Implementing a LED-like widget

[Marcus Lundblad <ml Update UU SE>]

I'm trying to implement a widget simulating a LED.
What I have is a widget derived from Gtk::Frame (with style SHADOW_IN).
This frame holds a Gtk::DrawingArea (display in the follwing code..)

I have the following code intended to turn the inside of the widget yellow 
(as an example).

--------------------------------

Constructor contains this:

  set_shadow_type(Gtk::SHADOW_IN);
  set_size_request(10,10);
  display = new Gtk::DrawingArea;
  display->set_size_request(8,8);
  add(*display);

The method setting the LED in on-state:

    int width, height;
    Glib::RefPtr<Gdk::Window> win = display->get_window();
    win->get_size(width, height);
    Glib::RefPtr<Gdk::GC> gc = Gdk::GC::create(win);
    gc->set_foreground(Gdk::Color("Yellow"));
    win->draw_rectangle(gc, true, 0, 0, width, height);

----------------------------------

but nothing happens when calling the code to turn it on.
And by the way, I've set the minimum size of the frame and the drawing 
area using set_size_request.

Isn't this the correct way of using a Gtk::DrawingArea?
It seems to me not too far from the example code "example_drawingarea.cc".

//Marcus