Halkyon's shared packages

A pub workspace of the Dart packages Halkyon's apps share: halkyon_ui,
Halkyon's look (the theme, fonts, layout and shared widgets, with texts
in English and German), halkyon_core's low-level primitives and
halkyon_interop's cross-app contracts. Dart 3.13 with LeanCode's lints,
configured once at the root; apps take a package by git, pinned to a
signed commit.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

packages/halkyon_ui/test/theme/theme_test.dart

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+import 'dart:math';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:halkyon_ui/halkyon_ui.dart';
+import 'package:material_ui/material_ui.dart';
+
+/// WCAG's contrast ratio of two colours, from 1 (none) to 21.
+double _contrast(Color a, Color b) {
+  final (lighter, darker) = (
+    max(a.computeLuminance(), b.computeLuminance()),
+    min(a.computeLuminance(), b.computeLuminance()),
+  );
+  return (lighter + 0.05) / (darker + 0.05);
+}
+
+/// An app's own colours, beside the shared ones.
+final class const _AppColors(final Color special)
+    extends ThemeExtension<_AppColors> {
+  @override
+  _AppColors copyWith({Color? special}) => _AppColors(special ?? this.special);
+
+  @override
+  _AppColors lerp(_AppColors? other, double t) =>
+      other == null ? this : _AppColors(Color.lerp(special, other.special, t)!);
+}
+
+void main() {
+  group('the picker palette', () {
+    test('has the 20 colours content can be given', () {
+      expect(PaletteColor.values, hasLength(20));
+    });
+
+    for (final color in PaletteColor.values) {
+      test(
+        '${color.name}: its text colour is readable on its fill (WCAG AA)',
+        () {
+          expect(
+            _contrast(color.foreground, color.background),
+            greaterThanOrEqualTo(4.5),
+          );
+        },
+      );
+    }
+
+    test(
+      'finds a colour by its stored name, and nothing for an unknown one',
+      () {
+        expect(PaletteColor.byName('cobalt'), PaletteColor.cobalt);
+        expect(PaletteColor.byName('ultraviolet'), isNull);
+        expect(PaletteColor.byName(null), isNull);
+      },
+    );
+  });
+
+  group('the theme', () {
+    for (final brightness in Brightness.values) {
+      test('$brightness: Material 3, with the status colours', () {
+        final theme = appTheme(brightness);
+
+        expect(theme.useMaterial3, isTrue);
+        expect(theme.colorScheme.brightness, brightness);
+        expect(theme.extras, isA<ThemeExtras>());
+      });
+    }
+
+    test("takes an app's own extensions beside the shared ones", () {
+      const colors = _AppColors(Color(0xFF123456));
+
+      final theme = appTheme(Brightness.light, extensions: [colors]);
+
+      expect(theme.extension<_AppColors>(), colors);
+      expect(theme.extras, ThemeExtras.light);
+    });
+
+    test('light: cobalt is the primary colour, copper the accent', () {
+      final scheme = appTheme(Brightness.light).colorScheme;
+
+      expect(scheme.primary, Brand.primary);
+      expect(scheme.tertiary, Brand.accent);
+    });
+
+    test("dark: the primary colour's text stays readable", () {
+      final scheme = appTheme(Brightness.dark).colorScheme;
+
+      expect(
+        _contrast(scheme.onPrimary, scheme.primary),
+        greaterThanOrEqualTo(4.5),
+      );
+      expect(
+        _contrast(scheme.onSurface, scheme.surface),
+        greaterThanOrEqualTo(4.5),
+      );
+    });
+
+    test("the navigation bar is Material 3 Expressive's shorter one", () {
+      expect(appTheme(Brightness.light).navigationBarTheme.height, 64);
+    });
+  });
+}