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bug#15555: 24.3; Bidirectional display very slow with long lines
From: |
Eli Zaretskii |
Subject: |
bug#15555: 24.3; Bidirectional display very slow with long lines |
Date: |
Tue, 08 Oct 2013 21:07:39 +0300 |
> Cc: 15555@debbugs.gnu.org
> From: Jerome L Quinn <jlquinn@us.ibm.com>
> Date: Tue, 8 Oct 2013 11:39:58 -0400
>
> I'm not sure it is the same bug. When I disable the bidi reordering
> variable,
> navigation speed becomes reasonable, even with the very long line length.
> I'm on a very fast machine, so #13675 may not be impacting me that badly.
>
> When bidi reordering is enabled, it is multiple seconds to move the
> cursor up and down, which is unusable.
You are on a very fast machine, so you don't see the slow redisplay
with such lines. But the basic problem remains: Emacs does not cope
well with long lines. It's just that in your case the border of
"unbearable" is farther.
> Setting bidi-paragraph-direction to right-to-left improves the
> situation some but I'd still call it unusable in this situation.
> Disabling reordering makes emacs as responsive as I'd expect,
> comparable to emacs23.
Emacs 24 cannot possibly work as fast as Emacs 23, since reordering of
bidirectional text does need a lot of additional processing. There's
nothing that can be done about that, without a complete rewrite of the
Emacs display engine (or purchasing a faster machine).
> I don't see as bad behavior when the text is in the left buffer or
> if I have only 1 window.
Then don't do that.
Again, these all are signs of slow redisplay with long lines. They
just become a bot faster or slower in specific situations and screen
arrangements.
> And disabling bidi reordering completely eliminates the bad behavior.
If you can afford that, go for it.