Show overlay displaying the state of all sticky keys when it is enabled.

ash/sticky_keys/sticky_keys_overlay.h

+// Copyright 2014 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_STICKY_KEYS_STICKY_KEYS_OVERLAY_H_
+#define ASH_STICKY_KEYS_STICKY_KEYS_OVERLAY_H_
+
+#include "ash/sticky_keys/sticky_keys_constants.h"
+#include "base/memory/scoped_ptr.h"
+#include "ui/events/event_constants.h"
+#include "ui/gfx/animation/animation_delegate.h"
+
+namespace gfx {
+class Size;
+class SlideAnimation;
+}
+
+namespace views {
+class Widget;
+}
+
+namespace ash {
+
+class StickyKeysOverlayView;
+
+// Controls the overlay UI for sticky keys.

[James Cook, 2014/01/14 00:59:03]

nit: This comment could mention what the UI looks like, or where it goes on the
screen.

[Tim Song, 2014/01/14 03:01:10]

Done.

+class StickyKeysOverlay : public gfx::AnimationDelegate {
+ public:
+  StickyKeysOverlay();
+  virtual ~StickyKeysOverlay();
+
+  // Shows or hides the overlay.
+  void Show(bool visible);
+
+  // Updates the overlay with the current state of a sticky key modifier.
+  void SetModifierKeyState(StickyKeyModifier modifier,
+                           StickyKeyState state);
+
+ private:
+  // Returns the size of the overlay widget, which is based on its content
+  // view.
+  gfx::Size GetWidgetSize();
+
+  // gfx::AnimationDelegate overrides:
+  virtual void AnimationEnded(const gfx::Animation* animation) OVERRIDE;
+  virtual void AnimationProgressed(const gfx::Animation* animation) OVERRIDE;
+  virtual void AnimationCanceled(const gfx::Animation* animation) OVERRIDE;
+
+  bool is_showing_;
+  scoped_ptr<views::Widget> overlay_widget_;
+  scoped_ptr<gfx::Size> widget_size_;

[James Cook, 2014/01/14 00:59:03]

Why not just a member gfx::Size?

[Tim Song, 2014/01/14 03:01:10]

Done. We may need support for resizing the overlay based on left vs. right
modifier keys, but a member variable for this should be fine too.

+  StickyKeysOverlayView* overlay_view_;

[James Cook, 2014/01/14 00:59:03]

I presume this is not owned, might be nice to comment that.

[Tim Song, 2014/01/14 03:01:10]

Done.

+  scoped_ptr<gfx::SlideAnimation> animation_;
+};
+
+}  // ash
+
+#endif  //ASH_STICKY_KEYS_STICKY_KEYS_OVERLAY_H_

[James Cook, 2014/01/14 00:59:03]

nit: space after //

[Tim Song, 2014/01/14 03:01:10]

Done.