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 class ScaleGestureListener;
  15
  16 // Port of ScaleGestureDetector.java from Android
  17 // * platform/frameworks/base/core/java/android/view/ScaleGestureDetector.java
  18 // * Change-Id: I3e7926a4f6f9ab4951f380bd004499c78b3bda69
  19 // * Please update the Change-Id as upstream Android changes are pulled.
  20 class GESTURE_DETECTION_EXPORT ScaleGestureDetector {
  21  public:
  22   struct GESTURE_DETECTION_EXPORT Config {
  23     Config();
  24     ~Config();
  25
  26     // Distance the current span can deviate from the initial span before
  27     // scaling will start (in dips). The span is the diameter of the circle with
  28     // a radius of average pointer deviation from the focal point.
  29     float span_slop;
  30
  31     // Minimum accepted value for TouchMajor while scaling (in dips).
  32     float min_scaling_touch_major;
  33
  34     // Minimum span needed to initiate a scaling gesture (in dips).
  35     float min_scaling_span;
  36
  37     // Minimum pinch span change before pinch occurs (in dips). See
  38     // crbug.com/373318.
  39     float min_pinch_update_span_delta;
  40   };
  41
  42   ScaleGestureDetector(const Config& config, ScaleGestureListener* listener);
  43   virtual ~ScaleGestureDetector();
  44
  45   // Accepts MotionEvents and dispatches events to a |ScaleGestureListener|
  46   // when appropriate.
  47   //
  48   // Note: Applications should pass a complete and consistent event stream to
  49   // this method. A complete and consistent event stream involves all
  50   // MotionEvents from the initial ACTION_DOWN to the final ACTION_UP or
  51   // ACTION_CANCEL.
  52   //
  53   // Returns true if the event was processed and the detector wants to receive
  54   // the rest of the MotionEvents in this event stream.
  55   bool OnTouchEvent(const MotionEvent& event);
  56
  57   // This method may be called by the owner when a a double-tap event has been
  58   // detected *for the same event stream* being fed to this instance of the
  59   // ScaleGestureDetector. As call order is important here, the double-tap
  60   // detector should always be offered events *before* the ScaleGestureDetector.
  61   bool OnDoubleTap(const MotionEvent& event);
  62
  63   // Set whether the associated |ScaleGestureListener| should receive
  64   // OnScale callbacks when the user performs a doubletap followed by a swipe.
  65   bool IsInProgress() const;
  66   bool InDoubleTapMode() const;
  67   float GetFocusX() const;
  68   float GetFocusY() const;
  69   float GetCurrentSpan() const;
  70   float GetCurrentSpanX() const;
  71   float GetCurrentSpanY() const;
  72   float GetPreviousSpan() const;
  73   float GetPreviousSpanX() const;
  74   float GetPreviousSpanY() const;
  75   float GetScaleFactor() const;
  76   base::TimeDelta GetTimeDelta() const;
  77   base::TimeTicks GetEventTime() const;
  78
  79  private:
  80   enum DoubleTapMode { DOUBLE_TAP_MODE_NONE, DOUBLE_TAP_MODE_IN_PROGRESS };
  81
  82   // The TouchMajor/TouchMinor elements of a MotionEvent can flutter/jitter on
  83   // some hardware/driver combos. Smooth out to get kinder, gentler behavior.
  84   void AddTouchHistory(const MotionEvent& ev);
  85   void ResetTouchHistory();
  86
  87   void ResetScaleWithSpan(float span);
  88
  89   ScaleGestureListener* const listener_;
  90
  91   float focus_x_;
  92   float focus_y_;
  93   float curr_span_;
  94   float prev_span_;
  95   float initial_span_;
  96   float curr_span_x_;
  97   float curr_span_y_;
  98   float prev_span_x_;
  99   float prev_span_y_;
 100   base::TimeTicks curr_time_;
 101   base::TimeTicks prev_time_;
 102   bool in_progress_;
 103   float span_slop_;
 104   float min_span_;
 105
 106   // Bounds for recently seen values.
 107   float touch_upper_;
 108   float touch_lower_;
 109   float touch_history_last_accepted_;
 110   int touch_history_direction_;
 111   base::TimeTicks touch_history_last_accepted_time_;
 112   float touch_min_major_;
 113   float touch_max_major_;
 114   float double_tap_focus_x_;
 115   float double_tap_focus_y_;
 116   DoubleTapMode double_tap_mode_;
 117
 118   bool event_before_or_above_starting_gesture_event_;
 119
 120   DISALLOW_COPY_AND_ASSIGN(ScaleGestureDetector);
 121 };
 122
 123 }  // namespace ui
 124
 125 #endif  // UI_EVENTS_GESTURE_DETECTION_SCALE_GESTURE_DETECTOR_H_