bug#14259: 24.1; global-linum-mode slows down scrolling and user input in DocView

[James Hudon <jameshudon@gmail.com>]

Yes, with nlinum-mode, I don't notice the lag at all.

I should add the problem gets much worse as the document you're using
grows, which would explain why the lag you're getting is worse than a
"noticeable lag". With a 20-page doc, it's just really annoying. With
a 50-page doc [1], Emacs is completely unusable.

[1] a 50-page pdf:
http://www.symantec.com/content/en/us/enterprise/media/security_response/whitepapers/w32_stuxnet_dossier.pdf

hudon


On Wed, Apr 24, 2013 at 2:47 PM, Stefan Monnier
<monnier@iro.umontreal.ca> wrote:
>> 2. Open a PDF that has pages you can scroll
> [...]
>> 5. Ensure the global-linum-mode is enabled and now scroll around/change
>> pages/etc. There should be a noticeable lag that makes it very hard to use
>
> Indeed, I can reproduce it, and it's not just a "noticeable lag" for me,
> it's so dog slow that it makes you feel like Emacs is failing to respond.
>
>> Does it help to use nlinum from GNU ELPA instead?
>
> Yes, it's much faster.  With nlinum-mode, there is still a slowdown
> (slightly more noticeable for horizontal scrolls than vertical scrolls),
> but it's much less severe.
> You can see the exact same slow down if you just do:
>
>   M-: (set-window-margins (selected-window) 2) RET
>
> So the performance cost doesn't come from nlinum-mode.
> As for linum-mode, I'm not sure where the performance problem lies.
>
>
>         Stefan