withM3ETheme

snippet.dart

/// Inject (or replace) the M3ETheme extension on a ThemeData.
ThemeData withM3ETheme(ThemeData base, {M3ETheme? override}) {
  // Use any existing M3ETheme, else the provided override, else defaults.
  final current = base.extension<M3ETheme>();
  final next = override ?? current ?? M3ETheme.defaults(base.colorScheme);

  // Merge existing extensions (values) with our M3ETheme, replacing prior ones.
  final Iterable<ThemeExtension<dynamic>> existing = base.extensions.values;
  final List<ThemeExtension<dynamic>> merged = <ThemeExtension<dynamic>>[];
  for (final e in existing) {
    if (e is! M3ETheme) {
      merged.add(e);
    }
  }
  merged.add(next);

  return base.copyWith(extensions: merged);
}