Revert of Delete Mac & Cairo skia::BitmapPlatformDevice impls

skia/ext/bitmap_platform_device_cairo.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 SKIA_EXT_BITMAP_PLATFORM_DEVICE_CAIRO_H_
+#define SKIA_EXT_BITMAP_PLATFORM_DEVICE_CAIRO_H_
+
+#include <stdint.h>
+
+#include "base/compiler_specific.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "skia/ext/platform_device.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 skia {
+
+// -----------------------------------------------------------------------------
+// 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 BitmapPlatformDevice : public SkBitmapDevice, public PlatformDevice {
+ public:
+  // 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 @cairo.
+  BitmapPlatformDevice(const SkBitmap& other, cairo_t* cairo);
+  ~BitmapPlatformDevice() override;
+
+  // Constructs a device with size |width| * |height| with contents initialized
+  // to zero. |is_opaque| should be set if the caller knows the bitmap will be
+  // completely opaque and allows some optimizations.
+  static BitmapPlatformDevice* Create(int width, int height, bool is_opaque);
+
+  // This doesn't take ownership of |data|. If |data| is NULL, the contents
+  // of the device are initialized to 0.
+  static BitmapPlatformDevice* Create(int width, int height, bool is_opaque,
+                                      uint8_t* data);
+
+ protected:
+  SkBaseDevice* onCreateDevice(const CreateInfo&, const SkPaint*) override;
+
+ private:
+  // Overridden from PlatformDevice:
+  cairo_t* BeginPlatformPaint(const SkMatrix& transform,
+                              const SkIRect& clip_bounds) override;
+
+  static BitmapPlatformDevice* Create(int width, int height, bool is_opaque,
+                                      cairo_surface_t* surface);
+
+  // Loads the current transform and clip into the context.
+  void LoadConfig(const SkMatrix& transform, const SkIRect& clip_bounds);
+
+  // Graphics context used to draw into the surface.
+  cairo_t* cairo_;
+
+  DISALLOW_COPY_AND_ASSIGN(BitmapPlatformDevice);
+};
+
+}  // namespace skia
+
+#endif  // SKIA_EXT_BITMAP_PLATFORM_DEVICE_CAIRO_H_