Introduction

K4Oxygen is a variant of KDE4 Oxygen widget theme, released from KDE dependencies and supported both for Qt4, Qt5, and Qt6.

It is based on oxygen-transparent for KDE4 (as of commit aa154d4), but currently has some limitations:

• no window decorations implementation (it'd depend on KDE anyway, and the code would likely be different for KDE4 and KF5)
• no configuration utility
• translucency in Qt5 version is in experimental stage, and unchecked completely in Qt6 version

The theme does read Oxygen and global KDE settings similarly to how oxygen-gtk does it.

Installation

You can install it using the following commands

mkdir build
cd build
cmake .. -DQT_VERSION=5
make
sudo make install

Similarly, for Qt4 or Qt6 version replace -DQT_VERSION=5 with -DQT_VERSION=4 or -DQT_VERSION=6, respectively.

Configuration

Making K4Oxygen current Qt theme

• Qt4: You can choose current theme using qtconfig (or, on some distros, qtconfig-qt4)
• Qt5: Qt5 doesn't provide a standard utility to set its theme, but you can either try qt5ct utility, or set a global environment variable QT_STYLE_OVERRIDE to k4oxygen.
• Qt6: Qt6 doesn't provide a standard utility to set its theme, but you can either try qt6ct utility, or set a global environment variable QT_STYLE_OVERRIDE to k4oxygen.

Style settings

In a KDE session K4Oxygen should pick the Oxygen and global KDE settings automatically with no user intervention.

In a non-KDE session you can set non-default settings by editing oxygenrc and kdeglobals files. These files are searched as follows:

1. If kde4-config --path config works, its output paths are used
2. Otherwise, the path is set to $HOME/.config/k4oxygen (or $XDG_CONFIG_HOME/k4oxygen, if XDG_CONFIG_HOME is set).

If you've edited oxygenrc or kdeglobals, you can force configuration reloading using these commands (TypeOfChange is a parameter):

dbus-send --type=signal /KGlobalSettings org.kde.KGlobalSettings.notifyChange int32:TypeOfChange int32:0  # for kdeglobals
dbus-send --type=signal /OxygenStyle org.kde.Oxygen.Style.reparseConfiguration # for oxygenrc

Here TypeOfChange for kdeglobals is one of the following (the ones supported):

• 0 — means Palette Changed
• 1 — means Font Changed
• 3 — means Settings Changed

These commands simulate the signals sent by KDE's System Settings utility.