simple draw on gtk canvas example

gtkdraw_signal.jl

using Gtk #master -> commit 9fc2ca1feef0c90195e5da755debca02edc5f111 Merge: 32aad6d ceb861c Author: Tim Holy <tim.holy@gmail.com> Date:   Thu Sep 10 05:59:34 2015 -0500

type pgraph
    c::Gtk.GtkWidget
end

function on_draw_event(w::Ptr{Gtk.GObject},cc::Ptr{Void},p::pgraph) 
    display(w);
    display(cc);
    display(pointer_from_objref(p.c));
    #print(Gtk.allocation(w))
    Int32(false) 
end

function window1()
    c = Gtk.@GtkCanvas();
    w = Gtk.@GtkWindow(c,"title b1");

    p = pgraph(c); 
    
    signal_connect(on_draw_event,c,:draw,Cint,(Ptr{Void},),true,p);

    show(c);
    nothing
end