D10972 exposed Gwenview's slideshow as an MPRIS D-Bus object, which allows any MPRIS controller like KDE Connect or Plasma's media controller applet to remotely control various aspects of the slideshow, e.g. navigation, fullscreen, playback etc.
While basic functions work, there are various smaller and larger topics which could still be improved:
[] In fullscreen {nav Browse} mode, signal "Stopped" instead of "Playing/Paused".
[] Calling `Raise` should show the fullscreen toolbar on the top.
[] Implement handling of videos (length, position, playback etc.)
[] Signal updates to metadata changes.
[] Export other metadata where mapping works.
[] Pass along thumbnail cache URLs in order to display thumbnails in the controllers.
[] "Playlist/Tracklist" support.
[] Evaluate and polish the Gwenview-specific user experience in the most popular controllers.
See D10972 for details on some of those points.
Related:
Bug 391872 – [Allow to start slideshow from fullscreen browse mode](https://bugs.kde.org/show_bug.cgi?id=391872)
Bug 391873 – [Indicate timeout until next image is shown for running slideshows](https://bugs.kde.org/show_bug.cgi?id=391873)