Limit manual control of platform painting

skia/ext/platform_canvas.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 SKIA_EXT_PLATFORM_CANVAS_H_
 #define SKIA_EXT_PLATFORM_CANVAS_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 127 matching lines @@
 // Returns false on failure: if either argument is nullptr, or if the
 // pixels can not be retrieved from the canvas. In the latter case resets
 // the pixmap to empty.
 SK_API bool GetWritablePixels(SkCanvas* canvas, SkPixmap* pixmap);
 
 // Returns true if native platform routines can be used to draw on the
 // given canvas. If this function returns false, BeginPlatformPaint will
 // return NULL PlatformSurface.
 SK_API bool SupportsPlatformPaint(const SkCanvas* canvas);
 
-// These calls should surround calls to platform drawing routines, the
-// surface returned here can be used with the native platform routines.
-//
-// Call EndPlatformPaint when you are done and want to use skia operations
-// after calling the platform-specific BeginPlatformPaint; this will
-// synchronize the bitmap to OS if necessary.
-SK_API PlatformSurface BeginPlatformPaint(SkCanvas* canvas);
-SK_API void EndPlatformPaint(SkCanvas* canvas);
-
-// Helper class for pairing calls to BeginPlatformPaint and EndPlatformPaint.
-// Upon construction invokes BeginPlatformPaint, and upon destruction invokes
-// EndPlatformPaint.
+// This object guards calls to platform drawing routines. The surface
+// returned from GetPlatformSurface() can be used with the native platform
+// routines.
 class SK_API ScopedPlatformPaint {
  public:
-  explicit ScopedPlatformPaint(SkCanvas* canvas) : canvas_(canvas) {
-    platform_surface_ = BeginPlatformPaint(canvas);
-  }
-  ~ScopedPlatformPaint() { EndPlatformPaint(canvas_); }
+  explicit ScopedPlatformPaint(SkCanvas* canvas);
+  ~ScopedPlatformPaint();

[f(malita), 2016/03/29 17:31:08]

Nit: dtor no longer needed?

[tomhudson, 2016/03/29 17:47:32]

Done.

 
   // Returns the PlatformSurface to use for native platform drawing calls.
-  PlatformSurface GetPlatformSurface() { return platform_surface_; }
+  PlatformSurface GetPlatformSurface();

[f(malita), 2016/03/29 17:31:08]

Nit: this is trivial enough to keep inline.

[tomhudson, 2016/03/29 17:47:32]

I expect to change this soon enough that I wanted to move it out of the header,
but OK.

+
  private:
   SkCanvas* canvas_;
   PlatformSurface platform_surface_;
 
   // Disallow copy and assign
   ScopedPlatformPaint(const ScopedPlatformPaint&);
   ScopedPlatformPaint& operator=(const ScopedPlatformPaint&);
 };
 
 // Following routines are used in print preview workflow to mark the
 // preview metafile.
 SK_API SkMetaData& GetMetaData(const SkCanvas& canvas);
 
 #if defined(OS_MACOSX)
 SK_API void SetIsPreviewMetafile(const SkCanvas& canvas, bool is_preview);
 SK_API bool IsPreviewMetafile(const SkCanvas& canvas);
 
 // Returns the CGContext that backing the SkCanvas.
 // Returns NULL if none is bound.
 SK_API CGContextRef GetBitmapContext(const SkCanvas& canvas);
 #endif
 
 }  // namespace skia
 
 #endif  // SKIA_EXT_PLATFORM_CANVAS_H_