SDDM configuration

[davidbryant]

I used to be able to customize the login screen on my Gentoo system. That capability vanished about a year ago, when the stable branch switched to qt6 (from 5.15.16).

Today I started investigating this mystery. Reading /var/log/sddm.log I found that program sddm-greeter was missing. Looking at the build log for package x11-misc/sddm, I noticed that the "greeter" executable was now named sddm-greeter-qt6. So I created a symlink called sddm-greeter and made it point to sddm-greeter-qt6.

Now I'm getting a different error: QtQuickControls cannot be located. Any idea how to fix this? Thanks.

[davidbryant]

More information. The error message says "QtQuick.Controls 1.1 is not installed".

I have several other versions of Linux installed on my hard disk. Some of these use the KDE desktop. Here's a summary.

Kubuntu -- Mixture of qt5 and qt6. Login still works, but I can't install new login screens (i.e., when I try, I get the Gentoo error message).

Artix -- Mixture of qt5 and qt6. Login still works, and I can switch from ome SDDM login screen to another.

MX21 (Debian derivative) -- All qt5. No problems switching / installing login screens.

[rab0171610]

The transition from QT5 to QT6 will come with some growing pains if you are using old themes, styles, or plasmoids. The QML files will need to be updated. I had several things I had to update including my custom SDDM theme. It was a learning curve but I eventually was able to figure it out. That being said to get a better understanding of the general issue, please see:
https://www.reddit.com/r/archlinux/comm ... mes_error/


In order to update your own theme, you would have to copy the folder from /usr/share/sddm/themes to a directory in maybe your home to work on it. You would need to rename it to differentiate it from the QT5 version. You would need to change the name in the file metadata.desktop that is located in your theme directory. Then you would want to rename the directory of your theme to match. You can look at the system themes and their files in /usr/share/sddm/themes for guidance.

https://doc.qt.io/qt-6/qtquickcontrols-changes-qt6.html
https://doc.qt.io/qt-5/qtquickcontrols2 ... ences.html

I also found this link helpful, even though that is specifically for plasmoids, it was helpful in learning how to port/update my SDDM themes:

https://develop.kde.org/docs/plasma/widget/porting_kf6/

You can test themes. For example, to test the default breeze theme:

Code: Select all

sddm-greeter-qt6 --test-mode --theme /usr/share/sddm/themes/breeze

You will need to modify the QML file in your theme directory, usually named Main.qml.
For example, one of the system Main.QML files (Maldives theme) for QT 6 has this:

Code: Select all

import QtQuick 2.0
import SddmComponents 2.0

Yours, I will assume, probably says:
"import QtQuick 1.1"

That would have to be updated. You can compare files in the different OS theme directories in /usr/share/sddm/themes to get a sense of what they changed in the different version of the same theme, i.e. QT 5 vs QT 6. So I have a debian installation on my disk that is still using KDE 5. Looking at the old KDE 5 Breeze SDDM theme's Main.qml file:

Code: Select all

import QtQuick 2.15
import QtQuick.Layouts 1.15
import QtQuick.Controls 2.15 as QQC2
import QtGraphicalEffects 1.15


import org.kde.plasma.core 2.0 as PlasmaCore
import org.kde.plasma.components 3.0 as PlasmaComponents3
import org.kde.plasma.extras 2.0 as PlasmaExtras

import "components"
import "components/animation"

The new version for KDE 6:

Code: Select all

import QtQuick 2.15
import QtQuick.Layouts 1.15
import QtQuick.Controls 2.15 as QQC2
import Qt5Compat.GraphicalEffects

import org.kde.plasma.components 3.0 as PlasmaComponents3
import org.kde.plasma.private.keyboardindicator as KeyboardIndicator
import org.kde.kirigami 2.20 as Kirigami

import org.kde.breeze.components

You would have to research the differences and learn why they are no longer using QtGraphicalEffects for example
and how to use the Qt5Compat.GraphicalEffects. In my case, my theme is rather simple and does not have any avatars. It only shows a prompt for user name and password boxes with an arrow for enter, a shutdown and reboot button, time and date, and lastly a session drop down box. It has the same wallpaper as my desktop. I did not have to change much of anything in the actual QML code and it worked as expected just by updating the import lines at the top of the Main.qml file.

If all of that is above your patience and/or skill level, or you just don't have the time to tinker with it and experiment, then you should look into just adopting SDDM themes that have been ported to work on KDE 6. You can then experiment and modify them to your liking.

[davidbryant]

The transition from QT5 to QT6 will come with some growing pains if you are using old themes, styles, or plasmoids. The QML files will need to be updated. I had several things I had to update including my custom SDDM theme. It was a learning curve ...

Thank you for the information. It gives me some idea where to start.