Manage QEvent manual in different thread

Quiccz

I'm using glfw for gui, and use qt core library. Like this

int main()
{
    QApplication app;   // I also use QPainter for image and text. So i need QApplication in main thread
    std::thread([](){
             while(1)
             {
                   //render something with glfw
             }
     }).death();
    app.exec();
}

now i want to use qevent for render thread. Like this

int main()
{
    QCoreApplication app;
    std::thread([](){
             while(1)
             {
                    QCoreApplication::ProcessEvent(); //manage event manual before every render.
                   //render something with glfw
             }
     }).death();
    QTimer timer; // sent some event to glfw thread
    app.exec();
}

Can my goal be achieved?

jsulm

@Quiccz Why do you need a second thread?

Christian Ehrlicher

@jsulm ... and why use std::thread when one wants to use Qt signal/slot and other functionality in there?

Quiccz

@jsulm I thought qt event loop must start with exec().

Quiccz

@jsulm

int main()
{
    QCoreApplication app;
   QTimer timer; // sent some event to glfw thread

    while(1)
    {
            QCoreApplication::ProcessEvent(); //manage event manual before every render.
            //render something with glfw
     }
    return 0;
}

Can't believe this work.

However, i send Event to top object, it's seem not send to child object.
I want to create a static object as all receiver father. So i just need send event to this static object and it handle to child.
Like this

QObject top_object;
QObject r1(&top_object);
QObject r2(&top_object);

PostEvent(top_object, event);

//so r1 deal event first, then r2.

jsulm

@Quiccz said in Manage QEvent manual in different thread:

I thought qt event loop must start with exec().

Yes, you have it already: app.exec()
So, still don't know why you need a second thread.

Quiccz

@jsulm because app.exec() will block, and i need render my frame in while(1) loop. if in same thread, app.exec() will never run.

I found QEvent can be send and recive without exec(). So i don't need a second thread. which i don't know before

Christian Ehrlicher

@Quiccz said in Manage QEvent manual in different thread:

because app.exec() will block, a

app.exec() does not block anything. If you want to render something (to whereever) then do it inside the event loop e.g. with a QTimer or during the paintEvent() when you want to paint it on the screen.

Quiccz

@Christian-Ehrlicher I mean if i run this

app.exec();

//this won't run until app.quit()
while(1)
{
    //renderloop
}

Or

while(1)
{
   //renderloop
}

//exec won't run until render loop stop.
app.exec()

Or use timer

void loopfun
{
    while(1)
   {
      //render
   }
}
QSingalTimer ( 10, loopfun);

app.exec();

eventloop will be block, because my loopfun never end.

If need let them run both, thread must be used.

jsulm

Again: you don't need such a loop. As @Christian-Ehrlicher already suggested: either use a QTimer to trigger rendering or render in paintEvent()...