QThread: Thread does not leave event loop on quit() using Queued signals, why ?

[franku]

I have a small worker thread:

class ReloadDirectoryThread : public QThread
{
    Q_OBJECT
public:
    ReloadDirectoryThread()
        : QThread() {
    };
 
    ~ReloadDirectoryThread() {
    };
 
    void run() {
         exec();
    };
 
public slots:
    void importImage(int row, QString filePath);
signals:
    void imageImported(int row, QIcon* icon);
};

class ReloadDirectoryThread : public QThread
{
    Q_OBJECT
public:
    ReloadDirectoryThread()
        : QThread() {
    };

    ~ReloadDirectoryThread() {
    };

    void run() {
         exec();
    };

public slots:
    void importImage(int row, QString filePath);
signals:
    void imageImported(int row, QIcon* icon);
};

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Its task is to open Images pointed to by filePath, convert them into a QIcon and emit each new Icon:

void ReloadDirectoryThread::importImage(int row, QString filePath)
{
     QIcon* icon = new QIcon(QPixmap(filePath));
     emit imageImported(row, icon);
}

void ReloadDirectoryThread::importImage(int row, QString filePath)
{
     QIcon* icon = new QIcon(QPixmap(filePath));
     emit imageImported(row, icon);
}

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The thread will be started from the main-application thread:

{  ...
    reloadDirectoryThread = new ReloadDirectoryThread;
 
    connect(this, SIGNAL(importImage(int,QString)),
            reloadDirectoryThread, SLOT(importImage(int,QString)), Qt::QueuedConnection);
 
    connect(reloadDirectoryThread, SIGNAL(imageImported(int,QIcon*)),
            this, SLOT(imageImported(int,QIcon*)), Qt::QueuedConnection);
 
    reloadDirectoryThread->moveToThread(reloadDirectoryThread);
    reloadDirectoryThread->start();
...}

{  ...
    reloadDirectoryThread = new ReloadDirectoryThread;

    connect(this, SIGNAL(importImage(int,QString)),
            reloadDirectoryThread, SLOT(importImage(int,QString)), Qt::QueuedConnection);

    connect(reloadDirectoryThread, SIGNAL(imageImported(int,QIcon*)),
            this, SLOT(imageImported(int,QIcon*)), Qt::QueuedConnection);

    reloadDirectoryThread->moveToThread(reloadDirectoryThread);
    reloadDirectoryThread->start();
...}

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The Thread should be shut down when closing the app:

{... 
    reloadDirectoryThread->quit();
    reloadDirectoryThread->wait(3000);
    delete reloadDirectoryThread;
...}

{... 
    reloadDirectoryThread->quit();
    reloadDirectoryThread->wait(3000);
    delete reloadDirectoryThread;
...}

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This will tell the thread to quit its eventLoop and waits at most 3 seconds for the thread to finish. At this time all "importImage"-signals are already posted into the event queue.

My problem is that the worker-thread always completes all messages (what in fact lasts more than three seconds) until the Thread Object can be deleted safely.

Any ideas what's going wrong ? Why does the thread not stop executing events from the eventqueue when calling quit() ?

.. frank