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

ash/accelerators/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_ACCELERATORS_MAGNIFIER_KEY_SCROLLER_H_
+#define ASH_ACCELERATORS_MAGNIFIER_KEY_SCROLLER_H_
+
+#include "ash/accelerators/key_hold_detector.h"
+#include "ash/ash_export.h"
+#include "base/memory/scoped_ptr.h"
+#include "ui/events/event_handler.h"
+
+namespace ui {
+class KeyEvent;
+}
+
+namespace ash {
+
+// A KeyHoldDetector delegate to control control magnified screen.
+class ASH_EXPORT MagnifierKeyScroller : public KeyHoldDetector::Delegate {
+ public:
+  static bool IsEnabled();
+  static void SetEnabled(bool enabled);
+  static scoped_ptr<ui::EventHandler> CreateHandler();
+
+  // 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:
+  // 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;
+
+  MagnifierKeyScroller();
+  virtual ~MagnifierKeyScroller();
+
+  DISALLOW_COPY_AND_ASSIGN(MagnifierKeyScroller);
+};
+
+}  // namespace ash
+
+#endif  // ASH_ACCELERATORS_MAGNIFIER_KEY_SCROLLER_H_