diff --git a/src/core/mainwindow.cpp b/src/core/mainwindow.cpp
index 8baa50294..106b9af7c 100644
--- a/src/core/mainwindow.cpp
+++ b/src/core/mainwindow.cpp
@@ -528,7 +528,6 @@ MainWindow::MainWindow(Application *app, SystemTrayIcon *tray_icon, OSDBase *osd
   connect(app_->player(), SIGNAL(Stopped()), SLOT(MediaStopped()));
   connect(app_->player(), SIGNAL(Seeked(qlonglong)), SLOT(Seeked(qlonglong)));
   connect(app_->player(), SIGNAL(TrackSkipped(PlaylistItemPtr)), SLOT(TrackSkipped(PlaylistItemPtr)));
-  connect(this, SIGNAL(IntroPointReached()), app_->player(), SLOT(IntroPointReached()));
   connect(app_->player(), SIGNAL(VolumeChanged(int)), SLOT(VolumeChanged(int)));
 
   connect(app_->player(), SIGNAL(Paused()), ui_->playlist, SLOT(ActivePaused()));
@@ -1365,14 +1364,14 @@ void MainWindow::ResumePlaybackSeek(const int playback_position) {
 
 }
 
-void MainWindow::PlayIndex(const QModelIndex &index) {
+void MainWindow::PlayIndex(const QModelIndex &idx) {
 
-  if (!index.isValid()) return;
+  if (!idx.isValid()) return;
 
-  int row = index.row();
-  if (index.model() == app_->playlist_manager()->current()->proxy()) {
+  int row = idx.row();
+  if (idx.model() == app_->playlist_manager()->current()->proxy()) {
     // The index was in the proxy model (might've been filtered), so we need to get the actual row in the source model.
-    row = app_->playlist_manager()->current()->proxy()->mapToSource(index).row();
+    row = app_->playlist_manager()->current()->proxy()->mapToSource(idx).row();
   }
 
   app_->playlist_manager()->SetActiveToCurrent();
@@ -1380,14 +1379,14 @@ void MainWindow::PlayIndex(const QModelIndex &index) {
 
 }
 
-void MainWindow::PlaylistDoubleClick(const QModelIndex &index) {
+void MainWindow::PlaylistDoubleClick(const QModelIndex &idx) {
 
-  if (!index.isValid()) return;
+  if (!idx.isValid()) return;
 
-  int row = index.row();
-  if (index.model() == app_->playlist_manager()->current()->proxy()) {
+  int row = idx.row();
+  if (idx.model() == app_->playlist_manager()->current()->proxy()) {
     // The index was in the proxy model (might've been filtered), so we need to get the actual row in the source model.
-    row = app_->playlist_manager()->current()->proxy()->mapToSource(index).row();
+    row = app_->playlist_manager()->current()->proxy()->mapToSource(idx).row();
   }
 
   switch (doubleclick_playlist_addmode_) {
@@ -1397,7 +1396,7 @@ void MainWindow::PlaylistDoubleClick(const QModelIndex &index) {
       break;
 
     case BehaviourSettingsPage::PlaylistAddBehaviour_Enqueue:
-      app_->playlist_manager()->current()->queue()->ToggleTracks(QModelIndexList() << index);
+      app_->playlist_manager()->current()->queue()->ToggleTracks(QModelIndexList() << idx);
       if (app_->player()->GetState() != Engine::Playing) {
         app_->player()->PlayAt(app_->playlist_manager()->current()->queue()->TakeNext(), Engine::Manual, true);
       }
@@ -1482,7 +1481,7 @@ void MainWindow::FilePathChanged(const QString &path) {
   settings_.setValue("file_path", path);
 }
 
-void MainWindow::Seeked(qlonglong microseconds) {
+void MainWindow::Seeked(const qlonglong microseconds) {
 
   const int position = microseconds / kUsecPerSec;
   const int length = app_->player()->GetCurrentItem()->Metadata().length_nanosec() / kNsecPerSec;
@@ -1528,7 +1527,7 @@ void MainWindow::UpdateTrackSliderPosition() {
 
 }
 
-void MainWindow::ApplyAddBehaviour(BehaviourSettingsPage::AddBehaviour b, MimeData *mimedata) const {
+void MainWindow::ApplyAddBehaviour(const BehaviourSettingsPage::AddBehaviour b, MimeData *mimedata) const {
 
   switch (b) {
       case BehaviourSettingsPage::AddBehaviour_Append:
@@ -1552,7 +1551,7 @@ void MainWindow::ApplyAddBehaviour(BehaviourSettingsPage::AddBehaviour b, MimeDa
   }
 }
 
-void MainWindow::ApplyPlayBehaviour(BehaviourSettingsPage::PlayBehaviour b, MimeData *mimedata) const {
+void MainWindow::ApplyPlayBehaviour(const BehaviourSettingsPage::PlayBehaviour b, MimeData *mimedata) const {
 
   switch (b) {
     case BehaviourSettingsPage::PlayBehaviour_Always:
@@ -1973,10 +1972,10 @@ void MainWindow::RenumberTracks() {
 
 }
 
-void MainWindow::SongSaveComplete(TagReaderReply *reply, const QPersistentModelIndex &index) {
+void MainWindow::SongSaveComplete(TagReaderReply *reply, const QPersistentModelIndex &idx) {
 
-  if (reply->is_successful() && index.isValid()) {
-    app_->playlist_manager()->current()->ReloadItems(QList<int>()<< index.row());
+  if (reply->is_successful() && idx.isValid()) {
+    app_->playlist_manager()->current()->ReloadItems(QList<int>()<< idx.row());
   }
   reply->deleteLater();
 
@@ -2133,8 +2132,8 @@ void MainWindow::PlaylistClearCurrent() {
 
 }
 
-void MainWindow::PlaylistEditFinished(const QModelIndex &index) {
-  if (index == playlist_menu_index_) SelectionSetValue();
+void MainWindow::PlaylistEditFinished(const QModelIndex &idx) {
+  if (idx == playlist_menu_index_) SelectionSetValue();
 }
 
 void MainWindow::CommandlineOptionsReceived(const quint32 instanceId, const QByteArray &string_options) {
diff --git a/src/core/mainwindow.h b/src/core/mainwindow.h
index 99bc2e604..7449cff91 100644
--- a/src/core/mainwindow.h
+++ b/src/core/mainwindow.h
@@ -100,14 +100,14 @@ class MainWindow : public QMainWindow, public PlatformInterface {
   Q_OBJECT
 
  public:
-  explicit MainWindow(Application *app, SystemTrayIcon *tray_icon, OSDBase *osd, const CommandlineOptions& options, QWidget *parent = nullptr);
+  explicit MainWindow(Application *app, SystemTrayIcon *tray_icon, OSDBase *osd, const CommandlineOptions &options, QWidget *parent = nullptr);
   ~MainWindow() override;
 
   static const char *kSettingsGroup;
   static const char *kAllFilesFilterSpec;
 
   void SetHiddenInTray(const bool hidden);
-  void CommandlineOptionsReceived(const CommandlineOptions& options);
+  void CommandlineOptionsReceived(const CommandlineOptions &options);
 
  protected:
   void keyPressEvent(QKeyEvent *event) override;
@@ -120,7 +120,7 @@ class MainWindow : public QMainWindow, public PlatformInterface {
 
   // PlatformInterface
   void Activate() override;
-  bool LoadUrl(const QString& url) override;
+  bool LoadUrl(const QString &url) override;
 
  signals:
   void AlbumCoverReady(const Song &song, const QImage &image);
@@ -128,23 +128,21 @@ class MainWindow : public QMainWindow, public PlatformInterface {
   // Signals that stop playing after track was toggled.
   void StopAfterToggled(bool stop);
 
-  void IntroPointReached();
-
   void AuthorizationUrlReceived(const QUrl &url);
 
  private slots:
-  void FilePathChanged(const QString& path);
+  void FilePathChanged(const QString &path);
 
   void EngineChanged(Engine::EngineType enginetype);
   void MediaStopped();
   void MediaPaused();
   void MediaPlaying();
   void TrackSkipped(PlaylistItemPtr item);
-  void ForceShowOSD(const Song& song, const bool toggle);
+  void ForceShowOSD(const Song &song, const bool toggle);
 
   void PlaylistMenuHidden();
-  void PlaylistRightClick(const QPoint& global_pos, const QModelIndex& index);
-  void PlaylistCurrentChanged(const QModelIndex& current);
+  void PlaylistRightClick(const QPoint &global_pos, const QModelIndex &index);
+  void PlaylistCurrentChanged(const QModelIndex &current);
   void PlaylistViewSelectionModelChanged();
   void PlaylistPlay();
   void PlaylistStopAfter();
@@ -152,7 +150,7 @@ class MainWindow : public QMainWindow, public PlatformInterface {
   void PlaylistQueuePlayNext();
   void PlaylistSkip();
   void PlaylistRemoveCurrent();
-  void PlaylistEditFinished(const QModelIndex& index);
+  void PlaylistEditFinished(const QModelIndex &idx);
   void PlaylistClearCurrent();
   void RescanSongs();
   void EditTracks();
@@ -175,17 +173,17 @@ class MainWindow : public QMainWindow, public PlatformInterface {
 
   void ChangeCollectionQueryMode(QAction *action);
 
-  void PlayIndex(const QModelIndex& index);
-  void PlaylistDoubleClick(const QModelIndex& index);
+  void PlayIndex(const QModelIndex &idx);
+  void PlaylistDoubleClick(const QModelIndex &idx);
   void StopAfterCurrent();
 
-  void SongChanged(const Song& song);
+  void SongChanged(const Song &song);
   void VolumeChanged(const int volume);
 
-  void CopyFilesToCollection(const QList<QUrl>& urls);
-  void MoveFilesToCollection(const QList<QUrl>& urls);
-  void CopyFilesToDevice(const QList<QUrl>& urls);
-  void EditFileTags(const QList<QUrl>& urls);
+  void CopyFilesToCollection(const QList<QUrl> &urls);
+  void MoveFilesToCollection(const QList<QUrl> &urls);
+  void CopyFilesToDevice(const QList<QUrl> &urls);
+  void EditFileTags(const QList<QUrl> &urls);
 
   void AddToPlaylist(QMimeData *q_mimedata);
   void AddToPlaylist(QAction *action);
@@ -217,12 +215,12 @@ class MainWindow : public QMainWindow, public PlatformInterface {
 
   void PlayingWidgetPositionChanged(const bool above_status_bar);
 
-  void SongSaveComplete(TagReaderReply *reply, const QPersistentModelIndex& index);
+  void SongSaveComplete(TagReaderReply *reply, const QPersistentModelIndex &idx);
 
   void ShowCoverManager();
 
   void ShowAboutDialog();
-  void ShowErrorDialog(const QString& message);
+  void ShowErrorDialog(const QString &message);
   void ShowTranscodeDialog();
   SettingsDialog *CreateSettingsDialog();
   EditTagDialog *CreateEditTagDialog();
@@ -270,8 +268,8 @@ class MainWindow : public QMainWindow, public PlatformInterface {
 
   void SaveSettings();
 
-  void ApplyAddBehaviour(BehaviourSettingsPage::AddBehaviour b, MimeData *mimedata) const;
-  void ApplyPlayBehaviour(BehaviourSettingsPage::PlayBehaviour b, MimeData *mimedata) const;
+  void ApplyAddBehaviour(const BehaviourSettingsPage::AddBehaviour b, MimeData *mimedata) const;
+  void ApplyPlayBehaviour(const BehaviourSettingsPage::PlayBehaviour b, MimeData *mimedata) const;
 
   void CheckFullRescanRevisions();
 
diff --git a/src/core/player.cpp b/src/core/player.cpp
index 0c8cd91fc..51a977b26 100644
--- a/src/core/player.cpp
+++ b/src/core/player.cpp
@@ -354,7 +354,7 @@ void Player::HandleLoadResult(const UrlHandler::LoadResult &result) {
 
 void Player::Next() { NextInternal(Engine::Manual); }
 
-void Player::NextInternal(Engine::TrackChangeFlags change) {
+void Player::NextInternal(const Engine::TrackChangeFlags change) {
 
   if (HandleStopAfter()) return;
 
@@ -362,7 +362,7 @@ void Player::NextInternal(Engine::TrackChangeFlags change) {
 
 }
 
-void Player::NextItem(Engine::TrackChangeFlags change) {
+void Player::NextItem(const Engine::TrackChangeFlags change) {
 
   Playlist *active_playlist = app_->playlist_manager()->active();
 
@@ -487,7 +487,7 @@ bool Player::PreviousWouldRestartTrack() const {
 
 void Player::Previous() { PreviousItem(Engine::Manual); }
 
-void Player::PreviousItem(Engine::TrackChangeFlags change) {
+void Player::PreviousItem(const Engine::TrackChangeFlags change) {
 
   const bool ignore_repeat_track = change & Engine::Manual;
 
@@ -514,7 +514,7 @@ void Player::PreviousItem(Engine::TrackChangeFlags change) {
 
 }
 
-void Player::EngineStateChanged(Engine::State state) {
+void Player::EngineStateChanged(const Engine::State state) {
 
   if (Engine::Error == state) {
     nb_errors_received_++;
@@ -542,7 +542,7 @@ void Player::EngineStateChanged(Engine::State state) {
 
 }
 
-void Player::SetVolume(int value) {
+void Player::SetVolume(const int value) {
 
   int old_volume = engine_->volume();
 
@@ -558,7 +558,7 @@ void Player::SetVolume(int value) {
 
 int Player::GetVolume() const { return engine_->volume(); }
 
-void Player::PlayAt(int index, Engine::TrackChangeFlags change, bool reshuffle) {
+void Player::PlayAt(const int index, Engine::TrackChangeFlags change, const bool reshuffle) {
 
   if (current_item_ && change == Engine::Manual && engine_->position_nanosec() != engine_->length_nanosec()) {
     emit TrackSkipped(current_item_);
@@ -611,7 +611,7 @@ void Player::CurrentMetadataChanged(const Song &metadata) {
 
 }
 
-void Player::SeekTo(int seconds) {
+void Player::SeekTo(const int seconds) {
 
   const qint64 length_nanosec = engine_->length_nanosec();
 
@@ -662,7 +662,7 @@ void Player::EngineMetadataReceived(const Engine::SimpleMetaBundle &bundle) {
 
 }
 
-PlaylistItemPtr Player::GetItemAt(int pos) const {
+PlaylistItemPtr Player::GetItemAt(const int pos) const {
 
   if (pos < 0 || pos >= app_->playlist_manager()->active()->rowCount())
     return PlaylistItemPtr();
@@ -763,8 +763,6 @@ void Player::TrackAboutToEnd() {
 
 }
 
-void Player::IntroPointReached() { NextInternal(Engine::Intro); }
-
 void Player::FatalError() {
   nb_errors_received_ = 0;
   Stop();
diff --git a/src/core/player.h b/src/core/player.h
index ae27155af..702b8f2b9 100644
--- a/src/core/player.h
+++ b/src/core/player.h
@@ -72,7 +72,7 @@ class PlayerInterface : public QObject {
   virtual void ReloadSettings() = 0;
 
   // Manual track change to the specified track
-  virtual void PlayAt(int i, Engine::TrackChangeFlags change, bool reshuffle) = 0;
+  virtual void PlayAt(const int row, Engine::TrackChangeFlags change, const bool reshuffle) = 0;
 
   // If there's currently a song playing, pause it, otherwise play the track that was playing last, or the first one on the playlist
   virtual void PlayPause() = 0;
@@ -82,10 +82,10 @@ class PlayerInterface : public QObject {
   virtual void Next() = 0;
 
   virtual void Previous() = 0;
-  virtual void SetVolume(int value) = 0;
+  virtual void SetVolume(const int value) = 0;
   virtual void VolumeUp() = 0;
   virtual void VolumeDown() = 0;
-  virtual void SeekTo(int seconds) = 0;
+  virtual void SeekTo(const int seconds) = 0;
   // Moves the position of the currently playing song five seconds forward.
   virtual void SeekForward() = 0;
   // Moves the position of the currently playing song five seconds backwards.
@@ -109,14 +109,14 @@ class PlayerInterface : public QObject {
   void PlaylistFinished();
   void VolumeEnabled(bool);
   void VolumeChanged(int volume);
-  void Error(const QString &message);
+  void Error(QString message);
   void TrackSkipped(PlaylistItemPtr old_track);
   // Emitted when there's a manual change to the current's track position.
   void Seeked(qlonglong microseconds);
 
   // Emitted when Player has processed a request to play another song.
   // This contains the URL of the song and a flag saying whether it was able to play the song.
-  void SongChangeRequestProcessed(const QUrl &url, bool valid);
+  void SongChangeRequestProcessed(QUrl url, bool valid);
 
   // The toggle parameter is true when user requests to toggle visibility for Pretty OSD
   void ForceShowOSD(Song, bool toggle);
@@ -158,15 +158,15 @@ class Player : public PlayerInterface {
  public slots:
   void ReloadSettings() override;
 
-  void PlayAt(int i, Engine::TrackChangeFlags change, bool reshuffle) override;
+  void PlayAt(const int row, Engine::TrackChangeFlags change, const bool reshuffle) override;
   void PlayPause() override;
   void RestartOrPrevious() override;
   void Next() override;
   void Previous() override;
-  void SetVolume(int value) override;
+  void SetVolume(const int value) override;
   void VolumeUp() override { SetVolume(GetVolume() + 5); }
   void VolumeDown() override { SetVolume(GetVolume() - 5); }
-  void SeekTo(int seconds) override;
+  void SeekTo(const int seconds) override;
   void SeekForward() override;
   void SeekBackward() override;
 
@@ -176,7 +176,6 @@ class Player : public PlayerInterface {
   void Pause() override;
   void Stop(bool stop_after = false) override;
   void StopAfterCurrent();
-  void IntroPointReached();
   void Play() override;
   void ShowOSD() override;
   void TogglePrettyOSD();
@@ -187,15 +186,15 @@ class Player : public PlayerInterface {
   void EngineChanged(Engine::EngineType enginetype);
 
  private slots:
-  void EngineStateChanged(Engine::State);
+  void EngineStateChanged(const Engine::State);
   void EngineMetadataReceived(const Engine::SimpleMetaBundle &bundle);
   void TrackAboutToEnd();
   void TrackEnded();
   // Play the next item on the playlist - disregarding radio stations like last.fm that might have more tracks.
-  void NextItem(Engine::TrackChangeFlags change);
-  void PreviousItem(Engine::TrackChangeFlags change);
+  void NextItem(const Engine::TrackChangeFlags change);
+  void PreviousItem(const Engine::TrackChangeFlags change);
 
-  void NextInternal(Engine::TrackChangeFlags);
+  void NextInternal(const Engine::TrackChangeFlags);
 
   void FatalError();
   void ValidSongRequested(const QUrl&);
diff --git a/src/playlist/playlist.cpp b/src/playlist/playlist.cpp
index f42ae2b54..3149d8fc8 100644
--- a/src/playlist/playlist.cpp
+++ b/src/playlist/playlist.cpp
@@ -111,7 +111,7 @@ const int Playlist::kUndoItemLimit = 500;
 const qint64 Playlist::kMinScrobblePointNsecs = 31ll * kNsecPerSec;
 const qint64 Playlist::kMaxScrobblePointNsecs = 240ll * kNsecPerSec;
 
-Playlist::Playlist(PlaylistBackend *backend, TaskManager *task_manager, CollectionBackend *collection, int id, const QString &special_type, bool favorite, QObject *parent)
+Playlist::Playlist(PlaylistBackend *backend, TaskManager *task_manager, CollectionBackend *collection, const int id, const QString &special_type, const bool favorite, QObject *parent)
     : QAbstractListModel(parent),
       is_loading_(false),
       proxy_(new PlaylistFilter(this)),
@@ -161,7 +161,7 @@ Playlist::~Playlist() {
 }
 
 template <typename T>
-void Playlist::InsertSongItems(const SongList &songs, int pos, bool play_now, bool enqueue, bool enqueue_next) {
+void Playlist::InsertSongItems(const SongList &songs, const int pos, const bool play_now, const bool enqueue, const bool enqueue_next) {
 
   PlaylistItemList items;
 
@@ -360,38 +360,38 @@ QVariant Playlist::data(const QModelIndex &idx, int role) const {
 }
 
 #ifdef HAVE_MOODBAR
-void Playlist::MoodbarUpdated(const QModelIndex& index) {
-  emit dataChanged(index.sibling(index.row(), Column_Mood), index.sibling(index.row(), Column_Mood));
+void Playlist::MoodbarUpdated(const QModelIndex &idx) {
+  emit dataChanged(idx.sibling(idx.row(), Column_Mood), idx.sibling(idx.row(), Column_Mood));
 }
 #endif
 
-bool Playlist::setData(const QModelIndex &index, const QVariant &value, int role) {
+bool Playlist::setData(const QModelIndex &idx, const QVariant &value, int role) {
 
   Q_UNUSED(role);
 
-  int row = index.row();
+  int row = idx.row();
   PlaylistItemPtr item = item_at(row);
   Song song = item->OriginalMetadata();
 
-  if (index.data() == value) return false;
+  if (idx.data() == value) return false;
 
-  if (!set_column_value(song, static_cast<Column>(index.column()), value)) return false;
+  if (!set_column_value(song, static_cast<Column>(idx.column()), value)) return false;
 
   TagReaderReply *reply = TagReaderClient::Instance()->SaveFile(song.url().toLocalFile(), song);
-  NewClosure(reply, SIGNAL(Finished(bool)), this, SLOT(SongSaveComplete(TagReaderReply*, QPersistentModelIndex)), reply, QPersistentModelIndex(index));
+  NewClosure(reply, SIGNAL(Finished(bool)), this, SLOT(SongSaveComplete(TagReaderReply*, QPersistentModelIndex)), reply, QPersistentModelIndex(idx));
 
   return true;
 
 }
 
-void Playlist::SongSaveComplete(TagReaderReply *reply, const QPersistentModelIndex &index) {
+void Playlist::SongSaveComplete(TagReaderReply *reply, const QPersistentModelIndex &idx) {
 
-  if (reply->is_successful() && index.isValid()) {
+  if (reply->is_successful() && idx.isValid()) {
     if (reply->message().save_file_response().success()) {
-      PlaylistItemPtr item = item_at(index.row());
+      PlaylistItemPtr item = item_at(idx.row());
       if (!item) return;
       QFuture<void> future = item->BackgroundReload();
-      NewClosure(future, this, SLOT(ItemReloadComplete(QPersistentModelIndex)), index);
+      NewClosure(future, this, SLOT(ItemReloadComplete(QPersistentModelIndex)), idx);
     }
     else {
       emit Error(tr("An error occurred writing metadata to '%1'").arg(QString::fromStdString(reply->request_message().save_file_request().filename())));
@@ -401,17 +401,17 @@ void Playlist::SongSaveComplete(TagReaderReply *reply, const QPersistentModelInd
 
 }
 
-void Playlist::ItemReloadComplete(const QPersistentModelIndex &index) {
+void Playlist::ItemReloadComplete(const QPersistentModelIndex &idx) {
 
-  if (index.isValid()) {
+  if (idx.isValid()) {
 
-    PlaylistItemPtr item = item_at(index.row());
+    PlaylistItemPtr item = item_at(idx.row());
     if (item && item->HasTemporaryMetadata()) {  // Update temporary metadata.
       item->UpdateTemporaryMetadata(item->OriginalMetadata());
     }
 
-    emit dataChanged(index, index);
-    emit EditingFinished(index);
+    emit dataChanged(idx, idx);
+    emit EditingFinished(idx);
   }
 
 }
@@ -428,18 +428,18 @@ int Playlist::last_played_row() const {
   return last_played_item_index_.isValid() ? last_played_item_index_.row() : -1;
 }
 
-void Playlist::ShuffleModeChanged(PlaylistSequence::ShuffleMode mode) {
+void Playlist::ShuffleModeChanged(const PlaylistSequence::ShuffleMode mode) {
   is_shuffled_ = (mode != PlaylistSequence::Shuffle_Off);
   ReshuffleIndices();
 }
 
-bool Playlist::FilterContainsVirtualIndex(int i) const {
+bool Playlist::FilterContainsVirtualIndex(const int i) const {
   if (i < 0 || i >= virtual_items_.count()) return false;
 
   return proxy_->filterAcceptsRow(virtual_items_[i], QModelIndex());
 }
 
-int Playlist::NextVirtualIndex(int i, bool ignore_repeat_track) const {
+int Playlist::NextVirtualIndex(int i, const bool ignore_repeat_track) const {
 
   PlaylistSequence::RepeatMode repeat_mode = playlist_sequence_->repeat_mode();
   PlaylistSequence::ShuffleMode shuffle_mode = playlist_sequence_->shuffle_mode();
@@ -483,7 +483,7 @@ int Playlist::NextVirtualIndex(int i, bool ignore_repeat_track) const {
 
 }
 
-int Playlist::PreviousVirtualIndex(int i, bool ignore_repeat_track) const {
+int Playlist::PreviousVirtualIndex(int i, const bool ignore_repeat_track) const {
 
   PlaylistSequence::RepeatMode repeat_mode = playlist_sequence_->repeat_mode();
   PlaylistSequence::ShuffleMode shuffle_mode = playlist_sequence_->shuffle_mode();
@@ -521,7 +521,7 @@ int Playlist::PreviousVirtualIndex(int i, bool ignore_repeat_track) const {
 
 }
 
-int Playlist::next_row(bool ignore_repeat_track) const {
+int Playlist::next_row(const bool ignore_repeat_track) const {
 
   // Any queued items take priority
   if (!queue_->is_empty()) {
@@ -553,7 +553,7 @@ int Playlist::next_row(bool ignore_repeat_track) const {
 
 }
 
-int Playlist::previous_row(bool ignore_repeat_track) const {
+int Playlist::previous_row(const bool ignore_repeat_track) const {
 
   int prev_virtual_index = PreviousVirtualIndex(current_virtual_index_,ignore_repeat_track);
 
@@ -580,7 +580,7 @@ int Playlist::previous_row(bool ignore_repeat_track) const {
 
 }
 
-void Playlist::set_current_row(int i, bool is_stopping) {
+void Playlist::set_current_row(const int i, const bool is_stopping) {
 
   QModelIndex old_current_item_index = current_item_index_;
 
@@ -643,13 +643,13 @@ void Playlist::set_current_row(int i, bool is_stopping) {
 
 }
 
-Qt::ItemFlags Playlist::flags(const QModelIndex &index) const {
+Qt::ItemFlags Playlist::flags(const QModelIndex &idx) const {
 
   Qt::ItemFlags flags = Qt::ItemIsEnabled | Qt::ItemIsSelectable;
 
-  if (column_is_editable(static_cast<Column>(index.column()))) flags |= Qt::ItemIsEditable;
+  if (column_is_editable(static_cast<Column>(idx.column()))) flags |= Qt::ItemIsEditable;
 
-  if (index.isValid()) return flags | Qt::ItemIsDragEnabled;
+  if (idx.isValid()) return flags | Qt::ItemIsDragEnabled;
 
   return Qt::ItemIsDropEnabled;
 
@@ -758,7 +758,7 @@ bool Playlist::dropMimeData(const QMimeData *data, Qt::DropAction action, int ro
 
 }
 
-void Playlist::InsertUrls(const QList<QUrl> &urls, int pos, bool play_now, bool enqueue, bool enqueue_next) {
+void Playlist::InsertUrls(const QList<QUrl> &urls, const int pos, const bool play_now, const bool enqueue, const bool enqueue_next) {
 
   SongLoaderInserter *inserter = new SongLoaderInserter(task_manager_, collection_, backend_->app()->player());
   connect(inserter, SIGNAL(Error(QString)), SIGNAL(Error(QString)));
@@ -767,7 +767,7 @@ void Playlist::InsertUrls(const QList<QUrl> &urls, int pos, bool play_now, bool
 
 }
 
-void Playlist::MoveItemWithoutUndo(int source, int dest) {
+void Playlist::MoveItemWithoutUndo(const int source, const int dest) {
   MoveItemsWithoutUndo(QList<int>() << source, dest);
 }
 
@@ -871,7 +871,7 @@ void Playlist::MoveItemsWithoutUndo(int start, const QList<int> &dest_rows) {
 
 }
 
-void Playlist::InsertItems(const PlaylistItemList &itemsIn, int pos, bool play_now, bool enqueue, bool enqueue_next) {
+void Playlist::InsertItems(const PlaylistItemList &itemsIn, const int pos, const bool play_now, const bool enqueue, const bool enqueue_next) {
 
   if (itemsIn.isEmpty())
     return;
@@ -931,7 +931,7 @@ void Playlist::InsertItems(const PlaylistItemList &itemsIn, int pos, bool play_n
 
 }
 
-void Playlist::InsertItemsWithoutUndo(const PlaylistItemList &items, int pos, bool enqueue, bool enqueue_next) {
+void Playlist::InsertItemsWithoutUndo(const PlaylistItemList &items, const int pos, const bool enqueue, const bool enqueue_next) {
 
   if (items.isEmpty()) return;
 
@@ -1071,11 +1071,11 @@ QMimeData *Playlist::mimeData(const QModelIndexList &indexes) const {
 
   QList<QUrl> urls;
   QList<int> rows;
-  for (const QModelIndex &index : indexes) {
-    if (index.column() != first_column) continue;
+  for (const QModelIndex &idx : indexes) {
+    if (idx.column() != first_column) continue;
 
-    urls << items_[index.row()]->Url();
-    rows << index.row();
+    urls << items_[idx.row()]->Url();
+    rows << idx.row();
   }
 
   QBuffer buf;
@@ -1097,7 +1097,7 @@ QMimeData *Playlist::mimeData(const QModelIndexList &indexes) const {
 
 }
 
-bool Playlist::CompareItems(int column, Qt::SortOrder order, std::shared_ptr<PlaylistItem> _a, std::shared_ptr<PlaylistItem> _b) {
+bool Playlist::CompareItems(const int column, const Qt::SortOrder order, std::shared_ptr<PlaylistItem> _a, std::shared_ptr<PlaylistItem> _b) {
 
   std::shared_ptr<PlaylistItem> a = order == Qt::AscendingOrder ? _a : _b;
   std::shared_ptr<PlaylistItem> b = order == Qt::AscendingOrder ? _b : _a;
@@ -1148,7 +1148,7 @@ bool Playlist::CompareItems(int column, Qt::SortOrder order, std::shared_ptr<Pla
 
 }
 
-bool Playlist::ComparePathDepths(Qt::SortOrder order, std::shared_ptr<PlaylistItem> _a, std::shared_ptr<PlaylistItem> _b) {
+bool Playlist::ComparePathDepths(const Qt::SortOrder order, std::shared_ptr<PlaylistItem> _a, std::shared_ptr<PlaylistItem> _b) {
 
   std::shared_ptr<PlaylistItem> a = order == Qt::AscendingOrder ? _a : _b;
   std::shared_ptr<PlaylistItem> b = order == Qt::AscendingOrder ? _b : _a;
@@ -1201,7 +1201,7 @@ QString Playlist::column_name(Column column) {
 
 }
 
-QString Playlist::abbreviated_column_name(Column column) {
+QString Playlist::abbreviated_column_name(const Column column) {
 
   const QString &column_name = Playlist::column_name(column);
 
@@ -1276,7 +1276,7 @@ void Playlist::Paused() { SetCurrentIsPaused(true); }
 
 void Playlist::Stopped() { SetCurrentIsPaused(false); }
 
-void Playlist::SetCurrentIsPaused(bool paused) {
+void Playlist::SetCurrentIsPaused(const bool paused) {
 
   if (paused == current_is_paused_) return;
 
@@ -1469,7 +1469,7 @@ PlaylistItemList Playlist::RemoveItemsWithoutUndo(const int row, const int count
 
 }
 
-void Playlist::StopAfter(int row) {
+void Playlist::StopAfter(const int row) {
 
   QModelIndex old_stop_after = stop_after_;
 
@@ -1661,7 +1661,7 @@ void Playlist::Shuffle() {
 }
 
 namespace {
-bool AlbumShuffleComparator(const QMap<QString, int> &album_key_positions, const QMap<int, QString> &album_keys, int left, int right) {
+bool AlbumShuffleComparator(const QMap<QString, int> &album_key_positions, const QMap<int, QString> &album_keys, const int left, const int right) {
 
   const int left_pos = album_key_positions[album_keys[left]];
   const int right_pos = album_key_positions[album_keys[right]];
@@ -1777,7 +1777,7 @@ quint64 Playlist::GetTotalLength() const {
 
 }
 
-PlaylistItemList Playlist::collection_items_by_id(int id) const {
+PlaylistItemList Playlist::collection_items_by_id(const int id) const {
   return collection_items_by_id_.values(id);
 }
 
@@ -1791,15 +1791,15 @@ void Playlist::TracksAboutToBeDequeued(const QModelIndex&, int begin, int end) {
 
 void Playlist::TracksDequeued() {
 
-  for (const QModelIndex &index : temp_dequeue_change_indexes_) {
-    emit dataChanged(index, index);
+  for (const QModelIndex &idx : temp_dequeue_change_indexes_) {
+    emit dataChanged(idx, idx);
   }
   temp_dequeue_change_indexes_.clear();
   emit QueueChanged();
 
 }
 
-void Playlist::TracksEnqueued(const QModelIndex&, int begin, int end) {
+void Playlist::TracksEnqueued(const QModelIndex&, const int begin, const int end) {
 
   const QModelIndex &b = queue_->mapToSource(queue_->index(begin, Column_Title));
   const QModelIndex &e = queue_->mapToSource(queue_->index(end, Column_Title));
@@ -1810,8 +1810,8 @@ void Playlist::TracksEnqueued(const QModelIndex&, int begin, int end) {
 void Playlist::QueueLayoutChanged() {
 
   for (int i = 0; i < queue_->rowCount(); ++i) {
-    const QModelIndex &index = queue_->mapToSource(queue_->index(i, Column_Title));
-    emit dataChanged(index, index);
+    const QModelIndex &idx = queue_->mapToSource(queue_->index(i, Column_Title));
+    emit dataChanged(idx, idx);
   }
 
 }
@@ -1954,7 +1954,7 @@ void Playlist::RemoveUnavailableSongs() {
 
 }
 
-bool Playlist::ApplyValidityOnCurrentSong(const QUrl &url, bool valid) {
+bool Playlist::ApplyValidityOnCurrentSong(const QUrl &url, const bool valid) {
 
   PlaylistItemPtr current = current_item();
 
diff --git a/src/playlist/playlist.h b/src/playlist/playlist.h
index 81291029a..2ed43d131 100644
--- a/src/playlist/playlist.h
+++ b/src/playlist/playlist.h
@@ -93,7 +93,7 @@ class Playlist : public QAbstractListModel {
   friend class PlaylistUndoCommands::ReOrderItems;
 
  public:
-  explicit Playlist(PlaylistBackend *backend, TaskManager *task_manager, CollectionBackend *collection, int id, const QString &special_type = QString(), bool favorite = false, QObject *parent = nullptr);
+  explicit Playlist(PlaylistBackend *backend, TaskManager *task_manager, CollectionBackend *collection, const int id, const QString &special_type = QString(), const bool favorite = false, QObject *parent = nullptr);
   ~Playlist() override;
 
   void SkipTracks(const QModelIndexList &source_indexes);
@@ -166,7 +166,7 @@ class Playlist : public QAbstractListModel {
   static const qint64 kMinScrobblePointNsecs;
   static const qint64 kMaxScrobblePointNsecs;
 
-  static bool CompareItems(int column, Qt::SortOrder order, PlaylistItemPtr a, PlaylistItemPtr b);
+  static bool CompareItems(const int column, const Qt::SortOrder order, PlaylistItemPtr a, PlaylistItemPtr b);
 
   static QString column_name(Column column);
   static QString abbreviated_column_name(Column column);
@@ -186,13 +186,13 @@ class Playlist : public QAbstractListModel {
   const QString &ui_path() const { return ui_path_; }
   void set_ui_path(const QString &path) { ui_path_ = path; }
   bool is_favorite() const { return favorite_; }
-  void set_favorite(bool favorite) { favorite_ = favorite; }
+  void set_favorite(const bool favorite) { favorite_ = favorite; }
 
   int current_row() const;
   int last_played_row() const;
   void reset_last_played() { last_played_item_index_ = QPersistentModelIndex(); }
-  int next_row(bool ignore_repeat_track = false) const;
-  int previous_row(bool ignore_repeat_track = false) const;
+  int next_row(const bool ignore_repeat_track = false) const;
+  int previous_row(const bool ignore_repeat_track = false) const;
 
   const QModelIndex current_index() const;
 
@@ -201,15 +201,15 @@ class Playlist : public QAbstractListModel {
   QString special_type() const { return special_type_; }
   void set_special_type(const QString &v) { special_type_ = v; }
 
-  const PlaylistItemPtr &item_at(int index) const { return items_[index]; }
-  bool has_item_at(int index) const { return index >= 0 && index < rowCount(); }
+  const PlaylistItemPtr &item_at(const int index) const { return items_[index]; }
+  bool has_item_at(const int index) const { return index >= 0 && index < rowCount(); }
 
   PlaylistItemPtr current_item() const;
 
   PlaylistItem::Options current_item_options() const;
   Song current_item_metadata() const;
 
-  PlaylistItemList collection_items_by_id(int id) const;
+  PlaylistItemList collection_items_by_id(const int id) const;
 
   SongList GetAllSongs() const;
   PlaylistItemList GetAllItems() const;
@@ -222,8 +222,8 @@ class Playlist : public QAbstractListModel {
 
   bool scrobbled() const { return scrobbled_; }
   bool nowplaying() const { return nowplaying_; }
-  void set_scrobbled(bool state) { scrobbled_ = state; }
-  void set_nowplaying(bool state) { nowplaying_ = state; }
+  void set_scrobbled(const bool state) { scrobbled_ = state; }
+  void set_nowplaying(const bool state) { nowplaying_ = state; }
   void set_editing(const int row) { editing_ = row; }
   qint64 scrobble_point_nanosec() const { return scrobble_point_; }
   void UpdateScrobblePoint(const qint64 seek_point_nanosec = 0);
@@ -248,7 +248,7 @@ class Playlist : public QAbstractListModel {
   // Removes from the playlist all local files that don't exist anymore.
   void RemoveDeletedSongs();
 
-  void StopAfter(int row);
+  void StopAfter(const int row);
   void ReloadItems(const QList<int> &rows);
   void InformOfCurrentSongChange();
 
@@ -259,16 +259,16 @@ class Playlist : public QAbstractListModel {
 
   // Just emits the dataChanged() signal so the mood column is repainted.
 #ifdef HAVE_MOODBAR
-  void MoodbarUpdated(const QModelIndex& index);
+  void MoodbarUpdated(const QModelIndex &idx);
 #endif
 
   // QAbstractListModel
   int rowCount(const QModelIndex& = QModelIndex()) const override { return items_.count(); }
   int columnCount(const QModelIndex& = QModelIndex()) const override { return ColumnCount; }
   QVariant data(const QModelIndex &idx, int role = Qt::DisplayRole) const override;
-  bool setData(const QModelIndex &index, const QVariant &value, int role) override;
+  bool setData(const QModelIndex &idx, const QVariant &value, int role) override;
   QVariant headerData(int section, Qt::Orientation orientation, int role = Qt::DisplayRole) const override;
-  Qt::ItemFlags flags(const QModelIndex &index) const override;
+  Qt::ItemFlags flags(const QModelIndex &idx) const override;
   QStringList mimeTypes() const override;
   Qt::DropActions supportedDropActions() const override;
   QMimeData *mimeData(const QModelIndexList &indexes) const override;
@@ -279,11 +279,11 @@ class Playlist : public QAbstractListModel {
   static bool ComparePathDepths(Qt::SortOrder, PlaylistItemPtr, PlaylistItemPtr);
 
  public slots:
-  void set_current_row(int index, bool is_stopping = false);
+  void set_current_row(const int i, const bool is_stopping = false);
   void Paused();
   void Playing();
   void Stopped();
-  void IgnoreSorting(bool value) { ignore_sorting_ = value; }
+  void IgnoreSorting(const bool value) { ignore_sorting_ = value; }
 
   void ClearStreamMetadata();
   void SetStreamMetadata(const QUrl &url, const Song &song, const bool minor);
@@ -295,7 +295,7 @@ class Playlist : public QAbstractListModel {
   void RemoveUnavailableSongs();
   void Shuffle();
 
-  void ShuffleModeChanged(PlaylistSequence::ShuffleMode mode);
+  void ShuffleModeChanged(const PlaylistSequence::ShuffleMode mode);
 
   void SetColumnAlignment(const ColumnAlignmentMap &alignment);
 
@@ -306,34 +306,34 @@ class Playlist : public QAbstractListModel {
  signals:
   void RestoreFinished();
   void PlaylistLoaded();
-  void CurrentSongChanged(const Song &metadata);
-  void SongMetadataChanged(const Song &metadata);
-  void EditingFinished(const QModelIndex &index);
-  void PlayRequested(const QModelIndex &index);
+  void CurrentSongChanged(Song metadata);
+  void SongMetadataChanged(Song metadata);
+  void EditingFinished(QModelIndex idx);
+  void PlayRequested(QModelIndex idx);
 
   // Signals that the underlying list of items was changed, meaning that something was added to it, removed from it or the ordering changed.
   void PlaylistChanged();
   void DynamicModeChanged(bool dynamic);
 
-  void Error(const QString &message);
+  void Error(QString message);
 
   // Signals that the queue has changed, meaning that the remaining queued items should update their position.
   void QueueChanged();
 
  private:
-  void SetCurrentIsPaused(bool paused);
-  int NextVirtualIndex(int i, bool ignore_repeat_track) const;
-  int PreviousVirtualIndex(int i, bool ignore_repeat_track) const;
-  bool FilterContainsVirtualIndex(int i) const;
+  void SetCurrentIsPaused(const bool paused);
+  int NextVirtualIndex(int i, const bool ignore_repeat_track) const;
+  int PreviousVirtualIndex(int i, const bool ignore_repeat_track) const;
+  bool FilterContainsVirtualIndex(const int i) const;
 
   template <typename T>
-  void InsertSongItems(const SongList &songs, int pos, bool play_now, bool enqueue, bool enqueue_next = false);
+  void InsertSongItems(const SongList &songs, const int pos, const bool play_now, const bool enqueue, const bool enqueue_next = false);
 
   // Modify the playlist without changing the undo stack.  These are used by our friends in PlaylistUndoCommands
   void InsertItemsWithoutUndo(const PlaylistItemList &items, int pos, bool enqueue = false, bool enqueue_next = false);
   PlaylistItemList RemoveItemsWithoutUndo(const int row, const int count);
   void MoveItemsWithoutUndo(const QList<int> &source_rows, int pos);
-  void MoveItemWithoutUndo(int source, int dest);
+  void MoveItemWithoutUndo(const int source, const int dest);
   void MoveItemsWithoutUndo(int start, const QList<int> &dest_rows);
   void ReOrderWithoutUndo(const PlaylistItemList &new_items);
 
@@ -343,9 +343,9 @@ class Playlist : public QAbstractListModel {
   bool removeRows(QList<int> &rows);
 
  private slots:
-  void TracksAboutToBeDequeued(const QModelIndex&, int begin, int end);
+  void TracksAboutToBeDequeued(const QModelIndex&, const int begin, const int end);
   void TracksDequeued();
-  void TracksEnqueued(const QModelIndex&, int begin, int end);
+  void TracksEnqueued(const QModelIndex&, const int begin, const int end);
   void QueueLayoutChanged();
   void SongSaveComplete(TagReaderReply *reply, const QPersistentModelIndex &index);
   void ItemReloadComplete(const QPersistentModelIndex &index);
diff --git a/src/playlist/playlistmanager.cpp b/src/playlist/playlistmanager.cpp
index 950140409..baaf28b7d 100644
--- a/src/playlist/playlistmanager.cpp
+++ b/src/playlist/playlistmanager.cpp
@@ -98,7 +98,7 @@ void PlaylistManager::Init(CollectionBackend *collection_backend, PlaylistBacken
   connect(collection_backend_, SIGNAL(SongsStatisticsChanged(SongList)), SLOT(SongsDiscovered(SongList)));
 
   for (const PlaylistBackend::Playlist &p : playlist_backend->GetAllOpenPlaylists()) {
-    playlists_loading_++;
+    ++playlists_loading_;
     Playlist *ret = AddPlaylist(p.id, p.name, p.special_type, p.ui_path, p.favorite);
     connect(ret, SIGNAL(PlaylistLoaded()), SLOT(PlaylistLoaded()));
   }
@@ -115,7 +115,7 @@ void PlaylistManager::PlaylistLoaded() {
   Playlist *playlist = qobject_cast<Playlist*>(sender());
   if (!playlist) return;
   disconnect(playlist, SIGNAL(PlaylistLoaded()), this, SLOT(PlaylistLoaded()));
-  playlists_loading_--;
+  --playlists_loading_;
   if (playlists_loading_ == 0) emit AllPlaylistsLoaded();
 
 }
@@ -137,7 +137,7 @@ QItemSelection PlaylistManager::selection(int id) const {
   return it->selection;
 }
 
-Playlist *PlaylistManager::AddPlaylist(int id, const QString &name, const QString &special_type, const QString &ui_path, bool favorite) {
+Playlist *PlaylistManager::AddPlaylist(const int id, const QString &name, const QString &special_type, const QString &ui_path, const bool favorite) {
 
   Playlist *ret = new Playlist(playlist_backend_, app_->task_manager(), collection_backend_, id, special_type, favorite);
   ret->set_sequence(sequence_);
@@ -206,7 +206,7 @@ void PlaylistManager::Load(const QString &filename) {
 
 }
 
-void PlaylistManager::Save(int id, const QString &filename, Playlist::Path path_type) {
+void PlaylistManager::Save(const int id, const QString &filename, const Playlist::Path path_type) {
 
   if (playlists_.contains(id)) {
     parser_->Save(playlist(id)->GetAllSongs(), filename, path_type);
@@ -219,13 +219,13 @@ void PlaylistManager::Save(int id, const QString &filename, Playlist::Path path_
 
 }
 
-void PlaylistManager::ItemsLoadedForSavePlaylist(QFuture<SongList> future, const QString &filename, Playlist::Path path_type) {
+void PlaylistManager::ItemsLoadedForSavePlaylist(QFuture<SongList> future, const QString &filename, const Playlist::Path path_type) {
 
   parser_->Save(future.result(), filename, path_type);
 
 }
 
-void PlaylistManager::SaveWithUI(int id, const QString &playlist_name) {
+void PlaylistManager::SaveWithUI(const int id, const QString &playlist_name) {
 
   QSettings settings;
   settings.beginGroup(Playlist::kSettingsGroup);
@@ -291,7 +291,7 @@ void PlaylistManager::SaveWithUI(int id, const QString &playlist_name) {
 
 }
 
-void PlaylistManager::Rename(int id, const QString &new_name) {
+void PlaylistManager::Rename(const int id, const QString &new_name) {
 
   Q_ASSERT(playlists_.contains(id));
 
@@ -302,7 +302,7 @@ void PlaylistManager::Rename(int id, const QString &new_name) {
 
 }
 
-void PlaylistManager::Favorite(int id, bool favorite) {
+void PlaylistManager::Favorite(const int id, const bool favorite) {
 
   if (playlists_.contains(id)) {
     // If playlists_ contains this playlist, its means it's opened: star or unstar it.
@@ -319,7 +319,7 @@ void PlaylistManager::Favorite(int id, bool favorite) {
 
 }
 
-bool PlaylistManager::Close(int id) {
+bool PlaylistManager::Close(const int id) {
 
   // Won't allow removing the last playlist
   if (playlists_.count() <= 1 || !playlists_.contains(id)) return false;
@@ -349,7 +349,7 @@ bool PlaylistManager::Close(int id) {
 
 }
 
-void PlaylistManager::Delete(int id) {
+void PlaylistManager::Delete(const int id) {
 
   if (!Close(id)) {
     return;
@@ -364,7 +364,7 @@ void PlaylistManager::OneOfPlaylistsChanged() {
   emit PlaylistChanged(qobject_cast<Playlist*>(sender()));
 }
 
-void PlaylistManager::SetCurrentPlaylist(int id) {
+void PlaylistManager::SetCurrentPlaylist(const int id) {
 
   Q_ASSERT(playlists_.contains(id));
 
@@ -379,7 +379,7 @@ void PlaylistManager::SetCurrentPlaylist(int id) {
 
 }
 
-void PlaylistManager::SetActivePlaylist(int id) {
+void PlaylistManager::SetActivePlaylist(const int id) {
 
   Q_ASSERT(playlists_.contains(id));
 
@@ -489,7 +489,7 @@ void PlaylistManager::SongsDiscovered(const SongList &songs) {
 }
 
 // When Player has processed the new song chosen by the user...
-void PlaylistManager::SongChangeRequestProcessed(const QUrl &url, bool valid) {
+void PlaylistManager::SongChangeRequestProcessed(const QUrl &url, const bool valid) {
 
   for (Playlist *playlist : GetAllPlaylists()) {
     if (playlist->ApplyValidityOnCurrentSong(url, valid)) {
@@ -499,7 +499,7 @@ void PlaylistManager::SongChangeRequestProcessed(const QUrl &url, bool valid) {
 
 }
 
-void PlaylistManager::InsertUrls(int id, const QList<QUrl> &urls, int pos, bool play_now, bool enqueue) {
+void PlaylistManager::InsertUrls(const int id, const QList<QUrl> &urls, const int pos, const bool play_now, const bool enqueue) {
 
   Q_ASSERT(playlists_.contains(id));
 
@@ -507,7 +507,7 @@ void PlaylistManager::InsertUrls(int id, const QList<QUrl> &urls, int pos, bool
 
 }
 
-void PlaylistManager::InsertSongs(int id, const SongList &songs, int pos, bool play_now, bool enqueue) {
+void PlaylistManager::InsertSongs(const int id, const SongList &songs, const int pos, const bool play_now, const bool enqueue) {
 
   Q_ASSERT(playlists_.contains(id));
 
@@ -515,7 +515,7 @@ void PlaylistManager::InsertSongs(int id, const SongList &songs, int pos, bool p
 
 }
 
-void PlaylistManager::RemoveItemsWithoutUndo(int id, const QList<int> &indices) {
+void PlaylistManager::RemoveItemsWithoutUndo(const int id, const QList<int> &indices) {
 
   Q_ASSERT(playlists_.contains(id));
 
@@ -577,7 +577,7 @@ QString PlaylistManager::GetNameForNewPlaylist(const SongList &songs) {
 
 }
 
-void PlaylistManager::Open(int id) {
+void PlaylistManager::Open(const int id) {
 
   if (playlists_.contains(id)) {
     return;
@@ -592,13 +592,13 @@ void PlaylistManager::Open(int id) {
 
 }
 
-void PlaylistManager::SetCurrentOrOpen(int id) {
+void PlaylistManager::SetCurrentOrOpen(const int id) {
 
   Open(id);
   SetCurrentPlaylist(id);
 
 }
 
-bool PlaylistManager::IsPlaylistOpen(int id) {
+bool PlaylistManager::IsPlaylistOpen(const int id) {
   return playlists_.contains(id);
 }
diff --git a/src/playlist/playlistmanager.h b/src/playlist/playlistmanager.h
index cc5d18e4d..279cf5fa6 100644
--- a/src/playlist/playlistmanager.h
+++ b/src/playlist/playlistmanager.h
@@ -64,11 +64,11 @@ class PlaylistManagerInterface : public QObject {
   // Removes all deleted songs from all playlists.
   virtual void RemoveDeletedSongs() = 0;
 
-  virtual QItemSelection selection(int id) const = 0;
+  virtual QItemSelection selection(const int id) const = 0;
   virtual QItemSelection current_selection() const = 0;
   virtual QItemSelection active_selection() const = 0;
 
-  virtual QString GetPlaylistName(int index) const = 0;
+  virtual QString GetPlaylistName(const int index) const = 0;
 
   virtual CollectionBackend *collection_backend() const = 0;
   virtual PlaylistBackend *playlist_backend() const = 0;
@@ -79,17 +79,17 @@ class PlaylistManagerInterface : public QObject {
  public slots:
   virtual void New(const QString &name, const SongList& songs = SongList(), const QString &special_type = QString()) = 0;
   virtual void Load(const QString &filename) = 0;
-  virtual void Save(int id, const QString &filename, Playlist::Path path_type) = 0;
-  virtual void Rename(int id, const QString &new_name) = 0;
-  virtual void Delete(int id) = 0;
-  virtual bool Close(int id) = 0;
-  virtual void Open(int id) = 0;
+  virtual void Save(const int id, const QString &filename, const Playlist::Path path_type) = 0;
+  virtual void Rename(const int id, const QString &new_name) = 0;
+  virtual void Delete(const int id) = 0;
+  virtual bool Close(const int id) = 0;
+  virtual void Open(const int id) = 0;
   virtual void ChangePlaylistOrder(const QList<int>& ids) = 0;
 
-  virtual void SongChangeRequestProcessed(const QUrl &url, bool valid) = 0;
+  virtual void SongChangeRequestProcessed(const QUrl &url, const bool valid) = 0;
 
-  virtual void SetCurrentPlaylist(int id) = 0;
-  virtual void SetActivePlaylist(int id) = 0;
+  virtual void SetCurrentPlaylist(const int id) = 0;
+  virtual void SetActivePlaylist(const int id) = 0;
   virtual void SetActiveToCurrent() = 0;
 
   virtual void SelectionChanged(const QItemSelection &selection) = 0;
@@ -107,25 +107,25 @@ class PlaylistManagerInterface : public QObject {
   void PlaylistManagerInitialized();
   void AllPlaylistsLoaded();
 
-  void PlaylistAdded(int id, const QString &name, bool favorite);
+  void PlaylistAdded(int id, QString name, bool favorite);
   void PlaylistDeleted(int id);
   void PlaylistClosed(int id);
-  void PlaylistRenamed(int id, const QString &new_name);
+  void PlaylistRenamed(int id, QString new_name);
   void PlaylistFavorited(int id, bool favorite);
-  void CurrentChanged(Playlist *new_playlist, const int scroll_position = 0);
+  void CurrentChanged(Playlist *new_playlist, int scroll_position = 0);
   void ActiveChanged(Playlist *new_playlist);
 
-  void Error(const QString &message);
-  void SummaryTextChanged(const QString &summary);
+  void Error(QString message);
+  void SummaryTextChanged(QString summary);
 
   // Forwarded from individual playlists
-  void CurrentSongChanged(const Song& song);
-  void SongMetadataChanged(const Song& song);
+  void CurrentSongChanged(Song song);
+  void SongMetadataChanged(Song song);
 
   // Signals that one of manager's playlists has changed (new items, new ordering etc.) - the argument shows which.
   void PlaylistChanged(Playlist *playlist);
-  void EditingFinished(const QModelIndex& index);
-  void PlayRequested(const QModelIndex& index);
+  void EditingFinished(QModelIndex idx);
+  void PlayRequested(QModelIndex idx);
 };
 
 class PlaylistManager : public PlaylistManagerInterface {
@@ -138,7 +138,7 @@ class PlaylistManager : public PlaylistManagerInterface {
   int current_id() const override { return current_; }
   int active_id() const override { return active_; }
 
-  Playlist *playlist(int id) const override { return playlists_[id].p; }
+  Playlist *playlist(const int id) const override { return playlists_[id].p; }
   Playlist *current() const override { return playlist(current_id()); }
   Playlist *active() const override { return playlist(active_id()); }
 
@@ -149,12 +149,12 @@ class PlaylistManager : public PlaylistManagerInterface {
   // Removes all deleted songs from all playlists.
   void RemoveDeletedSongs() override;
   // Returns true if the playlist is open
-  bool IsPlaylistOpen(int id);
+  bool IsPlaylistOpen(const int id);
 
   // Returns a pretty automatic name for playlist created from the given list of songs.
   static QString GetNameForNewPlaylist(const SongList& songs);
 
-  QItemSelection selection(int id) const override;
+  QItemSelection selection(const int id) const override;
   QItemSelection current_selection() const override { return selection(current_id()); }
   QItemSelection active_selection() const override { return selection(active_id()); }
 
@@ -172,24 +172,24 @@ class PlaylistManager : public PlaylistManagerInterface {
  public slots:
   void New(const QString &name, const SongList &songs = SongList(), const QString &special_type = QString()) override;
   void Load(const QString &filename) override;
-  void Save(int id, const QString &filename, Playlist::Path path_type) override;
+  void Save(const int id, const QString &filename, const Playlist::Path path_type) override;
   // Display a file dialog to let user choose a file before saving the file
-  void SaveWithUI(int id, const QString &playlist_name);
-  void Rename(int id, const QString &new_name) override;
-  void Favorite(int id, bool favorite);
-  void Delete(int id) override;
-  bool Close(int id) override;
-  void Open(int id) override;
+  void SaveWithUI(const int id, const QString &playlist_name);
+  void Rename(const int id, const QString &new_name) override;
+  void Favorite(const int id, bool favorite);
+  void Delete(const int id) override;
+  bool Close(const int id) override;
+  void Open(const int id) override;
   void ChangePlaylistOrder(const QList<int>& ids) override;
 
-  void SetCurrentPlaylist(int id) override;
-  void SetActivePlaylist(int id) override;
+  void SetCurrentPlaylist(const int id) override;
+  void SetActivePlaylist(const int id) override;
   void SetActiveToCurrent() override;
 
   void SelectionChanged(const QItemSelection &selection) override;
 
   // Makes a playlist current if it's open already, or opens it and makes it current if it is hidden.
-  void SetCurrentOrOpen(int id);
+  void SetCurrentOrOpen(const int id);
 
   // Convenience slots that defer to either current() or active()
   void ClearCurrent() override;
@@ -198,12 +198,12 @@ class PlaylistManager : public PlaylistManagerInterface {
   void RemoveUnavailableCurrent() override;
   //void SetActiveStreamMetadata(const QUrl& url, const Song& song);
 
-  void SongChangeRequestProcessed(const QUrl& url, bool valid) override;
+  void SongChangeRequestProcessed(const QUrl& url, const bool valid) override;
 
-  void InsertUrls(int id, const QList<QUrl>& urls, int pos = -1, bool play_now = false, bool enqueue = false);
-  void InsertSongs(int id, const SongList& songs, int pos = -1, bool play_now = false, bool enqueue = false);
+  void InsertUrls(const int id, const QList<QUrl>& urls, const int pos = -1, const bool play_now = false, const bool enqueue = false);
+  void InsertSongs(const int id, const SongList& songs, const int pos = -1, const bool play_now = false, const bool enqueue = false);
   // Removes items with given indices from the playlist. This operation is not undoable.
-  void RemoveItemsWithoutUndo(int id, const QList<int>& indices);
+  void RemoveItemsWithoutUndo(const int id, const QList<int>& indices);
   // Remove the current playing song
   void RemoveCurrentSong();
 
@@ -215,15 +215,15 @@ class PlaylistManager : public PlaylistManagerInterface {
   void OneOfPlaylistsChanged();
   void UpdateSummaryText();
   void SongsDiscovered(const SongList& songs);
-  void ItemsLoadedForSavePlaylist(QFuture<SongList> future, const QString& filename, Playlist::Path path_type);
+  void ItemsLoadedForSavePlaylist(QFuture<SongList> future, const QString& filename, const Playlist::Path path_type);
   void PlaylistLoaded();
 
  private:
-  Playlist *AddPlaylist(int id, const QString& name, const QString &special_type, const QString& ui_path, bool favorite);
+  Playlist *AddPlaylist(const int id, const QString &name, const QString &special_type, const QString &ui_path, const bool favorite);
 
  private:
   struct Data {
-    explicit Data(Playlist *_p = nullptr, const QString& _name = QString()) : p(_p), name(_name), scroll_position(0) {}
+    explicit Data(Playlist *_p = nullptr, const QString &_name = QString()) : p(_p), name(_name), scroll_position(0) {}
     Playlist *p;
     QString name;
     QItemSelection selection;
diff --git a/src/playlist/playlistview.cpp b/src/playlist/playlistview.cpp
index 0aec0b443..01809279b 100644
--- a/src/playlist/playlistview.cpp
+++ b/src/playlist/playlistview.cpp
@@ -406,15 +406,15 @@ void PlaylistView::drawTree(QPainter *painter, const QRegion &region) const {
 
 }
 
-void PlaylistView::drawRow(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const {
+void PlaylistView::drawRow(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &idx) const {
 
   QStyleOptionViewItem opt(option);
 
-  bool is_current = index.data(Playlist::Role_IsCurrent).toBool();
-  bool is_paused = index.data(Playlist::Role_IsPaused).toBool();
+  bool is_current = idx.data(Playlist::Role_IsCurrent).toBool();
+  bool is_paused = idx.data(Playlist::Role_IsPaused).toBool();
 
   if (is_current) {
-    const_cast<PlaylistView*>(this)->last_current_item_ = index;
+    const_cast<PlaylistView*>(this)->last_current_item_ = idx;
     const_cast<PlaylistView*>(this)->last_glow_rect_ = opt.rect;
 
     int step = glow_intensity_step_;
@@ -433,7 +433,7 @@ void PlaylistView::drawRow(QPainter *painter, const QStyleOptionViewItem &option
     middle.setRight(middle.right() - currenttrack_bar_right_[0].width());
 
     // Selection
-    if (selectionModel()->isSelected(index))
+    if (selectionModel()->isSelected(idx))
       painter->fillRect(opt.rect, opt.palette.color(QPalette::Highlight));
 
     // Draw the bar
@@ -453,7 +453,7 @@ void PlaylistView::drawRow(QPainter *painter, const QStyleOptionViewItem &option
     opt.decorationSize = QSize(20, 20);
 
     // Draw the actual row data on top.  We cache this, because it's fairly expensive (1-2ms), and we do it many times per second.
-    const bool cache_dirty = cached_current_row_rect_ != opt.rect || cached_current_row_row_ != index.row() || cached_current_row_.isNull();
+    const bool cache_dirty = cached_current_row_rect_ != opt.rect || cached_current_row_row_ != idx.row() || cached_current_row_.isNull();
 
     // We can't update the cache if we're not drawing the entire region,
     // QTreeView clips its drawing to only the columns in the region, so it wouldn't update the whole pixmap properly.
@@ -464,31 +464,31 @@ void PlaylistView::drawRow(QPainter *painter, const QStyleOptionViewItem &option
     }
     else {
       if (whole_region) {
-        const_cast<PlaylistView*>(this)->UpdateCachedCurrentRowPixmap(opt, index);
+        const_cast<PlaylistView*>(this)->UpdateCachedCurrentRowPixmap(opt, idx);
         painter->drawPixmap(opt.rect, cached_current_row_);
       }
       else {
-        QTreeView::drawRow(painter, opt, index);
+        QTreeView::drawRow(painter, opt, idx);
       }
     }
   }
   else {
-    QTreeView::drawRow(painter, opt, index);
+    QTreeView::drawRow(painter, opt, idx);
   }
 
 }
 
-void PlaylistView::UpdateCachedCurrentRowPixmap(QStyleOptionViewItem option, const QModelIndex &index) {
+void PlaylistView::UpdateCachedCurrentRowPixmap(QStyleOptionViewItem option, const QModelIndex &idx) {
 
   cached_current_row_rect_ = option.rect;
-  cached_current_row_row_ = index.row();
+  cached_current_row_row_ = idx.row();
 
   option.rect.moveTo(0, 0);
   cached_current_row_ = QPixmap(option.rect.size());
   cached_current_row_.fill(Qt::transparent);
 
   QPainter p(&cached_current_row_);
-  QTreeView::drawRow(&p, option, index);
+  QTreeView::drawRow(&p, option, idx);
 
 }
 
@@ -611,15 +611,15 @@ void PlaylistView::RemoveSelected() {
 
   int new_row = last_row - rows_removed;
   // Index of the first column for the row to select
-  QModelIndex new_index = model()->index(new_row, 0);
+  QModelIndex new_idx = model()->index(new_row, 0);
 
   // Select the new current item, we want always the item after the last selected
-  if (new_index.isValid()) {
+  if (new_idx.isValid()) {
     // Workaround to update keyboard selected row, if it's not the first row (this also triggers selection)
     if (new_row != 0)
       keyPressEvent(new QKeyEvent(QEvent::KeyPress, Qt::Key_Down, Qt::NoModifier));
     // Update visual selection with the entire row
-    selectionModel()->select(new_index, QItemSelectionModel::ClearAndSelect | QItemSelectionModel::Rows);
+    selectionModel()->select(new_idx, QItemSelectionModel::ClearAndSelect | QItemSelectionModel::Rows);
   }
   else {
     // We're removing the last item, select the new last row
@@ -634,8 +634,8 @@ QList<int> PlaylistView::GetEditableColumns() {
   QHeaderView *h = header();
   for (int col = 0; col < h->count(); col++) {
     if (h->isSectionHidden(col)) continue;
-    QModelIndex index = model()->index(0, col);
-    if (index.flags() & Qt::ItemIsEditable) columns << h->visualIndex(col);
+    QModelIndex idx = model()->index(0, col);
+    if (idx.flags() & Qt::ItemIsEditable) columns << h->visualIndex(col);
   }
   std::sort(columns.begin(), columns.end());
   return columns;
@@ -646,12 +646,12 @@ QModelIndex PlaylistView::NextEditableIndex(const QModelIndex &current) {
 
   QList<int> columns = GetEditableColumns();
   QHeaderView *h = header();
-  int index = columns.indexOf(h->visualIndex(current.column()));
+  int idx = columns.indexOf(h->visualIndex(current.column()));
 
-  if (index + 1 >= columns.size())
+  if (idx + 1 >= columns.size())
     return model()->index(current.row() + 1, h->logicalIndex(columns.first()));
 
-  return model()->index(current.row(), h->logicalIndex(columns[index + 1]));
+  return model()->index(current.row(), h->logicalIndex(columns[idx + 1]));
 
 }
 
@@ -659,20 +659,20 @@ QModelIndex PlaylistView::PrevEditableIndex(const QModelIndex &current) {
 
   QList<int> columns = GetEditableColumns();
   QHeaderView *h = header();
-  int index = columns.indexOf(h->visualIndex(current.column()));
+  int idx = columns.indexOf(h->visualIndex(current.column()));
 
-  if (index - 1 < 0)
+  if (idx - 1 < 0)
     return model()->index(current.row() - 1, h->logicalIndex(columns.last()));
 
-  return model()->index(current.row(), h->logicalIndex(columns[index - 1]));
+  return model()->index(current.row(), h->logicalIndex(columns[idx - 1]));
 
 }
 
-bool PlaylistView::edit(const QModelIndex &index, QAbstractItemView::EditTrigger trigger, QEvent *event) {
+bool PlaylistView::edit(const QModelIndex &idx, QAbstractItemView::EditTrigger trigger, QEvent *event) {
 
-  bool result = QAbstractItemView::edit(index, trigger, event);
+  bool result = QAbstractItemView::edit(idx, trigger, event);
   if (result && trigger == QAbstractItemView::AllEditTriggers && !event) {
-    playlist_->set_editing(index.row());
+    playlist_->set_editing(idx.row());
   }
   return result;
 
@@ -685,19 +685,19 @@ void PlaylistView::closeEditor(QWidget *editor, QAbstractItemDelegate::EndEditHi
   }
   else if (hint == QAbstractItemDelegate::EditNextItem || hint == QAbstractItemDelegate::EditPreviousItem) {
 
-    QModelIndex index;
+    QModelIndex idx;
     if (hint == QAbstractItemDelegate::EditNextItem)
-      index = NextEditableIndex(currentIndex());
+      idx = NextEditableIndex(currentIndex());
     else
-      index = PrevEditableIndex(currentIndex());
+      idx = PrevEditableIndex(currentIndex());
 
-    if (!index.isValid()) {
+    if (!idx.isValid()) {
       QTreeView::closeEditor(editor, QAbstractItemDelegate::SubmitModelCache);
     }
     else {
       QTreeView::closeEditor(editor, QAbstractItemDelegate::NoHint);
-      setCurrentIndex(index);
-      QAbstractItemView::edit(index);
+      setCurrentIndex(idx);
+      QAbstractItemView::edit(idx);
     }
   }
   else {
@@ -787,7 +787,6 @@ void PlaylistView::JumpToCurrentlyPlayingTrack() {
 
   // Scroll to the item
   scrollTo(current, QAbstractItemView::PositionAtCenter);
-
   currently_autoscrolling_ = false;
 
 }
@@ -975,12 +974,12 @@ void PlaylistView::dragMoveEvent(QDragMoveEvent *event) {
   QTreeView::dragMoveEvent(event);
 
 #if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
-  QModelIndex index(indexAt(event->position().toPoint()));
+  QModelIndex idx(indexAt(event->position().toPoint()));
 #else
-  QModelIndex index(indexAt(event->pos()));
+  QModelIndex idx(indexAt(event->pos()));
 #endif
 
-  drop_indicator_row_ = index.isValid() ? index.row() : 0;
+  drop_indicator_row_ = idx.isValid() ? idx.row() : 0;
 
 }
 
@@ -1154,7 +1153,7 @@ void PlaylistView::SaveSettings() {
 
 }
 
-void PlaylistView::StretchChanged(bool stretch) {
+void PlaylistView::StretchChanged(const bool stretch) {
 
   if (!initialized_) return;
   setHorizontalScrollBarPolicy(stretch ? Qt::ScrollBarAlwaysOff : Qt::ScrollBarAsNeeded);
@@ -1205,7 +1204,7 @@ ColumnAlignmentMap PlaylistView::DefaultColumnAlignment() {
 
 }
 
-void PlaylistView::SetColumnAlignment(int section, Qt::Alignment alignment) {
+void PlaylistView::SetColumnAlignment(const int section, const Qt::Alignment alignment) {
 
   if (section < 0) return;
 
@@ -1327,7 +1326,7 @@ void PlaylistView::set_background_image(const QImage &image) {
 
 }
 
-void PlaylistView::FadePreviousBackgroundImage(qreal value) {
+void PlaylistView::FadePreviousBackgroundImage(const qreal value) {
 
   previous_background_image_opacity_ = value;
   if (qFuzzyCompare(previous_background_image_opacity_, qreal(0.0))) {
diff --git a/src/playlist/playlistview.h b/src/playlist/playlistview.h
index 1a4520217..17ba6ec07 100644
--- a/src/playlist/playlistview.h
+++ b/src/playlist/playlistview.h
@@ -118,19 +118,19 @@ class PlaylistView : public QTreeView {
   void ReloadSettings();
   void SaveGeometry();
   void SaveSettings();
-  void SetColumnAlignment(int section, Qt::Alignment alignment);
+  void SetColumnAlignment(const int section, const Qt::Alignment alignment);
   void JumpToCurrentlyPlayingTrack();
-  void edit(const QModelIndex &index) { return QAbstractItemView::edit(index); }
+  void edit(const QModelIndex &idx) { return QAbstractItemView::edit(idx); }
 
  signals:
-  void PlayItem(const QModelIndex &index);
+  void PlayItem(QModelIndex idx);
   void PlayPause();
-  void RightClicked(const QPoint &global_pos, const QModelIndex &index);
+  void RightClicked(QPoint global_pos, QModelIndex idx);
   void SeekForward();
   void SeekBackward();
   void FocusOnFilterSignal(QKeyEvent *event);
   void BackgroundPropertyChanged();
-  void ColumnAlignmentChanged(const ColumnAlignmentMap &alignment);
+  void ColumnAlignmentChanged(ColumnAlignmentMap alignment);
 
  protected:
   // QWidget
@@ -152,14 +152,14 @@ class PlaylistView : public QTreeView {
 
   // QTreeView
   void drawTree(QPainter *painter, const QRegion &region) const;
-  void drawRow(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const override;
+  void drawRow(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &idx) const override;
 
   // QAbstractScrollArea
   void scrollContentsBy(int dx, int dy) override;
 
   // QAbstractItemView
   void rowsInserted(const QModelIndex &parent, int start, int end) override;
-  bool edit(const QModelIndex &index, QAbstractItemView::EditTrigger trigger, QEvent *event) override;
+  bool edit(const QModelIndex &idx, QAbstractItemView::EditTrigger trigger, QEvent *event) override;
   void closeEditor(QWidget *editor, QAbstractItemDelegate::EndEditHint hint) override;
 
  private slots:
@@ -167,8 +167,8 @@ class PlaylistView : public QTreeView {
   void MaybeAutoscroll();
   void InvalidateCachedCurrentPixmap();
   void PlaylistDestroyed();
-  void StretchChanged(bool stretch);
-  void FadePreviousBackgroundImage(qreal value);
+  void StretchChanged(const bool stretch);
+  void FadePreviousBackgroundImage(const qreal value);
   void StopGlowing();
   void StartGlowing();
   void JumpToLastPlayedTrack();
@@ -182,7 +182,7 @@ class PlaylistView : public QTreeView {
   void LoadGeometry();
   void ReloadBarPixmaps();
   QList<QPixmap> LoadBarPixmap(const QString &filename);
-  void UpdateCachedCurrentRowPixmap(QStyleOptionViewItem option, const QModelIndex &index);
+  void UpdateCachedCurrentRowPixmap(QStyleOptionViewItem option, const QModelIndex &idx);
 
   void set_background_image_type(AppearanceSettingsPage::BackgroundImageType bg) {
     background_image_type_ = bg;