If not call "Draw.Command(cam)" in DrawShapes,drawing will flicker!

I thought that when there is no content to be drawn, there is no need to call "Draw.Command(cam)"

So my code is:

public override void DrawShapes(Camera cam)
{
    if (selction == null || selction.Length < 1)
    {
        return;
    }

    using (Draw.Command(cam))
    {
        // set up static parameters. these are used for all following Draw.Line calls

        // todo 要显示在上层
        Draw.ZOffsetUnits = -2;
        Draw.ZOffsetFactor = 0;
        Draw.Color = color;
        Draw.Matrix = transform.localToWorldMatrix * coordToLocalMatrix;

        foreach (var coord in selction)
        {
            Draw.Rectangle(new Rect(coord.x, coord.y, 1f, 1f));
        }
    }
}

then drawing will flicker!

then I move the return logic into `using (Draw.Command(cam))`

public override void DrawShapes(Camera cam)
{
    using (Draw.Command(cam))
    {
        // todo 要显示在上层
        Draw.ZOffsetUnits = -2;
        Draw.ZOffsetFactor = 0;
        Draw.Color = color;
        Draw.Matrix = transform.localToWorldMatrix * coordToLocalMatrix;

        if (selction != null && selction.Length >= 1)
        {
            foreach (var coord in selction)
            {
                Draw.Rectangle(new Rect(coord.x, coord.y, 1f, 1f));
            }
        }
    }
}

problem fixed!