JQuery-UI Autocomplete, source callback and 'this' keyword

JQuery-UI Autocomplete, source callback and 'this' keyword

I'm confused what's going on with the source callback in JQuery-UI Autocomplete, and the 'this' keyword.

$('.selector).autocomplete({   source:  function(request, response) {
      $(this)    # is what?
}
});

I want $(this) to be the element that matched the original selector, so I can explore $(this).closest("form") to get some information about it's context, all unobtrusive style.  But that doesn't seem to be what "this" is there, oddly.

Anyone understand what 'this' is there?  Anyone understand the best way to have a source function that references the element it's attached to, so it can navigate the dom around it?