public void MousePressed(object sender, MouseEventArgs e)
{
// TODO: is Shift down -> fastMode=true
Debug.WriteLine("MousePressed!!");
startPoint.ProjectionStoE((int)e.GetPosition((UIElement)sender).X, (int)e.GetPosition((UIElement)sender).Y,
model.GetSOrigin(), model.GetSMax());
isDragging = true;
}