How to make a delay in a Qt loop so that the UI thread does not stop?

Question

Qt

I need to make a delay in the code during the for loop, but so that the Ui thread does not stop (the sleep function will not help). A mockup of what it should look like: below .

void View::viruspodMoving(QGraphicsItem *virus) {  // функция, не слот
    for(int y = vir.y; y < 501;){
            delay() // реализованная задержка
            y = y + 4;
            vir.y = vir.y + 4;
            virus->setPos(vir.x, y);
    }

    if(vir.y >= 500){
        deleteVirus(virus);
    }

}

Answer 1

You need to separate this by thread. Data separately, yuai separately.
Although apparently in Qt you are trying to make a game, this is done if something is completely wrong:
- implement a certain function, let's call it Update, and make it so that it is called 60 times per second (approximately)
- it is in this function that you output graphics
- it is in this function that you make the movement, but without delays, and with reference to the frequency of the function call (more precisely, to the time since the previous call)
- but with the input it is more interesting - it must be processed separately and cumulatively

Answer 2

You were answered correctly above, it is necessary to separate into different streams. But if, nevertheless, you want to write a delay in the UI thread, then here

void delay(int ms)
{
  QElapsedTimer et;
  et.start();
  while(true)
  {
    qApp->processEvents();
    if(et.elapsed() > ms) break;
  }
}