From: Ken Hollis <khollis@northwest.com>
>fl_get_button_numb is the source of the problem.
fl_get_button_numb should only be used with button class.
It is unpredicable what would happen if the object
passed to the funciton is not a button.
If you must find out which mouse button is pressed,
you can use fl_get_last_xevent or fl_get_mouse.
It might be useful to have a function that works
in a similar way to fl_get_button_numb, but works
for all object classes.