Origin: upstream, commit:8b9a81e73c2500ead7ef5bfc5b84b0838c792e08
Author: Jérôme Duval <jerome.duval@gmail.com>
Description:fix build with Qt5.14
 .
 Specializes template routines.
 Qt 5.14 introduces serialisation/deserialisation for enum classes,
 this results in ambiguous templates between qdatastream.h and preferences.h.
 we specialize everything to workaround this.
 .
 fix warnings: replace QString::null, with QString()

--- a/mscore/capella.cpp
+++ b/mscore/capella.cpp
@@ -2708,7 +2708,7 @@ Score::FileError importCapella(MasterSco
                   QMessageBox::warning(0,
                      QWidget::tr("Import Capella"),
                      QWidget::tr("Load failed: %1").arg(cf.error(errNo)),
-                     QString::null, QWidget::tr("Quit"), QString::null, 0, 1);
+                     QString(), QWidget::tr("Quit"), QString(), 0, 1);
                   }
             fp.close();
             // avoid another error message box
--- a/mscore/importmidi/importmidi.cpp
+++ b/mscore/importmidi/importmidi.cpp
@@ -1200,7 +1200,7 @@ Score::FileError importMidi(MasterScore
                         QMessageBox::warning(0,
                            QWidget::tr("Load MIDI"),
                            QWidget::tr("Load failed: %1").arg(errorText),
-                           QString::null, QWidget::tr("Quit"), QString::null, 0, 1);
+                           QString(), QWidget::tr("Quit"), QString(), 0, 1);
                         }
                   fp.close();
                   qDebug("importMidi: bad file format");
--- a/mscore/instrdialog.cpp
+++ b/mscore/instrdialog.cpp
@@ -138,7 +138,7 @@ void InstrumentsDialog::on_loadButton_cl
             QMessageBox::warning(0,
                QWidget::tr("Load Style Failed"),
                QString(strerror(errno)),
-               QString::null, QWidget::tr("Quit"), QString::null, 0, 1);
+               QString(), QWidget::tr("Quit"), QString(), 0, 1);
             return;
             }
       instrumentsWidget->buildTemplateList();
--- a/mscore/musescore.cpp
+++ b/mscore/musescore.cpp
@@ -4022,7 +4022,7 @@ bool MuseScore::readLanguages(const QStr
                 QMessageBox::warning(0,
                    QWidget::tr("Load Languages Failed:"),
                    error,
-                   QString::null, QWidget::tr("Quit"), QString::null, 0, 1);
+                   QString(), QWidget::tr("Quit"), QString(), 0, 1);
                 return false;
                 }
 
@@ -6813,7 +6813,7 @@ bool MuseScore::saveMp3(Score* score, co
                   QMessageBox::warning(0,
                                        tr("Encoding Error"),
                                        tr("Unable to open target file for writing"),
-                                       QString::null, QString::null);
+                                       QString(), QString());
                   }
             return false;
             }
@@ -6841,7 +6841,7 @@ bool MuseScore::saveMp3(Score* score, QI
                   QMessageBox::warning(0,
                                tr("Error Opening LAME library"),
                                tr("Could not open MP3 encoding library!"),
-                               QString::null, QString::null);
+                               QString(), QString());
             qDebug("Could not open MP3 encoding library!");
             return false;
             }
@@ -6853,7 +6853,7 @@ bool MuseScore::saveMp3(Score* score, QI
                   QMessageBox::warning(0,
                                tr("Error Opening LAME library"),
                                tr("Not a valid or supported MP3 encoding library!"),
-                               QString::null, QString::null);
+                               QString(), QString());
             qDebug("Not a valid or supported MP3 encoding library!");
             return false;
             }
@@ -6878,7 +6878,7 @@ bool MuseScore::saveMp3(Score* score, QI
             if (!MScore::noGui) {
                   QMessageBox::warning(0, tr("Encoding Error"),
                      tr("Unable to initialize MP3 stream"),
-                     QString::null, QString::null);
+                     QString(), QString());
                   }
             qDebug("Unable to initialize MP3 stream");
             MScore::sampleRate = oldSampleRate;
@@ -7045,7 +7045,7 @@ bool MuseScore::saveMp3(Score* score, QI
                                     QMessageBox::warning(0,
                                        tr("Encoding Error"),
                                        tr("Error %1 returned from MP3 encoder").arg(bytes),
-                                       QString::null, QString::null);
+                                       QString(), QString());
                               break;
                               }
                         else
--- a/mscore/musescore.h
+++ b/mscore/musescore.h
@@ -135,7 +135,7 @@ struct LanguageItem {
       LanguageItem(const QString k, const QString n) {
             key = k;
             name = n;
-            handbook = QString::null;
+            handbook = QString();
             }
       LanguageItem(const QString k, const QString n, const QString h) {
             key = k;
--- a/mscore/network/loginmanager.cpp
+++ b/mscore/network/loginmanager.cpp
@@ -793,7 +793,7 @@ void LoginManager::mediaUploadFinished()
             QMessageBox::warning(0,
                      tr("Upload Error"),
                      tr("Sorry, MuseScore couldn't upload the audio file. Error %1").arg(e),
-                     QString::null, QString::null);
+                     QString(), QString());
             }
       }
 
--- a/mscore/preferences.h
+++ b/mscore/preferences.h
@@ -372,21 +372,52 @@ extern Preferences preferences;
 
 // Stream operators for enum classes
 // enum classes don't play well with QSettings without custom serialization
-template<typename T, typename std::enable_if<std::is_enum<T>::value>::type* = nullptr>
-inline QDataStream &operator<<(QDataStream &out, const T &val)
+inline QDataStream&
+operator<<(QDataStream &out, const Ms::MuseScoreStyleType &val)
 {
     return out << static_cast<int>(val);
 }
 
-template<typename T, typename std::enable_if<std::is_enum<T>::value>::type* = nullptr>
-inline QDataStream &operator>>(QDataStream &in, T &val)
+inline QDataStream&
+operator>>(QDataStream &in, Ms::MuseScoreStyleType &val)
 {
     int tmp;
     in >> tmp;
-    val = static_cast<T>(tmp);
+    val = static_cast<Ms::MuseScoreStyleType>(tmp);
     return in;
 }
 
+inline QDataStream&
+operator<<(QDataStream &out, const Ms::SessionStart &val)
+{
+    return out << static_cast<int>(val);
+}
+
+inline QDataStream&
+operator>>(QDataStream &in, Ms::SessionStart &val)
+{
+    int tmp;
+    in >> tmp;
+    val = static_cast<Ms::SessionStart>(tmp);
+    return in;
+}
+
+inline QDataStream&
+operator<<(QDataStream &out, const Ms::MusicxmlExportBreaks &val)
+{
+    return out << static_cast<int>(val);
+}
+
+inline QDataStream&
+operator>>(QDataStream &in, Ms::MusicxmlExportBreaks &val)
+{
+    int tmp;
+    in >> tmp;
+    val = static_cast<Ms::MusicxmlExportBreaks>(tmp);
+    return in;
+}
+
+
 class PreferenceVisitor {
    public:
       virtual void visit(QString key, IntPreference*) = 0;