menus whose contents change

[Deborah Swayne <dfs research att com>]

I have some menus whose contents are not static -- cascading menus
may be needed sometimes but not always, for instance, and the state
of checkboxes may change.

If there's only one source of change, then I can call a routine that
destroys and rebuilds a menu, and that works reasonably well.
Sometimes, though, it seems preferable to build the menu on the fly.
I can do that by making some menus popup menus, and it works
wonderfully -- but they no longer behave like other menus.

I understand that they can't open when the mouse floats over, but I
don't like it that they trigger on a mouse-up instead of a
mouse-down, or that they position themselves at the center of the
menu item from which they're triggered.

Maybe this just isn't the best way to deal with menus whose contents
change -- does someone else have a better approach?  

Debby