void gtk_window_set_keep_above ( GtkWindow* window, gboolean setting )
Asks to keep
window above, so that it stays on top. Note that
you shouldn’t assume the window is definitely above afterward,
because other entities (e.g. the user or
[window manager][gtk-X11-arch]) could not keep it above,
and not all window managers support keeping windows above. But
normally the window will end kept above. Just don’t write code
that crashes if not.
It’s permitted to call this function before showing a window, in which case the window will be kept above when it appears onscreen initially.
You can track the above state via the “window-state-event” signal
Note that, according to the Extended Window Manager Hints Specification, the above state is mainly meant for user preferences and should not be used by applications e.g. for drawing attention to their dialogs.