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. IsCycling()54 bool IsCycling() const { return windows_.get() != NULL; } 55 56 // Returns the WindowCycleList. Really only useful for testing. windows()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_ 83