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
new file mode 100644
index 0000000000000000000000000000000000000000..2cb027f2d692c9f37357e4198efbc1fa464948aa
--- /dev/null
+++ b/ash/sticky_keys/sticky_keys_overlay.h
@@ -0,0 +1,68 @@
+// 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_constants.h"
+#include "base/memory/scoped_ptr.h"
+#include "ui/compositor/layer_animation_observer.h"
+#include "ui/gfx/geometry/size.h"
+
+namespace gfx {
+class Transform;
+}
+
+namespace views {
+class Widget;
+}
+
+namespace ash {
+
+class StickyKeysOverlayView;
+
+// Controls the overlay UI for sticky keys, a transparent overlay at the top

[James Cook, 2014/01/15 22:53:53]

nit: Might mention the word "accessibility" in this comment.  (I'm on a
class-header-comment rampage right now, since I'm refactoring code I've never
seen before and good class header descriptions make it much much easier.)

[Tim Song, 2014/01/16 00:01:59]

Done.

+// left of the screen that shows the state of every 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(StickyKeyModifier modifier,
+                           StickyKeyState state);
+
+  // Get the current state of the sticky key modifier in the overlay.
+  StickyKeyState GetModifierKeyState(StickyKeyModifier modifier);
+
+  // Returns true if the overlay is currently showing. If the overlay is
+  // animating, the returned value is the target of the animation.
+  bool is_showing() { return is_showing_; }

[James Cook, 2014/01/15 22:53:53]

optional: Would this be better as is_visible()?  I first thought "is_showing()"
meant that the show-animation was playing.

[Tim Song, 2014/01/16 00:01:59]

Done.

+
+ private:
+  // Returns the current transform of the overlay, based on if it is showing.
+  gfx::Transform CalculateOverlayTransform();
+
+  // 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_showing_;
+  scoped_ptr<views::Widget> overlay_widget_;
+  gfx::Size widget_size_;
+  // Ownership of |overlay_view_| is passed to the view heirarchy.
+  StickyKeysOverlayView* overlay_view_;
+};
+
+}  // ash

[James Cook, 2014/01/15 22:53:53]

"namespace ash"

[Tim Song, 2014/01/16 00:01:59]

Done.

+
+#endif  // ASH_STICKY_KEYS_STICKY_KEYS_OVERLAY_H_