Bug 437046

Summary:	Flickering at the bottom of the window after finding text
Product:	[Applications] kate	Reporter:	php4fan
Component:	application	Assignee:	KWrite Developers <kwrite-bugs-null>
Status:	RESOLVED WORKSFORME
Severity:	major	CC:	christoph, waqar.17a
Priority:	NOR
Version First Reported In:	20.12.3
Target Milestone:	---
Platform:	openSUSE
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description php4fan 2021-05-13 13:10:29 UTC

SUMMARY

STEPS TO REPRODUCE
1. Open a text file that is at least big enough to exceed the height of the screen (or of the Kate window)
2. Hit ctrl+F and type a string that occurs several times in the text file
3. Hit F3 to find next

OBSERVED RESULT

At some point it will almost certainly happen that the next occurrence of the string is outside of the current window, and therefore Kate will scroll just enough so that it gets inside of the current window, and it will be close to the bottom of the window. So far so good.

Very often, it happens at this point that the bottom part of the window starts flickering randomly. At short irregular intervals of time, it alternates between viewing what is expected, and viewing another unrelated portion of the text. However, it's not as if the whole window was scrolling up and down, it's as if only a portion of the bottom part of the window was.

I hope this explains what happens. I can't take a screencast because as soon as I take focus away from Kate the issue stops.

The workaround is to scroll up and down, or switch to another window and back to Kate. Basically any interaction with the window will stop the flickering.

EXPECTED RESULT

This obviously shouldn't happen.

Operating System: openSUSE Tumbleweed 20210414
KDE Plasma Version: 5.21.4
KDE Frameworks Version: 5.81.0
Qt Version: 5.15.2
Kernel Version: 5.11.12-1-default
OS Type: 64-bit
Graphics Platform: X11
Processors: 8 × Intel® Core™ i7-1065G7 CPU @ 1.30GHz
Memory: 7.3 GiB of RAM
Graphics Processor: Mesa DRI Intel® Iris® Plus Graphics

Comment 1 Christoph Cullmann 2022-01-29 20:21:52 UTC

Hi, I can't reproduce that.
I both use Kate on X11 and Wayland daily and never got this.
Can others reproduce?
Is that perhaps some issue with your graphics driver & stack?

Comment 2 Waqar Ahmed 2022-01-29 20:27:40 UTC

I can say that flickers are there, not sure about find but random and not that often for ne. I often get a flicker over projects plugin or some other part of the editor. The flicker usually contains random garbage.

Could be related to graphics driver.

Comment 3 php4fan 2022-01-29 22:19:10 UTC

> The flicker usually contains random garbage

I get that too sometimes, usually small areas with flickering garbage. I think there's a separate bug report about that.
The root cause might be  the same, I don't know.

> Is that perhaps some issue with your graphics driver & stack?

It *looks* like the kind of thing that one would expect to be related to graphics drivers (or even hardware), but if that was the case, wouldn't it be very unlikely for it to only systematically affect one single application?

(P.S. not sure why this was in "needsinfo" status)

Comment 4 Christoph Cullmann 2022-03-06 19:50:17 UTC

I don't see how we can fix this.
Looking at the drawing code, we can not cause this.
e.g. we don't draw a lot of stuff on our own, Qt does that for us in most cases.
Therefore I close this as worksforme.
If you have more issues of such kind, please try to report them to the distro.
This is either a issue with your graphics driver or another part of the lower stack.

e.g. for me, everything flickers shortly after unlocking my wayland session after the last round of system updates, but that is no Kate issue either.

Comment 5 Christoph Cullmann 2022-03-06 19:52:52 UTC

Upsa, wanted works for me.
As said, I don't see how we either cause nor could fix this.