I meant an option to rescan/refresh the folder, thanks
Maybe this would be easy possible if the playlist was directory based, like in Apollo. Another player which uses a directory based playlist is QuickPlayer, but so this one might be able to support such feature, it only supports a list of folder which is updated (removed and re-added) on certain events (F5, changes, startup). It doesn't support tags etc in playlist (so it doesn't have to synchronize), and it does not support 'flat' playlists, nor rearrangements of songs in playlist.
For 'flat' playlists, if you could determinate which is the 'root' of a folder, e.g.:
could be either
(That's why a list of folders to be synchronized/updated/re-read is handy, or you ask the user etc)
You could either (if you like the challange)
a)* remove all songs which are withing and readd them
(either playlist end, or even the position where the selected song itself was/is/would be)
b) remove all preceding and following songs until you encounter a song that is not within the directory (here you should definitely re-add there)
till now, guess a) makes thinks bit easier, because the playlist can only go shorter, so you could add new songs to the same array as your regular playlist, then process and sync all songs.
c) determinate the 'root' which all songs have in common (for each drive?)... propably best for users using (adding) one folder where all music is stored
Both ways you would have to either synchronize tags (best create the new list and sync when removing afterwards?), or read them again (bad - at all I dislike tags for playlists because I already have name them on disk, and don't want to have to fix all those messed up / add new tags too just to have each player work hard on all my music files each time and not showing trash)
Still leaves the problem that if you have a 'perfect arranged' playlist synchronizing will probably mess this totally up (guess nobody would sync such a list anyway), so you could
d) process all affected songs, remove missing songs only, and add those not yet present in the playlist to the end of the playlist. That way all still existing files stay in position (and no synchronizing of tags is needed, you just would have to scan tags for the new entries)
If you implent, don't forget to add detection of removable devices and add a menu to easliy 'sync' those too.
Don't haste and choose wisely!