generate method

ThemeSpec generate(int seed, ThemeFamily family, int engineVersion, { bool accessible = false, int? seedHueTenths, })

The theme for (seed, family, engineVersion) — and the Accessible lock when accessible (labels and display text ≥ 7:1).

Throws UnsupportedEngineVersion for versions this build cannot reproduce, and ArgumentError for ThemeFamily.plain and for families engineVersion has not shipped (their placeholder definitions are not frozen, so their output would not be a pure function of the version).

seedHueTenths (0–3599, M3 Expressive only) is the Android "Match my wallpaper" variant (spec §5.3 #1): it replaces the palette stream's base-hue draw (every other draw is unchanged), the result is marked ThemeVariant.wallpaper, and every guardrail runs exactly as for a generated theme.

Implementation

ThemeSpec generate(
  int seed,
  ThemeFamily family,
  int engineVersion, {
  bool accessible = false,
  int? seedHueTenths,
}) {
  if (!supportedEngineVersions.contains(engineVersion)) {
    throw UnsupportedEngineVersion(engineVersion);
  }
  if (family == ThemeFamily.plain) {
    throw ArgumentError.value(family, 'family', 'plain is never generated');
  }
  if (!familyShippedAt(family, engineVersion)) {
    throw ArgumentError.value(
      family,
      'family',
      'not shipped at engine version $engineVersion',
    );
  }
  if (seedHueTenths != null && family != ThemeFamily.m3Expressive) {
    throw ArgumentError.value(
      family,
      'family',
      'only Material 3 Expressive has a wallpaper variant',
    );
  }
  final s = seed & 0xFFFFFFFF;
  for (var attempt = 0; attempt < maxAttempts; attempt++) {
    final candidate = buildCandidate(
      s,
      family,
      engineVersion,
      attempt: attempt,
      accessible: accessible,
      seedHueTenths: seedHueTenths,
    );
    final fixed = repairTheme(candidate);
    if (fixed != null) return fixed;
  }
  return heroFallback(s, family, accessible: accessible);
}