Limit manual control of platform painting

skia/ext/bitmap_platform_device_cairo.h

 // Copyright 2013 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_CAIRO_H_
 #define SKIA_EXT_BITMAP_PLATFORM_DEVICE_CAIRO_H_
 
 #include <stdint.h>
 
 #include "base/compiler_specific.h"
@@ skipping 28 matching lines @@
 // typically don't do alpha blending of drawables at the user level. Composite
 // extensions aside.)
 //
 // We don't use GdkPixbuf because its byte order differs from the rest. Most
 // importantly, it differs from Cairo which, being a system library, is
 // something that we can't easily change.
 // -----------------------------------------------------------------------------
 
 namespace skia {
 
+class ScopedPlatformPaint;
+
 // -----------------------------------------------------------------------------
 // This is the Linux bitmap backing for Skia. We create a Cairo image surface
 // to store the backing buffer. This buffer is BGRA in memory (on little-endian
 // machines).
 //
 // For now we are also using Cairo to paint to the Drawables so we provide an
 // accessor for getting the surface.
 //
 // This is all quite ok for test_shell. In the future we will want to use
 // shared memory between the renderer and the main process at least. In this
@@ skipping 18 matching lines @@
   // This doesn't take ownership of |data|. If |data| is NULL, the contents
   // of the device are initialized to 0.
   static BitmapPlatformDevice* Create(int width, int height, bool is_opaque,
                                       uint8_t* data);
 
   // Overridden from SkBaseDevice:
   void setMatrixClip(const SkMatrix& transform,
                      const SkRegion& region,
                      const SkClipStack&) override;
 
-  // Overridden from PlatformDevice:
-  cairo_t* BeginPlatformPaint() override;
-
  protected:
   SkBaseDevice* onCreateDevice(const CreateInfo&, const SkPaint*) override;
 
  private:
+  // Overridden from PlatformDevice:
+  cairo_t* BeginPlatformPaint() override;
+
   static BitmapPlatformDevice* Create(int width, int height, bool is_opaque,
                                       cairo_surface_t* surface);
 
   // Sets the transform and clip operations. This will not update the Cairo
   // context, 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.
   void LoadConfig();
 
   // Graphics context used to draw into the surface.
   cairo_t* cairo_;
 
   // True when there is a transform or clip that has not been set to the
   // context.  The context is retrieved for every text operation, and the
   // transform and clip do not change as much. We can save time by not loading
   // the clip and transform for every one.
   bool config_dirty_;
 
   // Translation assigned to the context: we need to keep track of this
   // separately so it can be updated even if the context isn't created yet.
   SkMatrix transform_;
 
   // The current clipping
   SkRegion clip_region_;
 
   DISALLOW_COPY_AND_ASSIGN(BitmapPlatformDevice);
+  friend class ScopedPlatformPaint;
 };
 
 }  // namespace skia
 
 #endif  // SKIA_EXT_BITMAP_PLATFORM_DEVICE_CAIRO_H_