Limit manual control of platform painting

skia/ext/bitmap_platform_device_win.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_BITMAP_PLATFORM_DEVICE_WIN_H_
 #define SKIA_EXT_BITMAP_PLATFORM_DEVICE_WIN_H_
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "skia/ext/platform_device.h"
 #include "skia/ext/refptr.h"
 
 namespace skia {
 
+class ScopedPlatformPaint;
+
 // A device is basically a wrapper around SkBitmap that provides a surface for
 // SkCanvas to draw into. Our device provides a surface Windows can also write
 // to. BitmapPlatformDevice creates a bitmap using CreateDIBSection() in a
 // format that Skia supports and can then use this to draw ClearType into, etc.
 // This pixel data is provided to the bitmap that the device contains so that it
 // can be shared.
 class SK_API BitmapPlatformDevice : public SkBitmapDevice, public PlatformDevice {
  public:
   // Factory function. is_opaque should be set if the caller knows the bitmap
   // will be completely opaque and allows some optimizations.
   //
   // The |shared_section| parameter is optional (pass NULL for default
   // behavior). If |shared_section| is non-null, then it must be a handle to a
   // file-mapping object returned by CreateFileMapping.  See CreateDIBSection
   // for details. If |shared_section| is null, the bitmap backing store is not
   // initialized.
   static BitmapPlatformDevice* Create(int width, int height,
                                       bool is_opaque, HANDLE shared_section,
                                       bool do_clear = false);
 
   // Create a BitmapPlatformDevice with no shared section. The bitmap is not
   // initialized to 0.
   static BitmapPlatformDevice* Create(int width, int height, bool is_opaque);
 
   ~BitmapPlatformDevice() override;
 
-  // PlatformDevice overrides
-  // Retrieves the bitmap DC, which is the memory DC for our bitmap data. The
-  // bitmap DC is lazy created.
-  PlatformSurface BeginPlatformPaint() override;
-  void EndPlatformPaint() override;
-
-  // Loads the given transform and clipping region into the HDC. This is
-  // overridden from SkBaseDevice.
+  // Loads (lazily) the given transform and clipping region into the HDC. This
+  // is overridden from SkBaseDevice, where it is deprecated.
   void setMatrixClip(const SkMatrix& transform,
                      const SkRegion& region,
                      const SkClipStack&) override;
 
   void DrawToHDC(HDC dc, int x, int y, const RECT* src_rect) override;
 
  protected:
   // Flushes the Windows device context so that the pixel data can be accessed
   // directly by Skia. Overridden from SkBaseDevice, this is called when Skia
   // starts accessing pixel data.
   const SkBitmap& onAccessBitmap() override;
 
   SkBaseDevice* onCreateDevice(const CreateInfo&, const SkPaint*) override;
 
  private:
+  // PlatformDevice override
+  // Retrieves the bitmap DC, which is the memory DC for our bitmap data. The
+  // bitmap DC may be lazily created.
+  PlatformSurface BeginPlatformPaint() override;
+
   // Private constructor.
   BitmapPlatformDevice(HBITMAP hbitmap, const SkBitmap& bitmap);
 
   // Bitmap into which the drawing will be done. This bitmap not owned by this
   // class, but by the BitmapPlatformPixelRef inside the device's SkBitmap.
   // It's only stored here in order to lazy-create the DC (below).
   HBITMAP hbitmap_;
 
   // Previous bitmap held by the DC. This will be selected back before the
   // DC is destroyed.
@@ skipping 22 matching lines @@
 
   // Sets the transform and clip operations. This will not update the DC,
   // but will mark the config as dirty. The next call of LoadConfig will
   // pick up these changes.
   void SetMatrixClip(const SkMatrix& transform, const SkRegion& region);
 
   // Loads the current transform and clip into the context. Can be called even
   // when |hbitmap_| is NULL (will be a NOP).
   void LoadConfig();
 
-#ifdef SK_DEBUG
-  int begin_paint_count_;
-#endif
-
   DISALLOW_COPY_AND_ASSIGN(BitmapPlatformDevice);
+  friend class ScopedPlatformPaint;
 };
 
 }  // namespace skia
 
 #endif  // SKIA_EXT_BITMAP_PLATFORM_DEVICE_WIN_H_