In ClientWin.c, TryChildren() calls XQueryTree and returns the first window in
the list with a WM_STATE property set. However, XQueryTree returns a list of
children that "are listed in current stacking order, from bottom-most (first) to
top-most (last)." Thus, when a window contains more than one client,
XmuClientWindow returns the bottom-most one. This affects the behavior of tools
like xprop in fluxbox and probably ion, pekwm, etc. I've tested the following
patch, and it fixes the behavior:

--- oldClientWin.c      2006-07-10 00:26:04.000000000 -0500
+++ ClientWin.c 2006-07-10 00:09:26.000000000 -0500
@@ -82,18 +82,18 @@

     if (!XQueryTree(dpy, win, &root, &parent, &children, &nchildren))
        return 0;
-    for (i = 0; !inf && (i < nchildren); i++) {
+    for (i = nchildren; !inf && i; i--) {
        data = NULL;
-       XGetWindowProperty(dpy, children[i], WM_STATE, 0, 0, False,
+       XGetWindowProperty(dpy, children[i-1], WM_STATE, 0, 0, False,
                           AnyPropertyType, &type, &format, &nitems,
                           &after, &data);
        if (data)
            XFree(data);
        if (type)
-           inf = children[i];
+           inf = children[i-1];
     }
-    for (i = 0; !inf && (i < nchildren); i++)
-       inf = TryChildren(dpy, children[i], WM_STATE);
+    for (i = nchildren; !inf && i; i--)
+       inf = TryChildren(dpy, children[i-1], WM_STATE);
     if (children)
        XFree(children);
     return inf;