public static List <iText.Layout.Element.IElement> ToIText(this CanvasControl control)
        {
            List <iText.Layout.Element.IElement> list = new List <iText.Layout.Element.IElement>();

            if (control is CanvasRichTextBox rtb)
            {
                list.Add(rtb.ToIText());
            }
            else if (control is CanvasImage image)
            {
                list.Add(image.ToIText());
            }
            else if (control.GetType().IsSubclassOf(typeof(CanvasVariable)))
            {
                CanvasVariable cv = control as CanvasVariable;
                list.Add(cv.ToIText());
            }
            else
            {
                Logger.Log(Severity.ERROR, LogCategory.CONTROL,
                           "Conversion from " + control.GetType().ToString() +
                           " to iText element array not implemented.");
            }

            return(list);
        }