Hotfix: excessive CPU use in the MIDI SenderThread

src/midi/Metronome.cpp

@@ -6,7 +6,9 @@
 #include <QFile>
 #include <QFileInfo>
 
-#include <QMediaPlayer>
+#include <QAudioDeviceInfo>
+#include <QSoundEffect>
+#include <QtGlobal>
 
 Metronome *Metronome::_instance = new Metronome();
 bool Metronome::_enable = false;
@@ -15,9 +17,13 @@ Metronome::Metronome(QObject *parent) :	QObject(parent) {
     _file = 0;
     num = 4;
     denom = 2;
-    _player = new QMediaPlayer(this, QMediaPlayer::LowLatency);
-    _player->setVolume(100);
-    _player->setMedia(QUrl::fromLocalFile(QFileInfo("metronome/metronome-01.wav").absoluteFilePath()));
+#if QT_VERSION >= 0x050D00
+    _player = new QSoundEffect(QAudioDeviceInfo::defaultOutputDevice(), this);
+#else
+    _player = new QSoundEffect(this);
+#endif
+    _player->setVolume(1.0);
+    _player->setSource(QUrl("qrc:/run_environment/metronome/metronome-01.wav"));
 }
 
 void Metronome::setFile(MidiFile *file){
@@ -87,9 +93,9 @@ void Metronome::setEnabled(bool b){
 }
 
 void Metronome::setLoudness(int value){
-    _instance->_player->setVolume(value);
+    _instance->_player->setVolume(value / 100.0);
 }
 
 int Metronome::loudness(){
-    return _instance->_player->volume();
+    return (int)(_instance->_player->volume() * 100);
 }

src/midi/Metronome.h

@@ -3,7 +3,7 @@
 
 #include <QObject>
 
-#include <QMediaPlayer>
+#include <QSoundEffect>
 
 class MidiFile;
 
@@ -35,7 +35,7 @@ public slots:
     void click();
     static bool _enable;
 
-    QMediaPlayer* _player;
+    QSoundEffect* _player;
 };
 
 #endif

src/midi/SenderThread.cpp

@@ -25,12 +25,17 @@ SenderThread::SenderThread()
 {
     _eventQueue = new QQueue<MidiEvent*>;
     _noteQueue = new QQueue<MidiEvent*>;
+    _mutex = new QMutex();
+    _waitCondition = new QWaitCondition();
 }
 
 void SenderThread::run()
 {
+    _mutex->lock();
 
     while (true) {
+        _waitCondition->wait(_mutex, 500);
+
         // First, send the misc events, such as control change and program change events.
         while (!_eventQueue->isEmpty()) {
             // send command
@@ -43,16 +48,22 @@ void SenderThread::run()
             MidiOutput::sendEnqueuedCommand(_noteQueue->head()->save());
             _noteQueue->pop_front();
         }
-        msleep(1);
     }
+
+    _mutex->unlock();
 }
 
 void SenderThread::enqueue(MidiEvent* event)
 {
+    _mutex->lock();
+
     // If it is a NoteOnEvent or an OffEvent, we put it in _noteQueue.
     if (dynamic_cast<NoteOnEvent*>(event) || dynamic_cast<OffEvent*>(event))
         _noteQueue->push_back(event);
     // Otherwise, it goes into _eventQueue.
     else
         _eventQueue->push_back(event);
+
+    _waitCondition->wakeOne();
+    _mutex->unlock();
 }

src/midi/SenderThread.h

@@ -19,8 +19,10 @@
 #ifndef SENDERTHREAD_H_
 #define SENDERTHREAD_H_
 
+#include <QMutex>
 #include <QQueue>
 #include <QThread>
+#include <QWaitCondition>
 
 #include "MidiOutput.h"
 
@@ -34,6 +36,8 @@ class SenderThread : public QThread {
 private:
     QQueue<MidiEvent*>* _eventQueue;
     QQueue<MidiEvent*>* _noteQueue;
+    QMutex* _mutex;
+    QWaitCondition* _waitCondition;
 };
 
 #endif