Limit manual control of platform painting

skia/ext/platform_device.h

 // Copyright (c) 2012 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 SKIA_EXT_PLATFORM_DEVICE_H_
 #define SKIA_EXT_PLATFORM_DEVICE_H_
 
 #include "build/build_config.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #include <vector>
 #endif
 
+#include "skia/ext/platform_canvas.h"
 #include "skia/ext/platform_surface.h"
 #include "third_party/skia/include/core/SkBitmapDevice.h"
 #include "third_party/skia/include/core/SkTypes.h"
 
 class SkMatrix;
 class SkPath;
 class SkRegion;
 
 namespace skia {
 
@@ skipping 29 matching lines @@
  public:
   virtual ~PlatformDevice() {}
 
 #if defined(OS_MACOSX)
   // The CGContext that corresponds to the bitmap, used for CoreGraphics
   // operations drawing into the bitmap. This is possibly heavyweight, so it
   // should exist only during one pass of rendering.
   virtual CGContextRef GetBitmapContext() = 0;
 #endif
 
-  // The DC that corresponds to the bitmap, used for GDI operations drawing
-  // into the bitmap. This is possibly heavyweight, so it should be existant
-  // only during one pass of rendering.
-  virtual PlatformSurface BeginPlatformPaint();
-
-  // Finish a previous call to beginPlatformPaint.
-  virtual void EndPlatformPaint();
-
 #if defined(OS_WIN)
   // Loads a SkPath into the GDI context. The path can there after be used for
   // clipping or as a stroke. Returns false if the path failed to be loaded.
   static bool LoadPathToDC(HDC context, const SkPath& path);
 
   // Loads a SkRegion into the GDI context.
   static void LoadClippingRegionToDC(HDC context, const SkRegion& region,
                                      const SkMatrix& transformation);
 
   // Draws to the given screen DC, if the bitmap DC doesn't exist, this will
   // temporarily create it. However, if you have created the bitmap DC, it will
   // be more efficient if you don't free it until after this call so it doesn't
   // have to be created twice.  If src_rect is null, then the entirety of the
   // source device will be copied.
   virtual void DrawToHDC(HDC, int x, int y, const RECT* src_rect);
 #endif
 
  protected:
+  // The DC that corresponds to the bitmap, used for GDI operations drawing
+  // into the bitmap. This is possibly heavyweight, so it should be existant
+  // only during one pass of rendering.
+  virtual PlatformSurface BeginPlatformPaint();
+
 #if defined(OS_WIN)
   // Arrays must be inside structures.
   struct CubicPoints {
     SkPoint p[4];
   };
   typedef std::vector<CubicPoints> CubicPath;
   typedef std::vector<CubicPath> CubicPaths;
 
   // Loads the specified Skia transform into the device context, excluding
   // perspective (which GDI doesn't support).
   static void LoadTransformToDC(HDC dc, const SkMatrix& matrix);
 
   // Transforms SkPath's paths into a series of cubic path.
   static bool SkPathToCubicPaths(CubicPaths* paths, const SkPath& skpath);
 #endif
+
+  friend class skia::ScopedPlatformPaint;
 };
 
 }  // namespace skia
 
 #endif  // SKIA_EXT_PLATFORM_DEVICE_H_