Sticky pop-up menus

["Ratcliffe, Jeffrey (Peters)" <Jeffrey Ratcliffe External eads com>]

The pop-up menus in my little scanning application work fine in themselves, but they are only visible whilst 
the right mouse button is pressed.

A user has requested that they should work ala Nautilus, i.e. in addition to the current behaviour, on a 
single right click, the pop-up stays visible and the item can then be selected with left or right clicks.

I've had a search around, but can't find a standard solution to this.

I presumably need to distinguish the two types of click with something like 

$event->type eq 'click'

$event->type eq 'click_and_hold'

How do I go about implementing this?

Thanks for any ideas

Jeff