Bug 414228

Summary:	100% CPU usage and lag when scrolling
Product:	[Applications] okular	Reporter:	Lars Veldscholte <lars>
Component:	general	Assignee:	Okular developers <okular-devel>
Status:	REPORTED ---
Severity:	normal	CC:	yurchor
Priority:	NOR
Version:	1.8.3
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description Lars Veldscholte 2019-11-17 12:26:40 UTC

SUMMARY
Scrolling of PDF files in Okular 1.8.3 is very laggy and consumes 100% CPU (on one thread) while the scrolling animation is running.

STEPS TO REPRODUCE
1. Open a PDF file in Okular.
2. Scroll.

OBSERVED RESULT
The scrolling animation has low framerate, lags behind the input actions, and consumes 100% CPU on one thread.

EXPECTED RESULT
Smooth, snappy scrolling.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma
KDE Plasma Version: 5.17.3
KDE Frameworks Version: 5.64.0
Qt Version: 5.13.2

ADDITIONAL INFORMATION

Comment 1 Yuri Chornoivan 2019-11-17 12:36:44 UTC

Does it happen for every possible file or just for the files with images/background? If it is some specific file can you share it for testing?

Does switching off optimizations in "Settings -> Configure Backends..." help?

Are you running the default Okular without any additional configurations?

Thanks in advance for your answers.

Comment 2 Lars Veldscholte 2019-11-17 12:39:33 UTC

It happens with every PDF I've tried so far. In fact, it even happens with plain text files; it seems to be unrelated to the backend.

This is just Okular from the Arch repositories, I did not customise it in any way.

Comment 3 Yuri Chornoivan 2019-11-17 12:44:32 UTC

The answers were given.