bug#56393: Actually fix the long lines display bug

[Lars Ingebrigtsen]

Gregory Heytings <gregory@heytings.org> writes:

> Auto-narrow mode is now entered only when the buffer is actually
> displayed, which solves the problem of (with-temp-buffer
> (insert-file-contents ...) ...) and friends.

Great!  I think that'll take care of the vast majority of potential
problems in this area.

I've now tried the branch with a couple of files that Emacs currently
chokes on, and it seems to work well -- for instance, with the
dictionary.json file, I can search for "aan zich" and then edit the JSON
with the normal commands like `C-M-k' to kill a sexps -- which is
totally impossible on the current trunk.

There's some slight hangs when `C-s'-ing the file, but none that last
longer than a second or two.  (Perhaps that has something to do with
`C-s' trying to add highlights to all the matches?)

-- 
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   bloggy blog: http://lars.ingebrigtsen.no