readPlaylist
The items of the playlist file at uri, for openQueue once the application has filtered or ordered them (#490). See Playlists for what is read.
The bytes come through the same doors as an external subtitle's: an http or https address through the network resolver, with headers, and a path from disk. Their encoding is decided from the bytes as a subtitle file's is, so a list another player wrote in a legacy code page keeps its titles. A list it names is read in its place, one level deep, and the items it names from the playlist's own server carry headers too.
Throws
when the list cannot be read, is no playlist, names nothing, or names itself.