Created attachment 120812 [details]
kcm_fonts screenshot #1
After update to plasma 5.16.0 I can't see font previews in kcm_fonts.
It works for me in version 5.15 though.
There is some messages when starting kcmshell5 from the console:
file:///usr/share/kpackage/kcms/kcm_fonts/contents/ui/main.qml:197:21: QML Image: Invalid image provider: image://preview/0_0.png
file:///usr/share/kpackage/kcms/kcm_fonts/contents/ui/main.qml:160:21: QML Image: Invalid image provider: image://preview/0_0.png
file:///usr/lib64/qt5/qml/QtQuick/Controls.2/org.kde.desktop/private/MobileTextActionsToolBar.qml:62: TypeError: Cannot read property 'selectedText' of null
file:///usr/lib64/qt5/qml/QtQuick/Controls.2/org.kde.desktop/private/MobileTextActionsToolBar.qml:70: TypeError: Cannot read property 'selectedText' of null
file:///usr/lib64/qt5/qml/QtQuick/Controls.2/org.kde.desktop/private/MobileTextActionsToolBar.qml:78: TypeError: Cannot read property 'canPaste' of null
See screenshots in the attachments.
Linux/KDE Plasma: Fedora 30 x86_64
KDE Plasma Version: 5.16.0
KDE Frameworks Version: 5.59.0
Qt Version: 5.12.1
Created attachment 120813 [details]
kcm_fonts screenshot #2
Just found strange thing: if I run systemsettings under kwin_wayland - I can see font previews (somehow looking very bad, but it's better then nothing :)
See screenshot #3 in the attachments.
Created attachment 120815 [details]
kcm_fonts screenshot #3
Fixed in 5.17!
Bug still is there and can be reproduced on NVidia videocard with proprietary driver.
Created attachment 133197 [details]
Same bug on plasma-workspace-5.19.5-3.fc33 (NVidia prop. driver)
Bug was caused by wrong pixel format (expected: RGB32, 0xffRRGGBB), but first byte of pixel is not 0xFF - so white rectangle is displayed.
We need same fix as in spectacle code: https://lxr.kde.org/source/kde/kdegraphics/spectacle/src/Platforms/PlatformXcb.cpp#0311.
I'll do PR.
A possibly relevant merge request was started @ https://invent.kde.org/plasma/plasma-workspace/-/merge_requests/440
Bug is still there and MR is not reviewed.
Git commit bc2276aaf9952a13843d3cd1fe19ab81c05064d9 by Yaroslav Sidlovsky.
Committed on 17/01/2021 at 10:14.
Pushed by ngraham into branch 'master'.
Fix pixel format RGB32 is some cases (NVidia proprietary driver)
M +8 -0 kcms/kfontinst/lib/FcEngine.cpp