Subject: bug#148: [Bernardo Dal Seno]: scroll-margin and scroll-preserve-screen-position cause refresh problem

From: Sven Joachim <[email-masked]>
Date: Sun, 20 Apr 2008 15:57:18 +0200

On 2008-04-19 16:20 +0200, Stefan Monnier wrote:

> This behavior is not a bug in itself, it's just a symptom: it means that
> redisplay was interrupted by user input before it had time
> to terminate.  See redisplay-dont-pause.

Okay, maybe the submitter of the Debian bug should set
redisplay-dont-pause to t to work around the problem.

> So, the problem you're reporting is that Emacs's redisplay is too slow
> to keep up with the scrolling (which is indeed a problem).  This may of
> course depend on the file's content and the major-mode (since part of the
> redisplay time might be used by font-locking, for example).

Do you have an explanation why the combination of

(setq scroll-margin 2)
(setq scroll-preserve-screen-position)

slows down redisplay so much on C-v, especially if point is in the
middle of the window?  I've never seen the problem in the default
settings.

Sven