Fixed bug with null discnumbers and added discnumbers to view.

Fix bug in the taghandlers where a discnumber polluted null entries in
the database.
Also made the tree model so that the discnumber appears before the track
number if it's defined.

src/libtomahawk/playlist/treemodel.cpp

@@ -271,6 +271,12 @@ TreeModel::data( const QModelIndex& index, int role ) const
     else if ( !entry->result().isNull() )
     {
         const result_ptr& result = entry->result();
+        unsigned int discnumber = 0;
+        if( !entry->query().isNull() )
+            discnumber = entry->query()->discnumber();
+        if( discnumber == 0 )
+            discnumber = result->discnumber();
+
         unsigned int albumpos = 0;
         if ( !entry->query().isNull() )
             albumpos = entry->query()->albumpos();
@@ -280,8 +286,9 @@ TreeModel::data( const QModelIndex& index, int role ) const
         switch( index.column() )
         {
             case Name:
-                return QString( "%1%2" ).arg( albumpos > 0 ? QString( "%1. ").arg( albumpos ) : QString() )
+                return QString( "%1%2%3" ).arg( discnumber > 0 ? QString( "%1." ).arg( discnumber ) : QString() )
-                                        .arg( result->track() );
+                                          .arg( albumpos > 0 ? QString( "%1. ").arg( albumpos ) : QString() )
+                                          .arg( result->track() );
 
             case Duration:
                 return TomahawkUtils::timeToString( result->duration() );
@@ -310,6 +317,9 @@ TreeModel::data( const QModelIndex& index, int role ) const
             case AlbumPosition:
                 return result->albumpos();
 
+            case Composer:
+                return result->composer()->name();
+
             default:
                 return QVariant();
         }

src/libtomahawk/playlist/treemodel.h

@@ -50,7 +50,8 @@ public:
         Year,
         Filesize,
         Origin,
-        AlbumPosition
+        AlbumPosition,
+        Composer
     };
 
     enum ColumnStyle

src/libtomahawk/query.cpp

@@ -116,6 +116,7 @@ Query::init()
     m_playable = false;
     m_duration = -1;
     m_albumpos = 0;
+    m_discnumber = 0;
 
     updateSortNames();
 }

src/libtomahawk/taghandlers/tag.h

@@ -57,7 +57,7 @@ public:
     //TODO: add support for writing those 3 items with TagLib's addField/setField
 
 protected:
-    Tag( TagLib::Tag *tag ) : m_tag( tag ) {}
+    Tag( TagLib::Tag *tag ) : m_tag( tag ), m_discNumber( 0 ) {}
 
     unsigned int processDiscNumber( const QString & ) const;