Finally, a feature I really like: a modified mode line.
When I work over a network, I forget which machine I am using. Also, I tend to I lose track of where I am, and which line point is on.
So I reset my mode line to look like this:
-:-- foo.texi rattlesnake:/home/bob/ Line 1 (Texinfo Fill) Top
I am visiting a file called foo.texi, on my machine rattlesnake in my /home/bob buffer. I am on line 1, in Texinfo mode, and am at the top of the buffer.
My .emacs file has a section that looks like this:
;; Set a Mode Line that tells me which machine, which directory, ;; and which line I am on, plus the other customary information. (setq-default mode-line-format (quote (#("-" 0 1 (help-echo "mouse-1: select window, mouse-2: delete others ...")) mode-line-mule-info mode-line-modified mode-line-frame-identification " "
mode-line-buffer-identification " " (:eval (substring (system-name) 0 (string-match "\\..+" (system-name)))) ":" default-directory #(" " 0 1 (help-echo "mouse-1: select window, mouse-2: delete others ...")) (line-number-mode " Line %l ") global-mode-string
#(" %[(" 0 6 (help-echo "mouse-1: select window, mouse-2: delete others ...")) (:eval (mode-line-mode-name)) mode-line-process minor-mode-alist #("%n" 0 2 (help-echo "mouse-2: widen" local-map (keymap ...))) ")%] " (-3 . "%P") ;; "-%-" )))
Here, I redefine the default mode line. Most of the parts are from the original; but I make a few changes. I set the default mode line format so as to permit various modes, such as Info, to override it.
Many elements in the list are self-explanatory:
mode-line-modified is a variable that tells whether the buffer
has been modified,
mode-name tells the name of the mode, and so
on. However, the format looks complicated because of two features we
have not discussed.
The first string in the mode line is a dash or hyphen, ‘-’. In
the old days, it would have been specified simply as
nowadays, Emacs can add properties to a string, such as highlighting
or, as in this case, a help feature. If you place your mouse cursor
over the hyphen, some help information appears (By default, you must
wait seven-tenths of a second before the information appears. You can
change that timing by changing the value of
The new string format has a special syntax:
#("-" 0 1 (help-echo "mouse-1: select window, ..."))
#( begins a list. The first element of the list is the
string itself, just one ‘-’. The second and third
elements specify the range over which the fourth element applies. A
range starts after a character, so a zero means the range
starts just before the first character; a 1 means that the range ends
just after the first character. The third element is the property for
the range. It consists of a property list, a
property name, in this case, ‘help-echo’, followed by a value, in this
case, a string. The second, third, and fourth elements of this new
string format can be repeated.
See Text Properties in The GNU Emacs Lisp Reference Manual, and see Mode Line Format in The GNU Emacs Lisp Reference Manual, for more information.
displays the current buffer name. It is a list
(#("%12b" 0 4 ….
#( begins the list.
The ‘"%12b"’ displays the current buffer name, using the
buffer-name function with which we are familiar; the ‘12’
specifies the maximum number of characters that will be displayed.
When a name has fewer characters, whitespace is added to fill out to
this number. (Buffer names can and often should be longer than 12
characters; this length works well in a typical 80 column wide
:eval says to evaluate the following form and use the result as
a string to display. In this case, the expression displays the first
component of the full system name. The end of the first component is
a ‘.’ (‘period’), so I use the
string-match function to
tell me the length of the first component. The substring from the
zeroth character to that length is the name of the machine.
This is the expression:
(:eval (substring (system-name) 0 (string-match "\\..+" (system-name))))
‘%[’ and ‘%]’ cause a pair of square brackets to appear for each recursive editing level. ‘%n’ says ‘Narrow’ when narrowing is in effect. ‘%P’ tells you the percentage of the buffer that is above the bottom of the window, or ‘Top’, ‘Bottom’, or ‘All’. (A lower case ‘p’ tell you the percentage above the top of the window.) ‘%-’ inserts enough dashes to fill out the line.
Remember, “You don’t have to like Emacs to like it”—your own Emacs can have different colors, different commands, and different keys than a default Emacs.
On the other hand, if you want to bring up a plain ‘out of the box’ Emacs, with no customization, type:
This will start an Emacs that does not load your ~/.emacs initialization file. A plain, default Emacs. Nothing more.