Add the xrender backend to the window manager.

compositor/xrender/xrender_visitor.h

+// Copyright (c) 2011 The Chromium OS 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 WINDOW_MANAGER_COMPOSITOR_XRENDER_XRENDER_VISITOR_H_
+#define WINDOW_MANAGER_COMPOSITOR_XRENDER_XRENDER_VISITOR_H_
+
+#include <vector>
+
+#include "base/logging.h"
+#include "base/scoped_ptr.h"
+#include "window_manager/compositor/compositor.h"
+#include "window_manager/compositor/real_compositor.h"
+#include "window_manager/compositor/texture_data.h"
+#include "window_manager/x11/x_connection.h"
+
+namespace window_manager {
+
+class ImageContainer;
+
+// This class visits an actor tree and draws it using the XRender extension.
+class XRenderDrawVisitor : virtual public RealCompositor::ActorVisitor {
+ public:
+  XRenderDrawVisitor(RealCompositor* compositor,
+                     Compositor::StageActor* stage);

[Daniel Erat, 2011/04/04 21:16:35]

not your fault (the gl and gles implementations do it too), but just pointing it
out in case you feel like fixing it: it's weird that this is a
Compositor::StageActor instead of a RealCompositor::StageActor

+  virtual ~XRenderDrawVisitor();
+
+  XConnection* xconn() { return xconn_; }
+  void set_has_fullscreen_actor(bool has_fullscreen_actor) {
+    has_fullscreen_actor_ = has_fullscreen_actor;
+  }
+  void set_damaged_region(Rect damaged_region) {

[Daniel Erat, 2011/04/04 21:16:35]

nit: s/Rect/const Rect&/ (i'm cleaning this up in the other visitors in
http://codereview.chromium.org/6691037/)

+    damaged_region_ = damaged_region;
+  }
+
+  void BindImage(const ImageContainer* container,
+                 RealCompositor::ImageActor* actor);
+
+  virtual void VisitActor(RealCompositor::Actor* actor) {}
+  virtual void VisitStage(RealCompositor::StageActor* actor);
+  virtual void VisitContainer(RealCompositor::ContainerActor* actor);
+  virtual void VisitImage(RealCompositor::ImageActor* actor);
+  virtual void VisitTexturePixmap(RealCompositor::TexturePixmapActor* actor);
+  virtual void VisitQuad(RealCompositor::QuadActor* actor);
+
+ private:
+  // So it can get access to the config data.
+  friend class XRenderPixmapData;
+
+  XWindow root_window;

[Daniel Erat, 2011/04/04 21:16:35]

add trailing underscore

+  XConnection::WindowGeometry root_geometry;

[Daniel Erat, 2011/04/04 21:16:35]

add trailing underscore

+
+  XPicture back_picture_;

[Daniel Erat, 2011/04/04 21:16:35]

these should still have comments with brief descriptions of their purposes

+  XPixmap back_pixmap_;
+
+  XPicture stage_picture_;
+
+  // The visitor should not change settings in the compositor while visiting
+  // actors throughout the drawing process because the compositor may decide
+  // to skip drawing frames as an optimization.
+  RealCompositor* compositor_;  // Not owned.
+  XConnection* xconn_;  // Not owned.
+  RealCompositor::StageActor* stage_; // Not owned.
+
+  // This is the cumulative opacity of all the ancestors of the
+  // currently visited node. It is recalculated each time we enter or
+  // leave a container node.
+  float ancestor_opacity_;
+
+  // The rectangular region of the screen that is damaged in the frame.
+  // This information allows the draw visitor to perform partial updates.
+  Rect damaged_region_;
+
+  // This is used to indicate whether the entire screen will be covered by an
+  // actor so we can optimize by not clearing the back buffer.
+  bool has_fullscreen_actor_;
+
+  DISALLOW_COPY_AND_ASSIGN(XRenderDrawVisitor);
+};
+
+}  // namespace window_manager
+
+#endif  // WINDOW_MANAGER_COMPOSITOR_XRENDER_XRENDER_VISITOR_H_