Optionally clear PlatformCanvas instances.

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_
 #pragma once
 
 // The platform-specific device will include the necessary platform headers
 // to get the surface type.
 #include "skia/ext/platform_device.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 
 namespace skia {
 
 // This class is a specialization of the regular SkCanvas that is designed to
 // work with a PlatformDevice to manage platform-specific drawing. It allows
 // using both Skia operations and platform-specific operations.
 class SK_API PlatformCanvas : public SkCanvas {
  public:
   // If you use the version with no arguments, you MUST call initialize()
   PlatformCanvas();
-  // Set is_opaque if you are going to erase the bitmap and not use
+  // Set flags to FLAGS_OPAQUE  if you are going to erase the bitmap and not use
   // transparency: this will enable some optimizations.
-  PlatformCanvas(int width, int height, bool is_opaque);
+  // Set flags to FLAGS_INITIALIZED if the canvas should be initialized to 0.
+  PlatformCanvas(int width, int height, int flags);
 
 #if defined(WIN32)
   // The shared_section parameter is passed to gfx::PlatformDevice::create.
   // See it for details.
-  PlatformCanvas(int width, int height, bool is_opaque, HANDLE shared_section);
+  PlatformCanvas(int width, int height, int flags, HANDLE shared_section);
 #elif defined(__APPLE__)
-  PlatformCanvas(int width, int height, bool is_opaque,
-                 CGContextRef context);
-  PlatformCanvas(int width, int height, bool is_opaque, uint8_t* context);
+  PlatformCanvas(int width, int height, int flags, CGContextRef context);
+  PlatformCanvas(int width, int height, int flags, uint8_t* context);
 #elif defined(__linux__) || defined(__FreeBSD__) || defined(__OpenBSD__) || \
       defined(__sun) || defined(ANDROID)
   // Linux ---------------------------------------------------------------------
 
   // Construct a canvas from the given memory region. The memory is not cleared
   // first. @data must be, at least, @height * StrideForWidth(@width) bytes.
-  PlatformCanvas(int width, int height, bool is_opaque, uint8_t* data);
+  PlatformCanvas(int width, int height, int flags, uint8_t* data);
 #endif
 
   virtual ~PlatformCanvas();
 
 #if defined(WIN32)
   // For two-part init, call if you use the no-argument constructor above. Note
   // that we want this to optionally match the Linux initialize if you only
   // pass 3 arguments, hence the evil default argument.
-  bool initialize(int width, int height, bool is_opaque,
+  bool initialize(int width, int height, int flags,
                   HANDLE shared_section = NULL);
 #elif defined(__APPLE__)
   // For two-part init, call if you use the no-argument constructor above
-  bool initialize(CGContextRef context, int width, int height, bool is_opaque);
-  bool initialize(int width, int height, bool is_opaque, uint8_t* data = NULL);
+  bool initialize(CGContextRef context, int width, int height, int flags);
+  bool initialize(int width, int height, int flags, uint8_t* data = NULL);
 
 #elif defined(__linux__) || defined(__FreeBSD__) || defined(__OpenBSD__) || \
       defined(__sun) || defined(ANDROID)
   // For two-part init, call if you use the no-argument constructor above
-  bool initialize(int width, int height, bool is_opaque, uint8_t* data = NULL);
+  bool initialize(int width, int height, int flags, uint8_t* data = NULL);
 #endif
 
   // Shared --------------------------------------------------------------------
 
   // Return the stride (length of a line in bytes) for the given width. Because
   // we use 32-bits per pixel, this will be roughly 4*width. However, for
   // alignment reasons we may wish to increase that.
   static size_t StrideForWidth(unsigned width);
 
   // Allow callers to see the non-virtual function even though we have an
@@ skipping 31 matching lines @@
 //
 // Danger: the resulting device should not be saved. It will be invalidated
 // by the next call to save() or restore().
 SK_API SkDevice* GetTopDevice(const SkCanvas& canvas);
 
 // Creates a canvas with raster bitmap backing.
 // Set is_opaque if you are going to erase the bitmap and not use
 // transparency: this will enable some optimizations.
 SK_API SkCanvas* CreateBitmapCanvas(int width, int height, bool is_opaque);
 
+// Creates a canvas with raster bitmap backing.
+// Set flags to FLAGS_OPAQUE  if you are going to erase the bitmap and not use
+// transparency: this will enable some optimizations.
+// Set flags to FLAGS_INITIALIZED if the canvas should be initialized to 0.
+SK_API SkCanvas* CreateBitmapCanvas(int width, int height, int flags);
+
 // Non-crashing version of CreateBitmapCanvas
 // returns NULL if allocation fails for any reason.
 // Use this instead of CreateBitmapCanvas in places that are likely to
 // attempt to allocate very large canvases (therefore likely to fail),
 // and where it is possible to recover gracefully from the failed allocation.
 SK_API SkCanvas* TryCreateBitmapCanvas(int width, int height, bool is_opaque);
+SK_API SkCanvas* TryCreateBitmapCanvas(int width, int height, int flags);
 
 // 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);
 
 // Draws into the a native platform surface, |context|.  Forwards to
 // DrawToNativeContext on a PlatformDevice instance bound to the top device.
 // If no PlatformDevice instance is bound, is a no-operation.
 SK_API void DrawToNativeContext(SkCanvas* canvas, PlatformSurface context,
@@ skipping 28 matching lines @@
   PlatformSurface platform_surface_;
 
   // Disallow copy and assign
   ScopedPlatformPaint(const ScopedPlatformPaint&);
   ScopedPlatformPaint& operator=(const ScopedPlatformPaint&);
 };
 
 }  // namespace skia
 
 #endif  // SKIA_EXT_PLATFORM_CANVAS_H_