private void drawBox_onMousedown(object sender, MouseEventArgs e)
{
if (!backgroundWorker.IsBusy)
{
this.Invoke((Action)(() =>
{
var point = drawBox.PointToClient(Cursor.Position);
int x = point.X / (drawBox.Width / grid.Width + 1);
int y = point.Y / (drawBox.Height / grid.Height + 1);
grid.flipPoint(x, y);
DrawGrid();
}));
}
}