[GUI] Menu Command Events

[Daan Leijen]

>> Also, should enabling/disabling menu items be handled in a similar way, using a callback, or should menu items be explicitly enabled/disabled by IO actions like enableMenuItem and disableMenuItem?
>
> Preferably the latter. If a toolkit supports "tear-off" menus, the
> menu can remain on screen for an extended period, so the status of the
> individual menu items can change while the menu is displayed.
>
> Relying upon an on-popup callback is likely to result in tear-off
> menus not working properly.

Well said. I also vote for the latter. Why? it is simpler, it can be implemented anywhere, it is well understood, it is needed anyway to support
tear-off menus, and finally, a toolkit can optionally emit "initmenu" events
for application writers that want to optimize their calls to enable/disableMenuItem.

-- Daan.