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From: acevedo@james-tiptree-jr.mit.edu (Gabriel)
Newsgroups: comp.emacs,gnu.emacs
Subject: little kill-region hack
Message-ID: <1990Aug29.022757.2855@athena.mit.edu>
Date: 29 Aug 90 05:27:30 GMT
Sender: daemon@athena.mit.edu (Mr Background)
Distribution: comp
Organization: /mit/acevedo/.organization
Lines: 29

I don't know how many people are annoyed by this, but I imagine that
it's a significant amount. 

The scenario:
You are editing. Hitting keys really fast. Then all of a sudden
WHOOOSH!!! half your file disappears. "Ah, no problem" you think; but
you hit C-x u and get "No further undo information available"!!! Doing
C-h l reveals that you [once again] hit C-w accidentally. 

Thank God for auto-save!

Emacs has a kill limit of 8000 characters or so; kill a region larger
than that, and you get the "No more undo" business. The following little
modified version of `kill-region' simply checks to see the size of the
region you are killing; if it's larger than 7000, it does an auto-save.

(defun kill-region-safe (beg end)
  (interactive "*r")
  (if (< 7000 (- end beg))
      (do-auto-save))
  (copy-region-as-kill beg end)
  (delete-region beg end))

(define-key global-map "\C-w" 'kill-region-safe)

Very simple, but VERY useful. If you accidentally destroy your file, you
can just recover it right away with M-x recover-file. 
--
Raul