I recently noticed that Kirigami.Units.devicePixelRatio was 1.3 even though I was at the default 96dpi when writing a widget's config.
There's 4 different Units.qml, and I'm not certain which does what. 2 are in krigiami and the other 2 are in plasma-framework.
$ locate /Units.qml | grep /usr/ /usr/lib/qt/qml/org/kde/kirigami.2/Units.qml /usr/lib/qt/qml/org/kde/kirigami.2/styles/Plasma/Units.qml /usr/lib/qt/qml/org/kde/kirigami.2/styles/org.kde.desktop/Units.qml /usr/lib/qt/qml/org/kde/kirigami.2/styles/org.kde.desktop.plasma/Units.qml
- 2 years ago kirigami/src/controls/Units.qml (/usr/lib/qt/qml/org/kde/kirigami.2/Units.qml) was changed from 13/10 = 1.3 to multiply by 13*0.75 so that 9.75/10 = 0.975 (then max(1, 0.975) = 1).
There's 2 files owned by plasma-framework. The /styles/Plasma/Units.qml binds PlasmaCore's units.devicePixelRatio, so that leaves /styles/org.kde.desktop.plasma/Units.qml.
$ pacman -Qo /usr/lib/qt/qml/org/kde/kirigami.2/styles/org.kde.desktop.plasma/Units.qml /usr/lib/qt/qml/org/kde/kirigami.2/styles/org.kde.desktop.plasma/Units.qml is owned by plasma-framework 5.69.0-2
This patch edits the org.kde.desktop.plasma style, and fixes qmlscene KirigamiDevicePixelRatioTest.qml, and plasmashell widget configs, and plasmoidviewer widget configs.
The Kirigami patch is D29462