Adds a new slide to the widget.
        
        :param      slide | <XWalkthroughSlide>
        
        :return     <QtGui.QGraphicsView>

def addSlide(self, slide):
        """
        Adds a new slide to the widget.
        
        :param      slide | <XWalkthroughSlide>
        
        :return     <QtGui.QGraphicsView>
        """
        # create the scene
        scene = XWalkthroughScene(self)
        scene.setReferenceWidget(self.parent())
        scene.load(slide)
        
        # create the view
        view = QtGui.QGraphicsView(self)
        view.setCacheMode(view.CacheBackground)
        view.setScene(scene)
        view.setStyleSheet('background: transparent')
        view.setFrameShape(view.NoFrame)
        view.setInteractive(False)
        view.setFocusPolicy(QtCore.Qt.NoFocus)
        view.setAttribute(QtCore.Qt.WA_TransparentForMouseEvents)
        view.setAlignment(QtCore.Qt.AlignTop | QtCore.Qt.AlignLeft)
        view.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOff)
        view.setHorizontalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOff)
        
        # add the slide
        self._slideshow.addWidget(view)
        self.updateUi()
        
        return view