Support auto-setting dark mode on Linux with `org.freedesktop.appearance.color-scheme`

[louwers]

There should be an option to use the system wide dark mode setting on startup on Linux.

org.freedesktop.appearance.color-scheme can be used, see:

• https://blogs.gnome.org/alexm/2021/10/04/dark-style-preference/

Watching the dark mode preference and updating it real-time would be even cooler, but this is a good fist step.

Example apps that use it:

• Telegram Desktop: [Feature Request] org.freedesktop.appearance.color-scheme support to read dark mode preference telegramdesktop/tdesktop#17061
• Firefox: https://bugzilla.mozilla.org/show_bug.cgi?id=1734934

[pbek]

This only works for Gnome, right?
And it looks like you need to use GTK to check the setting, which QOwnNotes doesn't want to depend on...

[louwers]

It should also work for KDE. See the Telegram issue. It's also an official freedesktop spec.

[pbek]

But is there a way to include this without getting GTK (or KDE) dependencies?

[louwers]

It seems that a D-Bus library is intergrated into Qt? https://doc.qt.io/qt-5/qtdbus-index.html

I can take look at some point. For myself I found the following solution, that might be helpful to other people that want to toggle dark mode automatically. My solution is GNOME specific but can probably be adapted for KDE.

There is a very nice GNOME extension called Night Theme Switcher. You can run custom commands on toggle:

I run this script to modify the config and to restart QOwnNotes:

#!/usr/bin/bash

if [[ $1 = "on" ]]; then
  dark=true
elif [[ $1 = "off" ]]; then
  light=true
else
  echo "Usage: dark-mode on|off"
  exit 1
fi

replace() {
  sed -ie --follow-symlinks 's/'$1'=.*/'$1'='$2'/' "$3"
}

qon=~/.config/PBE/QOwnNotes.conf

if [[ $dark ]]; then
  replace darkMode true $qon
  replace darkModeColors true $qon
  replace darkModeIconTheme true $qon
  replace CurrentSchemaKey EditorColorSchema-cdbf28fc-1ddc-4d13-bb21-6a4043316a2f  $qon
elif [[ $light ]]; then
  replace darkMode false $qon
  replace darkModeColors false $qon
  replace darkModeIconTheme false $qon
  replace CurrentSchemaKey EditorColorSchema-6033d61b-cb96-46d5-a3a8-20d5172017eb $qon
fi
killall QOwnNotes
if [[ $? == 0 ]]; then
  QOwnNotes &
fi

[pbek]

It seems that a D-Bus library is intergrated into Qt? https://doc.qt.io/qt-5/qtdbus-index.html

hm, which also adds another Qt library dependency just for this small feature... QT += dbus 😬
https://code.qt.io/cgit/qt/qtbase.git/tree/examples/dbus/chat/chat.pro?h=5.15#n1

[louwers]

@pbek The following command line argument would avoid that dependency:

dbus-send --session --print-reply=literal --reply-timeout=1000 --dest=org.freedesktop.portal.Desktop /org/freedesktop/portal/desktop org.freedesktop.portal.Settings.Read string:'org.freedesktop.appearance' string:'color-scheme'

dbus-send should be available on all systems where D-Bus is installed. It returns

variant       variant          uint32 1

to indicate a dark-mode preference (see here) for both KDE and GNOME (and other DEs that support this spec).

[pbek]

Sounds like a nice alternative, thank you. I wonder if you are able to execute that from a flatpak or snap... 🤔

[pbek]

All I got so far when running with QProcess under Linux natively with...

    auto parameters = QStringList() <<
                    QStringLiteral("--session") << QStringLiteral("--print-reply=literal") << QStringLiteral("--reply-timeout=1000") <<
                    QStringLiteral("--dest=org.freedesktop.portal.Desktop") << QStringLiteral("/org/freedesktop/portal/desktop") <<
                    QStringLiteral("org.freedesktop.portal.Settings.Read") << QStringLiteral("string:'org.freedesktop.appearance' string:'color-scheme'");

    QProcess process;
    process.start(QStringLiteral("dbus-send"), parameters);

is

Error org.freedesktop.DBus.Error.InvalidArgs: Type of message, “(s)”, does not match expected type “.

Other permutations of input arguments (e.g. every part is a different argument item) got me: Error org.freedesktop.portal.Error.NotFound: Requested setting not found\n

[pbek]

Running it with sh seems to work.

[louwers]

@pbek I think you have to separate those two strings, otherwise it is interpreting it as one string.

QStringLiteral("string:'org.freedesktop.appearance' string:'color-scheme'");

⬇️

QStringLiteral("string:'org.freedesktop.appearance') <<  QStringLiteral("string:'color-scheme'");

I am not a D-Bus expert, but this method requires two strings as input. I used an app called D-Feet to figure it out: