ui(motion): TabStrip Reduced cubic indicator (#493)

lib/core/motion/querya_spring_controller.dart

@@ -8,14 +8,19 @@ import 'querya_spring.dart';
 /// Drives a scalar with interruptible / redirectable spring motion.
 ///
 /// Call [animateTo] to retarget; the current presentation value and velocity
-/// are preserved (no brick-wall). When [useSprings] is false, snaps via
-/// [jumpTo].
+/// are preserved (no brick-wall).
+///
+/// When [useSprings] is false:
+/// - if [cubicDuration] is non-null and non-zero → duration-token cubic (#493)
+/// - otherwise → snap via [jumpTo] (Off / drag settle)
 class QueryaSpringController extends ChangeNotifier {
   QueryaSpringController({
     required TickerProvider vsync,
     double value = 0,
     this.spring = QueryaSpring.snappy,
     this.useSprings = true,
+    this.cubicDuration,
+    this.cubicCurve = Curves.easeOutCubic,
   }) : _value = value,
        _target = value {
     _ticker = vsync.createTicker(_onTick);
@@ -24,13 +29,21 @@ class QueryaSpringController extends ChangeNotifier {
   SpringDescription spring;
   bool useSprings;
 
+  /// Cubic fallback when springs are off (Reduced motion). Null / zero → snap.
+  Duration? cubicDuration;
+  Curve cubicCurve;
+
   late final Ticker _ticker;
   double _value;
   double _velocity = 0;
   double _target;
   SpringSimulation? _simulation;
   Duration? _simulationStart;
 
+  double? _cubicFrom;
+  Duration? _cubicTotal;
+  Curve? _cubicActiveCurve;
+
   double get value => _value;
   double get velocity => _velocity;
   double get target => _target;
@@ -39,8 +52,7 @@ class QueryaSpringController extends ChangeNotifier {
   /// Instantly sets value (and clears velocity).
   void jumpTo(double value) {
     _ticker.stop();
-    _simulation = null;
-    _simulationStart = null;
+    _clearMotion();
     _velocity = 0;
     _target = value;
     if (_value == value) return;
@@ -54,7 +66,12 @@ class QueryaSpringController extends ChangeNotifier {
     final startVelocity = velocity ?? _velocity;
 
     if (!useSprings) {
-      jumpTo(target);
+      final duration = cubicDuration;
+      if (duration == null || duration == Duration.zero) {
+        jumpTo(target);
+        return;
+      }
+      _startCubic(target, duration);
       return;
     }
 
@@ -63,6 +80,9 @@ class QueryaSpringController extends ChangeNotifier {
       return;
     }
 
+    _cubicFrom = null;
+    _cubicTotal = null;
+    _cubicActiveCurve = null;
     _simulation = QueryaSpring.simulation(
       description: spring,
       start: _value,
@@ -75,7 +95,37 @@ class QueryaSpringController extends ChangeNotifier {
     }
   }
 
+  void _startCubic(double target, Duration duration) {
+    if ((_value - target).abs() < 0.0001) {
+      jumpTo(target);
+      return;
+    }
+    _simulation = null;
+    _cubicFrom = _value;
+    _cubicTotal = duration;
+    _cubicActiveCurve = cubicCurve;
+    _velocity = 0;
+    _simulationStart = null;
+    if (!_ticker.isActive) {
+      _ticker.start();
+    }
+  }
+
+  void _clearMotion() {
+    _simulation = null;
+    _simulationStart = null;
+    _cubicFrom = null;
+    _cubicTotal = null;
+    _cubicActiveCurve = null;
+  }
+
   void _onTick(Duration elapsed) {
+    final cubicTotal = _cubicTotal;
+    if (cubicTotal != null) {
+      _onCubicTick(elapsed, cubicTotal);
+      return;
+    }
+
     final simulation = _simulation;
     if (simulation == null) {
       _ticker.stop();
@@ -93,8 +143,7 @@ class QueryaSpringController extends ChangeNotifier {
     if (settled) {
       _value = _target;
       _velocity = 0;
-      _simulation = null;
-      _simulationStart = null;
+      _clearMotion();
       _ticker.stop();
       notifyListeners();
       return;
@@ -104,6 +153,33 @@ class QueryaSpringController extends ChangeNotifier {
     notifyListeners();
   }
 
+  void _onCubicTick(Duration elapsed, Duration cubicTotal) {
+    _simulationStart ??= elapsed;
+    final micros = cubicTotal.inMicroseconds;
+    if (micros <= 0) {
+      jumpTo(_target);
+      return;
+    }
+    final t =
+        (elapsed - _simulationStart!).inMicroseconds / micros;
+    final from = _cubicFrom ?? _value;
+    final curve = _cubicActiveCurve ?? cubicCurve;
+
+    if (t >= 1) {
+      _value = _target;
+      _velocity = 0;
+      _clearMotion();
+      _ticker.stop();
+      notifyListeners();
+      return;
+    }
+
+    final curved = curve.transform(t.clamp(0.0, 1.0));
+    _value = from + (_target - from) * curved;
+    _velocity = 0;
+    notifyListeners();
+  }
+
   @override
   void dispose() {
     _ticker.dispose();

lib/shared/widgets/querya_tab_strip.dart

@@ -9,10 +9,11 @@ import 'package:shadcn_flutter/shadcn_flutter.dart';
 
 /// A compact, keyboard-operable tab strip using Querya's motion and theme.
 ///
-/// Selection uses a sliding pill indicator (spring when [QueryaSpring.springsEnabled])
-/// so tab changes feel continuous / redirectable.
+/// Selection uses a sliding pill indicator: spring when Full
+/// ([QueryaSpring.springsEnabled]), duration-token cubic under Reduced (#493),
+/// snap when Off / OS `disableAnimations`.
 ///
-/// Spring ticks rebuild only the pill ([_TabStripIndicator]), not the tab row.
+/// Spring/cubic ticks rebuild only the pill ([_TabStripIndicator]), not the tab row.
 class QueryaTabStrip extends material.StatefulWidget {
   const QueryaTabStrip({
     super.key,
@@ -55,6 +56,18 @@ class _QueryaTabStripState extends material.State<QueryaTabStrip>
     final springs = QueryaSpring.springsEnabled(context);
     _indicatorLeft.useSprings = springs;
     _indicatorWidth.useSprings = springs;
+
+    // Reduced: animate with halved fast token; Off / disableAnimations → snap.
+    Duration? cubic;
+    if (!springs) {
+      final d = context.motionDuration(QueryaMotion.fast);
+      if (d > Duration.zero) cubic = d;
+    }
+    final curve = context.motionCurve(QueryaMotion.enter);
+    _indicatorLeft.cubicDuration = cubic;
+    _indicatorWidth.cubicDuration = cubic;
+    _indicatorLeft.cubicCurve = curve;
+    _indicatorWidth.cubicCurve = curve;
   }
 
   @override

test/core/motion/querya_spring_test.dart

@@ -251,6 +251,47 @@ void main() {
       expect(controller.isAnimating, isFalse);
     });
 
+    testWidgets('cubics when springs off and cubicDuration set', (tester) async {
+      late QueryaSpringController controller;
+      await tester.pumpWidget(
+        MaterialApp(
+          home: _SpringHost(
+            useSprings: false,
+            cubicDuration: const Duration(milliseconds: 100),
+            onCreated: (c) => controller = c,
+          ),
+        ),
+      );
+
+      controller.animateTo(1);
+      await tester.pump();
+      await tester.pump(const Duration(milliseconds: 40));
+      expect(controller.value, greaterThan(0));
+      expect(controller.value, lessThan(1));
+      expect(controller.isAnimating, isTrue);
+
+      await tester.pumpAndSettle();
+      expect(controller.value, closeTo(1, 0.001));
+      expect(controller.isAnimating, isFalse);
+    });
+
+    testWidgets('cubic Duration.zero snaps', (tester) async {
+      late QueryaSpringController controller;
+      await tester.pumpWidget(
+        MaterialApp(
+          home: _SpringHost(
+            useSprings: false,
+            cubicDuration: Duration.zero,
+            onCreated: (c) => controller = c,
+          ),
+        ),
+      );
+
+      controller.animateTo(1);
+      expect(controller.value, 1);
+      expect(controller.isAnimating, isFalse);
+    });
+
     testWidgets('notifies listeners on animate', (tester) async {
       late QueryaSpringController controller;
       var notifications = 0;
@@ -295,11 +336,13 @@ class _SpringHost extends StatefulWidget {
     required this.onCreated,
     this.useSprings = true,
     this.spring = QueryaSpring.snappy,
+    this.cubicDuration,
   });
 
   final ValueChanged<QueryaSpringController> onCreated;
   final bool useSprings;
   final SpringDescription spring;
+  final Duration? cubicDuration;
 
   @override
   State<_SpringHost> createState() => _SpringHostState();
@@ -316,6 +359,7 @@ class _SpringHostState extends State<_SpringHost>
       vsync: this,
       useSprings: widget.useSprings,
       spring: widget.spring,
+      cubicDuration: widget.cubicDuration,
     );
     widget.onCreated(_controller);
   }

test/shared/querya_tab_strip_test.dart

@@ -201,6 +201,45 @@ void main() {
     );
   });
 
+  testWidgets('reduced motion slides indicator with cubic (not snap)',
+      (tester) async {
+    var selected = 0;
+    await tester.pumpWidget(
+      stripShell(
+        level: QueryaMotionLevel.reduced,
+        child: material.StatefulBuilder(
+          builder: (context, setState) => material.Center(
+            child: QueryaTabStrip(
+              labels: const ['Server', 'SQL', 'History'],
+              selectedIndex: selected,
+              onSelected: (index) => setState(() => selected = index),
+            ),
+          ),
+        ),
+      ),
+    );
+    await tester.pump();
+    await tester.pumpAndSettle();
+
+    final startLeft = indicatorOf(tester).left!;
+
+    await tester.tap(find.bySemanticsLabel('History'));
+    await tester.pump();
+    await tester.pump(); // post-frame sync starts cubic
+    await tester.pump(const Duration(milliseconds: 20));
+
+    final midLeft = indicatorOf(tester).left!;
+    expect(midLeft, greaterThan(startLeft));
+    final history =
+        tester.getRect(find.byKey(const material.ValueKey('querya_tab_History')));
+    final strip = tester.getRect(find.byType(QueryaTabStrip));
+    final endLeft = history.left - strip.left;
+    expect(midLeft, lessThan(endLeft - 0.5));
+
+    await tester.pumpAndSettle();
+    expect(indicatorOf(tester).left, closeTo(endLeft, 1.0));
+  });
+
   testWidgets('redirect mid-slide settles on final selection', (tester) async {
     var selected = 0;
     await tester.pumpWidget(