drawing line in foreground

[Victor Hsieh <victor csie org>]

Greeting,

    I'm writing a program to draw a logic gate diagram.  I have a grid
    map in the background (Gtk::Layout), and some gates(Gtk::Image) on it.
    Now I'm trying to draw some wire to connect them together.  But here's
    a problem.

    If I draw the line in the backgroud, it'll cause problem if I want
    to remove the line or to move the line.  So I'd like to know if
    there's any proper solution here?

    Another problem, I wonder if it's possible to raise/lower a item in
    a container, e.g. if image a and b overlap, I want to sort them by
    myself.  I've tried to read gdk and gtk's code, but I can't find a good
    solution.

    Could any one help me to solve these two problem?
    Thanks for your help! :)

Best,
    Victor