https://www.spotair.mobi/leaflet/Leaflet.DoubleTapDragZoom-0.3.2.js

1L.Map.mergeOptions({
2  doubleTapDragZoom: L.Browser.touch && !L.Browser.android23,
3  doubleTapDragZoomOptions: {
4    reverse: false,
5  },
6});
7
8var DoubleTapDragZoom = L.Handler.extend({
9  addHooks: function () {
10    this._map.on('doubletapdragstart', this._onDoubleTapDragStart, this);
11    this._map.on('doubletapdrag', this._onDoubleTapDrag, this);
12    this._map.on('doubletapdragend', this._onDoubleTapDragEnd, this);
13    L.DomEvent.on(this._map._container, 'touchmove', this._onDragging, this);
14  },
15
16  removeHooks: function () {
17    this._map.off('doubletapdragstart', this._onDoubleTapDragStart, this);
18    this._map.off('doubletapdrag', this._onDoubleTapDrag, this);
19    this._map.off('doubletapdragend', this._onDoubleTapDragEnd, this);
20  },
21
22  _onDoubleTapDragStart: function (e) {
23    var map = this._map;
24    if (!e.touches || e.touches.length !== 1 || map._animatingZoom) { return; }
25
26    var p = map.mouseEventToContainerPoint(e.touches[0]);
27    this._startPointY = p.y;
28    this._startPoint = p;
29
30    this._centerPoint = map.getSize()._divideBy(2);
31
32    if (map.options.doubleTapDragZoom === 'center') {
33      this._startLatLng = map.containerPointToLatLng(this._centerPoint);
34    } else {
35      this._startLatLng = map.containerPointToLatLng(p);
36    }
37
38    this._startZoom = map.getZoom();
39
40    map._stop();
41    map._moveStart(true, false);
42    this._doubleTapDragging = true;
43  },
44
45  _onDoubleTapDrag: function (e) {
46    if (!e.touches || e.touches.length !== 1) { return; }
47
48    var map = this._map;
49    var reverse = this._map.options.doubleTapDragZoomOptions.reverse;
50    var p = map.mouseEventToContainerPoint(e.touches[0]);
51
52    if (p.y <= 0) {
53      return;
54    }
55
56    var distance = reverse ? p.y - this._startPointY : this._startPointY - p.y;
57
58    var scale = Math.pow(Math.E, distance / 200);
59
60    if (scale === 1) { return; }
61
62    this._zoom = map.getScaleZoom(scale, this._startZoom);
63
64    if (map.options.doubleTapDragZoom === 'center') {
65      this._center = this._startLatLng;
66    } else {
67      var delta =
68        L.point(this._startPoint.x, p.y)
69          ._add(this._startPoint)
70          .divideBy(2)
71          ._subtract(this._centerPoint);
72
73      this._center = map.unproject(map.project(this._startLatLng, this._zoom).subtract(delta), this._zoom);
74    }
75
76    L.Util.cancelAnimFrame(this._animRequest);
77
78    var moveFn = L.Util.bind(map._move, map, this._center, this._zoom, {pinch: true, round: false});
79    this._animRequest = L.Util.requestAnimFrame(moveFn, this, true);
80  },
81
82  _onDoubleTapDragEnd: function (e) {
83    this._doubleTapDragging = false;
84
85    if (!this._center) { return; }
86    L.Util.cancelAnimFrame(this._animRequest);
87
88    // Pinch updates GridLayers' levels only when zoomSnap is off, so zoomSnap becomes noUpdate.
89    if (this._map.options.zoomAnimation) {
90      this._map._animateZoom(this._center, this._map._limitZoom(this._zoom), true, this._map.options.zoomSnap);
91    } else {
92      this._map._resetView(this._center, this._map._limitZoom(this._zoom));
93    }
94
95    this._center = null;
96  },
97
98  _onDragging: function (e) {
99    if (this._doubleTapDragging) {
100      L.DomEvent.preventDefault(e);
101      L.DomEvent.stopPropagation(e);
102    }
103  }
104});
105
106L.Map.addInitHook('addHandler', 'doubleTapDragZoom', DoubleTapDragZoom);