void OnActiveDocumentChanged(object sender, Gui.DocumentEventArgs e)
 {
     ActiveDocumentChanged?.Invoke(this, TryGetActiveDocument());
     activeDocument = e.Document;
 }
 void OnDocumentClosed(object sender, Gui.DocumentEventArgs e)
 {
     // TODO: Figure out how to detect this is a non-roslyn document.
     //e.Document.Editor.TextView.TextBuffer.PostChanged -= OnNonRoslynBufferChanged;
 }