Question

I have a software that sends JPGs over the network to a GUI client that is supposed to display those images. I basically want to display them to a qt window but I’m having problems with how qt displays consecutive JPGs. I made a test to see if I’m getting the image correctly by printing it to a file and that checks out fine. Here’s the main code:

int main(int argc, char *argv[]) {
    // initialize resources, if needed
    // Q_INIT_RESOURCE(resfile);

    QApplication app(argc, argv);
    CameraWindow cw;
    cw.show();
    //app.setActiveWindow(&cw);
    cw.getData();       // this paints the window  
    return app.exec();
}

Here’s the code that initializes the widget:

class CameraWindow : public QDialog {
    Q_OBJECT
    public:
    bool serverConnected;
    void getData();
    CameraWindow()
    {
        imgl = new QLabel;
        widget.scrollImage->setWidget(imgl);
        widget.scrollImage->setBackgroundRole(QPalette::Dark);
    }
    QLabel *imgl;
    virtual ~CameraWindow();
    private:
    Ui::CameraWindow widget;
};

This is the relevant part of the code that is supposed to paint the image to the screen which is inside an infinite loop:

getData() called from main:

while (myrval < Header.imageSize) {
    myrval = myrval + recv(msgsock, (char*) ((int) buff + myrval),
        Header.imageSize- myrval, 0);
}

//buff contains the jpg at this point
QPixmap imgjpg;
imgjpg.loadFromData((const unsigned char*)buff, Header.imageSize, "JPG");
//scroll image is the parent that displays child
//in this case, the label
imgl->setPixmap(imgjpg);

I got this to work for just one image that was loaded from a file but when I use the same method for a set of streaming images, this doesn’t work. I’m new to Qt so I’m sure I have a subtle mistake.

Many thanks!

Answer 1

Because you are in a infinite loop, the Qt may not have chance to handle event. Could you try to call QCoreApplication::processEvents after you setPixmap?