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Gh0str1d3r
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Joined: 27 May 2008
Posts: 411

PostPosted: Tue Jul 24, 2018 5:09 pm    Post subject: okular slow rendering when scrolling Reply with quote

I am experiencing very slow rendering when I scroll in an okular document that fills my 4k screen or nearly fills it (window maximized or almost maximized, zoom to "fit width" or something close to it). Slow means it takes ~3 seconds to load a page (depending on content of course, but in an average research paper with figures). The same paper renders in almost no time using evince.

The worst case is that scrolling down only one line requires me to wait the same 3 seconds. That makes scrolling effectively impossible.

In addition, a page is often not rendered at all before I scroll to the bottom half of it (approximately). Before then, it's just white.

Does anyone else experience these problems? I have plenty of RAM (16 GB), and okular is allowed to make good use of it (set to "aggressive").

It's a bit faster when I disable text and figure anti-aliasing, but not by much.

Also, neither CPU nor RAM usage go up significantly when I am waiting for the page to render, at least in most cases.

Thanks for any hints.
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gorg86
Tux's lil' helper
Tux's lil' helper


Joined: 20 May 2011
Posts: 123

PostPosted: Tue Jul 24, 2018 7:20 pm    Post subject: Reply with quote

That's odd Okular is rendering a bit faster than Evince on my machine :O
I just have a 1080p monitor though.
3s is unacceptably slow though, do your PDFs have fancy pancy vector-graphics in them?
Both Okular and Evince should render at almost the same speed... both use poppler which uses cairo.
Those are my useflags:
Code:
kde-apps/okular-17.12.3:5::gentoo  USE="chm crypt djvu handbook image-backend mobi pdf postscript tiff -debug -epub -markdown -mobile -plucker -share -speech {-test}"
app-text/evince-3.24.2-r1:0/evd3.4-evv3.3::gentoo  USE="introspection postscript tiff -djvu -dvi -gnome -gnome-keyring -gstreamer -nautilus -nsplugin -t1lib -xps"

app-text/poppler-0.62.0-r1:0/73::gentoo  USE="cairo cxx introspection jpeg jpeg2k lcms png qt5 tiff utils -cjk -curl -debug -doc -nss"
x11-libs/cairo-1.14.12::gentoo  USE="X glib opengl svg xcb (-aqua) -debug (-gles2) -static-libs -valgrind" ABI_X86="32 (64) (-x32)"
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Gh0str1d3r
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Joined: 27 May 2008
Posts: 411

PostPosted: Tue Jul 24, 2018 10:00 pm    Post subject: Reply with quote

I have pretty much the same useflags. It must be related to the resolution. Even if I use just half of my sceen Okular works just fine. But on a 13" laptop, I really want to use all the screen when reading a paper.

The graphics are not super complicated. In fact, any PDF shows this behavior (pure text is faster but there is still a very annoying lag).
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