Re: Performance degradation from long lines

[Michael Heerdegen <michael_heerdegen@web.de>]

Eli Zaretskii <eliz@gnu.org> writes:

> First, it isn't visiting the file (i.e. reading it into a buffer) that
> takes time; in fact, the time to visit is almost entirely unaffected
> by line length.  What takes time is the display of the initial
> windowful of the file's text (and following redisplay as result of
> editing).  So I guess the proposal is to have a time-out on that
> initial display and on redisplay cycles.

BTW (I already discussed this with Eli some time ago), we already have a
solution in Emacs: longlines.el.  It's obsoleted and a bit complicated,
but something like

#+begin_src emacs-lisp
(add-hook 'find-file-hook
          (defun my-find-file-care-about-long-lines ()
            (save-excursion
              (goto-char (point-min))
              (when (and (not (eq major-mode 'image-mode))
                         (search-forward-regexp ".\\{2000\\}" 50000 t)
                         (y-or-n-p "Very long lines detected - enable longlines-mode? "))
                (require 'longlines)
                (longlines-mode +1)))))
#+end_src

solves the problem (though, using a heuristic in this case).

If someone would want write a slim version of longlines, it could be
part of a solution.


Michael.