XmAddToPostFromList man page
XmAddToPostFromList — a RowColumn function that makes a menu accessible from more than one widget
#include <Xm/RowColumn.h> void XmAddToPostFromList( Widget menu, Widget post_from_widget);
XmAddToPostFromList makes a menu accessible from more than one widget. After a menu is once created, this function may be used to make that menu accessible from a second widget. The process may be repeated indefinitely. In other words, where an application would use XmCreatePopupMenu or XmCreatePulldownMenu or their equivalent to create a new menu identical to one that already exists, it can use this function to reuse that earlier menu.
If menu refers to a Popup menu, then the post_from_widget widget can now pop up the specified menu. The actual posting of the menu occurs as it always does, either through an event handler, or the automatic popup menu support (see the XmRowColumn(3) reference page).
If menu refers to a Pulldown menu, its ID is placed in the XmNsubMenuId resource of the specified post_from_widget. In this case, the post_from_widget widget must be either a CascadeButton or a CascadeButtonGadget.
Note that this function manipulates the internal structures themselves, not a copy of them.
Specifies the ID of the RowColumn widget containing the menu (Popup or Pulldown) to be made accessible from the widget.
Specifies the widget ID of the widget which will now be able to post the menu specified by menu.
For a complete definition of RowColumn and its associated resources, see XmRowColumn(3).
XmGetPostedFromWidget(3), XmRemoveFromPostFromList(3), and XmRowColumn(3).