Reference

XIconSize(3x) on Linux

The text 20c06ddd1f8e, as Debian 2.2 (Potato), Debian 2.1 (Slink), Debian 2.0 (Hamm), Debian 1.3 (Bo) shipped it.

allocate icon size structure and set or read a window's WM_ICON_SIZES property

XIconSize(3x) on Linux now