git clone https://github.com/dsmorozov/qmmp-modern.git
qmake
make
sudo make install
Go to Qmmp settings -> Plugins -> User Interfaces -> Select "Modern User Interface" -> Close -> Restart the program
or
find "current_plugin" config entry in qmmprc and set it to "modern"
The latter is the only option to switch back to "skinned" plugin for now.
One can try this skin to see what has been implemented so far.
QT_LOGGING_RULES="modernui.xml.parser.debug=true" qmmp
enables skin xml parser debug
QT_LOGGING_RULES="modernui.script.loader.debug=true" qmmp
enables script loader debug
QT_LOGGING_RULES="modernui.script.interpreter.debug=true" qmmp
enables bytecode interpreter debug
Huge amount of things still remains to be implemented. Don't even try loading any complex skin.