fix root prop watcher: was not listening for root window property cha…

…nge events! (so nothing ever fired)

git-svn-id: https://xpra.org/svn/Xpra/trunk@4526 3bb7dfac-3a0b-4e04-842a-767bc560f471

src/xpra/x11/xroot_props.py

@@ -24,18 +24,23 @@ def __init__(self, props):
         gobject.GObject.__init__(self)
         self._props = props
         self._root = gtk.gdk.get_default_root_window()
+        self._saved_event_mask = self._root.get_events()
+        self._root.set_events(self._saved_event_mask | gtk.gdk.PROPERTY_CHANGE_MASK)
         add_event_receiver(self._root, self)
 
     def cleanup(self):
         remove_event_receiver(self._root, self)
+        self._root.set_events(self._saved_event_mask)
 
     def do_xpra_property_notify_event(self, event):
         log("XRootPropWatcher.do_xpra_property_notify_event(%s) props=%s", event, self._props)
         if event.atom in self._props:
             self._notify(event.atom)
 
     def _notify(self, prop):
-        v = prop_get(self._root, prop, "latin1", ignore_errors=True)
+        ptype = "latin1"
+        v = prop_get(self._root, prop, ptype, ignore_errors=True)
+        log("XRootPropWatcher._notify(%s) value(%s)=%s", prop, ptype, v)
         self.emit("root-prop-changed", prop, str(v))
 
     def notify_all(self):