Coder la lentille de trace appartenant à un flot Drawer.

import broad.gfx.draw.Drawer;
import java.awt.Graphics2D;
import broad.util.CannotBeNullException;
import broad.string.output.StringOutput;

public class TraceDrawer implements Drawer {
    private StringOutput output;
    private Drawer lensee;
    public TraceDrawer(StringOutput output, Drawer lensee) {
        if(output == null) throw new CannotBeNullException(this, "output");
        if(lensee == null) throw new CannotBeNullException(this, "lensee");
        this.output = output;
        this.lensee = lensee;
    }
    public void draw(Graphics2D g) {
        output.setString("Trace: lensee called: " + lensee);
        lensee.draw(g);
    }
}

new TraceDrawer t1

new TraceDrawer t2

new TraceDrawer t3

new broad.string.output.util.ConsoleStringOutput consoleOut

tie t1 0 consoleOut 0

tie t2 0 consoleOut 0

tie t3 0 consoleOut 0

group trace t1 t2 t3 consoleOut