XmListYToPos(3) on Linux
The text 034c637ad2d4, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie) shipped it.
A List function that returns the position of the item at a specified y-coordinate "XmListYToPos" "List functions" "XmListYToPos"