Как в этом вашем GTK+ принято делать?

 /*
  * java-gnome, a UI library for writing GTK and GNOME programs from Java!
  *
  * Copyright © 2007-2010 Operational Dynamics Consulting, Pty Ltd and Others
  *
  * The code in this file, and the program it is a part of, is made available
  * to you by its authors as open source software: you can redistribute it
  * and/or modify it under the terms of the GNU General Public License version
  * 2 ("GPL") as published by the Free Software Foundation.
  *
  * This program is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE. See the GPL for more details.
  *
  * You should have received a copy of the GPL along with this program. If not,
  * see http://www.gnu.org/licenses/. The authors of this program may be
  * contacted through http://java-gnome.sourceforge.net/.
  */ 
 package cairo;
 
 import org.freedesktop.cairo.Context;
 import org.freedesktop.cairo.LinearPattern;
 import org.freedesktop.cairo.Pattern;
 import org.freedesktop.cairo.RadialPattern;
 import org.gnome.gdk.Event;
 import org.gnome.gtk.DrawingArea;
 import org.gnome.gtk.Gtk;
 import org.gnome.gtk.Widget;
 import org.gnome.gtk.Window;
 
 /**
  * Exercise drawing with the Cairo API. If you are rendering a custom Widget
  * or otherwise drawing stuff with Cairo that is to be presented by GTK, you
  * are expected to do this in the Widget.ExposeEvent handler for that Widget.
  * 
  * @author Andrew Cowie
  * @author Carl Worth
  * @author Dmitry Golovin
  */
 public class ExampleDrawing
 {
     public static void main(String[] args) {
         final Window w;
         final DrawingArea d;
 
         Gtk.init(args);
 
         w = new Window();
         w.setTitle("Drawing");
         w.setDefaultSize(150, 150);
 
         d = new DrawingArea();
         w.add(d);
         w.showAll();
 
         d.connect(new Widget.Draw() {
             public boolean onDraw(Widget source, Context cr) {
                 final Pattern linear, radial;
 
                 /*
                  * Now, finally do some drawing:
                  */
 
                 cr.setSource(1.0, 0.1, 0.0, 1.0);
                 cr.moveTo(10, 40);
                 cr.lineTo(120, 145);
                 cr.stroke();
 
                 /*
                  * If youre used to using RGB triplets, just normalize them to
                  * the 0.0 to 1.0 range by dividing by 255. It's all the same
                  * to Cairo, really.
                  */
 
                 cr.setSource(225 / 255.0, 148 / 255.0, 11 / 255.0, 1.0);
                 cr.rectangle(70, 70, 20, 40);
                 cr.fill();
 
                 /*
                  * Now a much more complicated example of drawing: a linear
                  * colour gradiant with a radial alpha mask.
                  */
 
                 linear = new LinearPattern(0, 0, 150, 150);
                 linear.addColorStopRGB(0.0, 0.0, 0.3, 0.8);
                 linear.addColorStopRGB(1.0, 0.0, 0.8, 0.3);
 
                 radial = new RadialPattern(75, 75, 15, 75, 75, 60);
                 radial.addColorStopRGBA(0, 0.0, 0.0, 0.0, 0.0);
                 radial.addColorStopRGBA(1, 0.0, 0.0, 0.0, 1.0);
 
                 cr.setSource(linear);
                 cr.mask(radial);
 
                 return true;
             }
         });
 
         /*
          * And that's it. Conclude with connecting the usual tear-down
          * handler, and then fire up the main loop.
          */
 
         w.connect(new Window.DeleteEvent() {
             public boolean onDeleteEvent(Widget source, Event event) {
                 Gtk.mainQuit();
                 return false;
             }
         });
 
         Gtk.main();
     }
 }