在Mode-Line上显示当前Buffer的行数

代码：

(setq-default mode-line-format             (append mode-line-format                     '((:eval                        (let ((lines (count-lines (point-min) (point-max))))                          (propertize (format "[%d Lines]" lines)                                      'face '(:foreground "red" :background "green")                                      'mouse-face 'mode-line-highlightn                                      'help-echo (format "Current buffer contains %d lines." lines)))))))

效果：