libxcb finding PID of window

[ben]

Hello, misc;

I've been attempting to use OpenBSD libxcb to find the process ID of a window.
The function used to retrieve the PID is as follows:

pid_t
winpid(Window w)
{
        pid_t result = 0;

        xcb_res_client_id_spec_t spec = {0};
        spec.client = w;
        spec.mask = XCB_RES_CLIENT_ID_MASK_LOCAL_CLIENT_PID;

        xcb_res_query_client_ids_cookie_t c = xcb_res_query_client_ids(xcon, 1, 
&spec);
        xcb_res_query_client_ids_reply_t *r = 
xcb_res_query_client_ids_reply(xcon, c, NULL);

        if (!r)
                return (pid_t)0;

        xcb_res_client_id_value_iterator_t i = 
xcb_res_query_client_ids_ids_iterator(r);
        for (; i.rem; xcb_res_client_id_value_next(&i)) {
                spec = i.data->spec;
                if (spec.mask & XCB_RES_CLIENT_ID_MASK_LOCAL_CLIENT_PID) {
                        uint32_t *t = xcb_res_client_id_value_value(i.data);
                        result = *t;
                        break;
                }
        }

        free(r);

        if (result == (pid_t)-1)
                result = 0;
        return result;
}

The code compiles, however the function returns 0 as a result. I've checked
the value of i.rem; it's always 0. I've made sure that the XCB connection
(represented by xcon) exists.

Has anyone else encountered this error? Thank you in advance.

Ben Raskin.