Re: Property notify on root window in Gtk2.0

[Peter Zelezny <pzel dodo com au>]

On Mon,  7 Oct 2002 10:03:37 -0400 (EDT)
Owen Taylor <otaylor redhat com> wrote:

> > Could somone suggest a way to get property notifies on the root window 
> > using GTK2's signal system?
> >
> > In 1.2, I'd do it something like this:

[snip]

> I'd suggest that gdk_window_add_filter() and dealing with the raw X events
> is the best approach. (I'd think the above would still work, but it's 
> definitely a hack.)

That means to work, but something strange is happening. I'm doing
something like this:

gdk_window_set_events (GDK_ROOT_PARENT (), GDK_PROPERTY_CHANGE_MASK);
gdk_window_add_filter (GDK_ROOT_PARENT (), root_event_cb, NULL);

But in the callback function, event->type is always GDK_NOTHING. Although,
if I treat "event" as a GdkEventProperty, event->atom is often valid, and one
I'm interested in. Just wondering how I can know that event->atom is valid?
Because when it's not, I get gdk warnings when running gdk_x11_atom_to_xatom()
on it.

My code:

static GdkFilterReturn
root_event_cb (GdkXEvent *xevent, GdkEventProperty *event, gpointer data)
{
        Atom at = None;

        if (at == None)
                at = XInternAtom (GDK_DISPLAY (), "_XROOTPMAP_ID", True);

        if (at == gdk_x11_atom_to_xatom (event->atom))
                redraw_trans_xtexts (); /* redraw transparent backgrounds */

        return GDK_FILTER_CONTINUE;
}


-- 
Peter Zelezny.