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

12 files changed, 33 insertions, 30 deletions

diff --git a/src/util/color/colorpalette.h b/src/util/color/colorpalette.h
index b3c4872013..48a8d0c3c8 100644
--- a/src/util/color/colorpalette.h
+++ b/src/util/color/colorpalette.h
@@ -10,9 +10,9 @@
 class ColorPalette final {
   public:
     ColorPalette(
-            QString name,
-            QList<mixxx::RgbColor> colorList,
-            QList<int> colorIndicesByHotcue = {})
+            const QString& name,
+            const QList<mixxx::RgbColor>& colorList,
+            const QList<int>& colorIndicesByHotcue = {})
             : m_name(name),
               m_colorList(colorList),
               m_colorIndicesByHotcue(colorIndicesByHotcue) {
@@ -49,7 +49,7 @@ class ColorPalette final {
         return m_name;
     }
 
-    void setName(const QString name) {
+    void setName(const QString& name) {
         m_name = name;
     }
 
diff --git a/src/util/db/dbconnection.cpp b/src/util/db/dbconnection.cpp
index 850c47c55a..e9b65d3188 100644
--- a/src/util/db/dbconnection.cpp
+++ b/src/util/db/dbconnection.cpp
@@ -24,7 +24,7 @@ const mixxx::Logger kLogger("DbConnection");
 
 QSqlDatabase createDatabase(
         const DbConnection::Params& params,
-        const QString connectionName) {
+        const QString& connectionName) {
     kLogger.info()
         << "Available drivers for database connections:"
         << QSqlDatabase::drivers();
@@ -41,7 +41,7 @@ QSqlDatabase createDatabase(
 
 QSqlDatabase cloneDatabase(
         const QSqlDatabase& database,
-        const QString connectionName) {
+        const QString& connectionName) {
     DEBUG_ASSERT(!database.isOpen());
     return QSqlDatabase::cloneDatabase(database, connectionName);
 }
@@ -233,7 +233,7 @@ void sqliteLike(sqlite3_context *context,
 
 #endif // __SQLITE3__
 
-bool initDatabase(QSqlDatabase database, StringCollator* pCollator) {
+bool initDatabase(const QSqlDatabase& database, StringCollator* pCollator) {
     DEBUG_ASSERT(database.isOpen());
 #ifdef __SQLITE3__
     QVariant v = database.driver()->handle();
diff --git a/src/util/db/fwdsqlquery.cpp b/src/util/db/fwdsqlquery.cpp
index d11b5327e9..d3b0467475 100644
--- a/src/util/db/fwdsqlquery.cpp
+++ b/src/util/db/fwdsqlquery.cpp
@@ -33,10 +33,10 @@ bool prepareQuery(QSqlQuery& query, const QString& statement) {
 } // anonymous namespace
 
 FwdSqlQuery::FwdSqlQuery(
-        QSqlDatabase database,
+        const QSqlDatabase& database,
         const QString& statement)
-    : QSqlQuery(database),
-      m_prepared(prepareQuery(*this, statement)) {
+        : QSqlQuery(database),
+          m_prepared(prepareQuery(*this, statement)) {
     if (!m_prepared) {
         DEBUG_ASSERT(!database.isOpen() || hasError());
         kLogger.critical()
diff --git a/src/util/db/fwdsqlquery.h b/src/util/db/fwdsqlquery.h
index 734c2c1392..2ab2413587 100644
--- a/src/util/db/fwdsqlquery.h
+++ b/src/util/db/fwdsqlquery.h
@@ -36,7 +36,7 @@ class FwdSqlQuery: protected QSqlQuery {
 
   public:
     FwdSqlQuery(
-            QSqlDatabase database,
+            const QSqlDatabase& database,
             const QString& statement);
 
     bool isPrepared() const {
diff --git a/src/util/db/sqlqueryfinisher.h b/src/util/db/sqlqueryfinisher.h
index 2eb16525dc..299bb7733b 100644
--- a/src/util/db/sqlqueryfinisher.h
+++ b/src/util/db/sqlqueryfinisher.h
@@ -10,9 +10,9 @@
 // resources of prepared statements until the next execution.
 class SqlQueryFinisher final {
 public:
-    explicit SqlQueryFinisher(QSqlQuery query)
-        : m_query(query) { // implicitly shared (not copied)
-    }
+  explicit SqlQueryFinisher(const QSqlQuery& query)
+          : m_query(query) { // implicitly shared (not copied)
+  }
     SqlQueryFinisher(SqlQueryFinisher&& other)
         : m_query(std::move(other.m_query)) { // implicitly shared (not moved)
         other.release();
diff --git a/src/util/db/sqlstorage.h b/src/util/db/sqlstorage.h
index fa42bf4ab2..7b5fb461a5 100644
--- a/src/util/db/sqlstorage.h
+++ b/src/util/db/sqlstorage.h
@@ -18,7 +18,7 @@ class SqlStorage {
     // strayed rows should be deleted.
     // This function will only be called while no database
     // is attached to avoid invalidation of internal caches!
-    virtual void repairDatabase(QSqlDatabase database) = 0;
+    virtual void repairDatabase(const QSqlDatabase& database) = 0;
 
     // Attach an open database connection to the storage class.
     // Implementations might need to do the following:
@@ -29,7 +29,7 @@ class SqlStorage {
     // until it is detached (see below). Implementations must
     // store an implicitly shared copy of the QSqlDatabase for
     // accessing it.
-    virtual void connectDatabase(QSqlDatabase database) = 0;
+    virtual void connectDatabase(const QSqlDatabase& database) = 0;
 
     // Detach the currently attached database, e.g. before
     // closing it.
diff --git a/src/util/debug.h b/src/util/debug.h
index e1a59e86bd..f405e70b8a 100644
--- a/src/util/debug.h
+++ b/src/util/debug.h
@@ -23,7 +23,7 @@ QString toDebugString(const T& object) {
 // the Qt event loop to continue processing. This means that you must not call
 // this function from a code section which is not re-entrant (e.g. paintEvent on
 // a QWidget).
-inline void reportFatalErrorAndQuit(QString message) {
+inline void reportFatalErrorAndQuit(const QString& message) {
     QByteArray message_bytes = message.toLocal8Bit();
     qFatal("%s", message_bytes.constData());
     ErrorDialogHandler* dialogHandler = ErrorDialogHandler::instance();
@@ -37,7 +37,7 @@ inline void reportFatalErrorAndQuit(QString message) {
 // user which allows the Qt event loop to continue processing. This means that
 // you must not call this function from a code section which is not re-entrant
 // (e.g. paintEvent on a QWidget).
-inline void reportCriticalErrorAndQuit(QString message) {
+inline void reportCriticalErrorAndQuit(const QString& message) {
     qCritical() << message;
     ErrorDialogHandler* dialogHandler = ErrorDialogHandler::instance();
     if (dialogHandler) {
diff --git a/src/util/dnd.cpp b/src/util/dnd.cpp
index 947e435b4d..5dd3c3d11f 100644
--- a/src/util/dnd.cpp
+++ b/src/util/dnd.cpp
@@ -15,7 +15,7 @@ namespace {
 QDrag* dragUrls(
         const QList<QUrl>& trackUrls,
         QWidget* pDragSource,
-        QString sourceIdentifier) {
+        const QString& sourceIdentifier) {
     if (trackUrls.isEmpty()) {
         return NULL;
     }
@@ -188,7 +188,7 @@ bool DragAndDropHelper::dragEnterAccept(
 QDrag* DragAndDropHelper::dragTrack(
         TrackPointer pTrack,
         QWidget* pDragSource,
-        QString sourceIdentifier) {
+        const QString& sourceIdentifier) {
     QList<QUrl> trackUrls;
     trackUrls.append(pTrack->getFileInfo().toUrl());
     return dragUrls(trackUrls, pDragSource, sourceIdentifier);
@@ -198,7 +198,7 @@ QDrag* DragAndDropHelper::dragTrack(
 QDrag* DragAndDropHelper::dragTrackLocations(
         const QList<QString>& locations,
         QWidget* pDragSource,
-        QString sourceIdentifier) {
+        const QString& sourceIdentifier) {
     QList<QUrl> trackUrls;
     foreach (QString location, locations) {
         trackUrls.append(TrackFile(location).toUrl());
diff --git a/src/util/dnd.h b/src/util/dnd.h
index 77d2b5a077..efd4d40e37 100644
--- a/src/util/dnd.h
+++ b/src/util/dnd.h
@@ -34,12 +34,12 @@ class DragAndDropHelper final {
     static QDrag* dragTrack(
             TrackPointer pTrack,
             QWidget* pDragSource,
-            QString sourceIdentifier);
+            const QString& sourceIdentifier);
 
     static QDrag* dragTrackLocations(
             const QList<QString>& locations,
             QWidget* pDragSource,
-            QString sourceIdentifier);
+            const QString& sourceIdentifier);
 
     static void handleTrackDragEnterEvent(
             QDragEnterEvent* event,
diff --git a/src/util/translations.h b/src/util/translations.h
index 7597e0e675..117cb2a402 100644
--- a/src/util/translations.h
+++ b/src/util/translations.h
@@ -78,9 +78,12 @@ class Translations {
     }
 
   private:
-    static bool loadTranslations(const QLocale& systemLocale, QString userLocale,
-                                 const QString& translation, const QString& prefix,
-                                 const QString& translationPath, QTranslator* pTranslator) {
+    static bool loadTranslations(const QLocale& systemLocale,
+            const QString& userLocale,
+            const QString& translation,
+            const QString& prefix,
+            const QString& translationPath,
+            QTranslator* pTranslator) {
         if (userLocale.size() == 0) {
             QStringList uiLanguages = systemLocale.uiLanguages();
             if (uiLanguages.size() > 0 && uiLanguages.first() == "en") {
diff --git a/src/util/valuetransformer.cpp b/src/util/valuetransformer.cpp
index f62da80ad2..f412d0da86 100644
--- a/src/util/valuetransformer.cpp
+++ b/src/util/valuetransformer.cpp
@@ -25,8 +25,8 @@ double ValueTransformer::transformInverse(double argument) const {
 }
 
 // static
-ValueTransformer* ValueTransformer::parseFromXml(QDomElement transformElement,
-                                                 const SkinContext& context) {
+ValueTransformer* ValueTransformer::parseFromXml(const QDomElement& transformElement,
+        const SkinContext& context) {
     if (transformElement.isNull() || !transformElement.hasChildNodes()) {
         return NULL;
     }
diff --git a/src/util/valuetransformer.h b/src/util/valuetransformer.h
index 7d84369202..12018c666b 100644
--- a/src/util/valuetransformer.h
+++ b/src/util/valuetransformer.h
@@ -84,8 +84,8 @@ class ValueTransformer {
     double transform(double argument) const;
     double transformInverse(double argument) const;
 
-    static ValueTransformer* parseFromXml(QDomElement transformElement,
-                                          const SkinContext& context);
+    static ValueTransformer* parseFromXml(const QDomElement& transformElement,
+            const SkinContext& context);
 
   private:
     ValueTransformer();