Toggle spoken feedback if two fingers are held down.

ui/chromeos/touch_accessibility_enabler.h

+// Copyright 2016 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 UI_CHROMEOS_TOUCH_ACCESSIBILITY_ENABLER_H_
+#define UI_CHROMEOS_TOUCH_ACCESSIBILITY_ENABLER_H_
+
+#include "base/macros.h"
+#include "base/time/tick_clock.h"
+#include "base/timer/timer.h"
+#include "base/values.h"
+#include "ui/chromeos/ui_chromeos_export.h"
+#include "ui/events/event.h"
+#include "ui/events/event_rewriter.h"
+#include "ui/events/gesture_detection/gesture_detector.h"
+
+namespace aura {
+class Window;
+}
+
+namespace ui {
+
+class Event;
+class EventHandler;
+class TouchEvent;
+
+// A delegate to handle commands in response to detected accessibility gesture
+// events.
+class TouchAccessibilityEnablerDelegate {
+ public:
+  virtual ~TouchAccessibilityEnablerDelegate() {}
+
+  // While the user holds down two fingers on a touch screen, which is the
+  // gesture to enable spoken feedback (if held down long enough), play a sound
+  // every "tick" (approximately every half-second) to warn the user something
+  // is about to happen.
+  virtual void PlaySpokenFeedbackToggleCountdown(int tick_count) = 0;

[oshima, 2016/11/08 18:14:43]

optional: you may have empty impl for void functions in pure interface.

[dmazzoni, 2016/11/08 20:43:47]

Done.

+
+  // Toggles spoken feedback.
+  virtual void ToggleSpokenFeedback() = 0;
+};
+
+// TouchAccessibilityEnabler triggers turning spoken feedback on or off
+// by holding down two fingers on the touch screen for several seconds.
+class UI_CHROMEOS_EXPORT TouchAccessibilityEnabler : public ui::EventRewriter {
+ public:
+  explicit TouchAccessibilityEnabler(

[oshima, 2016/11/08 18:14:43]

nit: remove explicit

[dmazzoni, 2016/11/08 20:43:47]

Done.

+      aura::Window* root_window,
+      ui::TouchAccessibilityEnablerDelegate* delegate);
+  ~TouchAccessibilityEnabler() override;
+
+  bool IsInNoFingersDownForTesting() { return state_ == NO_FINGERS_DOWN; }
+  bool IsInOneFingerDownForTesting() { return state_ == ONE_FINGER_DOWN; }
+  bool IsInTwoFingersDownForTesting() { return state_ == TWO_FINGERS_DOWN; }
+  bool IsInWaitForNoFingersForTesting() {
+    return state_ == WAIT_FOR_NO_FINGERS;
+  }
+  void TriggerOnTimerForTesting() { OnTimer(); }
+
+ protected:

[oshima, 2016/11/08 18:14:43]

is there subclass for this?

[dmazzoni, 2016/11/08 20:43:47]

No, changed to private.

+  // Overridden from ui::EventRewriter
+  ui::EventRewriteStatus RewriteEvent(
+      const ui::Event& event,
+      std::unique_ptr<ui::Event>* rewritten_event) override;
+  ui::EventRewriteStatus NextDispatchEvent(
+      const ui::Event& last_event,
+      std::unique_ptr<ui::Event>* new_event) override;
+
+  void HandleTouchEvent(const ui::TouchEvent& event);
+
+  void StartTimer();
+  void CancelTimer();
+  void OnTimer();
+
+  // Returns the current time of the tick clock.
+  base::TimeTicks Now();
+
+  enum State {
+    // No fingers are down.
+    NO_FINGERS_DOWN,
+
+    // One finger is down and it's possible this could be a two-finger-hold.
+    ONE_FINGER_DOWN,
+
+    // Two fingers are down and stationary and we will trigger enabling
+    // spoken feedback after a delay.
+    TWO_FINGERS_DOWN,
+
+    // This is the "reject" state when we get anything other than two fingers
+    // held down and stationary. Stay in this state until all fingers are
+    // removed.
+    WAIT_FOR_NO_FINGERS
+  };
+
+  aura::Window* root_window_;
+
+  // Called when we detect a long-press of two fingers. Not owned.
+  ui::TouchAccessibilityEnablerDelegate* delegate_;
+
+  // The current state.
+  State state_;
+
+  // The time when we entered the two finger state.
+  base::TimeTicks two_finger_start_time_;
+
+  // A set of touch ids for fingers currently touching the screen.
+  std::vector<int> touch_ids_;
+
+  // Map of touch ids to their initial locations.
+  std::map<int, gfx::PointF> touch_locations_;
+
+  // A timer that triggers repeatedly while two fingers are held down.
+  base::RepeatingTimer timer_;
+
+  // A default gesture detector config, so we can share the same
+  // timeout and pixel slop constants.
+  ui::GestureDetector::Config gesture_detector_config_;
+
+  // When touch_accessibility_enabler gets time relative to real time during
+  // testing, this clock is set to the simulated clock and used.
+  base::TickClock* tick_clock_;
+
+  DISALLOW_COPY_AND_ASSIGN(TouchAccessibilityEnabler);
+};
+
+}  // namespace ui
+
+#endif  // UI_CHROMEOS_TOUCH_ACCESSIBILITY_ENABLER_H_