Performs the following steps
- If the popup has a -pullright and the event is on an item of this
menu, popup
->close
the pullright menu.
- If the popup has a -pullright and the event is a button-up of
the same button that started the popup, assign
popup
<-selected_item with the pullright
menu, assign -pullright with
@nil and popup->close
the pullright.
- If there is no -pullright and the event is the button-up event,
assign popup
<-selected_item with menu<-preview
and popup->close
the popup.
- If the event is a button-down, set popup
<-selected_item
to @nil and
send popup<-button to the event<-button
- If the event is a drag event, update menu
->preview.
If a pullright area is entered, popup->update
the pullright and popup->open
it.
