full theme extension with design tokens

snippet.dart

// Copyright 2026 Fredrick Allan Grott. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//
// Modified from m3e_design package
// Copyright (c) 2025 Emily Moonstone
// MIT Licnese

// ignore_for_file: prefer_constructors_over_static_methods

import 'package:flutter/material.dart';
import 'package:material_expressive_collection/src/tokens/m_3_e_custom__shapes.dart';
import 'package:material_expressive_collection/src/tokens/m_3_e_custom_color_tokens.dart';
import 'package:material_expressive_collection/src/tokens/m_3_e_custom_motion.dart';
import 'package:material_expressive_collection/src/tokens/m_3_e_custom_spacing.dart';
import 'package:material_expressive_collection/src/tokens/m_3_e_custom_typography_tokens.dart';

/// Typically it is used in this manner:
///
/// ```dart
/// @override
///  Widget build(BuildContext context) {
///    final light = ColorScheme.fromSeed(
///        seedColor: Colors.purple, brightness: Brightness.light);
///    final dark = ColorScheme.fromSeed(
///        seedColor: Colors.purple, brightness: Brightness.dark);
///    return MaterialApp(
///      title: 'M3E Gallery',
///      theme: light.toM3EThemeData(override: m3eOverride, base: themeDataWithCustomComponentThemes ),
///      darkTheme: dark.toM3EThemeData(),
///      themeMode: _mode,
///      home: GalleryHome(
///        isDark: _mode == ThemeMode.dark,
///        onToggleBrightness: _toggleMode,
///      ),
///      debugShowCheckedModeBanner: false,
///    );
///  }
/// ```
///
/// Typically an m3eOverride is used so as to provide the custom GoogleFont stuff via the
/// text theme and the expressive text themes and ThemeData base to supply the custom 
/// component themes especially if you use FlexColorScheme package to generate 
/// component themes.
@immutable
class M3ETheme extends ThemeExtension<M3ETheme> {
  final M3ECustomColors colors;
  final M3ECustomTypography typography;
  final M3ECustomShapes shapes;
  final M3ECustomSpacing spacing;
  final M3EMotion motion;

  const M3ETheme({
    required this.colors,
    required this.typography,
    required this.shapes,
    required this.spacing,
    required this.motion,
  });

  // Convenience proxy for commonly used text styles in packages (m3e.type.*)
  @override
  _M3ETypeProxy get type => _M3ETypeProxy(typography);

  static M3ETheme defaults(ColorScheme scheme) => M3ETheme(
    colors: M3ECustomColors.from(scheme),
    typography: M3ECustomTypography.defaultFor(scheme.brightness),
    shapes: M3ECustomShapes.expressive(),
    spacing: const M3ECustomSpacing.regular(),
    motion: const M3EMotion.expressive(),
  );

  @override
  M3ETheme copyWith({
    M3ECustomColors? colors,
    M3ECustomTypography? typography,
    M3ECustomShapes? shapes,
    M3ECustomSpacing? spacing,
    M3EMotion? motion,
  }) => M3ETheme(
    colors: colors ?? this.colors,
    typography: typography ?? this.typography,
    shapes: shapes ?? this.shapes,
    spacing: spacing ?? this.spacing,
    motion: motion ?? this.motion,
  );

  @override
  M3ETheme lerp(covariant M3ETheme? other, double t) {
    if (other == null) return this;
    return M3ETheme(
      colors: M3ECustomColors.lerp(colors, other.colors, t),
      typography: M3ECustomTypography.lerp(typography, other.typography, t),
      shapes: M3ECustomShapes.lerp(shapes, other.shapes, t),
      spacing: M3ECustomSpacing.lerp(spacing, other.spacing, t),
      motion: M3EMotion.lerp(motion, other.motion, t),
    );
  }
}