XmNotebookGetPageInfo(3) on Linux
The text ff2989aef48b, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie) shipped it.
A Notebook function that returns page information "XmNotebookGetPageInfo" "Notebook functions" "XmNotebookGetPageInfo"