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/widget/tab_visibility_test.dart

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+import 'package:flutter_test/flutter_test.dart';
+import 'package:halkyon_ui/halkyon_ui.dart';
+import 'package:material_ui/material_ui.dart';
+
+import '../support/test_app.dart';
+
+void main() {
+  /// Pumps [child] under a screen tint, in a medium window, so a gradient
+  /// in it claims its colour while in view.
+  Future<ScreenTint> show(WidgetTester tester, {required bool visible}) async {
+    tester.view.physicalSize = const Size(800, 600);
+    tester.view.devicePixelRatio = 1;
+    addTearDown(tester.view.reset);
+    final tint = ScreenTint();
+    addTearDown(tint.dispose);
+    await tester.pumpWidget(
+      testApp(
+        ScreenTintScope(
+          notifier: tint,
+          child: TabVisibility(
+            visible: visible,
+            child: const TopGradient(
+              color: Color(0xFFBA1E55),
+              background: Color(0xFFFFFFFF),
+              child: SizedBox.expand(),
+            ),
+          ),
+        ),
+      ),
+    );
+    await tester.pump();
+    return tint;
+  }
+
+  testWidgets('a screen whose tab shows gives the frame its colour', (
+    tester,
+  ) async {
+    final tint = await show(tester, visible: true);
+
+    expect(tint.color, const Color(0xFFBA1E55));
+  });
+
+  testWidgets("a hidden tab's screen leaves the frame's colour alone", (
+    tester,
+  ) async {
+    final tint = await show(tester, visible: false);
+
+    expect(tint.color, Brand.primary);
+  });
+
+  testWidgets('outside any tabs, a screen counts as shown', (tester) async {
+    late bool visible;
+    await tester.pumpWidget(
+      Builder(
+        builder: (context) {
+          visible = TabVisibility.of(context);
+          return const SizedBox();
+        },
+      ),
+    );
+
+    expect(visible, isTrue);
+  });
+}