Just For The Fun Of It: Browsing Music With Nepomuk

Since implementing the TV Show KIO slave was that easy I decided I could do the same for music – just to show how simple it can be. There a a few more lines but that is only because I added browsing by album, artist, and genre. So there are a lot of if/else constructs. Anyway, here goes:

Browsing music by artist is easy. As you can see I also implemented a preview generator plugin the same way I did for the TV Shows. The only problem is that there is no tool yet that automatically fetches those images. Thus, I had to do it manually for one example which looks somewhat like this:

qdbus org.kde.NepomukStorage 
  /datamanagement
  org.kde.nepomuk.DataManagement.addProperty
  "nepomuk:/res/0152825f-5c49-4ca8-aa0a-23fc9a1305f1"
  "nfo:depiction"
  "/home/trueg/atb2.jpg"
  "shell"

This is part of the fancy Data management API which allows me to add the file atb2.jg as a nfo:depiction of the nco:Contact resource identifying the artist ATB.

Anyway, entering the artist themselves and what lies beyond:

(Again I had to fetch the cover art manually. I did not want to implement my own cover art retrieval tool and I found the Amarok code not to be very reusable. Again maybe someone wants to take up this task?)

Finally we end up in the album tracks. Sadly dragging an album to a media player playlist does not work yet. I am not quite sure how to fix that.

Last but not least a quick look at browsing by genre:

This was fun. But before I go to bed let me share with you the very simple code which is responsible for the nice previews (abbreviated of course):

bool MusicThumbCreator::create(const QString &path,
                               int w, int h,
                               QImage &img)
{
  KUrl url(path);
  QStringList pathTokens
      = url.path().split('/', QString::SkipEmptyParts);
  if(pathTokens.count() < 2) {
    return false;
  }

  // there are only two cases for us: artists and albums
  if(pathTokens[pathTokens.count()-2] == QLatin1String("artists") ||
     pathTokens[pathTokens.count()-2] == QLatin1String("albums")) {
      const QUrl uri = recoverUriFromUrlToken(pathTokens.last());
    // we just query the first depiction there is
    Soprano::QueryResultIterator it
       = Nepomuk::ResourceManager::instance()->mainModel()
         ->executeQuery(
              QString::fromLatin1("select ?u where { "
                                  "%1 nfo:depiction [ nie:url ?u ] . "
                                  "} LIMIT 1")
              .arg(Soprano::Node::resourceToN3(uri)),
              Soprano::Query::QueryLanguageSparql);
    if(it.next()) {
      img.load(it["u"].uri().toLocalFile());
      return true;
    }
  }

  return false;
}

The rest of the code can be found in the nepomuk-audio-kio-slave scratch repository. Maybe at some point I could just throw all of those things into some “Nepomuk KIO extensions” package… oh, well, off to bed now…