JQuery sortable lists and fixed/locked items

Question

Is it possible to lock list items in JQuery sortable list in a way that those items will stay in that particular place in the list.

For example,

consider this pseudo list with locked items...

item A
item B(locked)
item C(locked)
item D
item E
item F
item G(locked)

So, I'd like to have the items B,C and G to be fixed in a way that if user drag and drop item D at the start of the list, the item A "jumps" over fixed/locked items B and C with following results...

item D
item B(locked)
item C(locked)
item A
item E
item F
item G(locked)

I've been searching for something like this without luck. Is it possible..?

Answer 1

Here's a hopefully bug-free version, updating as you drag. It's generating the current desired positions of the items when sorting starts, which means you should be able to change the classes whenever you need, refresh the widget's list items and you're good to go.

It also uses the sortable's built-in items property to prevent dragging the fixed items and to sort out any sorting problems at the top and the bottom of the list.

I tried to move the fixed items around, but that resulted in horribly buggy behaviour, especially when there are multiple fixed items in groups. The final solution detaches all fixed items from the list, adds a helper element to the front, then re-inserts the fixed elements to their desired position, which seems to fix all bugs.

Try the demo here: http://jsfiddle.net/PQrqS/1/

HTML:

<ul id="sortable">
    <li>oranges</li>
    <li class="static">apples</li>
    <li>bananas</li>
    <li>pineapples</li>
    <li>grapes</li>
    <li class="static">pears</li>
    <li>mango</li>
</ul>

CSS:

.static { color:red; }

li { background-color:whitesmoke; border:1px solid silver; width:100px; padding:2px; margin:2px; }

Javascript:

$('#sortable').sortable({
    items: ':not(.static)',
    start: function(){
        $('.static', this).each(function(){
            var $this = $(this);
            $this.data('pos', $this.index());
        });
    },
    change: function(){
        $sortable = $(this);
        $statics = $('.static', this).detach();
        $helper = $('<li></li>').prependTo(this);
        $statics.each(function(){
            var $this = $(this);
            var target = $this.data('pos');

            $this.insertAfter($('li', $sortable).eq(target));
        });
        $helper.remove();
    }
});