FontFeature.notationalForms constructor Null safety

const FontFeature.notationalForms(
  1. [int value = 1]
)

Display alternative glyphs for numerals (alternate annotation forms). (nalt)

Replaces glyphs used in numbering lists (e.g. 1, 2, 3...; or a, b, c...) with notational variants that might be more typographically interesting.

Fonts sometimes support multiple alternatives, and the argument selects the set to use (a positive integer, or 0 to disable the feature). The default set if none is specified is 1.

link
The Gothic A1 font supports several notational variant sets via the nalt feature.

Set 1 changes the spacing of the glyphs. Set 2 parenthesizes the latin letters and reduces the numerals to subscripts. Set 3 circles the glyphs. Set 4 parenthesizes the digits. Set 5 uses reverse-video circles for the digits. Set 7 superscripts the digits.

The code below shows how to select set 3.

To create a local project with this code sample, run:
flutter create --sample=dart.dart_ui.FontFeature.notationalForms.1 mysample 
import 'dart:ui';

import 'package:flutter/widgets.dart';

void main() => runApp(const ExampleApp());

class ExampleApp extends StatelessWidget {
  const ExampleApp({super.key});

  @override
  Widget build(BuildContext context) {
    return WidgetsApp(
      builder: (BuildContext context, Widget? navigator) =>
          const ExampleWidget(),
      color: const Color(0xffffffff),
    );
  }
}

class ExampleWidget extends StatelessWidget {
  const ExampleWidget({super.key});

  @override
  Widget build(BuildContext context) {
    // The Gothic A1 font can be downloaded from Google Fonts (https://www.google.com/fonts).
    return const Text(
      'abc 123',
      style: TextStyle(
        fontFamily: 'Gothic A1',
        fontFeatures: <FontFeature>[
          FontFeature.notationalForms(3), // circled letters and digits
        ],
      ),
    );
  }
}

See also:

Implementation

const FontFeature.notationalForms([this.value = 1]) : feature = 'nalt', assert(value >= 0);