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// Copyright (c) 2006-2008 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 BASE_GFX_BITMAP_PLATFORM_DEVICE_LINUX_H_
#define BASE_GFX_BITMAP_PLATFORM_DEVICE_LINUX_H_
#include "base/gfx/platform_device_linux.h"
#include "base/ref_counted.h"
typedef struct _cairo_surface cairo_surface_t;
// -----------------------------------------------------------------------------
// Image byte ordering on Linux:
//
// Pixels are packed into 32-bit words these days. Even for 24-bit images,
// often 8-bits will be left unused for alignment reasons. Thus, when you see
// ARGB as the byte order you have to wonder if that's in memory order or
// little-endian order. Here I'll write A.R.G.B to specifiy the memory order.
//
// GdkPixbuf's provide a nice backing store and defaults to R.G.B.A order.
// They'll do the needed byte swapping to match the X server when drawn.
//
// Skia can be controled in skia/include/corecg/SkUserConfig.h (see bits about
// SK_R32_SHIFT). For Linux we define it to be ARGB in registers. For little
// endian machines that means B.G.R.A in memory.
//
// The image loaders are controlled in
// webkit/port/platform/image-decoders/ImageDecoder.h (see setRGBA). These are
// also configured for ARGB in registers.
//
// Cairo's only 32-bit mode is ARGB in registers.
//
// X servers commonly have a 32-bit visual with xRGB in registers (since they
// 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 gfx {
// -----------------------------------------------------------------------------
// 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
// case we'll probably create the buffer from a precreated region of memory.
// -----------------------------------------------------------------------------
class BitmapPlatformDeviceLinux : public PlatformDeviceLinux {
public:
/// Static constructor. I don't understand this, it's just a copy of the mac
static BitmapPlatformDeviceLinux* Create(int width, int height,
bool is_opaque);
// Create a BitmapPlatformDeviceLinux from an already constructed bitmap;
// you should probably be using Create(). This may become private later if
// we ever have to share state between some native drawing UI and Skia, like
// the Windows and Mac versions of this class do.
//
// This object takes ownership of @surface.
BitmapPlatformDeviceLinux(const SkBitmap& other, cairo_surface_t* surface);
virtual ~BitmapPlatformDeviceLinux();
// A stub copy constructor. Needs to be properly implemented.
BitmapPlatformDeviceLinux(const BitmapPlatformDeviceLinux& other);
// Bitmaps aren't vector graphics.
virtual bool IsVectorial() { return false; }
cairo_surface_t* surface() const { return surface_; }
private:
cairo_surface_t* surface_;
};
} // namespace gfx
#endif // BASE_GFX_BITMAP_PLATFORM_DEVICE_LINUX_H_
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