Wait/sleep 100ms during QPixmap in QLabel slideshow

Reply to Wait/sleep 100ms during QPixmap in QLabel slideshow on Sat, 06 Aug 2016 20:19:22 GMT

mrjj — Sat, 06 Aug 2016 20:19:22 GMT

@cpper
ok. super.
Nope, in this case using non pointers is very correct since
there is no need for pointers here. :)

Reply to Wait/sleep 100ms during QPixmap in QLabel slideshow on Sat, 06 Aug 2016 20:02:18 GMT

cpper — Sat, 06 Aug 2016 20:02:18 GMT

@mrjj
It's clear now.

Since I want to keep everything in the clicked() function (and not call update() slot) I used both QTimer and QEventLoop:


void MainWindow::on_pushButton_clicked()
{
    QTimer timer(this);
    QEventLoop loop;
    timer.setInterval(100);
    QObject::connect(&timer, &QTimer::timeout,&loop,&QEventLoop::quit);

    for(const QPixmap& x: pics){
        ui->label->setPixmap(x);
        timer.start();
        loop.exec();
    }



}

It works as I wished now. But would it be better to use pointer to QTimer and QEventLoop in such situations ?

Reply to Wait/sleep 100ms during QPixmap in QLabel slideshow on Sat, 06 Aug 2016 19:54:52 GMT

mrjj — Sat, 06 Aug 2016 19:54:52 GMT

@cpper
well you pause the GUI thread with msleep.

The reason you dont see each image is that the for loop
don't allow events to be processed.

You can use QApplication::processEvents();
in the loop and it will sort of work - but you will still make the
GUI a big laggy as long for loops in gui thread is just not a good idea.

Reply to Wait/sleep 100ms during QPixmap in QLabel slideshow on Sat, 06 Aug 2016 19:05:31 GMT

cpper — Sat, 06 Aug 2016 19:05:31 GMT

Thanks, I'll try this method. However, is there no simpler way to do it ? Such as a single function call. Why doesn't msleep work in this case ?

Reply to Wait/sleep 100ms during QPixmap in QLabel slideshow on Sat, 06 Aug 2016 18:10:24 GMT

mrjj — Sat, 06 Aug 2016 18:10:24 GMT

Hi
You could use a timer and a slot and do it sort of reverse

in constructor
QTimer *timer = new QTimer(this);
connect(timer, SIGNAL(timeout()), this, SLOT(update()));
timer->start(1000);
..

// this is called every second. adjust if need to be faster/slower
void MainWindow::update()
{
if (currentimage ui->label->setPixmap( pics[ currentimage++ ] );

}