After discussion in #qt, I looked at our threading code and it's all wrong/unsafe. This properly threads scanning. Also makes it idle priority and splits it into a separate scan manager

src/CMakeLists.txt

@@ -42,6 +42,7 @@ SET( tomahawkSources ${tomahawkSources}
      scrobbler.cpp
      shortcuthandler.cpp
 
+     scanmanager.cpp
      tomahawkapp.cpp
      main.cpp
 )
@@ -81,6 +82,7 @@ SET( tomahawkHeaders ${tomahawkHeaders}
      musicscanner.h
      scriptresolver.h
      scrobbler.h
+     scanmanager.h
      shortcuthandler.h
 )
 

src/musicscanner.cpp

@@ -8,14 +8,13 @@
 
 using namespace Tomahawk;
 
-
 MusicScanner::MusicScanner( const QString& dir, quint32 bs )
-    : QThread()
+    : QObject()
     , m_dir( dir )
     , m_batchsize( bs )
+    , m_dirLister( 0 )
+    , m_dirListerThreadController( 0 )
 {
-    moveToThread( this );
-
     m_ext2mime.insert( "mp3",  "audio/mpeg" );
 
 #ifndef NO_OGG
@@ -31,15 +30,6 @@ MusicScanner::MusicScanner( const QString& dir, quint32 bs )
    // m_ext2mime.insert( "mp4",  "audio/mp4" );
 }
 
-
-void
-MusicScanner::run()
-{
-    QTimer::singleShot( 0, this, SLOT( startScan() ) );
-    exec(); 
-}
-
-
 void
 MusicScanner::startScan()
 {
@@ -74,18 +64,21 @@ MusicScanner::scan()
     connect( this, SIGNAL( batchReady( QVariantList ) ),
                      SLOT( commitBatch( QVariantList ) ), Qt::DirectConnection );
 
-    DirLister* lister = new DirLister( QDir( m_dir, 0 ), m_dirmtimes );
+    m_dirListerThreadController = new QThread( this );
+    m_dirLister = new DirLister( QDir( m_dir, 0 ), m_dirmtimes );
+    m_dirLister->moveToThread( m_dirListerThreadController );
 
-    connect( lister, SIGNAL( fileToScan( QFileInfo ) ),
+    connect( m_dirLister, SIGNAL( fileToScan( QFileInfo ) ),
                        SLOT( scanFile( QFileInfo ) ), Qt::QueuedConnection );
 
     // queued, so will only fire after all dirs have been scanned:
-    connect( lister, SIGNAL( finished( const QMap<QString, unsigned int>& ) ),
+    connect( m_dirLister, SIGNAL( finished( const QMap<QString, unsigned int>& ) ),
                        SLOT( listerFinished( const QMap<QString, unsigned int>& ) ), Qt::QueuedConnection );
 
-    connect( lister, SIGNAL( finished() ), lister, SLOT( deleteLater() ) );
-
-    lister->start();
+    connect( m_dirLister, SIGNAL( destroyed(QObject*) ), this, SLOT( listerDestroyed(QObject*) ) );
+    
+    m_dirListerThreadController->start();
+    QMetaObject::invokeMethod( m_dirLister, "go" );
 }
 
 
@@ -111,9 +104,20 @@ MusicScanner::listerFinished( const QMap<QString, unsigned int>& newmtimes )
     qDebug() << "Skipped the following files (no tags / no valid audio):";
     foreach( const QString& s, m_skippedFiles )
         qDebug() << s;
+    
+    m_dirLister->deleteLater();
 }
 
 
+void
+MusicScanner::listerDestroyed( QObject* dirLister )
+{
+    qDebug() << Q_FUNC_INFO;
+    m_dirLister = 0;
+    m_dirListerThreadController->deleteLater();
+    m_dirListerThreadController = 0;
+}
+
 void
 MusicScanner::commitBatch( const QVariantList& tracks )
 {

src/musicscanner.h

@@ -5,69 +5,26 @@
 #include <taglib/tag.h>
 
 #include <QVariantMap>
-#include <QThread>
 #include <QDir>
 #include <QFileInfo>
 #include <QString>
 #include <QDebug>
 #include <QDateTime>
 
-class MusicScanner : public QThread
-{
-Q_OBJECT
-
-public:
-    MusicScanner( const QString& dir, quint32 bs = 0 );
-
-protected:
-    void run();
-
-signals:
-    //void fileScanned( QVariantMap );
-    void finished( int, int );
-    void batchReady( const QVariantList& );
-
-private:
-    QVariant readFile( const QFileInfo& fi );
-
-private slots:
-    void listerFinished( const QMap<QString, unsigned int>& newmtimes );
-    void scanFile( const QFileInfo& fi );
-    void startScan();
-    void scan();
-    void setMtimes( const QMap<QString, unsigned int>& m );
-    void commitBatch( const QVariantList& );
-
-private:
-    QString m_dir;
-    QMap<QString,QString> m_ext2mime; // eg: mp3 -> audio/mpeg
-    unsigned int m_scanned;
-    unsigned int m_skipped;
-
-    QList<QString> m_skippedFiles;
-
-    QMap<QString, unsigned int> m_dirmtimes;
-    QMap<QString, unsigned int> m_newdirmtimes;
-
-    QList<QVariant> m_scannedfiles;
-    quint32 m_batchsize;
-};
-
 
 #include <QTimer>
 
 // descend dir tree comparing dir mtimes to last known mtime
 // emit signal for any dir with new content, so we can scan it.
 // finally, emit the list of new mtimes we observed.
-class DirLister : public QThread
+class DirLister : public QObject
 {
     Q_OBJECT
 public:
     DirLister( QDir d, QMap<QString, unsigned int>& mtimes )
-        : QThread(), m_dir( d ), m_dirmtimes( mtimes )
+        : QObject(), m_dir( d ), m_dirmtimes( mtimes )
     {
         qDebug() << Q_FUNC_INFO;
-        moveToThread(this);
     }
 
     ~DirLister()
@@ -75,13 +32,6 @@ public:
         qDebug() << Q_FUNC_INFO;
     }
 
-protected:
-    void run()
-    {
-        QTimer::singleShot(0,this,SLOT(go()));
-        exec();
-    }
-
 signals:
     void fileToScan( QFileInfo );
     void finished( const QMap<QString, unsigned int>& );
@@ -130,4 +80,46 @@ private:
     QMap<QString, unsigned int> m_newdirmtimes;
 };
 
+class MusicScanner : public QObject
+{
+Q_OBJECT
+
+public:
+    MusicScanner( const QString& dir, quint32 bs = 0 );
+
+signals:
+    //void fileScanned( QVariantMap );
+    void finished( int, int );
+    void batchReady( const QVariantList& );
+
+private:
+    QVariant readFile( const QFileInfo& fi );
+
+private slots:
+    void listerFinished( const QMap<QString, unsigned int>& newmtimes );
+    void listerDestroyed( QObject* dirLister );
+    void scanFile( const QFileInfo& fi );
+    void startScan();
+    void scan();
+    void setMtimes( const QMap<QString, unsigned int>& m );
+    void commitBatch( const QVariantList& );
+
+private:
+    QString m_dir;
+    QMap<QString,QString> m_ext2mime; // eg: mp3 -> audio/mpeg
+    unsigned int m_scanned;
+    unsigned int m_skipped;
+
+    QList<QString> m_skippedFiles;
+
+    QMap<QString, unsigned int> m_dirmtimes;
+    QMap<QString, unsigned int> m_newdirmtimes;
+
+    QList<QVariant> m_scannedfiles;
+    quint32 m_batchsize;
+    
+    DirLister* m_dirLister;
+    QThread* m_dirListerThreadController;
+};
+
 #endif

src/scanmanager.cpp

@@ -0,0 +1,58 @@
+#include "scanmanager.h"
+#include "musicscanner.h"
+
+#include <QDebug>
+#include <QThread>
+
+ScanManager* ScanManager::s_instance = 0;
+
+
+ScanManager*
+ScanManager::instance()
+{
+    return s_instance;
+}
+
+
+ScanManager::ScanManager( QObject* parent )
+    : QObject( parent )
+    , m_scanner( 0 )
+    , m_musicScannerThreadController( 0 )
+{
+    s_instance = this;
+}
+
+
+ScanManager::~ScanManager()
+{
+    s_instance = 0;
+    m_musicScannerThreadController->deleteLater();
+    m_musicScannerThreadController = 0;
+    m_scanner->deleteLater();
+    m_scanner = 0;    
+}
+
+void
+ScanManager::runManualScan( const QString &path )
+{
+    qDebug() << Q_FUNC_INFO;
+    if ( !m_musicScannerThreadController && !m_scanner ) //still running if these are not zero
+    {
+        m_musicScannerThreadController = new QThread( this );
+        MusicScanner* m_scanner = new MusicScanner( path );
+        m_scanner->moveToThread( m_musicScannerThreadController );
+        connect( m_scanner, SIGNAL( finished() ), m_scanner, SLOT( deleteLater() ) );
+        connect( m_scanner, SIGNAL( destroyed(QObject*) ), this, SLOT( scanDestroyed(QObject*) ) );
+        m_musicScannerThreadController->start( QThread::IdlePriority );
+        QMetaObject::invokeMethod( m_scanner, "startScan" );
+    }
+}
+
+void
+ScanManager::scannerDestroyed( QObject* scanner )
+{
+    qDebug() << Q_FUNC_INFO;
+    m_scanner = 0;
+    m_musicScannerThreadController->deleteLater();
+    m_musicScannerThreadController = 0;
+}

src/scanmanager.h

@@ -0,0 +1,32 @@
+#ifndef SCANMANAGER_H
+#define SCANMANAGER_H
+
+#include <QObject>
+
+#include "dllmacro.h"
+
+class MusicScanner;
+class QThread;
+
+class DLLEXPORT ScanManager : public QObject
+{
+    Q_OBJECT
+public:
+    static ScanManager* instance();
+
+    explicit ScanManager( QObject* parent = 0 );
+    virtual ~ScanManager();
+    
+    void runManualScan( const QString &path );
+
+private slots:
+    void scannerDestroyed( QObject *scanner );
+    
+private:
+    static ScanManager* s_instance;
+    
+    MusicScanner* m_scanner;
+    QThread* m_musicScannerThreadController;
+};
+
+#endif

src/settingsdialog.cpp

@@ -22,6 +22,7 @@
 #include "sip/SipHandler.h"
 #include "sip/twitter/tomahawkoauthtwitter.h"
 #include <database/database.h>
+#include "scanmanager.h"
 
 static QString
 md5( const QByteArray& src )
@@ -145,11 +146,7 @@ SettingsDialog::~SettingsDialog()
         s->setScriptResolvers( resolvers );
         
         if( rescan )
-        {
-            MusicScanner* scanner = new MusicScanner(s->scannerPath() );
-            connect( scanner, SIGNAL( finished() ), scanner, SLOT( deleteLater() ) );
-            scanner->start();
-        }
+            ScanManager::instance()->runManualScan( s->scannerPath() );
 
         if( rejabber )
         {
@@ -180,21 +177,6 @@ SettingsDialog::showPathSelector()
 }
 
 
-void
-SettingsDialog::doScan()
-{
-    // TODO this doesnt really belong here..
-    QString path = ui->lineEditMusicPath->text();
-    MusicScanner* scanner = new MusicScanner( path );
-    connect( scanner, SIGNAL( finished() ), scanner, SLOT( deleteLater() ) );
-    scanner->start();
-
-    QMessageBox::information( this, tr( "Scanning Started" ),
-                                    tr( "Scanning now, check console output. TODO." ),
-                                    QMessageBox::Ok );
-}
-
-
 void
 SettingsDialog::onRejected()
 {

src/settingsdialog.h

@@ -48,8 +48,7 @@ protected:
 private slots:
     void onRejected();
     void showPathSelector();
-    void doScan();
-    
+
     void toggleUpnp( bool preferStaticEnabled );
     
     void showProxySettings();

src/sip/jabber/jabber_p.cpp

@@ -5,6 +5,7 @@
 #include <QTimer>
 #include <QString>
 #include <QRegExp>
+#include <QThread>
 #include <utils/tomahawkutils.h>
 
 using namespace gloox;

src/sip/jabber/jabber_p.h

@@ -10,7 +10,6 @@
 #include <QSharedPointer>
 #include <QMap>
 #include <QNetworkProxy>
-#include <QThread>
 
 #include <string>
 

src/tomahawkapp.cpp

@@ -25,6 +25,7 @@
 #include "scriptresolver.h"
 #include "sourcelist.h"
 #include "shortcuthandler.h"
+#include "scanmanager.h"
 #include "tomahawksettings.h"
 
 #include "audio/audioengine.h"
@@ -149,10 +150,11 @@ TomahawkApp::TomahawkApp( int& argc, char *argv[] )
     
     new TomahawkSettings( this );
     m_audioEngine = new AudioEngine;
-
+    new ScanManager( this );
+    
     new Pipeline( this );
     new SourceList( this );
-
+    
     m_servent = new Servent( this );
     connect( m_servent, SIGNAL( ready() ), SLOT( setupSIP() ) );
 

src/tomahawkwindow.cpp

@@ -32,13 +32,13 @@
 #include "widgets/welcomewidget.h"
 
 #include "audiocontrols.h"
-#include "musicscanner.h"
 #include "settingsdialog.h"
 #include "tomahawksettings.h"
 #include "sourcelist.h"
 #include "transferview.h"
 #include "tomahawktrayicon.h"
 #include "playlist/dynamic/GeneratorInterface.h"
+#include "scanmanager.h"
 
 using namespace Tomahawk;
 
@@ -249,23 +249,9 @@ TomahawkWindow::rescanCollectionManually()
                                                 s->scannerPath(), &ok );
     s->setValue( "scannerpath", path );
     if ( ok && !path.isEmpty() )
-    {
-        MusicScanner* scanner = new MusicScanner( path );
-        connect( scanner, SIGNAL( finished() ), this, SLOT( scanFinished() ) );
-        scanner->start();
-    }
+        ScanManager::instance()->runManualScan( path );
 }
 
-
-void
-TomahawkWindow::scanFinished()
-{
-    qDebug() << Q_FUNC_INFO;
-    MusicScanner* scanner = (MusicScanner*) sender();
-    scanner->deleteLater();
-}
-
-
 void
 TomahawkWindow::addPeerManually()
 {

src/tomahawkwindow.h

@@ -12,6 +12,7 @@
 
 class QAction;
 
+class MusicScanner;
 class AudioControls;
 class TomahawkTrayIcon;
 
@@ -46,11 +47,9 @@ public slots:
     void createPlaylist();
     void loadSpiff();
     void showSettingsDialog();
+    void rescanCollectionManually();
     
 private slots:
-    void scanFinished();
-    void rescanCollectionManually();
-
     void onSipConnected();
     void onSipDisconnected();
     void onSipError();