private void DrawLine(VisualTextLine line) {
     if (line.Index < visuals.Count) {
         visuals.Insert(line.Index, line);
         visuals.RemoveAt(line.Index + 1);
         line.Draw();
     } else {
         visuals.Add(line);
         line.Draw();
     }
 }
        private void RedrawCollapsedLine(VisualTextLine collapsedLine, int line) {
            if (line >= visuals.Count) {
                visuals.Add(null);
            } else {
                visuals[line] = null;
            }

            visuals[line] = collapsedLine;

            collapsedLine.Draw();
        }