Crash when dragging the map as a first action in IE11

[fnicollet]

Hi,
Just got a comment on my application from a user. The map crashes if the first interaction is a gesture (such as zooming with 2 fingers), it works well if you move (pan) the map first.
I can reproduce this bug with the Windows 8 simulator (I don't have a touch device), the error is in

_onDragEnd: function (e) {
        var map = this._map,
            options = map.options,
            delay = +new Date() - this._lastTime,

            noInertia = !options.inertia || delay > options.inertiaThreshold || !this._positions[0];

        map.fire('dragend', e);

Basically, this._positions is undefined and the noInertia check produce a NPE when trying to access this._positions[0].

The _onDragStart function is never called, even if the hook is on, not sure why, will investigate.

I don't know if that's also the case with other browsers.

Fabien

[danzel]

Will take a look later today, probably my fault :)

[mourner]

Thanks for the report, should go into 0.7.1.

[danzel]

Took a look at the code for this, looks like the bug would exist on touch devices too.

If you put 2 fingers down and start a pinch movement then Draggable._onMove won't fire a dragstart, but it does set _moved.
When _onUp happens we will then fire a dragend event, we probably shouldn't in this case as we never fired dragstart.

We might be able to change https://github.com/Leaflet/Leaflet/blob/master/src/dom/Draggable.js#L124 to this._moved && this._moving, that would probably fix it. Not sure if that is what _moving is for @mourner?

[mourner]

As far as I remember, moved is not reset in onUp so that click handler can later cancel firing listeners if it happened immediately after dragging event, and moving is a flag that is only true during the dragging movement but not after.

[danzel]

@fnicollet I've pushed up a potential fix, please check it out https://github.com/danzel/Leaflet/tree/fix2256

[fnicollet]

@danzel Thanks! Will try it out tonight and let you know

[fnicollet]

Just tried it, it looks like it does the trick

[danzel]

Cool, PR sent #2259