bug#15555: Re: bug#15555: 24.3; Bidirectional display very slow with long lines

[Eli Zaretskii]

> Date: Tue, 18 Feb 2014 18:31:22 +0400
> From: Dmitry Antipov <dmantipov@yandex.ru>
> Cc: 15555@debbugs.gnu.org
> 
> Now I'm seeing the use case where each trivial cursor movement causes
> ~100 calls to bidi_shelve_cache, and each call copies ~1.5M of data.

Starting with revision 116494, bidi_shelve_cache should be called much
less, normally just once and sometimes twice per call to
move_it_in_display_line_to.

This doesn't solve the original bug, so the cursor will occasionally
still get stuck in that 4000.txt file, but at least it will do that
with much less noise.