XmStringBaseline(3) on Linux
The text 7fbbd84299bd, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie) shipped it.
A compound string function that returns the number of pixels between the top of the character box and the baseline of the first line of text "XmStringBaseline" "compound string functions" "XmStringBaseline"