How to make my app title and tab labels as large as possible in Flutter

Question

I'm making a flutter app which will be used by people with limited vision and I want to make the size of all text as large as fits the view port width up to a specified maximum font size. The actual widths and heights are dynamic so I'd like to use something like media queries to set sane sizes.

Nothing I have tried moves the text size and I can't find any SO answers which help me.

Here's the code I am attempting to use now but it doesn't work.

class HomeTabs extends StatefulWidget {
  const HomeTabs({Key? key}) : super(key: key);

  @override
  State<StatefulWidget> createState() => HomeTabsState();
}

class HomeTabsState extends State<HomeTabs> {
  @override
  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) {

    User _user = Provider.of<User>(context, listen: false);

    return DefaultTabController(
    
      length: 2,
    
      child: Scaffold(

        drawer: AppDrawer(),
            
        appBar: AppBar(

          toolbarHeight: 100,
            
          iconTheme: IconThemeData(color: iconColor),
            
          backgroundColor: branding,

          centerTitle: true,

          title: FittedBox(

                       fit: BoxFit.contain,
                       
                       child: Text(_user.companyName),

                    ),
            
          bottom: TabBar(
            
            isScrollable: false,
            
            tabs:  [

              SizedBox(

                height: 100,
            
                 child:  Tab( 
                
                    child: FittedBox(

                      fit: BoxFit.contain,
                
                      child: Text( 'Notifications', style: tabStyle))
                
                  ),
              ),

              SizedBox(

                height: 100,

                child:  Tab( 

                  child: FittedBox(

                    fit: BoxFit.contain,
                
                    child: Text( 'Cases', style: tabStyle))
                
                ),
              ),
            ],
          ),
        ),
....
            

Answer 1

for title use Container's constraints like this.

          title: Container(
            constraints: BoxConstraints(
                minWidth: MediaQuery.of(context).size.width - 50),
            child: FittedBox(
              child: Text(
                '_user.companyName',
              ),
            ),
          )

For Tabs just swap FittedBox with Tab.

FittedBox(
                  child: Tab(
                    child: Text(
                      'Cases',
                    ),
                  ),
                ),

Answer 2

Try this For App Bar Size Maintain

PreferredSize(
            preferredSize: Size.fromHeight(100.0), // here the desired height
            child: AppBar(
              centerTitle: true,
              title: Text("Example"),
            )
        )

Result ->