This function is obsolete and its behavior is replaced by setting
XmNnavigationType to XmEXCLUSIVE_TAB_GROUP.
When the keyboard is used to traverse through a widget hierarchy, primitive
widgets are grouped together into what are known as tab groups. Any
manager or primitive widget can be a tab group. Within
a tab group, move the focus to the next widget in the tab
group by using the arrow keys. To move to another tab group, use
KNextField or KPrevField.
Tab groups are ordinarily specified by the XmNnavigationType
XmAddTabGroup is called to control the order of traversal of tab
groups. The widget specified
by tab_group is appended to the list of tab
groups to be traversed, and the widgets XmNnavigationType is set
Specifies the manager or primitive widget ID