Created attachment 161867 [details]
Haruna (left) and Celluloid (right) showing their playlists after adding a link to a youtube playlist

SUMMARY
Adding for example a youtube playlist link to the Haruna playlist will get fed to libmpv like it's supposed to, but when libmpv expands the playlist link and resolves entry titles via youtube-dl, Haruna's playlist doesn't sync up with the changes. If you for example do this in real mpv and press F8 you can see that mpv's playlist doesn't contain the playlist url anymore but expands the playlist url into its contents, then as it's reading through the playlist those youtube links get replaced with the video titles.

Haruna does not do this, yet it does use libmpv so these things are available to it. Haruna's playlist function should be an interface to libmpv's playlist rather than a duplicate.


STEPS TO REPRODUCE
1. Add URL to online playlist on Youtube (for example: https://www.youtube.com/playlist?list=OLAK5uy_le-CwvaBy1A3FhWgvQYnAIUtnUv4nP50E)
2. Begin playing playlist

OBSERVED RESULT
The first entry in the linked playlist is played but Haruna's playlist does not update, only the title bar does.

EXPECTED RESULT
Haruna's playlist will update to include the expanded online playlist entries, allowing you to select them at will.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Debian GNU/Linux 12
(available in About System)
KDE Plasma Version: 5.27.8
KDE Frameworks Version: 5.107.0
Qt Version: 5.15.10

ADDITIONAL INFORMATION
Celluloid—a GTK-based libmpv player—does sync up with mpv's playlist properly and doesn't have a duplicate playlist. This could be looked at as a reference.

I have tested this on the latest git version at a62be80ffef4c63c7cc21a207a3d2e9e512469c4