Refactor the PlatformContext layer to have only one class.

skia/ext/platform_canvas_linux.h

-// 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 SKIA_EXT_PLATFORM_CANVAS_LINUX_H_
-#define SKIA_EXT_PLATFORM_CANVAS_LINUX_H_
-
-#include <unistd.h>
-
-#include "skia/ext/platform_device_linux.h"
-
-#include <cairo/cairo.h>
-#include <gdk/gdk.h>
-
-namespace skia {
-
-// This class is a specialization of the regular SkCanvas that is designed to
-// work with a gfx::PlatformDevice to manage platform-specific drawing. It
-// allows using both Skia operations and platform-specific operations.
-class PlatformCanvasLinux : public SkCanvas {
- public:
-  // Set is_opaque if you are going to erase the bitmap and not use
-  // tranparency: this will enable some optimizations.  The shared_section
-  // parameter is passed to gfx::PlatformDevice::create.  See it for details.
-  //
-  // If you use the version with no arguments, you MUST call initialize()
-  PlatformCanvasLinux();
-  PlatformCanvasLinux(int width, int height, bool is_opaque);
-  // Construct a canvas from the given memory region. The memory is not cleared
-  // first. @data must be, at least, @height * StrideForWidth(@width) bytes.
-  PlatformCanvasLinux(int width, int height, bool is_opaque, uint8_t* data);
-  virtual ~PlatformCanvasLinux();
-
-  // For two-part init, call if you use the no-argument constructor above
-  bool initialize(int width, int height, bool is_opaque);
-  bool initialize(int width, int height, bool is_opaque, uint8_t* data);
-
-  // These calls should surround calls to platform-specific drawing routines.
-  // The cairo_surface_t* returned by beginPlatformPaint represents the
-  // memory that can be used to draw into.
-  // endPlatformPaint is a no-op; it is used for symmetry with Windows.
-  cairo_surface_t* beginPlatformPaint();
-  void endPlatformPaint() {}
-
-  // Returns the platform device pointer of the topmost rect with a non-empty
-  // clip. Both the windows and mac versions have an equivalent of this method;
-  // a Linux version is added for compatibility.
-  PlatformDeviceLinux& getTopPlatformDevice() const;
-
-  // 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);
-
- protected:
-  // Creates a device store for use by the canvas. We override this so that
-  // the device is always our own so we know that we can use GDI operations
-  // on it. Simply calls into createPlatformDevice().
-  virtual SkDevice* createDevice(SkBitmap::Config, int width, int height,
-                                 bool is_opaque, bool isForLayer);
-
-  // Creates a device store for use by the canvas. By default, it creates a
-  // BitmapPlatformDevice object. Can be overridden to change the object type.
-  virtual SkDevice* createPlatformDevice(int width, int height, bool is_opaque);
-
-  // Disallow copy and assign.
-  PlatformCanvasLinux(const PlatformCanvasLinux&);
-  PlatformCanvasLinux& operator=(const PlatformCanvasLinux&);
-};
-
-// A class designed to translate skia painting into a region in a
-// GdkWindow. This class has been adapted from the class with the same name in
-// platform_canvas_win.h. On construction, it will set up a context for
-// painting into, and on destruction, it will commit it to the GdkWindow.
-template <class T>
-class CanvasPaintT : public T {
- public:
-  explicit CanvasPaintT(GdkEventExpose* event)
-      : surface_(NULL),
-        window_(event->window),
-        rectangle_(event->area),
-        composite_alpha_(false) {
-    init(true);
-  }
-
-  CanvasPaintT(GdkEventExpose* event, bool opaque)
-      : surface_(NULL),
-        window_(event->window),
-        rectangle_(event->area),
-        composite_alpha_(false) {
-    init(opaque);
-  }
-
-  virtual ~CanvasPaintT() {
-    if (!isEmpty()) {
-      T::restoreToCount(1);
-
-      // Blit the dirty rect to the window.
-      cairo_t* cr = gdk_cairo_create(window_);
-      if (composite_alpha_)
-        cairo_set_operator(cr, CAIRO_OPERATOR_SOURCE);
-      cairo_set_source_surface(cr, surface_, rectangle_.x, rectangle_.y);
-      cairo_rectangle(cr, rectangle_.x, rectangle_.y,
-                      rectangle_.width, rectangle_.height);
-      cairo_fill(cr);
-      cairo_destroy(cr);
-    }
-  }
-
-  // Sets whether the bitmap is composited in such a way that the alpha channel
-  // is honored. This is only useful if you've enabled an RGBA colormap on the
-  // widget. The default is false.
-  void set_composite_alpha(bool composite_alpha) {
-    composite_alpha_ = composite_alpha;
-  }
-
-  // Returns true if the invalid region is empty. The caller should call this
-  // function to determine if anything needs painting.
-  bool isEmpty() const {
-    return rectangle_.width == 0 || rectangle_.height == 0;
-  }
-
-  const GdkRectangle& rectangle() const {
-    return rectangle_;
-  }
-
- private:
-  void init(bool opaque) {
-    if (!T::initialize(rectangle_.width, rectangle_.height, opaque, NULL)) {
-      // Cause a deliberate crash;
-      *(char*) 0 = 0;
-    }
-
-    // Need to translate so that the dirty region appears at the origin of the
-    // surface.
-    T::translate(-SkIntToScalar(rectangle_.x), -SkIntToScalar(rectangle_.y));
-
-    surface_ = T::getTopPlatformDevice().beginPlatformPaint();
-  }
-
-  cairo_surface_t* surface_;
-  GdkWindow* window_;
-  GdkRectangle rectangle_;
-  // See description above setter.
-  bool composite_alpha_;
-
-  // Disallow copy and assign.
-  CanvasPaintT(const CanvasPaintT&);
-  CanvasPaintT& operator=(const CanvasPaintT&);
-};
-
-}  // namespace skia
-
-#endif  // SKIA_EXT_PLATFORM_CANVAS_LINUX_H_