x-window-property seems to return nil for most properties.

(x-window-property "WM_HINTS")  -> returns non-nil

(x-window-property "WM_NAME") -> returns nil even though the property is
set (and displayed by xprop)

(x-window-property "_NET_WM_STATE") -> returns nil even though property is
set

In fact I haven't found any property I can read other than WM_HINTS.

I know this worked with previous version of Emacs.

Version:

GNU Emacs 24.3.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.10.7) of
2014-01-28 on var-lib-archbuild-extra-x86_64-juergen