Pass non-trivial/large function args by reference

Fixes a bunch of `-Wclazy-function-args-by-ref` warnings. See
https://github.com/KDE/clazy/blob/master/docs/checks/README-function-args-by-ref.md
for details.

Most of these changes are automated, using the clazy fixit by setting
the `CLAZY_EXPORT_FIXES` before compilation and then running:

    $ mkdir /tmp/patch
    $ find ../src -iname "*.yaml" -exec mv {} /tmp/patch \;
    $ clang-apply-replacements /tmp/patch

7 files changed, 28 insertions, 24 deletions

diff --git a/src/library/dao/autodjcratesdao.cpp b/src/library/dao/autodjcratesdao.cpp
index 9ca5b4284b..90c745f91c 100644
--- a/src/library/dao/autodjcratesdao.cpp
+++ b/src/library/dao/autodjcratesdao.cpp
@@ -1072,8 +1072,8 @@ void AutoDJCratesDAO::slotPlaylistTrackRemoved(int playlistId,
 }
 
 // Signaled by the PlayerInfo singleton when a track is loaded to a deck.
-void AutoDJCratesDAO::slotPlayerInfoTrackLoaded(QString a_strGroup,
-                                                TrackPointer a_pTrack) {
+void AutoDJCratesDAO::slotPlayerInfoTrackLoaded(const QString& a_strGroup,
+        TrackPointer a_pTrack) {
     // This gets called with a null track during an unload.  Filter that out.
     if (a_pTrack == NULL) {
         return;
@@ -1103,8 +1103,8 @@ void AutoDJCratesDAO::slotPlayerInfoTrackLoaded(QString a_strGroup,
 }
 
 // Signaled by the PlayerInfo singleton when a track is unloaded from a deck.
-void AutoDJCratesDAO::slotPlayerInfoTrackUnloaded(QString group,
-                                                  TrackPointer pTrack) {
+void AutoDJCratesDAO::slotPlayerInfoTrackUnloaded(const QString& group,
+        TrackPointer pTrack) {
     // This counts as an auto-DJ reference.  The idea is to prevent tracks that
     // are loaded into a deck from being randomly chosen.
     TrackId trackId(pTrack->getId());
diff --git a/src/library/dao/autodjcratesdao.h b/src/library/dao/autodjcratesdao.h
index 35e45678ff..5b2ae70748 100644
--- a/src/library/dao/autodjcratesdao.h
+++ b/src/library/dao/autodjcratesdao.h
@@ -92,8 +92,8 @@ class AutoDJCratesDAO : public QObject {
 
     // Signaled by the PlayerInfo singleton when a track is loaded to, or
     // unloaded from, a deck.
-    void slotPlayerInfoTrackLoaded(QString group, TrackPointer pTrack);
-    void slotPlayerInfoTrackUnloaded(QString group, TrackPointer pTrack);
+    void slotPlayerInfoTrackLoaded(const QString& group, TrackPointer pTrack);
+    void slotPlayerInfoTrackUnloaded(const QString& group, TrackPointer pTrack);
 
   private:
     void updateAutoDjCrate(CrateId crateId);
diff --git a/src/library/dao/directorydao.cpp b/src/library/dao/directorydao.cpp
index 6594b21057..8ba7acae2b 100644
--- a/src/library/dao/directorydao.cpp
+++ b/src/library/dao/directorydao.cpp
@@ -9,7 +9,7 @@
 
 namespace {
 
-bool isChildDir(QString testDir, QString dirStr) {
+bool isChildDir(const QString& testDir, const QString& dirStr) {
     QDir test = QDir(testDir);
     QDir dir = QDir(dirStr);
     bool child = dir == test;
diff --git a/src/library/dao/playlistdao.cpp b/src/library/dao/playlistdao.cpp
index c6650a7c1c..5665b029a2 100644
--- a/src/library/dao/playlistdao.cpp
+++ b/src/library/dao/playlistdao.cpp
@@ -456,14 +456,15 @@ void PlaylistDAO::removeTrackFromPlaylist(int playlistId, int position) {
     emit tracksChanged(QSet<int>{playlistId});
 }
 
-void PlaylistDAO::removeTracksFromPlaylist(int playlistId, QList<int> positions) {
+void PlaylistDAO::removeTracksFromPlaylist(int playlistId, const QList<int>& positions) {
     // get positions in reversed order
-    std::sort(positions.begin(), positions.end(), std::greater<int>());
+    QList sortedPositons = positions;
+    std::sort(sortedPositons.begin(), sortedPositons.end(), std::greater<int>());
 
     //qDebug() << "PlaylistDAO::removeTrackFromPlaylist"
     //         << QThread::currentThread() << m_database.connectionName();
     ScopedTransaction transaction(m_database);
-    for (const auto position : qAsConst(positions)) {
+    for (const auto position : qAsConst(sortedPositons)) {
         removeTracksFromPlaylistInner(playlistId, position);
     }
     transaction.commit();
diff --git a/src/library/dao/playlistdao.h b/src/library/dao/playlistdao.h
index fba4602c3e..d161706bb1 100644
--- a/src/library/dao/playlistdao.h
+++ b/src/library/dao/playlistdao.h
@@ -92,7 +92,7 @@ class PlaylistDAO : public QObject, public virtual DAO {
     void removeHiddenTracks(const int playlistId);
     // Remove a track from a playlist
     void removeTrackFromPlaylist(int playlistId, int position);
-    void removeTracksFromPlaylist(int playlistId, QList<int> positions);
+    void removeTracksFromPlaylist(int playlistId, const QList<int>& positions);
     void removeTracksFromPlaylistById(int playlistId, TrackId trackId);
     // Insert a track into a specific position in a playlist
     bool insertTrackIntoPlaylist(TrackId trackId, int playlistId, int position);
@@ -123,11 +123,11 @@ class PlaylistDAO : public QObject, public virtual DAO {
   signals:
     void added(int playlistId);
     void deleted(int playlistId);
-    void renamed(int playlistId, QString newName);
+    void renamed(int playlistId, const QString& newName);
     void lockChanged(int playlistId);
     void trackAdded(int playlistId, TrackId trackId, int position);
     void trackRemoved(int playlistId, TrackId trackId, int position);
-    void tracksChanged(QSet<int> playlistIds); // added/removed/reordered
+    void tracksChanged(const QSet<int>& playlistIds); // added/removed/reordered
 
   private:
     bool removeTracksFromPlaylist(int playlistId, int startIndex);
diff --git a/src/library/dao/trackdao.cpp b/src/library/dao/trackdao.cpp
index 4f8ab1dbf6..e51ee5fbfd 100644
--- a/src/library/dao/trackdao.cpp
+++ b/src/library/dao/trackdao.cpp
@@ -45,7 +45,7 @@ mixxx::Logger kLogger("TrackDAO");
 
 enum { UndefinedRecordIndex = -2 };
 
-void markTrackLocationsAsDeleted(QSqlDatabase database, const QString& directory) {
+void markTrackLocationsAsDeleted(const QSqlDatabase& database, const QString& directory) {
     //qDebug() << "TrackDAO::markTrackLocationsAsDeleted" << QThread::currentThread() << m_database.connectionName();
     QSqlQuery query(database);
     query.prepare("UPDATE track_locations "
@@ -290,13 +290,13 @@ void TrackDAO::saveTrack(Track* pTrack) const {
     }
 }
 
-void TrackDAO::slotDatabaseTracksChanged(QSet<TrackId> changedTrackIds) {
+void TrackDAO::slotDatabaseTracksChanged(const QSet<TrackId>& changedTrackIds) {
     if (!changedTrackIds.isEmpty()) {
         emit tracksChanged(changedTrackIds);
     }
 }
 
-void TrackDAO::slotDatabaseTracksRelocated(QList<RelocatedTrack> relocatedTracks) {
+void TrackDAO::slotDatabaseTracksRelocated(const QList<RelocatedTrack>& relocatedTracks) {
     QSet<TrackId> removedTrackIds;
     QSet<TrackId> changedTrackIds;
     for (const auto& relocatedTrack : qAsConst(relocatedTracks)) {
@@ -493,7 +493,10 @@ namespace {
         pTrackLibraryQuery->bindValue(":key_id", static_cast<int>(key));
     }
 
-    bool insertTrackLibrary(QSqlQuery* pTrackLibraryInsert, const Track& track, DbId trackLocationId, QDateTime trackDateAdded) {
+    bool insertTrackLibrary(QSqlQuery* pTrackLibraryInsert,
+            const Track& track,
+            DbId trackLocationId,
+            const QDateTime& trackDateAdded) {
         bindTrackLibraryValues(pTrackLibraryInsert, track);
 
         if (!track.getDateAdded().isNull()) {
diff --git a/src/library/dao/trackdao.h b/src/library/dao/trackdao.h
index 19c2e09661..9df042b977 100644
--- a/src/library/dao/trackdao.h
+++ b/src/library/dao/trackdao.h
@@ -75,21 +75,21 @@ class TrackDAO : public QObject, public virtual DAO, public virtual GlobalTrackC
     void trackClean(TrackId trackId);
 
     // Multiple tracks
-    void tracksAdded(QSet<TrackId> trackIds);
-    void tracksChanged(QSet<TrackId> trackIds);
-    void tracksRemoved(QSet<TrackId> trackIds);
+    void tracksAdded(const QSet<TrackId>& trackIds);
+    void tracksChanged(const QSet<TrackId>& trackIds);
+    void tracksRemoved(const QSet<TrackId>& trackIds);
 
-    void progressVerifyTracksOutside(QString path);
-    void progressCoverArt(QString file);
+    void progressVerifyTracksOutside(const QString& path);
+    void progressCoverArt(const QString& file);
     void forceModelUpdate();
 
   public slots:
     // Slots to inform the TrackDAO about changes that
     // have been applied directly to the database.
     void slotDatabaseTracksChanged(
-            QSet<TrackId> changedTrackIds);
+            const QSet<TrackId>& changedTrackIds);
     void slotDatabaseTracksRelocated(
-            QList<RelocatedTrack> relocatedTracks);
+            const QList<RelocatedTrack>& relocatedTracks);
 
   private:
     friend class LibraryScanner;