ash: Clean up system background layer.

ash/wm/system_background_controller.h

+// Copyright (c) 2012 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 ASH_WM_SYSTEM_BACKGROUND_CONTROLLER_H_
+#define ASH_WM_SYSTEM_BACKGROUND_CONTROLLER_H_
+
+#include <string>
+
+#include "ash/ash_export.h"
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "third_party/skia/include/core/SkColor.h"
+#include "ui/aura/root_window_observer.h"
+
+namespace aura {
+class RootWindow;
+}
+
+namespace ui {
+class Layer;
+}
+
+namespace ash {
+namespace internal {
+
+// SystemBackgroundController manages a ui::Layer that's stacked at the bottom
+// of an aura::RootWindow's children.  It exists solely to obscure portions of
+// the root layer that aren't covered by any other layers (e.g. before the
+// desktop background image is loaded at startup, or when we scale down all of
+// the other layers as part of a power-button or window-management animation).
+// It should never be transformed or restacked.
+class ASH_EXPORT SystemBackgroundController : public aura::RootWindowObserver {
+ public:
+  enum Content {
+    CONTENT_INVALID,
+
+    // Copy the contents of the host window.  Useful when starting on X, where
+    // the host window can inherit content from the X root window -- with this,
+    // the compositor can continue drawing whatever was previously onscreen even
+    // while we're e.g. waiting for images to be loaded from disk.
+    CONTENT_COPY_FROM_HOST,
+
+    // Display a black screen.
+    CONTENT_BLACK,
+
+#if defined(OS_CHROMEOS)
+    // Display a solid-color screen matching the background color used for the
+    // Chrome OS boot splash screen.
+    CONTENT_CHROME_OS_BOOT_COLOR,
+#endif
+  };
+
+  SystemBackgroundController(aura::RootWindow* root_window,
+                             Content initial_content);
+  virtual ~SystemBackgroundController();
+
+  void SetContent(Content new_content);
+
+  // aura::RootWindowObserver overrides:
+  virtual void OnRootWindowResized(const aura::RootWindow* root,
+                                   const gfx::Size& old_size) OVERRIDE;
+
+ private:
+  class HostContentLayerDelegate;
+
+  // Initializes |layer_| as a textured layer containing a copy of the host
+  // window's content.
+  void CreateTexturedLayerWithHostContent();
+
+  // Initializes |layer_| as a solid-color layer containing |color|.
+  void CreateColoredLayer(SkColor color);
+
+  // Updates |layer|'s bounds to match those of |root_window_|'s layer.
+  void UpdateLayerBounds(ui::Layer* layer);
+
+  // Adds |layer| to |root_window_|'s layer and stacks it at the bottom of all
+  // its children.
+  void AddLayerToRootLayer(ui::Layer* layer);
+
+  aura::RootWindow* root_window_;  // not owned
+
+  // Type of content currently displayed in |layer_|.
+  Content content_;
+
+  // Paints |layer_| when |content_| is CONTENT_COPY_FROM_HOST.
+  scoped_ptr<HostContentLayerDelegate> layer_delegate_;
+
+  scoped_ptr<ui::Layer> layer_;
+
+  DISALLOW_COPY_AND_ASSIGN(SystemBackgroundController);
+};
+
+}  // namespace internal
+}  // namespace ash
+
+#endif  // ASH_WM_SYSTEM_BACKGROUND_CONTROLLER_H_