Linux: MPRIS volume control does not change Zuno's actual audio volume

[camilo2010FE]

What happens

What happens

On Linux, Zuno exposes an MPRIS interface and Plasma can control playback normally, but changing Zuno's volume through MPRIS does not change the actual audio stream volume.

The KDE Volume Mixer can change Zuno's volume correctly, but the KDE Plasma Media Player widget cannot.

Steps to reproduce

1. Start playing audio in Zuno.
2. Check the MPRIS volume:

busctl --user get-property \
  org.mpris.MediaPlayer2.zuno \
  /org/mpris/MediaPlayer2 \
  org.mpris.MediaPlayer2.Player \
  Volume

This reports:

d 1

3. Try changing the MPRIS volume:

busctl --user set-property \
  org.mpris.MediaPlayer2.zuno \
  /org/mpris/MediaPlayer2 \
  org.mpris.MediaPlayer2.Player \
  Volume d 0.5

4. Check the property again:

busctl --user get-property \
  org.mpris.MediaPlayer2.zuno \
  /org/mpris/MediaPlayer2 \
  org.mpris.MediaPlayer2.Player \
  Volume

It still reports:

d 1

5. However, the actual PipeWire stream volume can be changed successfully:

wpctl get-volume 246

Initially:

Volume: 0.23

Then:

wpctl set-volume 246 0.5
wpctl get-volume 246

returns:

Volume: 0.50

and the audible volume actually increases.

#Expected behavior

Changing org.mpris.MediaPlayer2.Player.Volume should change Zuno's actual playback volume, so KDE Plasma's MPRIS/media widget can control Zuno's volume.

Actual behavior

The MPRIS Volume property is exposed and writable, but changing it does not affect the actual audio stream and the property remains at 1.0.

The PipeWire stream itself can be controlled correctly.

Environment

• Zuno: 1.4.0
• OS: CachyOS (Arch Linux)
• Desktop: KDE Plasma 6.7.4
• Display server: Wayland
• PipeWire: 1.6.8
• Audio stream: alsa_playback.zuno

Additional information

I noticed that src-tauri/src/linux_media.rs handles several MediaControlEvent variants, including SetPosition, but does not appear to handle MediaControlEvent::SetVolume.

This may be related to the missing MPRIS volume control on Linux.

Thanks!

Zuno version

1.4.0

OS

Linux

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