Normalise offsetX and offsetY on the event

[chriscbrock]

According to the W3C Working Draft, offsetX and offsetY should be
relative to the padding edge of the target element. The only browser
using this convention is IE. Webkit uses the border edge, Opera uses the
content edge, and FireFox does not support the properties.

Normalizing to the border edge is easiest to do.

[vendruscolo]

👍 this also fixes the plugin on Firefox 27. At the moment, offsetX and offsetY are always undefined (they're fine on Safari & Chrome).

[brandonaaron]

Seems like this should be put into jQuery proper so that all events get the correct offsetX/Y.

[chriscbrock]

jQuery doesnt normalise offsetX and offsetY, only pageX and pageY, all they do is copy the event properties. I'm picking they have done this after discussion, and are unlikely to change their position. (https://api.jquery.com/category/events/event-object/)

It would be nice if jQuery normalised more of the properties, but I guess thats where this plugin comes in, to normalise the properties of the events specific to the mousewheel/DOMMouseScroll events

[brandonaaron]

True and thanks for the pull request. I'm hoping to make some time soon to test this and hopefully land it.