Fix Beats class hierarchy

src/track/beatgrid.cpp

@@ -55,8 +55,7 @@ BeatGrid::BeatGrid(
 }
 
 BeatGrid::BeatGrid(const BeatGrid& other)
-        : QObject(),
-          m_mutex(QMutex::Recursive),
+        : m_mutex(QMutex::Recursive),
           m_subVersion(other.m_subVersion),
           m_iSampleRate(other.m_iSampleRate),
           m_grid(other.m_grid),

src/track/beatgrid.h

@@ -2,7 +2,6 @@
 #define BEATGRID_H
 
 #include <QMutex>
-#include <QObject>
 
 #include "track/track.h"
 #include "track/beats.h"
@@ -14,8 +13,7 @@
 // BeatGrid is an implementation of the Beats interface that implements an
 // infinite grid of beats, aligned to a song simply by a starting offset of the
 // first beat and the song's average beats-per-minute.
-class BeatGrid : public QObject, public virtual Beats {
-    Q_OBJECT
+class BeatGrid final : public Beats {
   public:
     // Construct a BeatGrid. If a more accurate sample rate is known, provide it
     // in the iSampleRate parameter -- otherwise pass 0.
@@ -73,9 +71,6 @@ class BeatGrid : public QObject, public virtual Beats {
     virtual void scale(enum BPMScale scale);
     virtual void setBpm(double dBpm);
 
-  signals:
-    void updated();
-
   private:
     BeatGrid(const BeatGrid& other);
     double firstBeatSample() const;

src/track/beatmap.cpp

@@ -83,8 +83,7 @@ BeatMap::BeatMap(const Track& track, SINT iSampleRate,
 }
 
 BeatMap::BeatMap (const BeatMap& other)
-        : QObject(),
-          m_mutex(QMutex::Recursive),
+        : m_mutex(QMutex::Recursive),
           m_subVersion(other.m_subVersion),
           m_iSampleRate(other.m_iSampleRate),
           m_dCachedBpm(other.m_dCachedBpm),

src/track/beatmap.h

@@ -8,7 +8,6 @@
 #ifndef BEATMAP_H_
 #define BEATMAP_H_
 
-#include <QObject>
 #include <QMutex>
 
 #include "track/track.h"
@@ -19,8 +18,7 @@
 
 typedef QList<mixxx::track::io::Beat> BeatList;
 
-class BeatMap : public QObject, public Beats {
-    Q_OBJECT
+class BeatMap final : public Beats {
   public:
     // Construct a BeatMap. iSampleRate may be provided if a more accurate
     // sample rate is known than the one associated with the Track.
@@ -82,9 +80,6 @@ class BeatMap : public QObject, public Beats {
     virtual void scale(enum BPMScale scale);
     virtual void setBpm(double dBpm);
 
-  signals:
-    void updated();
-
   private:
     BeatMap(const BeatMap& other);
     bool readByteArray(const QByteArray& byteArray);

src/track/beats.h

@@ -1,6 +1,7 @@
 #ifndef BEATS_H
 #define BEATS_H
 
+#include <QObject>
 #include <QString>
 #include <QList>
 #include <QByteArray>
@@ -25,7 +26,8 @@ class BeatIterator {
 // Beats is a pure abstract base class for BPM and beat management classes. It
 // provides a specification of all methods a beat-manager class must provide, as
 // well as a capability model for representing optional features.
-class Beats {
+class Beats : public QObject {
+    Q_OBJECT
   public:
     Beats() { }
     virtual ~Beats() { }
@@ -161,6 +163,9 @@ class Beats {
     // Adjust the beats so the global average BPM matches dBpm. Beats class must
     // have the capability BEATSCAP_SET.
     virtual void setBpm(double dBpm) = 0;
+
+  signals:
+    void updated();
 };
 
 #endif /* BEATS_H */

src/track/track.cpp

@@ -353,23 +353,15 @@ void Track::setBeatsAndUnlock(QMutexLocker* pLock, BeatsPointer pBeats) {
     }
 
     if (m_pBeats) {
-        auto pObject = dynamic_cast<QObject*>(m_pBeats.data());
-        if (pObject) {
-            disconnect(pObject, SIGNAL(updated()),
-                       this, SLOT(slotBeatsUpdated()));
-        }
+        disconnect(m_pBeats.data(), &Beats::updated, this, &Track::slotBeatsUpdated);
     }
 
-    m_pBeats = pBeats;
+    m_pBeats = std::move(pBeats);
 
     auto bpmValue = mixxx::Bpm::kValueUndefined;
     if (m_pBeats) {
         bpmValue = m_pBeats->getBpm();
-        auto pObject = dynamic_cast<QObject*>(m_pBeats.data());
-        if (pObject) {
-            connect(pObject, SIGNAL(updated()),
-                    this, SLOT(slotBeatsUpdated()));
-        }
+        connect(m_pBeats.data(), &Beats::updated, this, &Track::slotBeatsUpdated);
     }
     m_record.refMetadata().refTrackInfo().setBpm(mixxx::Bpm(bpmValue));