Broken QT themes in KDE with qt5ct

[ethanwu10]

(Issue first brought up by @killajoe)

Since 1dec9de and the installation of qt5ct, KDE sessions' theming are overridden by that of qt5ct, and are unchangeable through KDE's settings modules, when using lightdm. This is caused by lightdm's check for QT-based DEs failing now that KDE's start command is startkde and not plasma, causing this to run and override QT styles:

# /etc/lightdm/Xsession lines 68-72
if ! [[ "${@}" =~ plasma|lxqt ]]; then
    # Fix ugly styles for Qt applications when running under GTK-based desktops and Qt 5.7+
    export QT_QPA_PLATFORMTHEME='qt5ct'
    unset QT_STYLE_OVERRIDE
fi

This can be fixed by simply commenting out these lines, or by adding |startkde to the if condition.

I'm not sure if anything can be done from Antergos's end other than a note saying to patch this file, as this is a bug in the Arch repo packages.

EDIT: these config lines don't appear to be from the Arch packages

[ethanwu10]

/etc/lightdm/Xresources is generated by Cnchi from this file; we can fix this for new installs but I don't know if there's a good way to fix this on existing installs...

[killajoe]

https://forum.antergos.com/topic/11568/kde-desktop-messed-up-after-last-system-update

[karasu]

Antergos/Cnchi@c6f5874

[jsinghrai]

Antergos/Cnchi@c6f5874

Hey karasu, would there be update coming from antergos regarding this issue or we should just manually change this. I'm not talking about the installer since you already fixed that.

[ethanwu10]

We could add a post_install script to antergos-common-meta that automatically applies a patch... It's not a very clean solution, but it would work

[adrfantini]

Antergos/Cnchi@c6f5874

This is the right fix, thanks for that.