Allow CanvasSkia to bind to an existing SkCanvas.

ui/gfx/canvas_skia.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_GFX_CANVAS_SKIA_H_
 #define UI_GFX_CANVAS_SKIA_H_
 #pragma once
 
 #include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/string16.h"
 #include "skia/ext/platform_canvas.h"
 #include "ui/gfx/canvas.h"
 
 #if defined(TOOLKIT_USES_GTK)
 typedef struct _GdkPixbuf GdkPixbuf;
 #endif
 
 namespace gfx {
 
 class Canvas;
 
 // CanvasSkia is a SkCanvas subclass that provides a number of methods for
 // common operations used throughout an application built using base/gfx and
 // app/gfx.
 //
 // All methods that take integer arguments (as is used throughout views)
 // end with Int. If you need to use methods provided by the superclass
 // you'll need to do a conversion. In particular you'll need to use
 // macro SkIntToScalar(xxx), or if converting from a scalar to an integer
 // SkScalarRound.
 //
 // A handful of methods in this class are overloaded providing an additional
 // argument of type SkXfermode::Mode. SkXfermode::Mode specifies how the
 // source and destination colors are combined. Unless otherwise specified,
 // the variant that does not take a SkXfermode::Mode uses a transfer mode
 // of kSrcOver_Mode.
-class UI_EXPORT CanvasSkia : public skia::PlatformCanvas, public Canvas {
+class UI_EXPORT CanvasSkia : public Canvas {
  public:
   enum TruncateFadeMode {
     TruncateFadeTail,
     TruncateFadeHead,
     TruncateFadeHeadAndTail,
   };
 
   // Creates an empty Canvas. Callers must use initialize before using the
   // canvas.
   CanvasSkia();
 
   CanvasSkia(int width, int height, bool is_opaque);
+  explicit CanvasSkia(SkCanvas* canvas);
 
   virtual ~CanvasSkia();
 
   // Compute the size required to draw some text with the provided font.
   // Attempts to fit the text with the provided width and height. Increases
   // height and then width as needed to make the text fit. This method
   // supports multiple lines.
   static void SizeStringInt(const string16& text,
                             const gfx::Font& font,
                             int* width, int* height,
@@ skipping 96 matching lines @@
                             int src_x, int src_y,
                             int dest_x, int dest_y, int w, int h);
   virtual gfx::NativeDrawingContext BeginPlatformPaint();
   virtual void EndPlatformPaint();
 #if !defined(OS_MACOSX)
   virtual void Transform(const ui::Transform& transform);
 #endif
   virtual ui::TextureID GetTextureID();
   virtual CanvasSkia* AsCanvasSkia();
   virtual const CanvasSkia* AsCanvasSkia() const;
+  virtual SkCanvas* GetSkCanvas();
+  virtual const SkCanvas* GetSkCanvas() const;
+  SkCanvas* sk_canvas() const { return canvas_; }
+  skia::PlatformCanvas* platform_canvas() const { return owned_canvas_.get(); }
 
  private:
   // Test whether the provided rectangle intersects the current clip rect.
   bool IntersectsClipRectInt(int x, int y, int w, int h);
 
 #if defined(OS_WIN)
   // Draws text with the specified color, font and location. The text is
   // aligned to the left, vertically centered, clipped to the region. If the
   // text is too big, it is truncated and '...' is added to the end.
   void DrawStringInt(const string16& text,
                      HFONT font,
                      const SkColor& color,
                      int x, int y, int w, int h,
                      int flags);
 #endif
 
+  scoped_ptr<skia::PlatformCanvas> owned_canvas_;
+  SkCanvas* canvas_;
   DISALLOW_COPY_AND_ASSIGN(CanvasSkia);
 };
 
 }  // namespace gfx;
 
 #endif  // UI_GFX_CANVAS_SKIA_H_