internal void SetText()
{
DockPane theOnlyPane = (this.VisibleNestedPanes.Count == 1) ? this.VisibleNestedPanes[0] : null;
if (theOnlyPane == null)
Text = " "; // use " " instead of string.Empty because the whole title bar will disappear when ControlBox is set to false.
else if (theOnlyPane.ActiveContent == null)
Text = " ";
else
Text = theOnlyPane.ActiveContent.DockHandler.TabText;
}