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| 1 // Copyright 2013 The Chromium Authors. All rights reserved. |
| 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. |
| 4 |
| 5 #ifndef SKIA_EXT_BITMAP_PLATFORM_DEVICE_CAIRO_H_ |
| 6 #define SKIA_EXT_BITMAP_PLATFORM_DEVICE_CAIRO_H_ |
| 7 |
| 8 #include <stdint.h> |
| 9 |
| 10 #include "base/compiler_specific.h" |
| 11 #include "base/macros.h" |
| 12 #include "base/memory/ref_counted.h" |
| 13 #include "skia/ext/platform_device.h" |
| 14 |
| 15 typedef struct _cairo_surface cairo_surface_t; |
| 16 |
| 17 // ----------------------------------------------------------------------------- |
| 18 // Image byte ordering on Linux: |
| 19 // |
| 20 // Pixels are packed into 32-bit words these days. Even for 24-bit images, |
| 21 // often 8-bits will be left unused for alignment reasons. Thus, when you see |
| 22 // ARGB as the byte order you have to wonder if that's in memory order or |
| 23 // little-endian order. Here I'll write A.R.G.B to specifiy the memory order. |
| 24 // |
| 25 // GdkPixbuf's provide a nice backing store and defaults to R.G.B.A order. |
| 26 // They'll do the needed byte swapping to match the X server when drawn. |
| 27 // |
| 28 // Skia can be controled in skia/include/corecg/SkUserConfig.h (see bits about |
| 29 // SK_R32_SHIFT). For Linux we define it to be ARGB in registers. For little |
| 30 // endian machines that means B.G.R.A in memory. |
| 31 // |
| 32 // The image loaders are controlled in |
| 33 // webkit/port/platform/image-decoders/ImageDecoder.h (see setRGBA). These are |
| 34 // also configured for ARGB in registers. |
| 35 // |
| 36 // Cairo's only 32-bit mode is ARGB in registers. |
| 37 // |
| 38 // X servers commonly have a 32-bit visual with xRGB in registers (since they |
| 39 // typically don't do alpha blending of drawables at the user level. Composite |
| 40 // extensions aside.) |
| 41 // |
| 42 // We don't use GdkPixbuf because its byte order differs from the rest. Most |
| 43 // importantly, it differs from Cairo which, being a system library, is |
| 44 // something that we can't easily change. |
| 45 // ----------------------------------------------------------------------------- |
| 46 |
| 47 namespace skia { |
| 48 |
| 49 // ----------------------------------------------------------------------------- |
| 50 // This is the Linux bitmap backing for Skia. We create a Cairo image surface |
| 51 // to store the backing buffer. This buffer is BGRA in memory (on little-endian |
| 52 // machines). |
| 53 // |
| 54 // For now we are also using Cairo to paint to the Drawables so we provide an |
| 55 // accessor for getting the surface. |
| 56 // |
| 57 // This is all quite ok for test_shell. In the future we will want to use |
| 58 // shared memory between the renderer and the main process at least. In this |
| 59 // case we'll probably create the buffer from a precreated region of memory. |
| 60 // ----------------------------------------------------------------------------- |
| 61 class BitmapPlatformDevice : public SkBitmapDevice, public PlatformDevice { |
| 62 public: |
| 63 // Create a BitmapPlatformDeviceLinux from an already constructed bitmap; |
| 64 // you should probably be using Create(). This may become private later if |
| 65 // we ever have to share state between some native drawing UI and Skia, like |
| 66 // the Windows and Mac versions of this class do. |
| 67 // |
| 68 // This object takes ownership of @cairo. |
| 69 BitmapPlatformDevice(const SkBitmap& other, cairo_t* cairo); |
| 70 ~BitmapPlatformDevice() override; |
| 71 |
| 72 // Constructs a device with size |width| * |height| with contents initialized |
| 73 // to zero. |is_opaque| should be set if the caller knows the bitmap will be |
| 74 // completely opaque and allows some optimizations. |
| 75 static BitmapPlatformDevice* Create(int width, int height, bool is_opaque); |
| 76 |
| 77 // This doesn't take ownership of |data|. If |data| is NULL, the contents |
| 78 // of the device are initialized to 0. |
| 79 static BitmapPlatformDevice* Create(int width, int height, bool is_opaque, |
| 80 uint8_t* data); |
| 81 |
| 82 protected: |
| 83 SkBaseDevice* onCreateDevice(const CreateInfo&, const SkPaint*) override; |
| 84 |
| 85 private: |
| 86 // Overridden from PlatformDevice: |
| 87 cairo_t* BeginPlatformPaint(const SkMatrix& transform, |
| 88 const SkIRect& clip_bounds) override; |
| 89 |
| 90 static BitmapPlatformDevice* Create(int width, int height, bool is_opaque, |
| 91 cairo_surface_t* surface); |
| 92 |
| 93 // Loads the current transform and clip into the context. |
| 94 void LoadConfig(const SkMatrix& transform, const SkIRect& clip_bounds); |
| 95 |
| 96 // Graphics context used to draw into the surface. |
| 97 cairo_t* cairo_; |
| 98 |
| 99 DISALLOW_COPY_AND_ASSIGN(BitmapPlatformDevice); |
| 100 }; |
| 101 |
| 102 } // namespace skia |
| 103 |
| 104 #endif // SKIA_EXT_BITMAP_PLATFORM_DEVICE_CAIRO_H_ |
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