Woody Hayday

The problem: You have a multi column (or area) JQuery UI Sortable (these are neat) which only needs to show a “drop zone” when the user has started to drag a sortable object.

The JQuery documentation for this doesn’t account for the reality of the above, its all very well if you want the empty column/div to SHOW all the time as empty, that is remain as some sort of visible placeholder, but if the empty list should show as empty, until an object is ready to be dropped on it then JQuery sortable’s don’t work. It all comes down to dimensions, if an empty list exists without a height value, you can’t drop onto it.

More specifically, if an empty jquery-sortable list exists without a specific height set at the point of [.sortable start] (that is BEFORE the event is fired) then you just cannot drop the sortable.

Image by Dmitry Baranovskiy

I played with fixing this by adjusting each empty list (in the example belows case #col1,#col2,#col3) to have a defined height (and background, which looks nice) within the sortable “start” option, but this just creates boxes (or landing pads/zones) you can see, but not drop on.

Long and short of it – the solution to being able to drop jquery sortable’s onto invisible empty lists is to bind a function which adds a css class (or sets the height specifically) to the empty (invisible) sortable list when a user clicks one of the goal objects. This is then fired BEFORE the sortable takes hold and so creates drag-droppable landing zones for the users held sortable. It then uses the sortables “stop” property to remove the class it has added to any columns which have it.

function sortAndDrag() {

	//show BEFORE sortable starts
     $("#col1, #col2, #col3").bind('click mousedown', function(){
          $(".col").each(function (c) {
                if ($("div", this).size() == 0) {
                    $(this).addClass("colZoneEmpty")
                }
            })
     });

	//enable sortable
    $("#col1, #col2, #col3").sortable({
        revert: true,
        connectWith: ".col",
        stop: function (a, d) {
            $(".col").removeClass("colZoneEmpty");
	    //any ajax processing
        }
    });

}
//in this example 3 column div's exist with the id's 'col1','col2','col3', all of which have the class 'col'
//colZoneEmpty is a css class which makes the empty list visible

There are of course improvements you could make here, like checking the users dragging before setting any styling, but this quick hackaround works where it shouldn’t.