Restrict jQuery draggable items from overlapping/colliding with sibling elements

Edit: New Solution

I found a plugin for this called JQuery UI Draggable Collision. Using this, implementing your desired functionality becomes trivial. See the following jsFiddle example: http://jsfiddle.net/q3x8w03y/1/ (This uses version 1.0.2 of JQuery UI Draggable Collision, along with JQuery 1.7.2 and JQueryUI 1.1.18.)

Here is the code:

$("#dragMe").draggable({
    obstacle: "#butNotHere",
    preventCollision: true,
    containment: "#moveInHere"
});

​

Old Solution

The following should work. It has a glitch, though. Once the divs collide, you have to “regrab” the div you are dragging, which can be a little annoying. Perhaps someone else will know how to fix this this. You can see my jsFiddle example here: http://jsfiddle.net/MrAdE/8/

var prevOffset, curOffset;
$("#dragMe").draggable({
    drag: function(e,ui) {
        prevOffset= curOffset;
        curOffset= $.extend({},ui.offset);
        return true;
    }
});

$("#butNotHere").droppable({
    greedy: true,
    over: function(e,ui) {
        ui.helper.offset(curOffset= prevOffset).trigger("mouseup");
    },
    tolerance: "touch"
});​