Subject: Re: bug#23861: 25.1.50; fast-but-imprecise-scrolling: What does "somewhat inaccurate" mean?

From: Eli Zaretskii <[email-masked]>
Date: Tue, 28 Jun 2016 19:14:58 +0300

> From: Phil Sainty <[email-masked]>
> Date: Wed, 29 Jun 2016 01:03:00 +1200
> 
> It's unclear to me what the following excerpt from the docstring
> for the `fast-but-imprecise-scrolling' variable actually means:
> 
>  > Note that this optimization can cause the portion of the buffer
>  > displayed after a scrolling operation to be somewhat inaccurate.
> 
> "somewhat inaccurate" is incredibly vague if you don't already
> know what it means.

It means that what's on the screen might not reflect what's in the
buffer.

It's hard to tell anything more specific, since which redisplay
optimizations will be taken in each case depends on many factors on
which the user has no control.

> Does it mean that the position scrolled to might be further (or
> less far) than it would have been otherwise?

It could.

> Does it mean that the font-locking may be incomplete or incorrect?

It could.

> Does it mean that the buffer text may appear corrupted?!

It could, if faces change the font size.