Right now there is no indication at when a window as the demands-attention state set (typically it tried to focus itself but was prevented by focus-stealing-prevention)

Often this happens for "messaging windows" - xchat, Pidgin, Empathy, etc; and these eventually will be handled by the message tray design. It can happen for slow-starting windows, where you go back and work on something else - we likely will have special design for that in the future. It can also happen because an obscured window pops up a dialog.

A quick design targetted at a 2.28.0 quick-fix:

  If a window is demands attention, show a small icon for the 
  application as if it was in the notification area (to the left of all the
  system icons), and make it glow and/or pulse. The same glow/pulse should
  be used for the icon in the Applications Well.

  We should try to detect when that application already has a status
  icon in the notification area, and omit the extra icon in this case
  (just assume that the application is blinking its icon.)