Add const/references to all signal parameters

src/core/application.h

@@ -118,9 +118,9 @@ class Application : public QObject {
   void OpenSettingsDialogAtPage(SettingsDialog::Page page);
 
  signals:
-  void ErrorAdded(QString message);
+  void ErrorAdded(const QString &message);
   void SettingsChanged();
-  void SettingsDialogRequested(SettingsDialog::Page page);
+  void SettingsDialogRequested(const SettingsDialog::Page page);
   void ExitFinished();
   void ClearPixmapDiskCache();
 

src/core/database.h

@@ -88,8 +88,8 @@ class Database : public QObject {
 
  signals:
   void ExitFinished();
-  void Error(QString error);
-  void Errors(QStringList errors);
+  void Error(const QString &error);
+  void Errors(const QStringList &errors);
 
  private slots:
   void Exit();

src/core/deletefiles.h

@@ -48,7 +48,7 @@ class DeleteFiles : public QObject {
   void Start(const QStringList &filenames);
 
  signals:
-  void Finished(SongList songs_with_errors);
+  void Finished(const SongList &songs_with_errors);
 
  private slots:
   void ProcessSomeFiles();

src/core/filesystemwatcherinterface.h

@@ -40,7 +40,7 @@ class FileSystemWatcherInterface : public QObject {
   static FileSystemWatcherInterface *Create(QObject *parent = nullptr);
 
  signals:
-  void PathChanged(QString path);
+  void PathChanged(const QString &path);
 };
 
 #endif

src/core/macfslistener.h

@@ -45,7 +45,7 @@ class MacFSListener : public FileSystemWatcherInterface {
   void Clear();
 
  signals:
-  void PathChanged(QString path);
+  void PathChanged(const QString &path);
 
  private slots:
   void UpdateStream();

src/core/macsystemtrayicon.h

@@ -76,7 +76,7 @@ class SystemTrayIcon : public QObject {
   void ActionChanged();
 
  signals:
-  void ChangeVolume(int delta);
+  void ChangeVolume(const int delta);
   void SeekForward();
   void SeekBackward();
   void NextTrack();

src/core/mainwindow.h

@@ -132,12 +132,12 @@ class MainWindow : public QMainWindow, public PlatformInterface {
   bool LoadUrl(const QString &url) override;
 
  signals:
-  void AlbumCoverReady(Song song, QImage image);
+  void AlbumCoverReady(const Song &song, const QImage &image);
   void SearchCoverInProgress();
   // Signals that stop playing after track was toggled.
-  void StopAfterToggled(bool stop);
+  void StopAfterToggled(const bool stop);
 
-  void AuthorizationUrlReceived(QUrl url);
+  void AuthorizationUrlReceived(const QUrl &url);
 
  private slots:
   void FilePathChanged(const QString &path);

src/core/mergedproxymodel.h

@@ -85,7 +85,7 @@ class MergedProxyModel : public QAbstractProxyModel {
   QModelIndexList mapToSource(const QModelIndexList &proxy_indexes) const;
 
  signals:
-  void SubModelReset(QModelIndex root, QAbstractItemModel *model);
+  void SubModelReset(const QModelIndex root, QAbstractItemModel *model);
 
  private slots:
   void SourceModelReset();

src/core/mpris2.h

@@ -188,18 +188,18 @@ class Mpris2 : public QObject {
 
  signals:
   // Player
-  void Seeked(qint64 position);
+  void Seeked(const qint64 position);
 
   // TrackList
-  void TrackListReplaced(Track_Ids Tracks, QDBusObjectPath CurrentTrack);
-  void TrackAdded(TrackMetadata Metadata, QDBusObjectPath AfterTrack);
-  void TrackRemoved(QDBusObjectPath trackId);
-  void TrackMetadataChanged(QDBusObjectPath trackId, TrackMetadata metadata);
+  void TrackListReplaced(const Track_Ids &tracks, const QDBusObjectPath &current_track);
+  void TrackAdded(const TrackMetadata &metadata, const QDBusObjectPath &after_track);
+  void TrackRemoved(const QDBusObjectPath &track_id);
+  void TrackMetadataChanged(const QDBusObjectPath &track_id, const TrackMetadata &metadata);
 
   void RaiseMainWindow();
 
   // Playlist
-  void PlaylistChanged(MprisPlaylist playlist);
+  void PlaylistChanged(const MprisPlaylist &playlist);
 
  private slots:
   void AlbumCoverLoaded(const Song &song, AlbumCoverLoaderResultPtr result = AlbumCoverLoaderResultPtr());

src/core/player.h

@@ -111,20 +111,20 @@ class PlayerInterface : public QObject {
   // Emitted only when playback is manually resumed
   void Resumed();
   void Stopped();
-  void Error(QString message = QString());
+  void Error(const QString &message = QString());
   void PlaylistFinished();
-  void VolumeEnabled(bool);
-  void VolumeChanged(uint volume);
+  void VolumeEnabled(const bool volume_enabled);
+  void VolumeChanged(const uint volume);
   void TrackSkipped(PlaylistItemPtr old_track);
   // Emitted when there's a manual change to the current's track position.
-  void Seeked(qint64 microseconds);
+  void Seeked(const qint64 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(QUrl url, bool valid);
+  void SongChangeRequestProcessed(const QUrl &url, const bool valid);
 
   // The toggle parameter is true when user requests to toggle visibility for Pretty OSD
-  void ForceShowOSD(Song, bool toggle);
+  void ForceShowOSD(const Song &song, const bool toggle);
 
   void Authenticated();
 
@@ -193,7 +193,7 @@ class Player : public PlayerInterface {
   void HandleAuthentication();
 
  signals:
-  void EngineChanged(Engine::EngineType enginetype);
+  void EngineChanged(const Engine::EngineType enginetype);
 
  private slots:
   void EngineStateChanged(const Engine::State);

src/core/qtsystemtrayicon.h

@@ -69,7 +69,7 @@ class SystemTrayIcon : public QSystemTrayIcon {
   void UpdateIcon();
 
  signals:
-  void ChangeVolume(int delta);
+  void ChangeVolume(const int delta);
   void SeekForward();
   void SeekBackward();
   void NextTrack();

src/core/songloader.h

@@ -89,7 +89,7 @@ class SongLoader : public QObject {
 
  signals:
   void AudioCDTracksLoadFinished();
-  void LoadAudioCDFinished(bool success);
+  void LoadAudioCDFinished(const bool success);
   void LoadRemoteFinished();
 
  private slots:

src/core/urlhandler.h

@@ -91,7 +91,7 @@ class UrlHandler : public QObject {
   virtual LoadResult StartLoading(const QUrl &url) { return LoadResult(url); }
 
  signals:
-  void AsyncLoadComplete(UrlHandler::LoadResult result);
+  void AsyncLoadComplete(const UrlHandler::LoadResult &result);
 
 };