ui/events/gesture_detection/scale_gesture_detector.h

   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 UI_EVENTS_GESTURE_DETECTION_SCALE_GESTURE_DETECTOR_H_
   6 #define UI_EVENTS_GESTURE_DETECTION_SCALE_GESTURE_DETECTOR_H_
   7
   8 #include "base/time/time.h"
   9 #include "ui/events/gesture_detection/gesture_detection_export.h"
  10
  11 namespace ui {
  12
  13 class MotionEvent;
  14
  15 // Port of ScaleGestureDetector.java from Android
  16 // * platform/frameworks/base/core/java/android/view/ScaleGestureDetector.java
  17 // * Change-Id: I3e7926a4f6f9ab4951f380bd004499c78b3bda69
  18 // * Please update the Change-Id as upstream Android changes are pulled.
  19 class ScaleGestureDetector {
  20  public:
  21   struct GESTURE_DETECTION_EXPORT Config {
  22     Config();
  23     ~Config();
  24
  25     // Distance the current span can deviate from the initial span before
  26     // scaling will start (in dips). The span is the diameter of the circle with
  27     // a radius of average pointer deviation from the focal point.
  28     float span_slop;
  29
  30     // Minimum accepted value for TouchMajor while scaling (in dips).
  31     float min_scaling_touch_major;
  32
  33     // Minimum span needed to initiate a scaling gesture (in dips).
  34     float min_scaling_span;
  35
  36     // Minimum pinch span change before pinch occurs (in dips). See
  37     // crbug.com/373318.
  38     float min_pinch_update_span_delta;
  39   };
  40
  41   class ScaleGestureListener {
  42    public:
  43     virtual ~ScaleGestureListener() {}
  44     virtual bool OnScale(const ScaleGestureDetector& detector,
  45                          const MotionEvent& e) = 0;
  46     virtual bool OnScaleBegin(const ScaleGestureDetector& detector,
  47                               const MotionEvent& e) = 0;
  48     virtual void OnScaleEnd(const ScaleGestureDetector& detector,
  49                             const MotionEvent& e) = 0;
  50   };
  51
  52   // A convenience class to extend when you only want to listen for a subset of
  53   // scaling-related events. This implements all methods in
  54   // |ScaleGestureListener| but does nothing.
  55   // |OnScale()| returns false so that a subclass can retrieve the accumulated
  56   // scale factor in an overridden |OnScaleEnd()|.
  57   // |OnScaleBegin() returns true.
  58   class SimpleScaleGestureListener : public ScaleGestureListener {
  59    public:
  60     // ScaleGestureListener implementation.
  61     virtual bool OnScale(const ScaleGestureDetector&,
  62                          const MotionEvent&) OVERRIDE;
  63     virtual bool OnScaleBegin(const ScaleGestureDetector&,
  64                               const MotionEvent&) OVERRIDE;
  65     virtual void OnScaleEnd(const ScaleGestureDetector&,
  66                             const MotionEvent&) OVERRIDE;
  67   };
  68
  69   ScaleGestureDetector(const Config& config, ScaleGestureListener* listener);
  70   virtual ~ScaleGestureDetector();
  71
  72   // Accepts MotionEvents and dispatches events to a |ScaleGestureListener|
  73   // when appropriate.
  74   //
  75   // Note: Applications should pass a complete and consistent event stream to
  76   // this method. A complete and consistent event stream involves all
  77   // MotionEvents from the initial ACTION_DOWN to the final ACTION_UP or
  78   // ACTION_CANCEL.
  79   //
  80   // Returns true if the event was processed and the detector wants to receive
  81   // the rest of the MotionEvents in this event stream.
  82   bool OnTouchEvent(const MotionEvent& event);
  83
  84   // This method may be called by the owner when a a double-tap event has been
  85   // detected *for the same event stream* being fed to this instance of the
  86   // ScaleGestureDetector. As call order is important here, the double-tap
  87   // detector should always be offered events *before* the ScaleGestureDetector.
  88   bool OnDoubleTap(const MotionEvent& event);
  89
  90   // Set whether the associated |ScaleGestureListener| should receive
  91   // OnScale callbacks when the user performs a doubletap followed by a swipe.
  92   bool IsInProgress() const;
  93   bool InDoubleTapMode() const;
  94   float GetFocusX() const;
  95   float GetFocusY() const;
  96   float GetCurrentSpan() const;
  97   float GetCurrentSpanX() const;
  98   float GetCurrentSpanY() const;
  99   float GetPreviousSpan() const;
 100   float GetPreviousSpanX() const;
 101   float GetPreviousSpanY() const;
 102   float GetScaleFactor() const;
 103   base::TimeDelta GetTimeDelta() const;
 104   base::TimeTicks GetEventTime() const;
 105
 106  private:
 107   enum DoubleTapMode { DOUBLE_TAP_MODE_NONE, DOUBLE_TAP_MODE_IN_PROGRESS };
 108
 109   // The TouchMajor/TouchMinor elements of a MotionEvent can flutter/jitter on
 110   // some hardware/driver combos. Smooth out to get kinder, gentler behavior.
 111   void AddTouchHistory(const MotionEvent& ev);
 112   void ResetTouchHistory();
 113
 114   void ResetScaleWithSpan(float span);
 115
 116   ScaleGestureListener* const listener_;
 117
 118   float focus_x_;
 119   float focus_y_;
 120   float curr_span_;
 121   float prev_span_;
 122   float initial_span_;
 123   float curr_span_x_;
 124   float curr_span_y_;
 125   float prev_span_x_;
 126   float prev_span_y_;
 127   base::TimeTicks curr_time_;
 128   base::TimeTicks prev_time_;
 129   bool in_progress_;
 130   float span_slop_;
 131   float min_span_;
 132
 133   // Bounds for recently seen values.
 134   float touch_upper_;
 135   float touch_lower_;
 136   float touch_history_last_accepted_;
 137   int touch_history_direction_;
 138   base::TimeTicks touch_history_last_accepted_time_;
 139   float touch_min_major_;
 140   float touch_max_major_;
 141   float double_tap_focus_x_;
 142   float double_tap_focus_y_;
 143   DoubleTapMode double_tap_mode_;
 144
 145   bool event_before_or_above_starting_gesture_event_;
 146
 147   DISALLOW_COPY_AND_ASSIGN(ScaleGestureDetector);
 148 };
 149
 150 }  // namespace ui
 151
 152 #endif  // UI_EVENTS_GESTURE_DETECTION_SCALE_GESTURE_DETECTOR_H_