ash/wm/window_cycle_controller.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef ASH_WM_WINDOW_CYCLE_CONTROLLER_H_
   6 #define ASH_WM_WINDOW_CYCLE_CONTROLLER_H_
   7
   8 #include "ash/ash_export.h"
   9 #include "base/basictypes.h"
  10 #include "base/memory/scoped_ptr.h"
  11
  12 namespace ui {
  13 class EventHandler;
  14 }
  15
  16 namespace ash {
  17
  18 class WindowCycleList;
  19
  20 // Controls cycling through windows with the keyboard, for example, via alt-tab.
  21 // Windows are sorted primarily by most recently used, and then by screen order.
  22 // We activate windows as you cycle through them, so the order on the screen
  23 // may change during the gesture, but the most recently used list isn't updated
  24 // until the cycling ends.  Thus we maintain the state of the windows
  25 // at the beginning of the gesture so you can cycle through in a consistent
  26 // order.
  27 class ASH_EXPORT WindowCycleController {
  28  public:
  29   enum Direction {
  30     FORWARD,
  31     BACKWARD
  32   };
  33   WindowCycleController();
  34   virtual ~WindowCycleController();
  35
  36   // Returns true if cycling through windows is enabled. This is false at
  37   // certain times, such as when the lock screen is visible.
  38   static bool CanCycle();
  39
  40   // Cycles between windows in the given |direction|. If |is_alt_down| then
  41   // interprets this call as the start of a multi-step cycle sequence and
  42   // installs a key filter to watch for alt being released.
  43   void HandleCycleWindow(Direction direction, bool is_alt_down);
  44
  45   // Cycles between windows without maintaining a multi-step cycle sequence
  46   // (see above).
  47   void HandleLinearCycleWindow();
  48
  49   // Informs the controller that the Alt key has been released and it can
  50   // terminate the existing multi-step cycle.
  51   void AltKeyReleased();
  52
  53   // Returns true if we are in the middle of a window cycling gesture.
  54   bool IsCycling() const { return windows_.get() != NULL; }
  55
  56   // Returns the WindowCycleList. Really only useful for testing.
  57   const WindowCycleList* windows() const { return windows_.get(); }
  58
  59  private:
  60   // Call to start cycling windows.  You must call StopCycling() when done.
  61   void StartCycling();
  62
  63   // Cycles to the next or previous window based on |direction|.
  64   void Step(Direction direction);
  65
  66   // Installs an event filter to watch for release of the alt key.
  67   void InstallEventFilter();
  68
  69   // Stops the current window cycle and cleans up the event filter.
  70   void StopCycling();
  71
  72   scoped_ptr<WindowCycleList> windows_;
  73
  74   // Event handler to watch for release of alt key.
  75   scoped_ptr<ui::EventHandler> event_handler_;
  76
  77   DISALLOW_COPY_AND_ASSIGN(WindowCycleController);
  78 };
  79
  80 }  // namespace ash
  81
  82 #endif  // ASH_WM_WINDOW_CYCLE_CONTROLLER_H_