Qt opacity

gistfile1.cs

class TestWidget : public QWidget
{
public:
    TestWidget(QWidget* parent = 0) : QWidget(parent)
    {
        this->setWindowOpacity(.5);
    }
};

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    TestWidget widget;

    QCheckBox* checkBox = new QCheckBox(&widget);
          checkBox->setObjectName(QStringLiteral("checkBox"));
          checkBox->setGeometry(QRect(0, 0, 89, 20));

    widget.setGeometry(QRect(0, 0, 240, 320));

    widget.show();

    return app.exec();
}