Autocomplete - show all values

Autocomplete - show all values

Hi
 
I'm using autocomplete on a project I'm working on, but there is one requirement that I can't meet at present, which is a 'show all' button that is supposed to trigger the drop down to appear, for an empty search.
 
I've done a lot of searching and haven't found a solution.  I'm currently attempting the following method:
 
When the Show All button is clicked, the autocomplete is updated so that minChars is 0.  I'm then setting focus to the field.
 
Unfortunately setting the focus isn't actually firing the search (although if I manually click into the field it does).
 
I'm not sure if this method is even possible - it seems reasonable, maybe I'm just going about it in the wrong way.  Any tips on how I could approach this would be greatly appreciated!