Perform widget rendering, but do not print anything.

def _render_content(self, content, **settings):
        """
        Perform widget rendering, but do not print anything.
        """
        if not self.SETTING_WIDTH in settings or not settings[self.SETTING_WIDTH]:
            settings[self.SETTING_WIDTH] = TERMINAL_WIDTH

        s = {k: settings[k] for k in (self.SETTING_WIDTH, self.SETTING_FLAG_BORDER, self.SETTING_MARGIN, self.SETTING_MARGIN_LEFT, self.SETTING_MARGIN_RIGHT, self.SETTING_PADDING, self.SETTING_PADDING_LEFT, self.SETTING_PADDING_RIGHT)}
        width_int = self.calculate_width_content(**s)

        lines = self._wrap_content(content, width_int)

        result = []
        if settings[self.SETTING_FLAG_BORDER]:
            result.append(self._render_border_line('t', settings))
        if settings[self.SETTING_FLAG_HEADER]:
            s = {k: settings[k] for k in settings.keys()}
            s[self.SETTING_TEXT_FORMATING] = s[self.SETTING_HEADER_FORMATING]
            result.append(self._render_line(settings[self.SETTING_HEADER_CONTENT], s))
            result.append(self._render_border_line('m', settings))
        for l in lines:
            result.append(self._render_line(l, settings))
        if settings[self.SETTING_FLAG_BORDER]:
            result.append(self._render_border_line('b', settings))
        return result