bug#18778: noticeable slowdown for buffers with long lines, word-wrap, and brackets

[Ivan Shmakov]

>>>>> Eli Zaretskii <eliz@gnu.org> writes:
>>>>> From: Ivan Shmakov <ivan@siamics.net>

[…]

 >> For the resulting buffer, operations like (next-line) or even
 >> (recenter) now result in a noticeable delay.

 >> The issue doesn’t appear when word-wrap is not used, or when there’s
 >> no brackets in the buffer.  Neither the issue appears in Emacs built
 >> 2014-10-09 from a then-recent Git clone.

 >> I’ve used the output of the following Shell command as a test.

 >> $ head -n 8192 < /usr/share/dict/american-english | fmt -w 1024

 > Is it an important use case?

        Is there any example of content for which using word-wrap would
        be reasonable, but which will never ever contain any braces?

 > If so, what is the real-life situation here?

        For one thing, MediaWiki (as in: Wikipedia) pages tend to use
        paragraph-long lines, and (just as any other human-readable text
        usually does) they use various braces more than occasionally;
        not to mention using [, ], {, } for the markup purposes.  (A few
        initial lines of the https://en.wikipedia.org/wiki/Emacs page
        source are MIMEd.)

        Using word-wrap when editing such pages is also more or less an
        obvious measure.

        (Now, for sure, I can try to mass-edit the pages I’m interested
        in to fit in 80 columns, but I doubt such a move would receive a
        warm welcome from the community.)

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