Pinta.ColorGradientWidget.HandleMotionNotifyEvent C# (CSharp) Method

        private void HandleMotionNotifyEvent(object o, Gtk.MotionNotifyEventArgs args)
        {
            int px, py;
            Gdk.ModifierType mask;
            GdkWindow.GetPointer (out px, out py, out mask);

            int index = FindValueIndex (py);
            py = (int)NormalizeY (index, py);

            if (mask == Gdk.ModifierType.Button1Mask) {
                if (index != -1) {
                    double y = GetValueFromY (py);

                    vals[index] = y;
                    OnValueChanged (index);
                }
            }

            //to avoid unnessesary costly redrawing
            if (index != -1)
                GdkWindow.Invalidate ();
        }