aura: Draw drop shadows under browsers and menus.

ui/aura_shell/shadow.h

+// Copyright (c) 2011 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 UI_AURA_SHELL_SHADOW_H_
+#define UI_AURA_SHELL_SHADOW_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "ui/gfx/rect.h"
+
+namespace ui {
+class Layer;
+}  // namespace ui
+
+namespace aura_shell {
+namespace internal {
+
+class ImageGrid;
+
+// Simple class that draws a drop shadow around content at given bounds.
+class Shadow {
+ public:
+  Shadow();
+  ~Shadow();
+
+  // Returns |image_grid_|'s ui::Layer.  This is exposed so it can be added to
+  // the same layer as the content and stacked below it.  SetContentBounds()
+  // should be used to adjust the shadow's size and position (rather than
+  // applying transformations to this layer).
+  ui::Layer* layer() const;
+
+  const gfx::Rect& content_bounds() const { return content_bounds_; }
+
+  void Init();
+
+  // Moves and resizes |image_grid_| to frame |content_bounds|.
+  void SetContentBounds(const gfx::Rect& content_bounds);
+
+ private:
+  scoped_ptr<ImageGrid> image_grid_;
+
+  // Bounds of the content that the shadow encloses.
+  gfx::Rect content_bounds_;
+
+  DISALLOW_COPY_AND_ASSIGN(Shadow);
+};
+
+}  // namespace internal
+}  // namespace aura_shell
+
+#endif  // UI_AURA_SHELL_SHADOW_H_