Method SingleApplication

src/singleapplication/singleapplication.cpp:39–163

* @brief Constructor. Checks and fires up LocalServer or closes the program * if another instance already exists * @param argc * @param argv * @param allowSecondary Whether to enable secondary instance support * @param options Optional flags to toggle specific behaviour * @param timeout Maximum time blocking functions are allowed during app load */

 * @param timeout Maximum time blocking functions are allowed during app load
 */
SingleApplication::SingleApplication( int &argc, char *argv[], bool allowSecondary, Options options, int timeout, const QString &userData )
    : app_t( argc, argv ), d_ptr( new SingleApplicationPrivate( this ) )
{
    Q_D( SingleApplication );

#if defined(Q_OS_ANDROID) || defined(Q_OS_IOS)
    // On Android and iOS since the library is not supported fallback to
    // standard QApplication behaviour by simply returning at this point.
    qWarning() << "SingleApplication is not supported on Android and iOS systems.";
    return;
#endif

    // Store the current mode of the program
    d->options = options;

    // Add any unique user data
    if ( ! userData.isEmpty() )
        d->addAppData( userData );

    // Generating an application ID used for identifying the shared memory
    // block and QLocalServer
    d->genBlockServerName();

    // To mitigate QSharedMemory issues with large amount of processes
    // attempting to attach at the same time
    SingleApplicationPrivate::randomSleep();

#ifdef Q_OS_UNIX
    // By explicitly attaching it and then deleting it we make sure that the
    // memory is deleted even after the process has crashed on Unix.
    d->memory = new QSharedMemory( d->blockServerName );
    d->memory->attach();
    delete d->memory;
#endif
    // Guarantee thread safe behaviour with a shared memory block.
    d->memory = new QSharedMemory( d->blockServerName );

    // Create a shared memory block
    if( d->memory->create( sizeof( InstancesInfo ) )){
        // Initialize the shared memory block
        if( ! d->memory->lock() ){
          qCritical() << "SingleApplication: Unable to lock memory block after create.";
          abortSafely();
        }
        d->initializeMemoryBlock();
    } else {
        if( d->memory->error() == QSharedMemory::AlreadyExists ){
          // Attempt to attach to the memory segment
          if( ! d->memory->attach() ){
              qCritical() << "SingleApplication: Unable to attach to shared memory block.";
              abortSafely();
          }
          if( ! d->memory->lock() ){
            qCritical() << "SingleApplication: Unable to lock memory block after attach.";
            abortSafely();
          }
        } else {
          qCritical() << "SingleApplication: Unable to create block.";