Bug 155566

Summary: Scrolling becomes slow when text is selected
Product: [Applications] okular Reporter: Robert Knight <robertknight>
Component: generalAssignee: Okular developers <okular-devel>
Status: RESOLVED FIXED    
Severity: normal CC: 16303, aacid, kitts.mailinglists, niburu1
Priority: NOR    
Version: 0.6   
Target Milestone: ---   
Platform: Compiled Sources   
OS: Linux   
Latest Commit: Version Fixed In:
Sentry Crash Report:

Description Robert Knight 2008-01-12 20:47:38 UTC
Version:            (using KDE KDE 4.0.0)
Installed from:    Compiled From Sources

Scrolling performance worsens noticeably when text is selected.

Steps to reproduce:

1.  Open a PDF document containing a mixture of text and pictures.
2.  Scroll up and down with the mousewheel.  Scrolling feels smooth and quick.
3.  Select the Text Selection tool from the menu and select a few words on a page.
4.  Scroll up and down with the mousewheel.  Scrolling feels choppy whether or not the selected text is currently visible in the viewport.
Comment 1 Pino Toscano 2008-01-12 21:28:19 UTC
THe text selection is painted by okular itself, the backend is not involved in that. We try to do our best in that, but of course the painting gets slower than w/o selection. (Although, I did remember it was not painful.)
Comment 2 Robert Knight 2008-01-12 21:55:42 UTC
With Qt's paint debugging feature enabled (export QT_FLUSH_PAINT=1) you can see that when selecting text, Okular repaints the entire viewport whenever the selection is changed.

When scrolling without a text selection, only the newly exposed content in the viewport is drawn.

When scrolling with a text selection, the entire viewport is repainted every time the content is moved.
Comment 3 Pino Toscano 2008-01-13 13:21:44 UTC
The problem seems related to the information widget (the small popup on the top right (or left for RTL languages) corner of the page view).
When you are in modes when that widget is shown persistently, or until you click it, (eg the zoom and the selection modes), then we get repaints for all the viewport, even if just scrolling with no rect/text selection and even if by just 1 pixel.
Comment 4 Pino Toscano 2008-02-06 17:18:57 UTC
Can you confirm clicking (thus hiding) the information widget making the scrolling fast again?
Comment 5 Robert Knight 2008-06-05 19:37:56 UTC
> Can you confirm clicking (thus hiding) the information widget making the scrolling fast again? 

Yes.  Turning off the hint/information option in Okular's settings also works as well.  
Comment 6 NapBon 2010-02-17 21:13:17 UTC
Whenever I use the filte or the search feature and results become highlighted, scrolling is extremely slow. I down't have the problem with the info-message. Turning it on or of, doesn't make any difference.
Srolling through a search result is unusable.
Comment 7 niburu1 2010-02-25 22:49:48 UTC
Scrolling is slow also when using certain annotation features such as highlighting. As soon as the highlighting is no longer visible, scrolling becomes normal (fast) again. This is in KDE 4.4.
Comment 8 Kishore 2010-09-15 06:17:36 UTC
I am experiencing this too when i use the search feature. Scrolling is slow only when i am on the page that contains the highlighted search text.
Comment 9 Davor Cubranic 2011-06-19 06:15:53 UTC
This bug has been quiet in a while, and I can't reproduce it with 0.12.2. Is this
still an issue for the original commiter? If not, we can close the bug.
Comment 10 Kishore 2011-06-19 07:27:19 UTC
Now in kde 4.6.4, I no longer experience this issue.
Comment 11 Davor Cubranic 2011-06-19 20:45:12 UTC
I propose to close as FIXED then.