protected override Gdk.Rectangle OnMouseMove (Context g, Color strokeColor, ImageSurface surface,
int x, int y, int lastX, int lastY)
{
double cx = Math.Round (x / 100.0) * 100.0;
double cy = Math.Round (y / 100.0) * 100.0;
double dx = (cx - x) * 10.0;
double dy = (cy - y) * 10.0;
for (int i = 0; i < 50; i++) {
g.MoveTo (cx, cy);
g.QuadraticCurveTo (
x + Random.NextDouble () * dx,
y + Random.NextDouble () * dy,
cx,
cy);
g.Stroke ();
}
return Gdk.Rectangle.Zero;
}