Draggable: ui.offset.left differs between the "start" and "drag" hooks

[traviscooper]

when using the 'ui.offset.left' value with the start, drag and stop events for DRAGGABLE, you get a different value range for the start event versus the drag and stop.

For example, the following output was generated by asking for the 'ui.position.left' and ui.offset.left' for each of the events listed (start, drag, stop), as I dragged the element 1px to the right.

Notice how on the [start] event, the ui.offset.left (ui.o.l value) is "645", but for the [drag] and [start] events, the values become exactly what the ui.position.left values are (ui.p.l).

[start]--ui.p.l(247)ui.o.l(645) [drag]--ui.p.l(248)ui.o.l(248) [stop]--ui.p.l(248)ui.o.l(248)

From my own calculations, the above output SHOULD be.

[start]--ui.p.l(247)ui.o.l(645) [drag]--ui.p.l(248)ui.o.l(646) [stop]--ui.p.l(248)ui.o.l(646)

Below is my code to reproduce.

$('.element_to_move').draggable({

containment: 'parent', cursor: 'pointer', scroll: true, axis: 'x' , grid: [1,0], start: function(event, ui) {

Update element data in Display $('#er2').append('[start]--ui.p.l('+ui.position.left+')ui.o.l('+ui.offset.left+')<br />');

}, drag: function(event, ui) {

Update element data in Display $('#er2').append('[drag]--ui.p.l('+ui.position.left+')ui.o.l('+ui.offset.left+')<br />');

}, stop: function(event, ui){

Update element data in Display $('#er2').append('[stop]--ui.p.l('+ui.position.left+')ui.o.l('+ui.offset.left+')<br />');

}

});

[traviscooper]

I'm thinking it shouldn't matter what the CSS positioning value is for the parent or element, since the initial value of the 'ui.offset.left' is correct.

[traviscooper]

Here is the jsbin working demo of the error.

​http://jsbin.com/ilike4

[mikesherov]

New demo using latest: ​http://jsfiddle.net/48uVM/1/ which confirms the discrepancy. It looks to be on purpose and part of the internals: ​https://github.com/jquery/jquery-ui/blob/039ee746d3eaeeaa4ad92ecd8ebf4e6fcd11768c/ui/jquery.ui.draggable.js#L426

However, this is not ideal, and if the internals need to rely on the "position" values provided, they should be named appropriately to signify they aren't equivalent to the common notion of position and offset.

[Mike Sherov]

Draggable: Recalculate hash offset on start after plugins run

Fixes #6884 Changeset: b5846bece34db31d69e75cb3a3537827c005910e

[mikesherov]

Better late than never!