event appears in thread without eventloop exec()

[Kabummski]

Help me, I do not understand it. My code works even I believe it shouldnt.

I can receive an event in a thread even though the eventloop of the thread has not been started with exec.

See the code appended. I used the example "calculatorform". When some special numbers are entered by user it sends a customevent
to my thread. The thread displays then a messagebox. The thread is running, this->ii increments and it costs full power of 1of 4 processor cores.


/***************** main.cpp ***************/

#include <QApplication>
#include <QEvent>
 
#include "calculatorform.h"
#include "mythread.h"
 
QApplication * appptr;
QObject * trhead;
QEvent::Type my_customevent;
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    CalculatorForm calculator;
    MyThread  testit1;
    MyThread  testit2;
    MyThread  testit3;
    MyThread  testit4;
    trhead = &testit1;
    appptr = &app;
    my_customevent = (QEvent::Type) QEvent::registerEventType ( -1 );
    testit1.start();
    //testit2.start();
    //testit3.start();
   // testit4.start();
    calculator.show();
    return app.exec();
}

#include <QApplication>
#include <QEvent>

#include "calculatorform.h"
#include "mythread.h"

QApplication * appptr;
QObject * trhead;
QEvent::Type my_customevent;
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    CalculatorForm calculator;
    MyThread  testit1;
    MyThread  testit2;
    MyThread  testit3;
    MyThread  testit4;
    trhead = &testit1;
    appptr = &app;
    my_customevent = (QEvent::Type) QEvent::registerEventType ( -1 );
    testit1.start();
    //testit2.start();
    //testit3.start();
   // testit4.start();
    calculator.show();
    return app.exec();
}

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/***************** my_thread.cpp ***************/

extern QEvent::Type my_customevent;
 
 
void MyThread::run()
{
    //exec();
    while(1) this->ii++;
}
 
int myMessageBox(long value);
 
void  MyThread::customEvent ( QEvent * event )
{
    if (event->type() == my_customevent)
    {
        myMessageBox(this->ii);
    }
    else
    {
        QThread::customEvent(event);
    }
 
}
 
int myMessageBox(long value)
{
    QMessageBox msgBox;
    QString result;
    QTextStream(&result) << "Resultcode = " << value;
    // result == "pi = 3.14"
 
    msgBox.setText("This is a test message box");
    msgBox.setInformativeText(result);
    msgBox.setStandardButtons(QMessageBox::Save | QMessageBox::Discard | QMessageBox::Cancel);
    msgBox.setDefaultButton(QMessageBox::Save);
    int ret = msgBox.exec();
    return ret;
}

extern QEvent::Type my_customevent;


void MyThread::run()
{
    //exec();
    while(1) this->ii++;
}

int myMessageBox(long value);

void  MyThread::customEvent ( QEvent * event )
{
    if (event->type() == my_customevent)
    {
        myMessageBox(this->ii);
    }
    else
    {
        QThread::customEvent(event);
    }

}

int myMessageBox(long value)
{
    QMessageBox msgBox;
    QString result;
    QTextStream(&result) << "Resultcode = " << value;
    // result == "pi = 3.14"

    msgBox.setText("This is a test message box");
    msgBox.setInformativeText(result);
    msgBox.setStandardButtons(QMessageBox::Save | QMessageBox::Discard | QMessageBox::Cancel);
    msgBox.setDefaultButton(QMessageBox::Save);
    int ret = msgBox.exec();
    return ret;
}

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[wysota]

The QThread subclassed object lives in the main thread thus it gets the event.