55) Can I grey out an item in a list? I want to make insensitive

items in a list so that they cannot be selected.

Answer:

From W. Scott Meeks of OSF:

Unfortunately, you can't do it directly since the list items aren't individual
widgets.  We've had other requests for this technology, but it didn't make the
cut for 1.2; it should be in some future release.

However, you can probably fake it in your application with some difficulty.
First, a list item is an XmString, so you can specify a different charset for
the item than for other items in the list and then specify a font in the
list's fontlist that matches the charset and gives you the visual you want.
The next problem is making the item unselectable.  One idea would be to have
the application keep track of the insensitive items and the items currently
selected.  Then you would set up a selection callback that when called would
check the item selected against the list of insensitive items and if the
selected item matched would deselect that item and reselect the previously
selected items.  Otherwise it would just update the application's list of
selected items.  The major drawback with this approach is that you'll get
flashing whenever the list selects an item and your application immediately
de-selects.  Unfortunately I can't think of a way around this without mucking
with the list internals.

Another alternative suggested is to use instead a column of say read only text
widgets which you can make insensitive.