Man pages matching name xcb_xinerama_is_active in section 3:

xcb_xinerama_is_active.3.en	debian 10 / libxcb-doc
xcb_xinerama_is_active.3.en	debian 11 / libxcb-doc
xcb_xinerama_is_active.3.en	debian 12 / libxcb-doc