DocView has a long delay between user input and UI update

[James Hudon]

Reproduced on 12.10 with emacs-snapshot. Also on 12.04 LTS with emacs24 (both from PPA and from canonical).
I don't have any special PDF viewers installed, just the stock Evince.

1. Launch emacs with "emacs -Q"
2. Open a large PDF that has pages you can scroll (the larger the doc, the worse it is. A ~4mb 50-page doc (attached) should be used to reproduce)
3. Scroll around (should be responsive)
4. Turn on `M-x global-linum-mode`
5. Ensure the global-linum-mode is enabled and now scroll around. There should be a noticeable lag that makes it really difficult to use.

[Damien Cassou (cassou)]

I can't reproduce on 12.10 with both emacs24 and emacs-snapshot. I suggest you use M-x report-emacs-bug.

I'm closing the issue right now. Please feel free to open it again should you have more information.

[James Hudon (jameshudon)]

@Damien Cassou
I think I narrowed it down:

1. Launch emacs with "emacs -Q"
2. Open a PDF that has pages you can scroll
3. Scroll around (should be responsive)
4. Turn on `M-x global-linum-mode`
5. Ensure the global-linum-mode is enabled and now scroll around (noticeable lag)

so when I comment out (global-linum-mode 1) in my init.el, the problem goes away.

[James Hudon (jameshudon)]

re-opened bug and reported it upstream as suggested. Let me know if you still can't repro

[Damien Cassou (cassou)]

I still can't reproduce. I see number 1 in the margin, but I can still scroll fast.

[James Hudon (jameshudon)]

Another observation is that the bigger the document, the worse the problem. On a 20-page document, it is noticeable. On a 50-page document, Emacs is completely unusable. I attached a 50-page doc where this happens. I can't even go to the next page now.

[Damien Cassou (cassou)]

I confirm the problem can be reproduced with a large document and global-linum-mode. If the document is small *or* if linum-mode is not active, everything is fine.

[James Hudon (jameshudon)]

Thanks. Updated description to mention file size.

[Damien Cassou (cassou)]

I'm closing this report as it doesn't look like I can do anything. Upstream needs to fix this.