[RFE] Add some logic to pick a Kvantum theme based on Gtk3 theme when the names don't match

[teohhanhui]

Distro: Manjaro GNOME Edition

gtk3 theme name: "Matcha-dark-sea"
kvantum theme name: "Matcha-Dark"

Is this a case of gtk3 / kvantum theme name mismatch?

Log: https://gist.github.com/teohhanhui/be57cbfe713a60047c2c3be8ef700c95

[teohhanhui]

Hmm... Looking at the code, that does seem to be the case. There's no fuzzy matching between gtk3 theme name and kvantum theme name.

Do you think this is something that should be fixed on the Kvantum / Manjaro end, or on the QGnomePlatform end?

[grulja]

There is none and most likely won't be one implemented, at least from my side. Our primary focus is Adwaita-qt theme, I have never used Kvantum and I don't plan extending its support. Feel free to send a patch and I will review it, otherwise you will have to wait if someone decides to fix it or rather fix it in Manjaro, if possible.

[yochananmarqos]

@teohhanhui
Try setting export QT_STYLE_OVERRIDE="kvantum" in your ~/.profile.

[teohhanhui]

@yochananmarqos Tried that. It didn't change anything.

But I've noticed that actually the client decorations are handled separately by https://github.com/FedoraQt/QGnomePlatform/blob/0.6.0/decoration/qgnomeplatformdecoration.cpp, which doesn't seem to support Kvantum.

Is my understanding correct?

[yochananmarqos]

@teohhanhui
You may have to edit /etc/environment instead and disable using qt5ct:

#QT_QPA_PLATFORMTHEME="qt5ct"
QT_STYLE_OVERRIDE="kvantum"

Have you added QT_QPA_PLATFORMTHEME="gnome" anywhere?

[teohhanhui]

@yochananmarqos Thanks for trying to help, but that's not going to change anything - yes, I'm already using QGnomePlatform:

$ QT_QPA_PLATFORM=wayland QT_QPA_PLATFORMTHEME=gnome QT_DEBUG_PLUGINS=1 telegram-desktop

Please see the link above. The client decorations are handled by a separate Qt plugin. QT_DEBUG_PLUGINS=1 helped figure that out.

[teohhanhui]

Unfortunately:

(2) Kvantum does not provide window decorations. Such jobs are done by the window manager.

https://store.kde.org/p/1005410/

See also tsujan/Kvantum#442 and https://bugreports.qt.io/browse/QTBUG-63969

[yochananmarqos]

Maybe it's just a Wayland thing, then. QBittorrent is using my Kvantum theme on GNOME using Xorg. I have qgnomeplatform-git and kvantum-qt5 installed; qt5ct and adwaita-qt are not installed.

/etc/environment:

QT_AUTO_SCREEN_SCALE_FACTOR=1

# Requires qt5ct
#QT_QPA_PLATFORMTHEME="qt5ct"

# Requires qgnomeplatform
# adwaita-qt theme will be used if installed, otherwise override with Kvantum
QT_QPA_PLATFORMTHEME="gnome"

# Requires kvantum-qt5
QT_STYLE_OVERRIDE="kvantum"

$ QT_LOGGING_RULES="qt.qpa.qgnomeplatform=true" qbittorrent
qt.qpa.qgnomeplatform: Font name:  "Noto Sans"  (size  12 )
qt.qpa.qgnomeplatform: Monospace font name:  "Hack"  (size  12 )
qt.qpa.qgnomeplatform: TitleBar font name:  "Noto Sans"  (size  12 )
qt.qpa.qgnomeplatform: Cursor blink time:  1200
qt.qpa.qgnomeplatform: Double click time:  400
qt.qpa.qgnomeplatform: Long press time:  500
qt.qpa.qgnomeplatform: Double click distance:  5
qt.qpa.qgnomeplatform: Dnd drag threshold:  8
qt.qpa.qgnomeplatform: Password hint timeout:  0
qt.qpa.qgnomeplatform: Icon theme:  "Papirus-Dark-Maia"
qt.qpa.qgnomeplatform: Theme name:  "Adwaita-maia-dark"
qt.qpa.qgnomeplatform: Dark version:  yes

[yochananmarqos]

@teohhanhui

Is my understanding correct?

In theory, it should find a matching Kvantum theme:

• QGnomePlatform/common/gnomehintssettings.cpp

  Line 324 in d4277c9

  QString kvTheme = kvantumThemeForGtkTheme();

• QGnomePlatform/common/gnomehintssettings.cpp

  Line 477 in d4277c9

  QString GnomeHintsSettings::kvantumThemeForGtkTheme() const

[memeplex]

@teohhanhui you can force usage of XWayland by doing QT_QPA_PLATFORM=xcb so that decorations are rendered by the compositor. You might also try luck with QT_WAYLAND_DISABLE_WINDOWDECORATION=1.

[teohhanhui]

@yochananmarqos @memeplex The point is to move forward with Wayland.

Let's continue the discussion in the Manjaro forum thread if it's not relevant to this issue: https://forum.manjaro.org/t/gnome-wayland-qt-kvantum-theme-not-being-used/126090

[Ste74]

Hi there, Manjaro dev here and Manjaro Gnome maintainer. This is the first time i'm pinged in our forum for this problem and i appreciate the feedback of @memeplex . Also i see for the first time this issue opend 2 months ago because @yochananmarqos point me out. Generally i don't use anything of qt app apart our manjaro settings manager, calamares and libreoffice but since i don't use also plasma or any other QT DE i never thinking more at this problems ( for calamares i have set the kvantum theme in live iso via .config as root user ). So at the end i really appreciate if we can find a confortable solution for this behaviours here or in our forum.