internal RibbonPanelPopup(RibbonPanel panel)
        {
            DoubleBuffered = true;

            _sensor = new RibbonSensor(this, panel.Owner, panel.OwnerTab);
            _sensor.PanelLimit = panel;
            _panel = panel;
            _panel.PopUp = this;

            using (Graphics g = CreateGraphics())
            {
                Size s = panel.MeasureSize(this, new RibbonElementMeasureSizeEventArgs(g,
                    GetSizeMode(panel)));
                //s.Width+=3; s.Height+=3;
                Size = s;
                panel.SetBounds(new Rectangle(0, 0, Size.Width, Size.Height));
                panel.UpdateItemsRegions(g, GetSizeMode(panel));
            }

            foreach (RibbonItem item in panel.Items)
            {
                item.SetCanvas(this);
            }
        }