'Update the current description.'

def __update(self):

    if (self.__currentIndex != (-1)):
        index = self.model().index(self.__currentIndex, 0)
    else:
        index = QModelIndex()
    if (not index.isValid()):
        description = ''
        name = ''
        path = ''
        svg = NO_PREVIEW_SVG
    else:
        description = str(index.data(Qt.WhatsThisRole))
        if (not description):
            description = 'No    description.'
        description = escape(description)
        description = description.replace('\n', '<br/>')
        name = str(index.data(Qt.DisplayRole))
        if (not name):
            name = 'Untitled'
        name = escape(name)
        path = str(index.data(Qt.StatusTipRole))
        svg = str(index.data(previewmodel.ThumbnailSVGRole))
    desc_text = self.__template.format(description=description, name=name)
    self.__label.setText(desc_text)
    self.__path.setText(path)
    if (not svg):
        svg = NO_PREVIEW_SVG
    if svg:
        self.__image.load(QByteArray(svg.encode('utf-8')))
