Upload GdkPixbufs into cairo surfaces so they (hopefully) live on X

chrome/browser/gtk/cairo_cached_surface.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 CHROME_BROWSER_GTK_CAIRO_CACHED_SURFACE_H_
+#define CHROME_BROWSER_GTK_CAIRO_CACHED_SURFACE_H_
+
+#include <gtk/gtk.h>
+
+// A helper class that takes a GdkPixbuf* and renders it to the screen. Unlike
+// gdk_cairo_set_source_pixbuf(), CairoCachedSurface assumes that the pixbuf is
+// immutable after UsePixbuf() is called and can be sent to the X server
+// once. From then on, that cached version is used so we don't upload the same
+// image each and every time we expose.
+//
+// Most cached surfaces are owned by the GtkThemeProvider, which associates
+// them with a certain XDisplay. Some users of surfaces (CustomDrawButtonBase,
+// for example) own their surfaces instead since they interact with the
+// ResourceBundle instead of the GtkThemeProvider.
+class CairoCachedSurface {
+ public:
+  CairoCachedSurface();
+  ~CairoCachedSurface();
+
+  // Whether this CairoCachedSurface owns a GdkPixbuf.
+  bool valid() const;

[tony, 2009/09/09 21:26:21]

Nit: Maybe include the implementation in the header for this since it's
lowercase?

+
+  // The dimensions of the underlying pixbuf/surface. (or -1 if invalid.)
+  int Width() const;
+  int Height() const;
+
+  // Sets the pixbuf that we pass to cairo. Calling UsePixbuf() only derefs the
+  // current pixbuf and surface (if they exist). Actually transfering data to
+  // the X Server occurs at SetSource() time. Calling UsePixbuf() should only

[Evan Martin, 2009/09/09 21:50:34]

I think "server" should be lowercase, here and below.

+  // be done once as it clears cached data from the X Server.
+  void UsePixbuf(GdkPixbuf* pixbuf);
+
+  // Sets our pixbuf as the active surface starting at (x, y), uploading it in
+  // case we don't have an X backed surface cached.
+  void SetSource(cairo_t* cr, int x, int y);
+
+  // Raw access to the pixbuf. May be NULL. Used for a few gdk operations
+  // regarding window shaping.
+  GdkPixbuf* pixbuf() { return pixbuf_; }
+
+ private:
+  // The source pixbuf.
+  GdkPixbuf* pixbuf_;

[tony, 2009/09/09 21:26:21]

Maybe make this a ScopedGObject (in base/gfx/gtk_util.h)?

+
+  // Our cached surface. This should be a xlib surface so the data lives on the
+  // server instead of on the client.
+  cairo_surface_t* surface_;
+};
+
+#endif  // CHROME_BROWSER_GTK_CAIRO_CACHED_SURFACE_H_