android_webview: changes to support Android GraphicBuffers

ui/gl/pixel_buffer.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 UI_GL_PIXEL_BUFFER_H_
+#define UI_GL_PIXEL_BUFFER_H_
+
+#include "base/basictypes.h"
+#include "base/callback.h"
+#include "base/memory/scoped_ptr.h"
+
+namespace gfx {
+class Size;
+
+// Interface for creating and accessing a zero-copy buffer such as GraphicBuffer
+// of Android framework.

[joth, 2013/04/04 21:53:34]

comment should be generalized. 
(could note the design evolved from a generalization of the GB API on android)

[kaanb, 2013/04/04 22:26:18]

Done.

+//
+// THREADING CONSIDERATIONS:

[joth, 2013/04/04 21:53:34]

also mention about the other non-mapping methods - are they OK to use on
multiple threads?

[kaanb, 2013/04/04 22:26:18]

Done.

+//
+// It is legal for several different threads to lock a buffer from
+// read access, none of the threads are blocked.

[joth, 2013/04/04 21:53:34]

remove - there is no read access now.

[kaanb, 2013/04/04 22:26:18]

Done.

+// However, locking a buffer simultaneously for write or read/write is
+// undefined, but:
+// - shall not result in termination of the process
+// - shall not block the caller

[joth, 2013/04/04 21:53:34]

This comment is too directed to the implementer, and we can't require other
platforms to confirm to this.

I'd say "Mapping a buffer simultaneously on multiple threads is undefined, and
not allowed"

also, Lock -> Map.

[kaanb, 2013/04/04 22:26:18]

I've somewhat modified your suggestion, PTAL.

+// It is acceptable to return an error or to leave the buffer's content
+// into an indeterminate state.

[joth, 2013/04/04 21:53:34]

? this is a comment to the implementer, not the user, and there's no error path
now?

[kaanb, 2013/04/04 22:26:18]

Removed

+class PixelBuffer {
+ public:
+  // The factory is set by the ContentRendererClient::GetPixelBufferFactory()
+  // method.
+  typedef base::Callback<scoped_ptr<gfx::PixelBuffer>(gfx::Size)> Create;
+
+  virtual ~PixelBuffer() {}
+
+  // Maps the buffer so the client can write the bitmap data in |*vaddr|
+  // subsequently. This call may block, for instance if the h/w needs
+  // to finish rendering or if CPU caches need to be synchronized.
+  virtual void MapForWrite(void** vaddr) = 0;
+
+  // Unmaps the buffer. Called after all changes to the buffer are
+  // completed.
+  virtual void Unmap() = 0;
+
+  // Returns the native pointer for the graphic buffer.
+  virtual void* GetNativeBuffer() = 0;
+
+  // Returns the stride for the graphic buffer.

[joth, 2013/04/04 21:53:34]

in pixels or bytes?

[kaanb, 2013/04/04 22:26:18]

pixels. Clarified the comment.

+  virtual uint32 GetStride() = 0;
+};
+
+}  // namespace gfx
+
+#endif  // UI_GL_PIXEL_BUFFER_H_