Pinta.CurvesDialog.HandleDrawingMotionNotifyEvent C# (CSharp) Method

        private void HandleDrawingMotionNotifyEvent(object o, Gtk.MotionNotifyEventArgs args)
        {
            int x, y;
            Gdk.ModifierType mask;
            drawing.GdkWindow.GetPointer (out x, out y, out mask);

            if (x < 0 || x >= size || y < 0 || y >=size)
                return;

            if (args.Event.State == Gdk.ModifierType.Button1Mask) {
                // first and last control point cannot be removed
                if (last_cpx != 0 && last_cpx != size - 1) {
                    foreach (var controlPoints in GetActiveControlPoints ()) {
                        if (controlPoints.ContainsKey (last_cpx))
                            controlPoints.Remove (last_cpx);
                    }
                }

                AddControlPoint (x, y);
            }

            InvalidateDrawing ();
        }