[MPRIS] [RFC] CanControlvolume property

[Nicolas Fella]

Hi,

during my work on KDE Connect [1] I came across multiple players that do 
not support setting the volume (e.g. Spotify) or do not have a concept 
of volume at all (e.g. Gwenview [2] which is being patched with MPRIS 
support [3]). As far as I understand there is no way for the player to 
signal that controlling the volume is unsupported. A canControlVolume 
property together with a canControlVolumeChanged signal would enable UIs 
to gracefully handle players that do not support it by disabling volume 
sliders when appropriate. This would lead to better user experience 
because otherwise the controller or player appears broken.

Best regards

Nicolas Fella

[1] https://community.kde.org/KDEConnect

[2] https://userbase.kde.org/Gwenview

[3] https://phabricator.kde.org/D10972