flutter-packages [Proposal] Add function to await any pending font loads.

The addition of the pendingFontLoads function would allow users to request multiple google fonts, then asynchronously wait for the fonts to be loaded. For example, the following snippet will show a progress indicator until the fonts have finished loading, then it will load the page.

https://github.com/material-foundation/google-fonts-flutter/issues/151

giphy-6

import 'package:flutter/material.dart';
import 'package:google_fonts/google_fonts.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    GoogleFonts.oswald();
    GoogleFonts.pacifico();
    return MaterialApp(
      home: FutureBuilder(
        future: GoogleFonts.pendingFontLoads(),
        builder: (context, snapshot) {
          if (snapshot.connectionState != ConnectionState.done) {
            return Center(child: CircularProgressIndicator());
          }
          return MyHomePage(title: 'Demo');
        },
      ),
    );
  }
}

class MyHomePage extends StatelessWidget {
  MyHomePage({Key? key, required this.title}) : super(key: key);

  final String title;

  @override
  Widget build(BuildContext context) {
    final TextStyle headline4 = Theme.of(context).textTheme.headline4!;
    return Scaffold(
      appBar: AppBar(
        title: Text(title, style: GoogleFonts.pacifico()),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'This is a google font',
              style: GoogleFonts.oswald(textStyle: headline4),
            ),
          ],
        ),
      ),
    );
  }
}

Possible improvements would be:

Making it so that the user can tell which font loads when.
Making it so that the user doesn't have to call all the fonts before hand, maybe add a way to pass in the fonts they want to load.

Nov 15 '21 23:11 johnsonmh

instead of return a Future of List of fonts, can this return a List of Future fonts? Also, consider renaming to `loadedFonts, since they aren't necessarily pending when this is called