[Tracking Patch] Unified gesture detection

ui/events/gesture_detection/gesture_detector.h

+// Copyright 2013 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_EVENTS_GESTURE_DETECTION_GESTURE_DETECTOR_H_
+#define UI_EVENTS_GESTURE_DETECTION_GESTURE_DETECTOR_H_
+
+#include "base/memory/scoped_ptr.h"
+#include "ui/events/gesture_detection/gesture_detection_export.h"
+#include "ui/events/gesture_detection/velocity_tracker_state.h"
+
+namespace ui {
+
+class MotionEvent;
+
+// Port of GestureDetector.java from Android
+// * platform/frameworks/base/core/java/android/view/GestureDetector.java
+// * Change-Id: Ib470735ec929b0b358fca4597e92dc81084e675f
+// * Please update the Change-Id as upstream Android changes are pulled.
+class GestureDetector {
+ public:
+  struct GESTURE_DETECTION_EXPORT Config {
+    Config();
+    ~Config();
+    base::TimeDelta longpress_timeout;
+    base::TimeDelta tap_timeout;
+    base::TimeDelta double_tap_timeout;
+    int scaled_touch_slop;

[tdresser, 2014/02/19 17:44:12]

I'm not too keen on the use of "scaled" in these names. Would a suffix
indicating the units be clearer?

[jdduke (slow), 2014/02/19 18:51:58]

Yeah, all of the scaled prefixes are remnants of the Android naming.  The
gesture detection is mostly scale agnostic; there are a few int's here and there
that we'll probably want to change if we want to properly support DIPs, but the
client is responsible for converting the output to the desired coordinate space.

+    int scaled_double_tap_slop;
+    int scaled_minimum_fling_velocity;
+    int scaled_maximum_fling_velocity;
+  };
+
+  class OnGestureListener {
+   public:
+    virtual ~OnGestureListener() {}
+    virtual bool OnDown(const MotionEvent& e) = 0;
+    virtual void OnShowPress(const MotionEvent& e) = 0;
+    virtual bool OnSingleTapUp(const MotionEvent& e) = 0;
+    virtual bool OnLongPress(const MotionEvent& e) = 0;
+    virtual bool OnScroll(const MotionEvent& e1, const MotionEvent& e2,
+                          float distance_x, float distance_y) = 0;
+    virtual bool OnFling(const MotionEvent& e1, const MotionEvent& e2,
+                         float velocity_x, float velocity_y) = 0;
+  };
+
+  class OnDoubleTapListener {
+   public:
+    virtual ~OnDoubleTapListener() {}
+    virtual bool OnSingleTapConfirmed(const MotionEvent& e) = 0;
+    virtual bool OnDoubleTap(const MotionEvent& e) = 0;
+    virtual bool OnDoubleTapEvent(const MotionEvent& e) = 0;
+  };
+
+  // A convenience class to extend when you only want to listen for a subset
+  // of all the gestures. This implements all methods in the
+  // |OnGestureListener| and |OnDoubleTapListener| but does
+  // nothing and returns false for all applicable methods.
+  class SimpleOnGestureListener : public OnGestureListener,
+                                  public OnDoubleTapListener {
+    // OnGestureListener
+    virtual bool OnDown(const MotionEvent& e) OVERRIDE;
+    virtual void OnShowPress(const MotionEvent& e) OVERRIDE;
+    virtual bool OnSingleTapUp(const MotionEvent& e) OVERRIDE;
+    virtual bool OnLongPress(const MotionEvent& e) OVERRIDE;
+    virtual bool OnScroll(const MotionEvent& e1, const MotionEvent& e2,
+                          float distance_x, float distance_y) OVERRIDE;
+    virtual bool OnFling(const MotionEvent& e1, const MotionEvent& e2,
+                         float velocity_x, float velocity_y) OVERRIDE;
+
+    // OnDoubleTapListener
+    virtual bool OnSingleTapConfirmed(const MotionEvent& e) OVERRIDE;
+    virtual bool OnDoubleTap(const MotionEvent& e) OVERRIDE;
+    virtual bool OnDoubleTapEvent(const MotionEvent& e) OVERRIDE;
+  };
+
+  GestureDetector(const Config& config,
+                  OnGestureListener* listener,
+                  OnDoubleTapListener* optional_double_tap_listener);
+  ~GestureDetector();
+
+  bool OnTouchEvent(const MotionEvent& ev);
+
+  void set_on_doubletap_listener(OnDoubleTapListener* double_tap_listener) {
+    double_tap_listener_ = double_tap_listener;
+  }
+
+  void set_is_longpress_enabled(bool is_longpress_enabled) {
+    is_longpress_enabled_ = is_longpress_enabled;
+  }
+
+  bool is_longpress_enabled() const { return is_longpress_enabled_; }
+
+ private:
+  void Init(Config config);
+  void OnShowPressTimeout();
+  void OnLongPressTimeout();
+  void OnTapTimeout();
+  void Cancel();
+  void CancelTaps();
+  bool IsConsideredDoubleTap(const MotionEvent& first_down,
+                             const MotionEvent& first_up,
+                             const MotionEvent& second_down);
+
+  class TimeoutGestureHandler;
+  scoped_ptr<TimeoutGestureHandler> timeout_handler_;
+  OnGestureListener* const listener_;
+  OnDoubleTapListener* double_tap_listener_;
+
+  int touch_slop_square_;
+  int double_tap_touch_slop_square_;
+  int double_tap_slop_square_;
+  int min_fling_velocity_;
+  int max_fling_velocity_;
+  base::TimeDelta double_tap_timeout_;
+
+  bool still_down_;
+  bool defer_confirm_single_tap_;
+  bool in_long_press_;
+  bool always_in_tap_region_;
+  bool always_in_bigger_tap_region_;
+
+  scoped_ptr<MotionEvent> current_down_event_;
+  scoped_ptr<MotionEvent> previous_up_event_;
+
+  // True when the user is still touching for the second tap (down, move, and
+  // up events). Can only be true if there is a double tap listener attached.
+  bool is_double_tapping_;
+
+  float last_focus_x_;
+  float last_focus_y_;
+  float down_focus_x_;
+  float down_focus_y_;
+
+  bool is_longpress_enabled_;
+
+  // Determines speed during touch scrolling.
+  VelocityTrackerState velocity_tracker_;
+
+  DISALLOW_COPY_AND_ASSIGN(GestureDetector);
+};
+
+}  // namespace ui
+
+#endif  // UI_EVENTS_GESTURE_DETECTION_GESTURE_DETECTOR_H_