xqf Depends and Build-Depends on packages from gdk-pixbuf-xlib, which is
no longer maintained upstream and has been archived, meaning that issue
reports and contributions are no longer accepted.

The readme of the archived project says:

    No newly written code should ever use this library.

    If your existing code depends on gdk-pixbuf-xlib, then you're strongly
    encouraged to port away from it.

This deprecation applies to <gdk-pixbuf-xlib/*.h> and the
gdk-pixbuf-xlib-2.0 pkg-config module, which means the
libgdk-pixbuf-xlib-2.0-dev and libgdk-pixbuf-xlib-2.0-0 Debian packages.

Please try to avoid this dependency. Copying the necessary functions
into the xqf source would probably be better than having the external
dependency, at this point.

Thanks,
    smcv