private void ShowCaret () {
if (Caret.On)
return;
Caret.On = true;
ShowWindow (CaretWindow);
Graphics g = Graphics.FromHwnd (HIViewGetRoot (CaretWindow));
g.FillRectangle (new SolidBrush (Color.Black), new Rectangle (0, 0, Caret.Width, Caret.Height));
g.Dispose ();
}