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(emacs-lisp-intro.info)Simple Extension

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A Simple Extension: `line-to-top-of-window'
===========================================

   Here is a simple extension to Emacs that moves the line point is on
to the top of the window.  I use this all the time, to make text easier
to read.

   You can put the following code into a separate file and then load it
from your `.emacs' file, or you can include it within your `.emacs'
file.

   Here is the definition:

     ;;; Line to top of window;
     ;;; replace three keystroke sequence  C-u 0 C-l
     (defun line-to-top-of-window ()
       "Move the line point is on to top of window."
       (interactive)
       (recenter 0))

   Now for the keybinding.

   Nowadays, function keys as well as mouse button events and non-ASCII
characters are written within square brackets, without quotation marks.
(In Emacs version 18 and before, you had to write different function
key bindings for each different make of terminal.)

   I bind `line-to-top-of-window' to my <F6> function key like this:

     (global-set-key [f6] 'line-to-top-of-window)

   For more information, see *Note Rebinding Keys in Your Init File:
(emacs)Init Rebinding.

   If you run two versions of GNU Emacs, such as versions 20 and 21, and
use one `.emacs' file, you can select which code to evaluate with the
following conditional:

     (cond
      ((string-equal (number-to-string 20) (substring (emacs-version) 10 12))
       ;; evaluate version 20 code
       ( ... ))
      ((string-equal (number-to-string 21) (substring (emacs-version) 10 12))
       ;; evaluate version 21 code
       ( ... )))

   For example, in contrast to version 20, version 21 blinks its cursor
by default.  I hate such blinking, as well as some other features in
version 21, so I placed the following in my `.emacs' file(1):

     (if (string-equal "21" (substring (emacs-version) 10 12))
         (progn
           (blink-cursor-mode 0)
           ;; Insert newline when you press `C-n' (next-line)
           ;; at the end of the buffer
           (setq next-line-add-newlines t)
           ;; Turn on image viewing
           (auto-image-file-mode t)
           ;; Turn on menu bar (this bar has text)
           ;; (Use numeric argument to turn on)
           (menu-bar-mode 1)
           ;; Turn off tool bar (this bar has icons)
           ;; (Use numeric argument to turn on)
           (tool-bar-mode nil)
           ;; Turn off tooltip mode for tool bar
           ;; (This mode causes icon explanations to pop up)
           ;; (Use numeric argument to turn on)
           (tooltip-mode nil)
           ;; If tooltips turned on, make tips appear promptly
           (setq tooltip-delay 0.1)  ; default is one second
            ))

(You will note that instead of typing `(number-to-string 21)', I
decided to save typing and wrote `21' as a string, `"21"', rather than
convert it from an integer to a string.  In this instance, this
expression is better than the longer, but more general
`(number-to-string 21)'.  However, if you do not know ahead of time
what type of information will be returned, then the `number-to-string'
function will be needed.)

   ---------- Footnotes ----------

   (1) When I start instances of Emacs that do not load my `.emacs'
file or any site file, I also turn off blinking:

     emacs -q --no-site-file -eval '(blink-cursor-mode nil)'