Verify tries to find the popup-menu to be displayed and sets the
-context attribute of the popup_gesture to the event-receiver
if it is not set to @nil.
If the popup_gesture<->popup
attribute of the gesture is set, this popup menu is used. If it is a function
object, the function is evaluated. See
popup_gesture<-popup.
Otherwise, the event<-master
is requested a popup with
popup_gesture<-popup.
After finding a popup
object, this object is sent popup->update
to update its menu_items. If, after graphical<-active
or‘popup
popup_gesture<-members’is empty, popup_gesture->verify
fails.
