Obey maxBounds during dragging a map on leaflet 0.7

obey-maxBounds-during-drag.js

/*
  Obey maxBounds during dragging a map on leaflet 0.7

  New option "maxBoundsResistance" (0.0 - 1.0) controls its reaction;
    0.0: No effect
    0.8: Modern reaction (default)
    1.0: Strictly forbid
*/ 

L.Map.addInitHook(function() {
  var map = this;

  this.dragging._draggable.on("predrag", function() {
        var viewHalf = map.getSize().divideBy(2);
        var centerPoint = map.getPixelOrigin().add(viewHalf).subtract(this._newPos);
        var viewBounds = new L.Bounds(centerPoint.subtract(viewHalf), centerPoint.add(viewHalf));
        var offset = map._getBoundsOffset(viewBounds, map.options.maxBounds, map.getZoom());

        this._newPos = this._newPos.subtract(offset.multiplyBy(map.options.maxBoundsResistance || 0.8));
  });
});