bug#38407: 27.0.50; infinite loop with display of large file without newlines

[Eli Zaretskii <eliz@gnu.org>]

> Cc: psainty@orcon.net.nz, pieter@vanoostrum.org, 38407@debbugs.gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Fri, 29 Nov 2019 16:31:44 +0200
> 
> On 29.11.2019 16:26, Eli Zaretskii wrote:
> > No, because programming-language modes include strings and comments,
> > where the correct rendering is important.
> 
> What about just compilation modes, then?
> 
> This is where I have routinely seen display slowdown because of long lines.

Are there a lot of parentheses/braces there? are they nested?

This variable will only have any visible effect when both of the
following conditions are true:

  . a physical line is very long
  . the line includes many parentheses and/or braces, especially if
    they are nested

If these conditions are not true, the variable will have no tangible
effect on redisplay performance.

Compilation buffers show errors and warnings, and this can easily
include strings.  For example, a code line that calls 'message' in
Lisp or 'printf' in C usually includes a string.  We don't want those
strings to be displayed incorrectly, unless displaying them correctly
takes a preposterous amount of time, at least not by default.