[Java-gnome-developer] Writing a Widget Using Cairo

[Sandor Bodo-M. <sbo...@gm...>]

I "ported" the example code found at
http://gnomejournal.org/article/34/writing-a-widget-using-cairo-and-gtk28 t=
o
libgtk-java.
To be able to run the code you need a patch from bugzilla
http://bugzilla.gnome.org/show_bug.cgi?id=3D328171 which exposes a
widgets allocation size.

import org.gnu.gdk.Color;
import org.gnu.gdk.GdkCairo;
import org.gnu.gtk.Allocation;
import org.gnu.gtk.DrawingArea;
import org.gnu.gtk.Gtk;
import org.gnu.gtk.Window;
import org.gnu.gtk.event.ExposeEvent;
import org.gnu.gtk.event.ExposeListener;
import org.gnu.gtk.event.LifeCycleEvent;
import org.gnu.gtk.event.LifeCycleListener;

public class EggClockFace extends DrawingArea implements ExposeListener {

    public EggClockFace() {
        super();
        this.addListener(this);
    }

    public boolean exposeEvent(ExposeEvent event) {

        GdkCairo cr =3D new GdkCairo(this.getWindow());

        cr.rectangle(event.getArea());
        cr.clip();

        draw(cr);

        return false;
    }

    private void draw(GdkCairo cr) {

        double x, y, radius;

        Allocation alloc =3D this.getAllocation();
        x =3D alloc.getX() + alloc.getWidth()  / 2;
        y =3D alloc.getY() + alloc.getHeight() / 2;
        radius =3D (x < y ? x : y) - 5;

        cr.arc(x, y, radius, 0, 2 * Math.PI);
        cr.setSourceRGB(1, 1, 1);
        cr.fillPreserve();
        cr.setSourceColor(Color.BLACK);
        cr.stroke();

        for (int i =3D 0; i < 12; i++) {
            double inset;

            cr.save();

            if ( i % 3 =3D=3D 0 ) {
                inset =3D 0.2 * radius;
            } else {
                inset =3D 0.1 * radius;
                cr.setLineWidth(0.5 * cr.getLineWidth());
            }

            cr.moveTo(x + (radius - inset) * Math.cos(i * Math.PI / 6),
                      y + (radius - inset) * Math.sin(i * Math.PI / 6));
            cr.lineTo(x + radius * Math.cos(i * Math.PI / 6),
                      y + radius * Math.sin(i * Math.PI / 6));
            cr.stroke();

            cr.restore();
        }
    }

    public static void main(String[] args) {
        Gtk.init(args);
        Window window =3D new Window();
        EggClockFace clock =3D new EggClockFace();

        window.add(clock);

        window.addListener(new LifeCycleListener() {
            public void lifeCycleEvent(LifeCycleEvent event) {
            };

            public boolean lifeCycleQuery(LifeCycleEvent event) {
                Gtk.mainQuit();
                return false;
            }
        });
        window.showAll();

        Gtk.main();
    }
}