u'''Scroll the window by the indicated number of lines.

def scroll_window(self, lines):
        u'''Scroll the window by the indicated number of lines.'''
        top = self.WindowTop + lines
        if top < 0:
            top = 0
        if top + System.Console.WindowHeight > System.Console.BufferHeight:
            top = System.Console.BufferHeight
        self.WindowTop = top