Subject: bug#11943: 24.1.50; Emacs unusably slow when looking at large files (bidi support at fault)

From: Lawrence Mitchell <[email-masked]>
Date: Sun, 15 Jul 2012 12:58:17 +0100

Eli Zaretskii wrote:

[...]

> What is the major mode in the buffer where you see this?  I mean the
> real-life example where you bumped into this, not the 'snippet' file
> produced by the above.

This appears to be an issue with buffers that have no strongly
R2L or L2R characters near point-min.

emacs -Q

C-x b *tmp* RET
M-x fundamental-mode RET
M-: (dotimes (i 100000) (insert "1\n")) RET
M-<

next-line now has a noticeable delay (especially when holding
down next-line, display doesn't update the cursor position).

Now insert an 'a' somewhere near the beginning of the buffer,
display updates appear instantaneous again.  If we instead go to
the end of the buffer and insert an 'a', no such change in the
response occurs.

Cheers,
Lawrence
-- 
Lawrence Mitchell <[email-masked]>