app = QtGui.QApplication([])
    w = QtGui.QWidget()
    s1 = ConstantSpectrum()
    s2 = GaussianSpectrum()
    s3 = LorentzianSpectrum()
    sc1 = SpectrumControlWidget(s1)
    # sc1.setStyleSheet("QObject { background-color: blue; }")
    sc2 = SpectrumControlWidget(s2)
    # sc2.setStyleSheet("QObject { background-color: red; }")
    sc3 = SpectrumControlWidget(s3)
    # sc3.setStyleSheet("QObject { background-color: green; }")
    layout = QtGui.QVBoxLayout(w)
    # layout.setSpacing(0)
    # layout.setContentsMargins(0, 0, 0, 0)
    layout.addWidget(sc1)
    layout.addWidget(sc2)
    layout.addWidget(sc3)
    layout.addStretch(1)
    # w.show()
    # w.raise_()
    scroll = VerticalScrollArea()
    scroll.setWidget(w)
    scroll.show()
    scroll.raise_()

    import sys

    if (sys.flags.interactive != 1) or not hasattr(QtCore, "PYQT_VERSION"):
        QtGui.QApplication.instance().exec_()