Gradient overlay for constrained window

chrome/renderer/webview_animating_overlay.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 CHROME_RENDERER_WEBVIEW_ANIMATING_OVERLAY_H_
+#define CHROME_RENDERER_WEBVIEW_ANIMATING_OVERLAY_H_
+
+#include "base/compiler_specific.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebPageOverlay.h"
+#include "ui/base/animation/animation_delegate.h"
+#include "ui/base/animation/linear_animation.h"
+
+namespace content {
+class RenderView;
+}
+
+// This class draws a gradient on a PageOverlay of a WebView. The gradient
+// fades in when shown and fades out when hidden.
+class WebViewAnimatingOverlay : public WebKit::WebPageOverlay,
+                                public ui::AnimationDelegate {
+ public:
+  enum State {
+    ANIMATING_IN,
+    VISIBLE,
+    ANIMATING_OUT,
+    HIDDEN
+  };
+
+  explicit WebViewAnimatingOverlay(content::RenderView* render_view);
+  virtual ~WebViewAnimatingOverlay();
+  void Show();
+  void Hide();
+
+  State state() { return state_; }
+
+  // WebKit::WebPageOverlay implementation:
+  virtual void paintPageOverlay(WebKit::WebCanvas* canvas) OVERRIDE;
+
+  // ui::AnimationDelegate implementation:
+  virtual void AnimationEnded(const ui::Animation* animation) OVERRIDE;
+  virtual void AnimationProgressed(const ui::Animation* animation) OVERRIDE;
+
+ private:
+  int GetCurrentAlpha();
+
+  content::RenderView* render_view_;
+  State state_;
+  ui::LinearAnimation animation_;
+
+  DISALLOW_COPY_AND_ASSIGN(WebViewAnimatingOverlay);
+};
+
+#endif  // CHROME_RENDERER_WEBVIEW_ANIMATING_OVERLAY_H_