public ThresholdMarker(ILineGraph graph, GLPoint location, GLSize size, GLColor color) { _graph = graph; _rectangle = new Rectangle(color, true, location, size); _rectangle.Origin = new GLPoint(_rectangle.Origin.X - size.Width / 2.0, _rectangle.Origin.Y - size.Height / 2.0); graph.Control.MouseMove += OnMouseMove; graph.Control.MouseDown += OnMouseDown; graph.Control.MouseUp += OnMouseUp; }