Refactor the PlatformContext layer to have only one class.

skia/ext/canvas_paint_linux.h

+
+// Copyright (c) 2009 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_CANVAS_PAINT_LINUX_H_
+#define SKIA_EXT_CANVAS_PAINT_LINUX_H_
+
+#include "skia/ext/platform_canvas.h"
+
+namespace skia {
+
+// 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:
+  // This constructor assumes the result is opaque.
+  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 (!is_empty()) {
+      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 is_empty() 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&);
+};
+
+typedef CanvasPaintT<PlatformCanvas> PlatformCanvasPaint;
+
+}  // namespace skia
+
+#endif  // SKIA_EXT_CANVAS_PAINT_LINUX_H_