No urgent bell (urgency hint) on a first message in the single window mode
If a successive message is received, then Gajim reports an urgent bell (makes a window title/bar blinking), but if a first message is received, it doesn't.
I've got the single window mode set, a tray icon disabled and when new event arrives: show notification set (but tried other options and they don't fix the problem).
If Gajim is in the detached roster mode, a roster sends an urgent bell on a first message received. So it looks like a chat window blocks roster events in the single window mode.