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

ash/sticky_keys/sticky_keys_overlay.h

Index: ash/sticky_keys/sticky_keys_overlay.h
diff --git a/ash/sticky_keys/sticky_keys_overlay.h b/ash/sticky_keys/sticky_keys_overlay.h
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+// 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/ash_export.h"
+#include "ash/sticky_keys/sticky_keys_state.h"
+#include "base/memory/scoped_ptr.h"
+#include "ui/compositor/layer_animation_observer.h"
+#include "ui/events/event_constants.h"
+#include "ui/gfx/geometry/size.h"
+
+namespace gfx {
+class Rect;
+}
+
+namespace views {
+class Widget;
+}
+
+namespace ash {
+
+class StickyKeysOverlayView;
+
+// Controls the overlay UI for sticky keys, an accessibility feature allowing
+// use of modifier keys without holding them down. This overlay will appear as
+// a transparent window on the top left of the screen, showing the state of
+// each sticky key modifier.
+class ASH_EXPORT StickyKeysOverlay : public ui::LayerAnimationObserver {
+ 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(ui::EventFlags modifier,
+                           StickyKeyState state);
+
+  // Get the current state of the sticky key modifier in the overlay.
+  StickyKeyState GetModifierKeyState(ui::EventFlags modifier);
+
+  // Returns true if the overlay is currently visible. If the overlay is
+  // animating, the returned value is the target of the animation.
+  bool is_visible() { return is_visible_; }
+
+ private:
+  // Returns the current bounds of the overlay, which is based on visibility.
+  gfx::Rect CalculateOverlayBounds();
+
+  // gfx::LayerAnimationObserver overrides:
+  virtual void OnLayerAnimationEnded(
+      ui::LayerAnimationSequence* sequence) OVERRIDE;
+  virtual void OnLayerAnimationAborted(
+      ui::LayerAnimationSequence* sequence) OVERRIDE;
+  virtual void OnLayerAnimationScheduled(
+      ui::LayerAnimationSequence* sequence) OVERRIDE;
+
+  bool is_visible_;
+  scoped_ptr<views::Widget> overlay_widget_;
+  // Ownership of |overlay_view_| is passed to the view heirarchy.
+  StickyKeysOverlayView* overlay_view_;
+  gfx::Size widget_size_;
+};
+
+}  // namespace ash
+
+#endif  // ASH_STICKY_KEYS_STICKY_KEYS_OVERLAY_H_