOptions);
+
+  virtual void DrawFilter(FilterNode *aNode,
+                          const Rect &aSourceRect,
+                          const Point &aDestPoint,
+                          const DrawOptions &aOptions = DrawOptions())
+  {
+    mA->DrawFilter(aNode, aSourceRect, aDestPoint, aOptions);
+    mB->DrawFilter(aNode, aSourceRect, aDestPoint, aOptions);
+  }
+
+  virtual void MaskSurface(const Pattern &aSource,
+                           SourceSurface *aMask,
+                           Point aOffset,
+                           const DrawOptions &aOptions = DrawOptions());
+
+  virtual void DrawSurfaceWithShadow(SourceSurface *aSurface, const Point &aDest,
+                                     const Color &aColor, const Point &aOffset,
+                                     Float aSigma, CompositionOp aOp);
+
+  virtual void CopySurface(SourceSurface *aSurface, const IntRect &aSourceRect,
+                           const IntPoint &aDestination);
+
+  virtual void FillRect(const Rect &aRect, const Pattern &aPattern, const DrawOptions &aOptions);
+
+  virtual void StrokeRect(const Rect &aRect, const Pattern &aPattern,
+                          const StrokeOptions &aStrokeOptions, const DrawOptions &aOptions);
+
+  virtual void StrokeLine(const Point &aStart, const Point &aEnd, const Pattern &aPattern,
+                          const StrokeOptions &aStrokeOptions, const DrawOptions &aOptions);
+
+  virtual void Stroke(const Path *aPath, const Pattern &aPattern,
+                      const StrokeOptions &aStrokeOptions, const DrawOptions &aOptions);
+
+  virtual void Fill(const Path *aPath, const Pattern &aPattern, const DrawOptions &aOptions);
+
+  virtual void FillGlyphs(ScaledFont *aScaledFont, const GlyphBuffer &aBuffer,
+                          const Pattern &aPattern, const DrawOptions &aOptions,
+                          const GlyphRenderingOptions *aRenderingOptions);
+  
+  virtual void Mask(const Pattern &aSource, const Pattern &aMask, const DrawOptions &aOptions);
+     
+  virtual TemporaryRef<SourceSurface>
+    CreateSourceSurfaceFromData(unsigned char *aData,
+                                const IntSize &aSize,
+                                int32_t aStride,
+                                SurfaceFormat aFormat) const
+  {
+    return mA->CreateSourceSurfaceFromData(aData, aSize, aStride, aFormat);
+  }
+     
+  virtual TemporaryRef<SourceSurface> OptimizeSourceSurface(SourceSurface *aSurface) const
+  {
+    return mA->OptimizeSourceSurface(aSurface);
+  }
+     
+  virtual TemporaryRef<SourceSurface>
+    CreateSourceSurfaceFromNativeSurface(const NativeSurface &aSurface) const
+  {
+    return mA->CreateSourceSurfaceFromNativeSurface(aSurface);
+  }
+     
+  virtual TemporaryRef<DrawTarget>
+    CreateSimilarDrawTarget(const IntSize &aSize, SurfaceFormat aFormat) const;
+     
+  virtual TemporaryRef<PathBuilder> CreatePathBuilder(FillRule aFillRule = FillRule::FILL_WINDING) const
+  {
+    return mA->CreatePathBuilder(aFillRule);
+  }
+     
+  virtual TemporaryRef<GradientStops>
+    CreateGradientStops(GradientStop *aStops,
+                        uint32_t aNumStops,
+                        ExtendMode aExtendMode = ExtendMode::CLAMP) const
+  {
+    return mA->CreateGradientStops(aStops, aNumStops, aExtendMode);
+  }
+
+  virtual TemporaryRef<FilterNode> CreateFilter(FilterType aType)
+  {
+    return mA->CreateFilter(aType);
+  }
+
+  virtual void *GetNativeSurface(NativeSurfaceType aType)
+  {
+    return nullptr;
+  }
+
+  virtual bool IsDualDrawTarget()
+  {
+    return true;
+  }
+     
+private:
+  RefPtr<DrawTarget> mA;
+  RefPtr<DrawTarget> mB;
+};
+     
+}
+}
+     
+#endif /* MOZILLA_GFX_DRAWTARGETDUAL_H_ */