XmStringIsVoid --- A compound string function that provides information on the existence of non-zero-length text components, tab components, or separator components
XmStringIsVoid returns a Boolean value indicating whether
or not string s1 is void.
s1
Specifies the compound string
RETURN
Returns True if any non-zero-length
text components,
tab components,
or separator components
exist in s1.
That is, the function returns True if the string has
no text, tabs, or separators.
If s1 contains the NULL string, the function returns True.