GtkEventBox::get_visible_window
Use this method to determine whether the event boxes' child window is visible or not. In case, it is invisible, that event box will only receive events and nothing else. On the other hand, if the child window is visible, it acts as the parent window for the widget contained in the event box.
The function will return true if the child window is visible, false otherwise.
See also: set_visible_window()