XmTextPosToXY(3) on Linux
The text 4155502cb655, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie) shipped it.
A Text function that accesses the x and y position of a character position "XmTextPosToXY" "Text functions" "XmTextPosToXY"