QT5: Unable to set stylesheet properties using qss file

I'm currently working on an app and I'm unable to set global stylesheet. Here's the code I've been trying:

QFile file(":/dark.qss");
        file.open(QFile::ReadOnly | QFile::Text);
        QTextStream stream(&file);
        qApp->setStyleSheet(stream.readAll()); '''

and

 QFile f(":/dark.qss");

if (!f.exists())   {
    printf("Unable to set stylesheet, file not found\n");
}
else   {
    f.open(QFile::ReadOnly | QFile::Text);
    QTextStream ts(&f);
    qApp->setStyleSheet(ts.readAll());
}

For the first one I'm getting : QIODevice::read \dark.qss device not open

and for the second one Unable to set stylesheet, file not found

The second one used to work fine 2 weeks ago (build with msys2, mingw64, qt5.14.1.3), unfortunately, I had to reinstall mysys2 and since then this is not working anymore.

I tried to build using msys2 with all the packages I used 2 weeks ago (had to downgrade about 80 packages manually ) also straight from qt creator with no luck.

Any idea what might be the problem?

Solution

The issue has nothing to do with msys. The most obvious reason is an incorrect project setup. Please make sure dark.qss is added into the resource (qrc) file under "/" prefix and the qrc file is added into RESOURCES in the pro file.

Also, there is a bug in qmake not adding newly added resources into the app sometimes. A full rebuild might help in this situation.

It would be great if you paste both the qrc and pro file here. A full build log could be very helpful as well.