This Thread will exit RSSOwl in a clean way in case the virtual machine is
terminated in response to a user interrupt, such as typing ^C, or a
system-wide event, such as user logoff or system shutdown.
If true, the topCenter will always appear on a separate line by itself,
otherwise the topCenter will appear in the top row if there is room and
will be moved to the second row if required.
Show Tray Popup if:
- GlobalSettings allow it (GlobalSettings.showTrayPopup = TRUE)
- Unread news are available (teasing = TRUE)
- RSSOwl is minimized to the tray and not visible (isMinimizedToTray)
- No tray popup was made before (rssOwlTrayPopup = NULL), or
- The previous tray popup was already closed