Applying a "selected" style

[Cruz]

I have a little style sheet, that I load from a file in the main class and apply it to the QApp like this:

QApplication a(argc, argv);
 
QFile file("styles.css");
file.open(QFile::ReadOnly);
QString styleSheet = QLatin1String(file.readAll());
a.setStyleSheet(styleSheet);
 
return a.exec();

QApplication a(argc, argv);

QFile file("styles.css");
file.open(QFile::ReadOnly);
QString styleSheet = QLatin1String(file.readAll());
a.setStyleSheet(styleSheet);

return a.exec();

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It's very convenient, because I can change the looks of my application without even having to recompile the code. Now here is the thing. I have QFrames on my gui, that I want to highlight when the mouse moves them and keep highlighted when they get clicked. So I need to set some kind of attribute in the code that the style sheet reacts to.

I have seen this thing in a style sheet before:

.selected {
    border-width: 3px;
}

.selected {
    border-width: 3px;
}

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and I figure it would apply to items that somehow get a "selected" attribute. Does anyone know how to do this?

Thanks
Cruz