public MyCanvas(Composite arg0, int arg1)
{
super(arg0, arg1);
addPaintListener(new PaintListener () {
public void paintControl(PaintEvent event){

GC gc = event.gc;
gc.setBackground(new Color(null, 0,0,0));
gc.setForeground(red);
Rectangle rect = getClientArea();
gc.fillRectangle(rect.x,rect.y,rect.width, rect.height);
}
});

}