How to detect the Text widget showed all data?

Question

The requirement is when the Text did not show all the data, detail dialog will show when use tap the Text widget.

Code just like:

class _DraftPage2State extends State<DraftPage2> {
  var _showedAllData = false;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: BaseAppBar(titleText: '判断Text文本是否显示完'),
      body: Center(
        child: GestureDetector(
          onTap: () {
            if (!_showedAllData) {
              // showDialog
            }
          },
          child: Container(
            width: 100,
            height: 30,
            color: Colors.red,
            child: const Text(
              'AAAAAAAAAAAAAAAAAAAA',
              style: TextStyle(fontSize: 20),
              maxLines: 1,
              overflow: TextOverflow.ellipsis,
            ),
          ),
        ),
      ),
    );
  }
}

For example:

• not showed all data

• showed all data

So how can I detect the Text widget showed all data?