#include <QtWidgets>

int main(int argc, char* argv[])
{
    QApplication app(argc, argv);
    auto createProgressBar = [](int val, Qt::Orientation orientation, bool inverted)
        {
            auto pb = new QProgressBar;
            if (val < 0) {
                pb->setRange(0, 0);
            }
            else {
                pb->setMaximum(100);
                pb->setValue(val);
            }
            pb->setOrientation(orientation);
            pb->setInvertedAppearance(inverted);
            return pb;
        };
    auto getLayout = [](QWidget* w, Qt::Orientation orientation) -> QBoxLayout*
        {
            if (orientation == Qt::Horizontal)
                return new QVBoxLayout(w);
            return new QHBoxLayout(w);
        };
    auto createWidget = [&](Qt::Orientation orientation, bool inverted, const char* title)
        {
            QWidget* w = new QWidget;
            w->setWindowTitle(title);
            auto lay = getLayout(w, orientation);
            for (int i : {-1, 0, 1, 48, 52, 99, 100})
                lay->addWidget(createProgressBar(i, orientation, inverted));
            w->show();
        };
    createWidget(Qt::Horizontal, false, "Horizontal, normal");
    createWidget(Qt::Vertical, false, "Vertical, normal");
    createWidget(Qt::Horizontal, true, "Horizontal, inverted");
    createWidget(Qt::Vertical, true, "Vertical, inverted");
    return app.exec();
}