Qt method override to paint a custom image on the Widget.

def paintEvent(self, event):
        """Qt method override to paint a custom image on the Widget."""
        super(FigureCanvas, self).paintEvent(event)
        # Prepare the rect on which the image is going to be painted :
        fw = self.frameWidth()
        rect = QRect(0 + fw, 0 + fw,
                     self.size().width() - 2 * fw,
                     self.size().height() - 2 * fw)

        if self.fig is None or self._blink_flag:
            return

        # Check/update the qpixmap buffer :
        qpix2paint = None
        for qpix in self._qpix_buffer:
            if qpix.size().width() == rect.width():
                qpix2paint = qpix
                break
        else:
            if self.fmt in ['image/png', 'image/jpeg']:
                qpix2paint = self._qpix_orig.scaledToWidth(
                    rect.width(), mode=Qt.SmoothTransformation)
            elif self.fmt == 'image/svg+xml':
                qpix2paint = QPixmap(svg_to_image(self.fig, rect.size()))
            self._qpix_buffer.append(qpix2paint)

        if qpix2paint is not None:
            # Paint the image on the widget :
            qp = QPainter()
            qp.begin(self)
            qp.drawPixmap(rect, qpix2paint)
            qp.end()