Add const/references to all signal parameters

src/playlist/playlist.h

@@ -325,11 +325,11 @@ class Playlist : public QAbstractListModel {
  signals:
   void RestoreFinished();
   void PlaylistLoaded();
-  void CurrentSongChanged(Song metadata);
-  void SongMetadataChanged(Song metadata);
-  void EditingFinished(const int playlist_id, QModelIndex idx);
-  void PlayRequested(QModelIndex idx, Playlist::AutoScroll autoscroll);
-  void MaybeAutoscroll(Playlist::AutoScroll autoscroll);
+  void CurrentSongChanged(const Song &metadata);
+  void SongMetadataChanged(const Song &metadata);
+  void EditingFinished(const int playlist_id, const QModelIndex idx);
+  void PlayRequested(const QModelIndex idx, const Playlist::AutoScroll autoscroll);
+  void MaybeAutoscroll(const Playlist::AutoScroll autoscroll);
 
   // 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();

src/playlist/playlistcontainer.h

@@ -65,8 +65,8 @@ class PlaylistContainer : public QWidget {
   bool eventFilter(QObject *objectWatched, QEvent *event) override;
 
  signals:
-  void TabChanged(int id);
-  void Rename(int id, QString new_name);
+  void TabChanged(const int id);
+  void Rename(const int id, const QString &new_name);
 
   void UndoRedoActionsChanged(QAction *undo, QAction *redo);
   void ViewSelectionModelChanged();

src/playlist/playlistheader.h

@@ -53,9 +53,9 @@ class PlaylistHeader : public StretchHeaderView {
 #endif
 
  signals:
-  void SectionVisibilityChanged(int logical, bool visible);
+  void SectionVisibilityChanged(const int logical, const bool visible);
   void MouseEntered();
-  void SectionRatingLockStatusChanged(bool);
+  void SectionRatingLockStatusChanged(const bool);
 
  private slots:
   void HideCurrent();

src/playlist/playlistlistmodel.h

@@ -81,8 +81,8 @@ class PlaylistListModel : public QStandardItemModel {
   bool setData(const QModelIndex &idx, const QVariant &value, int role) override;
 
  signals:
-  void PlaylistPathChanged(int id, QString new_path);
-  void PlaylistRenamed(int id, QString new_name);
+  void PlaylistPathChanged(const int id, const QString &new_path);
+  void PlaylistRenamed(const int id, const QString &new_name);
 
  private slots:
   void RowsChanged(const QModelIndex &begin, const QModelIndex &end);

src/playlist/playlistlistview.h

@@ -41,7 +41,7 @@ class PlaylistListView : public AutoExpandingTreeView {
   bool ItemsSelected() const;
 
  signals:
-  void ItemsSelectedChanged(bool);
+  void ItemsSelectedChanged(const bool);
 
  protected:
   // QWidget

src/playlist/playlistmanager.h

@@ -117,25 +117,25 @@ class PlaylistManagerInterface : public QObject {
   void PlaylistManagerInitialized();
   void AllPlaylistsLoaded();
 
-  void PlaylistAdded(int id, QString name, bool favorite);
-  void PlaylistDeleted(int id);
-  void PlaylistClosed(int id);
-  void PlaylistRenamed(int id, QString new_name);
-  void PlaylistFavorited(int id, bool favorite);
-  void CurrentChanged(Playlist *new_playlist, int scroll_position = 0);
+  void PlaylistAdded(const int id, const QString &name, const bool favorite);
+  void PlaylistDeleted(const int id);
+  void PlaylistClosed(const int id);
+  void PlaylistRenamed(const int id, const QString &new_name);
+  void PlaylistFavorited(const int id, const bool favorite);
+  void CurrentChanged(Playlist *new_playlist, const int scroll_position = 0);
   void ActiveChanged(Playlist *new_playlist);
 
-  void Error(QString message);
-  void SummaryTextChanged(QString summary);
+  void Error(const QString &message);
+  void SummaryTextChanged(const QString &summary);
 
   // Forwarded from individual playlists
-  void CurrentSongChanged(Song song);
-  void SongMetadataChanged(Song song);
+  void CurrentSongChanged(const Song &song);
+  void SongMetadataChanged(const 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(int playlist_id, QModelIndex idx);
-  void PlayRequested(QModelIndex idx, Playlist::AutoScroll autoscroll);
+  void EditingFinished(const int playlist_id, const QModelIndex idx);
+  void PlayRequested(const QModelIndex idx, const Playlist::AutoScroll autoscroll);
 };
 
 class PlaylistManager : public PlaylistManagerInterface {

src/playlist/playlistsequence.h

@@ -77,8 +77,8 @@ class PlaylistSequence : public QWidget {
   void CycleRepeatMode();
 
  signals:
-  void RepeatModeChanged(PlaylistSequence::RepeatMode mode);
-  void ShuffleModeChanged(PlaylistSequence::ShuffleMode mode);
+  void RepeatModeChanged(const PlaylistSequence::RepeatMode mode);
+  void ShuffleModeChanged(const PlaylistSequence::ShuffleMode mode);
 
  private slots:
   void RepeatActionTriggered(QAction *action);

src/playlist/playlisttabbar.h

@@ -72,12 +72,12 @@ class PlaylistTabBar : public QTabBar {
   void InsertTab(const int id, const int index, const QString &text, const bool favorite);
 
  signals:
-  void CurrentIdChanged(int id);
-  void Rename(int id, QString name);
-  void Close(int id);
-  void Save(int id);
-  void PlaylistOrderChanged(QList<int> ids);
-  void PlaylistFavorited(int id, bool favorite);
+  void CurrentIdChanged(const int id);
+  void Rename(const int id, const QString &name);
+  void Close(const int id);
+  void Save(const int id);
+  void PlaylistOrderChanged(const QList<int> &ids);
+  void PlaylistFavorited(const int id, const bool favorite);
 
  protected:
   void contextMenuEvent(QContextMenuEvent *e) override;

src/playlist/playlistview.h

@@ -127,14 +127,14 @@ class PlaylistView : public QTreeView {
   void edit(const QModelIndex &idx) { QAbstractItemView::edit(idx); }
 
  signals:
-  void PlayItem(QModelIndex idx, Playlist::AutoScroll autoscroll);
-  void PlayPause(const quint64 offset_nanosec = 0, Playlist::AutoScroll autoscroll = Playlist::AutoScroll::Never);
-  void RightClicked(QPoint global_pos, QModelIndex idx);
+  void PlayItem(const QModelIndex idx, const Playlist::AutoScroll autoscroll);
+  void PlayPause(const quint64 offset_nanosec = 0, const Playlist::AutoScroll autoscroll = Playlist::AutoScroll::Never);
+  void RightClicked(const QPoint global_pos, const QModelIndex idx);
   void SeekForward();
   void SeekBackward();
   void FocusOnFilterSignal(QKeyEvent *event);
   void BackgroundPropertyChanged();
-  void ColumnAlignmentChanged(ColumnAlignmentMap alignment);
+  void ColumnAlignmentChanged(const ColumnAlignmentMap alignment);
 
  protected:
   // QWidget

src/playlist/songloaderinserter.h

@@ -48,9 +48,9 @@ class SongLoaderInserter : public QObject {
   void LoadAudioCD(Playlist *destination, int row, bool play_now, bool enqueue, bool enqueue_next);
 
  signals:
-  void Error(QString message);
+  void Error(const QString &message);
   void PreloadFinished();
-  void EffectiveLoadFinished(SongList songs);
+  void EffectiveLoadFinished(const SongList &songs);
 
  private slots:
   void DestinationDestroyed();