9631043c110d introduced MPRIS support to Gwenview. Common MPRIS
controllers often only provide "Pause" in the main interface, with
"Stop" being non-existent or hidden. Therefore "holding" the slideshow
was mapped to "Pause". "Play" either "Resumes" automatically advancing
to the next image, or in non-fullscreen mode switches to fullscreen and
starts playback. Conversely, "Stop" ends playback and exits from
fullscreen.
To keep consistency, we change the tooltip text of the fullscreen button
controlling the playback to "Pause". In addition, the internal enum is
adapted accordingly to avoid confusing developers.
Note that the icon on the button still shows a "Pause" symbol as before
the patch.
Ref T8222