Sortable: Calculating item distance and direction using a more robust al...

[zhizhangchen]

...gorithm to better support sorting among embeded sortables

Use the item with lowest distance bettween the mouse pointer and
each of its borders to rearrange, the direction of which is
determined by the mouse postion relative to the item, with the
exception when the mouse pointer intersects with the item or
distance is zero, in which case mouse moving direction is used.
Also we use this algorithm to rearrange even when currentContainer
is not changed to override the defective rearranging in _mouseDrag

[scottgonzalez]

Can you provide a demo that shows the improvement?

[zhizhangchen]

Following are the problem examples and solutions provided by this PR:

Problem 1: http://jsfiddle.net/Zvvpt/15/

1. drag the first item and move slowly down, when getting to the bottom of the sortable, the placeholder moves to the top of the sortable
2. drag the second item and move slowly down, the placeholder doesn't move until the item is dragged out of the sortable, where the placeholder jumps quickly to the bottom of the sortable and then goes to the middle again

Solution: http://jsfiddle.net/kM4dR/2/

Problems 2: http://jsfiddle.net/6bsGx/3/

1. Click near the bottom of an item and move downwards, notice that the item can't be dragged out of the inner sortable
2. Click near the top of an item and move upward, notice that the item can't be dragged out of the inner sortable
   Solution: http://jsfiddle.net/6bsGx/6/

Problems 3: http://jsfiddle.net/k4nn3/3/

1. drag an item down, notice that it's hard to put the item between the two inner sortables. If you clicked the top of an item and drag it down , it can be put between the inner sortables, but you can never make it there when moving upwards.
   Solution: http://jsfiddle.net/k4nn3/5/

[zhizhangchen]

I've opened three tickets for the above problems:
http://bugs.jqueryui.com/ticket/8572
http://bugs.jqueryui.com/ticket/8573
http://bugs.jqueryui.com/ticket/8574

[scottgonzalez]

Thanks, landed in bae06d2.