def qteRegisterApplet(self, cls, replaceApplet: bool=False):
        if not issubclass(cls, QtmacsApplet):
            args = ('cls', 'class QtmacsApplet', inspect.stack()[0][3])
            raise QtmacsArgumentError(*args)
        class_name = cls.__name__
        if class_name in self._qteRegistryApplets:
            msg = 'The original applet <b>{}</b>'.format(class_name)
            if replaceApplet:
                msg += ' was redefined.'
                self.qteLogger.warning(msg)
            else:
                msg += ' was not redefined.'
                self.qteLogger.warning(msg)
                return class_name
        cls.__qteRegisterAppletInit__()
        self._qteRegistryApplets[class_name] = cls
        self.qteLogger.info('Applet <b>{}</b> now registered.'
                            .format(class_name))
        return class_name