change color of background if inverted mode is enable

        painter.save()

        # Draw background.

        painter.setBrush(self.background_color)

        painter.setPen(self.background_color)

        background_color = self.background_color

        if self.inverted_mode: # change color of background if inverted mode is enable

            background_color = QColor(20, 20, 20, 255)

        painter.setBrush(background_color)

        painter.setPen(background_color)

        painter.drawRect(0, 0, self.rect().width(), self.rect().height())

        # Get start/last render index.