Qlable.setpixmap showing segmentation fault

[swansorter]

if i use a qlable inside qtcuncurrent function showing segmentation fault

this is my code

void MainWindow::image_plot()
{

    while (1) {
        QImage img(RxBuffer, 2048, 1, QImage::Format_RGB888);
        ui->label->setPixmap(QPixmap::fromImage(img.rgbSwapped()));
         
    }
}

[JonB]

@swansorter

I assume your ui->port is a QLabel [sic.], though it makes life easier if you say so.

• You must not directly access any UI element from any thread other than the main UI one. I guess you are using your method above in a QtConcurrently-run thread?

• While you can use QImage in a non-UI thread, I believe you cannot use QPixmaps either.

[swansorter]

@JonB is there any alternative way.

[JonB]

@swansorter
I don't know why you are using threads --- about half the time people use them they don't need to. But assuming you do, you can only communicate with the main UI thread by sending a signal, with whatever (non-UI-type) parameters are necessary which the UI thread has a slot on and acts upon receiving the signal.

For example, since I believe secondary threads can use QImage but cannot use QPixmap (and certainly not call QLabel::setPixmap()) I think you could emit imageCaptured(img) from image_plot() and have a slot MainWindow::onImageCaptured(const QImage &img) which does the ui->label->setPixmap(QPixmap::fromImage(img.rgbSwapped())); in the main thread.