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      1 // Copyright 2014 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_ACCELERATOR_KEY_HOLD_DETECTOR_H_
      6 #define ASH_ACCELERATOR_KEY_HOLD_DETECTOR_H_
      7 
      8 #include "ash/ash_export.h"
      9 #include "base/memory/scoped_ptr.h"
     10 #include "ui/events/event_handler.h"
     11 
     12 namespace ui {
     13 class KeyEvent;
     14 }
     15 
     16 namespace ash {
     17 
     18 // This class is used to implement action when a user press and hold the key.
     19 // When a user just pressed and released a key, normal pressed event gets
     20 // generated upon release.
     21 class ASH_EXPORT KeyHoldDetector : public ui::EventHandler {
     22  public:
     23   class Delegate {
     24    public:
     25     virtual ~Delegate() {}
     26 
     27     // If this return false, the event handler does not process
     28     // the event at all.
     29     virtual bool ShouldProcessEvent(const ui::KeyEvent* event) const = 0;
     30 
     31     // This should return true if the event should start the state transition.
     32     virtual bool IsStartEvent(const ui::KeyEvent* event) const = 0;
     33 
     34     // Called when the key is held.
     35     virtual void OnKeyHold(const ui::KeyEvent* event) = 0;
     36 
     37     // Called when the key is release after hold.
     38     virtual void OnKeyUnhold(const ui::KeyEvent* event) = 0;
     39   };
     40 
     41   explicit KeyHoldDetector(scoped_ptr<Delegate> delegate);
     42   virtual ~KeyHoldDetector();
     43 
     44   // ui::EventHandler overrides:
     45   virtual void OnKeyEvent(ui::KeyEvent* key_event) OVERRIDE;
     46 
     47  private:
     48   // A state to keep track of one click and click and hold operation.
     49   //
     50   // One click:
     51   // INITIAL --(first press)--> PRESSED --(release)--> INITIAL[SEND PRESS]
     52   //
     53   // Click and hold:
     54   // INITIAL --(first press)--> PRESSED --(press)-->
     55   //   HOLD[OnKeyHold] --(press)--> HOLD[OnKeyHold] --(release)-->
     56   //   INITIAL[OnKeyUnhold]
     57   enum State {
     58     INITIAL,
     59     PRESSED,
     60     HOLD
     61   };
     62 
     63   State state_;
     64   scoped_ptr<Delegate> delegate_;
     65 
     66   DISALLOW_COPY_AND_ASSIGN(KeyHoldDetector);
     67 };
     68 
     69 }  // namespace ash
     70 
     71 #endif  // ASH_ACCELERATOR_KEY_HOLD_DETECTOR_H_
     72