When a window gets the demands attention hint (_NET_WM_STATE_DEMANDS_ATTENTION) or the urgency flag, the pager flashes the window’s entry on the taskbar. Other pagers such as AWN may bounce the window’s icon in their dock. However, the window itself doesn’t change at all. To remedy, this, GNOME bug 120406 suggests that the frame, or the titlebar, of a window which demands attention should flash as well.
One problem with this is that a window which demands attention necessarily isn’t on top, so is likely to be at least partly obscured. On the other hand, someone suggests that the existing visual-bell mechanism could be reused here instead.
Photo © juliebee, cc-by-nc-nd.