Long press menu (shift+f6) to toggle spoken feedback.

ash/magnifier/magnifier_key_scroller.h

 // 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.
 
 #ifndef ASH_MAGNIFIER_MAGNIFIER_KEY_SCROLLER_H_
 #define ASH_MAGNIFIER_MAGNIFIER_KEY_SCROLLER_H_
 
+#include "ash/accelerators/key_hold_detector.h"
 #include "ash/ash_export.h"
 #include "ui/events/event_handler.h"
 
 namespace ui {
 class KeyEvent;
 }
 
 namespace ash {
 
-// This class implements the press and hold key-bindings (shift-arrow keys)
-// to control magnified screen.
-class ASH_EXPORT MagnifierKeyScroller : public ui::EventHandler {
+// A KeyHoldDetector delegate to control control magnified screen.
+class ASH_EXPORT MagnifierKeyScroller : public KeyHoldDetector::Delegate {
  public:
   static bool IsEnabled();
   static void SetEnabled(bool enabled);
-
-  MagnifierKeyScroller();
-  virtual ~MagnifierKeyScroller();
-
-  // ui::EventHandler overrides:
-  virtual void OnKeyEvent(ui::KeyEvent* key_event) OVERRIDE;
+  static ui::EventHandler* CreateHandler();

[xiyuan, 2014/02/14 01:50:21]

Same here. Document the ownership of the returned object and maybe add
WARN_UNUSED_RESULT.

 
   // A scoped object to enable and disable the magnifier accelerator for test.
   class ScopedEnablerForTest {
    public:
     ScopedEnablerForTest() {
       SetEnabled(true);
     }
     ~ScopedEnablerForTest() {
       SetEnabled(false);
     }
 
    private:
     DISALLOW_COPY_AND_ASSIGN(ScopedEnablerForTest);
   };
 
  private:
-  // A state to keep track of one click and click and hold operation.
-  //
-  // One click:
-  // INITIAL --(first press)--> PRESSED --(release)--> INITIAL[SEND PRESS]
-  //
-  // Click and hold:
-  // INITIAL --(first press)--> PRESSED --(press)-->
-  //   HOLD[scroll] --(press)--> HOLD[scroll] --(release)-->
-  //   INITIAL[stop scroll]
-  enum State {
-    INITIAL,
-    PRESSED,
-    HOLD
-  };
+  // KeyHoldDetector overrides:
+  virtual bool ShouldProcessEvent(const ui::KeyEvent* event) const OVERRIDE;
+  virtual bool IsStartEvent(const ui::KeyEvent* event) const OVERRIDE;
+  virtual void OnKeyHold(const ui::KeyEvent* event) OVERRIDE;
+  virtual void OnKeyUnhold(const ui::KeyEvent* event) OVERRIDE;
 
-  State state_;
+  MagnifierKeyScroller();
+  virtual ~MagnifierKeyScroller();
 
   DISALLOW_COPY_AND_ASSIGN(MagnifierKeyScroller);
 };
 
 }  // namespace ash
 
 #endif  // ASH_MAGNIFIER_MAGNIFIER_KEY_SCROLLER_H_