public static IEnumerable <Run> ToRuns(this FormattedString formattedString, double defaultLineHeight = 0d, TextAlignment defaultHorizontalAlignment = TextAlignment.Start, Font?defaultFont = null, Color?defaultColor = null, TextTransform defaultTextTransform = TextTransform.Default, IFontManager?fontManager = null)
        {
            var runs = new List <Run>();

            if (formattedString != null && formattedString.Spans != null)
            {
                fontManager = fontManager ?? formattedString.RequireFontManager();

                for (var i = 0; i < formattedString.Spans.Count; i++)
                {
                    var span = formattedString.Spans[i];
                    var run  = span.ToRun(fontManager, defaultFont, defaultColor, defaultTextTransform);
                    runs.Add(run);
                }
            }

            return(runs);
        }