Bug 449618 - Some fonts have incorrect kerning only in KDE apps
Summary: Some fonts have incorrect kerning only in KDE apps
Status: RESOLVED UPSTREAM
Alias: None
Product: plasmashell
Classification: Plasma
Component: general (other bugs)
Version First Reported In: 5.23.5
Platform: Arch Linux Linux
: NOR normal
Target Milestone: 1.0
Assignee: David Edmundson
URL: https://bugreports.qt.io/browse/QTBUG...
Keywords:
Depends on:
Blocks:
 
Reported: 2022-02-04 19:52 UTC by walmartshopper
Modified: 2022-02-06 22:23 UTC (History)
2 users (show)

See Also:
Latest Commit:
Version Fixed/Implemented In:
Sentry Crash Report:

Attachments
Example with Source Sans 3 (83.67 KB, image/png)
2022-02-04 19:52 UTC, walmartshopper 		Details
Example with Ubuntu (85.70 KB, image/png)
2022-02-04 19:54 UTC, walmartshopper 		Details
Correct rendering in Font Management (40.25 KB, image/png)
2022-02-04 20:30 UTC, walmartshopper 		Details
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Description walmartshopper 2022-02-04 19:52:41 UTC 
Created attachment 146272 [details]
Example with Source Sans 3

SUMMARY
***
Font kerning is incorrect for certain fonts in KDE apps only. GTK apps have correct kerning. 
***


STEPS TO REPRODUCE
1. Open systemsettings > Fonts
2. Set general font to Ubuntu, Calibri, or Source Sans 3, size 8
3. Apply and then look at kerning in KDE apps

OBSERVED RESULT
Font kerning is wrong when using Ubuntu, Calibri, Source Sans Pro, or Source Sans 3.  Some other fonts I tested render correctly such as Liberation Sans, DejaVu Sans, Noto Sans, Roboto.

EXPECTED RESULT
Correct font kerning

SOFTWARE/OS VERSIONS
Operating System: Arch Linux
KDE Plasma Version: 5.23.5
KDE Frameworks Version: 5.90.0
Qt Version: 5.15.2
Fontconfig Version: 2:2.13.94-2
Kernel Version: 5.15.19-xanmod1-tt-1 (64-bit)
Graphics Platform: X11
Processors: 16 × Intel® Core™ i9-9900K CPU @ 3.60GHz
Memory: 31.3 GiB of RAM
Graphics Processor: NVIDIA GeForce RTX 3080 Ti/PCIe/SSE2

ADDITIONAL INFORMATION
I checked all my DPI settings.  Xorg is manually set to 108 DPI. KDE font settings are forced to 108 DPI.  ~/.config/fontconfig/fonts.conf DPI is set to 108. Xft.dpi is also set to 108. GTK apps render these same fonts correctly.
Comment 1 walmartshopper 2022-02-04 19:54:34 UTC 
Created attachment 146273 [details]
Example with Ubuntu
Comment 2 walmartshopper 2022-02-04 20:30:36 UTC 
Created attachment 146276 [details]
Correct rendering in Font Management

Source Sans 3 renders correctly in Font Management
Comment 3 walmartshopper 2022-02-04 20:33:34 UTC 
I have found that the same fonts I'm having trouble with do render correctly in Font Management.  The kerning seems to only be incorrect when the fonts are used in UI elements.
Comment 4 walmartshopper 2022-02-04 20:56:18 UTC 
Original report states that Noto Sans is not affected. Turns out it is, but it's less obvious.

When using the affected fonts, some letters appear to be shifted to the left when they follow certain other letters. For example the letter e is shifted to the left when it follows r, g, t.  The letter o gets shifted to the left when it follows c.  The letter x gets shifted when it follows p, etc.
Comment 5 Nate Graham 2022-02-05 22:30:02 UTC 
What about non-KDE Qt apps? For example: VLC, Clementine, QDirStat, or VirtualBox? Do those apps exhibit the issue as well?
Comment 6 walmartshopper 2022-02-06 22:07:01 UTC 
(In reply to Nate Graham from comment #5)
> What about non-KDE Qt apps? For example: VLC, Clementine, QDirStat, or
> VirtualBox? Do those apps exhibit the issue as well?

It does happen in VLC and Clementine, so I guess it needs to be reported to QT instead.
Comment 7 Nate Graham 2022-02-06 22:08:08 UTC 
Yep, sounds like it. You can do so at https://bugreports.qt.io. After doing so, could you paste it in the "URL" field of this ticket? Thanks!