apps/graphics/twm4nx: The Icon Manager now adds a Main Menu entry that will de-iconify the Icon Manager or raise to the top of the hieararchy if not iconfified. This is useful when there are many open windows.
apps/graphics/twm4nx: In resize operation, don't let window get narrower than the minimum toolbar width.
apps/graphics/twm4nx: Add logic so that the main menu is place at (or near) the position where the background was clicked.
apps/graphics/twm4nx: Better integrate menus and iconifiction: Bringup up a menu is like de-iconifcation, except there is no icon to be erases; taking down a menu is like iconification except that there is no icon to present.
apps/graphics/nxwidgets: Add methods to all windows to query if a window is visible or hidden.
apps/graphics/twm4nx: Use NxWidgets methods which work in all contexts instead of trying to come up with a way to know if a window is displayed through complex flags.
Squashed commit of the following:
Clean-up some include path problems introduced with the previous set of changes.
app/include/graphics, apps/NxWidgets/UnitTests: Update include paths for file in new location.
apps/NxWidgets/nxwidgets and nxwm: Update include paths for file in new location.
apps/graphics/NxWidgets: Move nxwidgets and nxwm include/ directories to apps/include/graphics
