XmMenuPosition(3) on Linux
The text e43afa18140f, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie) shipped it.
A RowColumn function that positions a Popup menu pane "XmMenuPosition" "RowColumn functions" "XmMenuPosition"