Bug 444261 - Wayland is unusable
Summary: Wayland is unusable
Status: RESOLVED DUPLICATE of bug 443951
Alias: None
Product: kwin
Classification: Plasma
Component: wayland-generic (show other bugs)
Version: 5.23.1
Platform: Kubuntu Linux
: NOR normal
Target Milestone: ---
Assignee: KWin default assignee
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2021-10-23 09:39 UTC by DimanNe
Modified: 2021-10-26 16:46 UTC (History)
2 users (show)

See Also:
Latest Commit:
Version Fixed In:


Attachments
upside down (739.83 KB, image/png)
2021-10-23 09:39 UTC, DimanNe
Details
problems with fonts (39.60 KB, image/png)
2021-10-23 09:43 UTC, DimanNe
Details

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Description DimanNe 2021-10-23 09:39:45 UTC
Created attachment 142784 [details]
upside down

SUMMARY

(you can see most of the issues described below on the screenshots)

* There are various artefacts:
    * text shown upside down with 4x scale (see upside_down_wayland.png)
    * some windows become filled with black colour permanently (see upside_down_wayland.png)
    * some windows become filled with black colour temporarily (for ~0.1s) while resizing.
    * duplicate content of a window flashing in a random place (for ~0.1s)
* It is very slow:
    * When I move a window I can see how it is shown in one place, then in ~0.3s it is shown where the cursor is. It is like fps = 3 (instead of usual 60-100).
    * Open and play any 4k 60fps Youtube video in Chrome in full screen, then open "Stats for nerds" (right click on video and click "Stats for nerds") and you will see that approximately HALF of all frames is dropped.
* Text is extremely blurry when display is scaled (it looks and feels as if scale was implemented as jpg scale, instead of rendering image with different settings/dpi/whatever).
* Also, some characters in text missing parts ("i" does not have the dot).
* The panel at the bottom disappears (see upside_down_wayland.png)

A couple more words about upside_down_wayland.png - one of the windows is Firefox, the other is System settings (but for some reason it displays parts of Konsole...)


STEPS TO REPRODUCE
1. Just try using it for about 5-10 min.

OBSERVED RESULT
See the attachments.



SOFTWARE/OS VERSIONS
Operating System: Kubuntu 21.10
KDE Plasma Version: 5.23.1
KDE Frameworks Version: 5.87.0
Qt Version: 5.15.2
Kernel Version: 5.13.0-20-generic (64-bit)
Graphics Platform: X11    # <---- I am reporting this bug in X session.
Processors: 32 × AMD Ryzen 9 5950X 16-Core Processor
Memory: 125.7 GiB of RAM
Graphics Processor: NVIDIA GeForce RTX 3060 Ti/PCIe/SSE2
Comment 1 DimanNe 2021-10-23 09:43:02 UTC
Created attachment 142785 [details]
problems with fonts

Another attachment where problems with fonts are visible much better
Comment 2 Nate Graham 2021-10-25 20:25:37 UTC
Thanks for the issue report. However we need for each issue to be a separate bug report so their root causes can be tracked separately. See https://community.kde.org/Get_Involved/Issue_Reporting#One_issue_per_Bugzilla_ticket

Based on your screenshot, it is highly likely that most or all of these issues are the same as the ones just fixed in Bug 443951, so I'm marking it as a duplicate.

If any of these issue persist once you update to Plasma 5.23.2 (which will have the fix), please file new bug reports--one per issue.

Thanks!

*** This bug has been marked as a duplicate of bug 443951 ***
Comment 3 DimanNe 2021-10-26 07:09:46 UTC
Thank you for the quick reply.
Yes, probably it is a duplicate.

But what about font rendering & scaling?

If you are interested as to why it is important:
There is this use-case when you have two displays of different _physical_ size (32 inches and 27 inches, for example), but the _same_ _resolution_. So, if you do not make any tweaks, the same character (GUI element) has different size on one display and the other.
So, the only solution is to scale one of them.
And that is where we are starting to have huge problems - check my "problems with fonts" screenshot - they are very blurry.
Comment 4 Nate Graham 2021-10-26 16:46:45 UTC
Fractional scaling (e.g. something other than 100%, 200%, or 300%) produces blurry results on Wayland due to a design decision in the Wayland protocol itself. See https://gitlab.freedesktop.org/wayland/wayland-protocols/-/issues/34. This is not a KDE problem but rather a Wayland problem. Hopefully someone eventually adds proper fractional scaling to Wayland.