Refreshing MainWindow in a loop to simulate a move of QWidget in QT

Question

I am new in QT and my problem is to refresh the page in a loop to make a move on QWidget.
In detail, I have too many points (It is the path which will be followed by an ellipse and they will be drawn as line) and I have an ellipse which will move on the screen according to given two points. During its move, the path is changed. So lines will be drawn again according to new path and the ellipse should follow the new path. What I did as follows:

void MainWindow::paint(...){
painter.drawEllipse(circle) //circle is QRectF
//Also I need to draw lines according to pathPlanned
}



bool MainWindow::replan(){
//it calculates the planned path and if the ellipse does not reached the destination it can change the planned path here 
}

void MainWindow::execute(){
   while(replan()){
      for (it = plannedPath->begin(); it != plannedPath->end(); it++){
          //Lines should be redraw according to new pathPlanned
       }
    circle(...) // new position of ellipse is changed here
    // I tried to put QThread::msleep(10) but I learned that it blocks GUI and then deleted it.
     }
}

My problem is that loop is working so fast (as usual) and it can not refresh the page until it finishes everything. Then Immediately ellipse is drawn on the destination. I can not see the moves of ellipse. How can I fix that?

Lahiru Chandima Lahiru Chandima · Accepted Answer · 2015-03-19T10:23:28

Instead of using QThread::msleep(10), use following

QEventLoop loop;
QTimer::singleShot(100, &loop, SLOT(quit()));
loop.exec();

This will process events after each redraw of ellipse so UI will get updated

Refreshing MainWindow in a loop to simulate a move of QWidget in QT

2 Answers