[Feedback] DBus Interface Needed Enhancements

[Sébastien Laoût]

I would add those "requierements":

I want to implement "Party Lock" to lock the screen when playing full screen 
during a party (like a screensaver can lock the screen).
But this locking forbid guests to browse the music collection in Amarok, pick 
the artist they want...
So I would like to add an iPod-like browsing: show a list of artists, when 
clicking one, animate and show a list of all albums of that artist, etc.

When the guest is clicking to play an album, I would want to have a DBus call 
to:
1. Replace the playlist with either:
   - all songs
   - all songs from artist "X"
   - all songs in album "Y" from artist "X"
   - this song, and this one, and this other one
   - the content of the playlist "Z"
   Basically, there should be 5 calls for those 5 use cases.
   And of course, a call to get all plyslists, and another one to get all the
   songs of a playlist.
2. Start playing that new playlist starting at the first item.
   I think if we clear and replace the playlist, the playPause() call already
   do that, so nothing to add.

And now, a bonus:
The calls "listAllArtists()", "listAlbumsOf(artist)" 
and "listAllSongsOf(artist, album)" are a bonus because this can be done 
using the query() call.

Having those calls is only a help for developers not knowing query() (like me 
at the start, I learned it quite late) or people not wanting to dig in the 
database to know what tables exist.