The current isIdle detection only works if the player has a title _and_ artist metadata,
which is not appropriate for all cases, e.g. MPV playing a video does not set artist.
In the current implementation, after a video stops playing in MPV, and the window closes
(but MPV and the MPRIS plugin server is still running as a background process), the playback controls remain
shown on the bar, and have non-functional controls.
It is sufficient to only check for the "Stopped" playing state. The MPRIS specification
states that Playback_Status==Stopped should be used to indicate that *NO* track is currently
playing. A compliant player should set that, and should also set the CanPlay/CanPause boolean
to false is not track is being played.
See: https://specifications.freedesktop.org/mpris/latest/Player_Interface.html#Enum:Playback_Status
jack-mil
49f968d26b