How to apply css styles to span using flutter_html

I'm using flutter_html package on my app to parse HTML from API. The html code is:

<p>Text text text text <span style="background: #FF0000; color: #FFFFFF; padding: 2px 5px; border-radius: 3px">XX</span> text text</p>

And it should print like https://i.imgur.com/0056kcT.png

But it prints this way https://i.imgur.com/FXO5dKD.png

The max I get to this is patching flutter_html packe like this:

if(node.attributes.isNotEmpty){
              if(node.attributes['background'] != null){
                childStyle = childStyle.merge(TextStyle(

                    //backgroundColor: Color(int.parse(node.attributes['background']))));
                    background: Paint()
                      ..color = Color(int.parse(node.attributes['background']))
                      ..style = PaintingStyle.fill
                      ..strokeCap = StrokeCap.round
                      ..strokeWidth = 2.0
                ));
              }
              if(node.attributes['color'] != null){
                childStyle = childStyle.merge(TextStyle(
                    color: Color(int.parse(node.attributes['color']))));
              }
              if(node.attributes['padding'] != null){
                childStyle = childStyle.merge(TextStyle(
                    wordSpacing: double.parse(node.attributes['padding'])));
              }
            }

But how can I add rounded border and padding?

Thanks