[gtkmm] Can't compile tutorial example "Drawing Lines".

[Charles LEONARD <charles leonard skynet be>]

Hello,

I'm trying to compile the tutorial example "Drawing Lines" from chapter 
14 (http://www.gtkmm.org/gtkmm2/docs/tutorial/html/ch14s03.html) with 
this command line:

gcc lines.cc -o lines `pkg-config gtkmm-2.0 --cflags --libs`

But the compiler returns the following errors:

lines.cc:12: conflicting return type specified for `virtual int
   cust_draw_area::on_expose_event(GdkEventExpose*)'
/usr/include/gtkmm-2.0/gtkmm/widget.h:342:   overriding `virtual bool
   Gtk::Widget::on_expose_event(GdkEventExpose*)'
lines.cc: In constructor `cust_draw_area::cust_draw_area(int, int)':
lines.cc:19: `size' undeclared (first use this function)
lines.cc:19: (Each undeclared identifier is reported only once for each
   function it appears in.)
lines.cc: In member function `virtual int
   cust_draw_area::on_expose_event(GdkEventExpose*)':
lines.cc:25: no matching function for call to `Glib::RefPtr<Gdk::Window>::
   draw_line(Glib::RefPtr<Gdk::GC>, int, int, int, int)'
lines.cc:26: no matching function for call to `Glib::RefPtr<Gdk::Window>::
   draw_line(Glib::RefPtr<Gdk::GC>, int, int, int, int)'
lines.cc:27: no matching function for call to `Glib::RefPtr<Gdk::Window>::
   draw_line(Glib::RefPtr<Gdk::GC>, int, int, int, int)'
lines.cc:28: no matching function for call to `Glib::RefPtr<Gdk::Window>::
   draw_line(Glib::RefPtr<Gdk::GC>, int, int, int, int)'
lines.cc:29: no matching function for call to `Glib::RefPtr<Gdk::Window>::
   draw_line(Glib::RefPtr<Gdk::GC>, int, int, int, int)'
lines.cc:30: no matching function for call to `Glib::RefPtr<Gdk::Window>::
   draw_line(Glib::RefPtr<Gdk::GC>, int, int, int, int)'

Could you help me?