[maemo-developers] How to judge if GtkWindow is on top of hildon desktop or NOT

[From: Zhu, Peter J]

I tried to use both gdk_window_is_visible and gtk_window_is_active to
judge if GtkWindow is on top of hildon desktop or not. But unfortunately
both fail to get correct result. 

For example, I launch my window and lauch another window on top of mine.
Then I judge if mine is still on top of desktop. But both methods return
TRUE. That's not correct. Anyone knows how to?

Thanks.