ash/accelerators/exit_warning_handler.h

   1 // Copyright 2013 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_ACCELERATORS_EXIT_WARNING_HANDLER_H_
   6 #define ASH_ACCELERATORS_EXIT_WARNING_HANDLER_H_
   7
   8 #include "ash/ash_export.h"
   9 #include "base/memory/scoped_ptr.h"
  10 #include "base/timer/timer.h"
  11 #include "ui/base/accelerators/accelerator.h"
  12
  13 namespace views {
  14 class Widget;
  15 }
  16
  17 namespace ash {
  18
  19 // In order to avoid accidental exits when the user presses the exit
  20 // shortcut by mistake, we require the user press it twice within a
  21 // period of time. During that time we show a popup informing the
  22 // user of this.
  23 //
  24 // Notes:
  25 //
  26 // The corresponding accelerator must be non-repeatable (see
  27 // kNonrepeatableActions in accelerator_table.cc). Otherwise the "Double Press
  28 // Exit" will be activated just by holding it down, i.e. probably every time.
  29 //
  30 // State Transition Diagrams:
  31 //
  32 //  IDLE
  33 //   | Press
  34 //  WAIT_FOR_DOUBLE_PRESS action: show ui & start timers
  35 //   | Press (before time limit )
  36 //  EXITING action: hide ui, stop timer, exit
  37 //
  38 //  IDLE
  39 //   | Press
  40 //  WAIT_FOR_DOUBLE_PRESS action: show ui & start timers
  41 //   | T timer expires
  42 //  IDLE action: hide ui
  43 //
  44
  45 class AcceleratorControllerTest;
  46
  47 class ASH_EXPORT ExitWarningHandler {
  48  public:
  49   ExitWarningHandler();
  50
  51   ~ExitWarningHandler();
  52
  53   // Handles accelerator for exit (Ctrl-Shift-Q).
  54   void HandleAccelerator();
  55
  56  private:
  57   friend class AcceleratorControllerTest;
  58
  59   enum State {
  60     IDLE,
  61     WAIT_FOR_DOUBLE_PRESS,
  62     EXITING
  63   };
  64
  65   // Performs actions when the time limit is exceeded.
  66   void TimerAction();
  67
  68   void StartTimer();
  69   void CancelTimer();
  70
  71   void Show();
  72   void Hide();
  73
  74   State state_;
  75   scoped_ptr<views::Widget> widget_;
  76   base::OneShotTimer<ExitWarningHandler> timer_;
  77
  78   // Flag to suppress starting the timer for testing. For test we call
  79   // TimerAction() directly to simulate the expiration of the timer.
  80   bool stub_timer_for_test_;
  81
  82   DISALLOW_COPY_AND_ASSIGN(ExitWarningHandler);
  83 };
  84
  85 }  // namespace ash
  86
  87 #endif  // ASH_ACCELERATORS_EXIT_WARNING_HANDLER_H_