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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.
#include "ash/ash_export.h"
#include "base/basictypes.h"
#include "base/memory/scoped_ptr.h"
#include "base/time/time.h"
namespace ui {
class EventHandler;
namespace ash {
class WindowCycleList;
// Controls cycling through windows with the keyboard via alt-tab.
// Windows are sorted primarily by most recently used, and then by screen order.
// We activate windows as you cycle through them, so the order on the screen
// may change during the gesture, but the most recently used list isn't updated
// until the cycling ends. Thus we maintain the state of the windows
// at the beginning of the gesture so you can cycle through in a consistent
// order.
class ASH_EXPORT WindowCycleController {
enum Direction {
virtual ~WindowCycleController();
// Returns true if cycling through windows is enabled. This is false at
// certain times, such as when the lock screen is visible.
static bool CanCycle();
// Cycles between windows in the given |direction|.
void HandleCycleWindow(Direction direction);
// Returns true if we are in the middle of a window cycling gesture.
bool IsCycling() const { return window_cycle_list_.get() != NULL; }
// Call to start cycling windows. This funtion adds a pre-target handler to
// listen to the alt key release.
void StartCycling();
// Stops the current window cycle and removes the event filter.
void StopCycling();
// Returns the WindowCycleList. Really only useful for testing.
const WindowCycleList* window_cycle_list() const {
return window_cycle_list_.get();
// Cycles to the next or previous window based on |direction|.
void Step(Direction direction);
scoped_ptr<WindowCycleList> window_cycle_list_;
// Event handler to watch for release of alt key.
scoped_ptr<ui::EventHandler> event_handler_;
base::Time cycle_start_time_;
} // namespace ash