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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 <memory>
#include "ash/ash_export.h"
#include "base/macros.h"
#include "base/time/time.h"
namespace aura {
class Window;
namespace ash {
class WindowCycleEventFilter;
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 { FORWARD, BACKWARD };
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 function adds a pre-target handler to
// listen to the alt key release.
void StartCycling();
// Both of these functions stop the current window cycle and removes the event
// filter. The former indicates success (i.e. the new window should be
// activated) and the latter indicates that the interaction was cancelled (and
// the originally active window should remain active).
void CompleteCycling();
void CancelCycling();
// Returns the WindowCycleList.
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);
void StopCycling();
std::unique_ptr<WindowCycleList> window_cycle_list_;
// Tracks what Window was active when starting to cycle and used to determine
// if the active Window changed in when ending cycling.
aura::Window* active_window_before_window_cycle_ = nullptr;
// Non-null while actively cycling.
std::unique_ptr<WindowCycleEventFilter> event_filter_;
base::Time cycle_start_time_;
} // namespace ash