bug#10835: 24.0.93; bidi-paragraph-direction slows down Shell mode

[Chong Yidong]

Eli Zaretskii <eliz@gnu.org> writes:

> Yes, the overlays together with the long search for paragraph
> beginning probably push the user experience from slightly below the
> annoyance threshold to just above it.
> ...
> How about setting bidi-paragraph-direction in comint buffers to
> left-to-right when the locale indicates that use of bidirectional
> scripts is unlikely?  We could use locale-language-names and an
> additional small database of languages that need bidi, to make that
> decision.  WDYT?

I'm not keen on bolting on this additional complexity.

I don't see any better way out, so we might as well take the risk and
switch to using text properties for color escape highlighting.  I just
committed a patch to do that, limiting the change to Shell mode and
leaving the other users of ansi-color.el unaffected (and still using
overlays).

Thanks for helping with this bug.  Hopefully the fix won't turn up any
problems...