JQuery UI draggable: Exceed containment on one side

I am using JQuery UI to implement resizable/draggable elements. Now I would like to define a containment for these elements that limits the resizing/dragging on exactly three(!) sides. E.g. have a look at this JSFiddle example. You can see that the contained element can only be resized/dragged inside the parent's area.

What I would like to achieve is that the element can exceed the bottom threshold and be moved to beyond the bottom border of the parent. Nevertheless the resizing/dragging should still be limited at the top, right and left sides as is prescribed by the parent's according borders.

So this modification is what I came up with:

// resizable/draggable option
resize/drag : function(event, ui) {
    expandParent("#parentElement", "#dragElement");
}

function expandParent(parentName, childName) {
    var dragEl = $(childName);
    var dragElTop = parseInt(dragEl.css("top"), 10);
    var dragElHeight = parseInt(dragEl.css("height"), 10);
    var dragElBottom = dragElTop + dragElHeight;
    var parentEl = $(parentName);
    var parentElBottom = parseInt(parentEl.css("height"));
    if(parentElBottom <= dragElBottom + 20) {
        parentEl.css("height", "+=2");
    }
}

If you play around with the bottom border you notice that the parent's area is expanded if the child gets too close to the bottom border of the parent. Unfortunately this stops after 20 pixels. You then have to release the mouse button and resize/drag again to extend the area further. Do you have any idea why that is?

Well that expandParent function is not going to work because container boundaries has been set by JQuery UI and it wont be updated until you release the mouse .

So i can think of two solution here one is elegant and the other is tricky

Obviously the elegant solution would be writing your own containing method which is free at bottom .

But now i have a tricky solution by using a dummy parent element and set its height to a large value like 1000 or height of window and then set overflow hidden attribute for real parent.

Here is my solution :

<div id="parentElement">
    <div id="dummy-parent">
        <div id="dragElement" class="dragClass">
            <p>Drag me around!</p>
        </div>
    </div>
</div>



function expandParent(parentName, childName) {
    var dragEl = $(childName);
    var parentEl = $(parentName);
    var dragElHeight=dragEl.height();
    if(parentEl.height() <= dragElHeight) {
        parentEl.height(dragElHeight);
    }
}

Check the JS Fiddle

You have to modify the code based on your application i just gave you the idea