The Meta key is an abstraction of the X Window System which is usually alt on most systems. ... Apple Macintoshes use the Apple key instead, for example. ... XmVACASCADEBUTTON actually specifies CascadeButtonGadgets as children of the MenuBar, but you need not worry about the implications of this for now ( see Section 6.3 )...colour . In order to illustrate the list example with a non-trivial and vaguely interesting application we actually use some Xlib colour routines. ...