add AnimatedScale and AnimatedRotation widgets (#83428)

packages/flutter/lib/src/widgets/implicit_animations.dart

@@ -255,6 +255,8 @@ class TextStyleTween extends Tween<TextStyle> {
 ///    [Container].
 ///  * [AnimatedDefaultTextStyle], which is an implicitly animated version of
 ///    [DefaultTextStyle].
+///  * [AnimatedScale], which is an implicitly animated version of [Transform.scale].
+///  * [AnimatedRotation], which is an implicitly animated version of [Transform.rotate].
 ///  * [AnimatedOpacity], which is an implicitly animated version of [Opacity].
 ///  * [AnimatedPadding], which is an implicitly animated version of [Padding].
 ///  * [AnimatedPhysicalModel], which is an implicitly animated version of
@@ -1410,6 +1412,265 @@ class _AnimatedPositionedDirectionalState extends AnimatedWidgetBaseState<Animat
   }
 }
 
+/// Animated version of [Transform.scale] which automatically transitions the child's
+/// scale over a given duration whenever the given scale changes.
+///
+/// {@tool snippet}
+///
+/// This code defines a widget that uses [AnimatedScale] to change the size
+/// of [FlutterLogo] gradually to a new scale whenever the button is pressed.
+///
+/// ```dart
+/// class LogoScale extends StatefulWidget {
+///   const LogoScale({Key? key}) : super(key: key);
+///
+///   @override
+///   State<LogoScale> createState() => LogoScaleState();
+/// }
+///
+/// class LogoScaleState extends State<LogoScale> {
+///   double scale = 1.0;
+///
+///   void _changeScale() {
+///     setState(() => scale = scale == 1.0 ? 3.0 : 1.0);
+///   }
+///
+///   @override
+///   Widget build(BuildContext context) {
+///     return Column(
+///       mainAxisAlignment: MainAxisAlignment.center,
+///       children: <Widget>[
+///         ElevatedButton(
+///           child: const Text('Scale Logo'),
+///           onPressed: _changeScale,
+///         ),
+///         Padding(
+///           padding: const EdgeInsets.all(50),
+///           child: AnimatedScale(
+///             scale: scale,
+///             duration: const Duration(seconds: 2),
+///             child: const FlutterLogo(),
+///           ),
+///         ),
+///       ],
+///     );
+///   }
+/// }
+/// ```
+/// {@end-tool}
+///
+/// See also:
+///
+///  * [AnimatedRotation], for animating the rotation of a child.
+///  * [AnimatedSize], for animating the resize of a child based on changes
+///    in layout.
+///  * [ScaleTransition], an explicitly animated version of this widget, where
+///    an [Animation] is provided by the caller instead of being built in.
+class AnimatedScale extends ImplicitlyAnimatedWidget {
+  /// Creates a widget that animates its scale implicitly.
+  ///
+  /// The [scale] argument must not be null.
+  /// The [curve] and [duration] arguments must not be null.
+  const AnimatedScale({
+    Key? key,
+    this.child,
+    required this.scale,
+    this.alignment = Alignment.center,
+    this.filterQuality,
+    Curve curve = Curves.linear,
+    required Duration duration,
+    VoidCallback? onEnd,
+  }) : assert(scale != null),
+       super(key: key, curve: curve, duration: duration, onEnd: onEnd);
+
+  /// The widget below this widget in the tree.
+  ///
+  /// {@macro flutter.widgets.ProxyWidget.child}
+  final Widget? child;
+
+  /// The target scale.
+  ///
+  /// The scale must not be null.
+  final double scale;
+
+  /// The alignment of the origin of the coordinate system in which the scale
+  /// takes place, relative to the size of the box.
+  ///
+  /// For example, to set the origin of the scale to bottom middle, you can use
+  /// an alignment of (0.0, 1.0).
+  final Alignment alignment;
+
+  /// The filter quality with which to apply the transform as a bitmap operation.
+  ///
+  /// {@macro flutter.widgets.Transform.optional.FilterQuality}
+  final FilterQuality? filterQuality;
+
+  @override
+  ImplicitlyAnimatedWidgetState<AnimatedScale> createState() => _AnimatedScaleState();
+
+  @override
+  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
+    super.debugFillProperties(properties);
+    properties.add(DoubleProperty('scale', scale));
+    properties.add(DiagnosticsProperty<Alignment>('alignment', alignment, defaultValue: Alignment.center));
+    properties.add(EnumProperty<FilterQuality>('filterQuality', filterQuality, defaultValue: null));
+  }
+}
+
+class _AnimatedScaleState extends ImplicitlyAnimatedWidgetState<AnimatedScale> {
+  Tween<double>? _scale;
+  late Animation<double> _scaleAnimation;
+
+  @override
+  void forEachTween(TweenVisitor<dynamic> visitor) {
+    _scale = visitor(_scale, widget.scale, (dynamic value) => Tween<double>(begin: value as double)) as Tween<double>?;
+  }
+
+  @override
+  void didUpdateTweens() {
+    _scaleAnimation = animation.drive(_scale!);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return ScaleTransition(
+      scale: _scaleAnimation,
+      alignment: widget.alignment,
+      filterQuality: widget.filterQuality,
+      child: widget.child,
+    );
+  }
+}
+
+/// Animated version of [Transform.rotate] which automatically transitions the child's
+/// rotation over a given duration whenever the given rotation changes.
+///
+/// {@tool snippet}
+///
+/// This code defines a widget that uses [AnimatedRotation] to rotate a [FlutterLogo]
+/// gradually by an eighth of a turn (45 degrees) with each press of the button.
+///
+/// ```dart
+/// class LogoRotate extends StatefulWidget {
+///   const LogoRotate({Key? key}) : super(key: key);
+///
+///   @override
+///   State<LogoRotate> createState() => LogoRotateState();
+/// }
+///
+/// class LogoRotateState extends State<LogoRotate> {
+///   double turns = 0.0;
+///
+///   void _changeRotation() {
+///     setState(() => turns += 1.0 / 8.0);
+///   }
+///
+///   @override
+///   Widget build(BuildContext context) {
+///     return Column(
+///       mainAxisAlignment: MainAxisAlignment.center,
+///       children: <Widget>[
+///         ElevatedButton(
+///           child: const Text('Rotate Logo'),
+///           onPressed: _changeRotation,
+///         ),
+///         Padding(
+///           padding: const EdgeInsets.all(50),
+///           child: AnimatedRotation(
+///             turns: turns,
+///             duration: const Duration(seconds: 1),
+///             child: const FlutterLogo(),
+///           ),
+///         ),
+///       ],
+///     );
+///   }
+/// }
+/// ```
+/// {@end-tool}
+///
+/// See also:
+///
+///  * [AnimatedScale], for animating the scale of a child.
+///  * [RotationTransition], an explicitly animated version of this widget, where
+///    an [Animation] is provided by the caller instead of being built in.
+class AnimatedRotation extends ImplicitlyAnimatedWidget {
+  /// Creates a widget that animates its rotation implicitly.
+  ///
+  /// The [turns] argument must not be null.
+  /// The [curve] and [duration] arguments must not be null.
+  const AnimatedRotation({
+    Key? key,
+    this.child,
+    required this.turns,
+    this.alignment = Alignment.center,
+    this.filterQuality,
+    Curve curve = Curves.linear,
+    required Duration duration,
+    VoidCallback? onEnd,
+  }) : assert(turns != null),
+        super(key: key, curve: curve, duration: duration, onEnd: onEnd);
+
+  /// The widget below this widget in the tree.
+  ///
+  /// {@macro flutter.widgets.ProxyWidget.child}
+  final Widget? child;
+
+  /// The animation that controls the rotation of the child.
+  ///
+  /// If the current value of the turns animation is v, the child will be
+  /// rotated v * 2 * pi radians before being painted.
+  final double turns;
+
+  /// The alignment of the origin of the coordinate system in which the rotation
+  /// takes place, relative to the size of the box.
+  ///
+  /// For example, to set the origin of the rotation to bottom middle, you can use
+  /// an alignment of (0.0, 1.0).
+  final Alignment alignment;
+
+  /// The filter quality with which to apply the transform as a bitmap operation.
+  ///
+  /// {@macro flutter.widgets.Transform.optional.FilterQuality}
+  final FilterQuality? filterQuality;
+
+  @override
+  ImplicitlyAnimatedWidgetState<AnimatedRotation> createState() => _AnimatedRotationState();
+
+  @override
+  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
+    super.debugFillProperties(properties);
+    properties.add(DoubleProperty('turns', turns));
+    properties.add(DiagnosticsProperty<Alignment>('alignment', alignment, defaultValue: Alignment.center));
+    properties.add(EnumProperty<FilterQuality>('filterQuality', filterQuality, defaultValue: null));
+  }
+}
+
+class _AnimatedRotationState extends ImplicitlyAnimatedWidgetState<AnimatedRotation> {
+  Tween<double>? _turns;
+  late Animation<double> _turnsAnimation;
+
+  @override
+  void forEachTween(TweenVisitor<dynamic> visitor) {
+    _turns = visitor(_turns, widget.turns, (dynamic value) => Tween<double>(begin: value as double)) as Tween<double>?;
+  }
+
+  @override
+  void didUpdateTweens() {
+    _turnsAnimation = animation.drive(_turns!);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return RotationTransition(
+      turns: _turnsAnimation,
+      alignment: widget.alignment,
+      filterQuality: widget.filterQuality,
+      child: widget.child,
+    );
+  }
+}
+
 /// Animated version of [Opacity] which automatically transitions the child's
 /// opacity over a given duration whenever the given opacity changes.
 ///

packages/flutter/test/widgets/implicit_animations_test.dart

@@ -171,6 +171,122 @@ void main() {
     expect(mockOnEndFunction.called, 1);
   });
 
+  testWidgets('AnimatedScale onEnd callback test', (WidgetTester tester) async {
+    await tester.pumpWidget(wrap(
+      child: TestAnimatedWidget(
+        callback: mockOnEndFunction.handler,
+        switchKey: switchKey,
+        state: _TestAnimatedScaleWidgetState(),
+      ),
+    ));
+
+    final Finder widgetFinder = find.byKey(switchKey);
+
+    await tester.tap(widgetFinder);
+    await tester.pump();
+    expect(mockOnEndFunction.called, 0);
+    await tester.pump(animationDuration);
+    expect(mockOnEndFunction.called, 0);
+    await tester.pump(additionalDelay);
+    expect(mockOnEndFunction.called, 1);
+  });
+
+  testWidgets('AnimatedScale transition test', (WidgetTester tester) async {
+    await tester.pumpWidget(wrap(
+      child: TestAnimatedWidget(
+        switchKey: switchKey,
+        state: _TestAnimatedScaleWidgetState(),
+      ),
+    ));
+
+    final RebuildCountingState<StatefulWidget> state = tester.widget<TestAnimatedWidget>(
+      find.byType(TestAnimatedWidget)
+    ).rebuildState!;
+    final Finder switchFinder = find.byKey(switchKey);
+    final ScaleTransition scaleWidget = tester.widget<ScaleTransition>(
+      find.ancestor(
+        of: find.byType(Placeholder),
+        matching: find.byType(ScaleTransition),
+      ).first,
+    );
+
+    expect(state.builds, equals(1));
+
+    await tester.tap(switchFinder);
+    expect(state.builds, equals(1));
+    await tester.pump();
+    expect(scaleWidget.scale.value, equals(1.0));
+    expect(state.builds, equals(2));
+
+    await tester.pump(const Duration(milliseconds: 500));
+    expect(scaleWidget.scale.value, equals(1.5));
+    expect(state.builds, equals(2));
+    await tester.pump(const Duration(milliseconds: 250));
+    expect(scaleWidget.scale.value, equals(1.75));
+    expect(state.builds, equals(2));
+    await tester.pump(const Duration(milliseconds: 250));
+    expect(scaleWidget.scale.value, equals(2.0));
+    expect(state.builds, equals(2));
+  });
+
+  testWidgets('AnimatedRotation onEnd callback test', (WidgetTester tester) async {
+    await tester.pumpWidget(wrap(
+      child: TestAnimatedWidget(
+        callback: mockOnEndFunction.handler,
+        switchKey: switchKey,
+        state: _TestAnimatedRotationWidgetState(),
+      ),
+    ));
+
+    final Finder widgetFinder = find.byKey(switchKey);
+
+    await tester.tap(widgetFinder);
+    await tester.pump();
+    expect(mockOnEndFunction.called, 0);
+    await tester.pump(animationDuration);
+    expect(mockOnEndFunction.called, 0);
+    await tester.pump(additionalDelay);
+    expect(mockOnEndFunction.called, 1);
+  });
+
+  testWidgets('AnimatedRotation transition test', (WidgetTester tester) async {
+    await tester.pumpWidget(wrap(
+      child: TestAnimatedWidget(
+        switchKey: switchKey,
+        state: _TestAnimatedRotationWidgetState(),
+      ),
+    ));
+
+    final RebuildCountingState<StatefulWidget> state = tester.widget<TestAnimatedWidget>(
+        find.byType(TestAnimatedWidget)
+    ).rebuildState!;
+    final Finder switchFinder = find.byKey(switchKey);
+    final RotationTransition rotationWidget = tester.widget<RotationTransition>(
+      find.ancestor(
+        of: find.byType(Placeholder),
+        matching: find.byType(RotationTransition),
+      ).first,
+    );
+
+    expect(state.builds, equals(1));
+
+    await tester.tap(switchFinder);
+    expect(state.builds, equals(1));
+    await tester.pump();
+    expect(rotationWidget.turns.value, equals(0.0));
+    expect(state.builds, equals(2));
+
+    await tester.pump(const Duration(milliseconds: 500));
+    expect(rotationWidget.turns.value, equals(0.75));
+    expect(state.builds, equals(2));
+    await tester.pump(const Duration(milliseconds: 250));
+    expect(rotationWidget.turns.value, equals(1.125));
+    expect(state.builds, equals(2));
+    await tester.pump(const Duration(milliseconds: 250));
+    expect(rotationWidget.turns.value, equals(1.5));
+    expect(state.builds, equals(2));
+  });
+
   testWidgets('AnimatedOpacity onEnd callback test', (WidgetTester tester) async {
     await tester.pumpWidget(wrap(
       child: TestAnimatedWidget(
@@ -199,6 +315,9 @@ void main() {
       ),
     ));
 
+    final RebuildCountingState<StatefulWidget> state = tester.widget<TestAnimatedWidget>(
+        find.byType(TestAnimatedWidget)
+    ).rebuildState!;
     final Finder switchFinder = find.byKey(switchKey);
     final FadeTransition opacityWidget = tester.widget<FadeTransition>(
       find.ancestor(
@@ -207,16 +326,23 @@ void main() {
       ).first,
     );
 
+    expect(state.builds, equals(1));
+
     await tester.tap(switchFinder);
+    expect(state.builds, equals(1));
     await tester.pump();
     expect(opacityWidget.opacity.value, equals(0.0));
+    expect(state.builds, equals(2));
 
     await tester.pump(const Duration(milliseconds: 500));
     expect(opacityWidget.opacity.value, equals(0.5));
+    expect(state.builds, equals(2));
     await tester.pump(const Duration(milliseconds: 250));
     expect(opacityWidget.opacity.value, equals(0.75));
+    expect(state.builds, equals(2));
     await tester.pump(const Duration(milliseconds: 250));
     expect(opacityWidget.opacity.value, equals(1.0));
+    expect(state.builds, equals(2));
   });
 
 
@@ -247,6 +373,9 @@ void main() {
       ),
     ));
 
+    final RebuildCountingState<StatefulWidget> state = tester.widget<TestAnimatedWidget>(
+        find.byType(TestAnimatedWidget)
+    ).rebuildState!;
     final Finder switchFinder = find.byKey(switchKey);
     final SliverFadeTransition opacityWidget = tester.widget<SliverFadeTransition>(
       find.ancestor(
@@ -255,16 +384,23 @@ void main() {
       ).first,
     );
 
+    expect(state.builds, equals(1));
+
     await tester.tap(switchFinder);
+    expect(state.builds, equals(1));
     await tester.pump();
     expect(opacityWidget.opacity.value, equals(0.0));
+    expect(state.builds, equals(2));
 
     await tester.pump(const Duration(milliseconds: 500));
     expect(opacityWidget.opacity.value, equals(0.5));
+    expect(state.builds, equals(2));
     await tester.pump(const Duration(milliseconds: 250));
     expect(opacityWidget.opacity.value, equals(0.75));
+    expect(state.builds, equals(2));
     await tester.pump(const Duration(milliseconds: 250));
     expect(opacityWidget.opacity.value, equals(1.0));
+    expect(state.builds, equals(2));
   });
 
   testWidgets('AnimatedDefaultTextStyle onEnd callback test', (WidgetTester tester) async {
@@ -414,6 +550,10 @@ Widget wrap({required Widget child}) {
   );
 }
 
+abstract class RebuildCountingState<T extends StatefulWidget> extends State<T> {
+  int builds = 0;
+}
+
 class TestAnimatedWidget extends StatefulWidget {
   const TestAnimatedWidget({
     Key? key,
@@ -425,11 +565,14 @@ class TestAnimatedWidget extends StatefulWidget {
   final Key switchKey;
   final State<StatefulWidget> state;
 
+  RebuildCountingState<StatefulWidget>? get rebuildState =>
+    state is RebuildCountingState<StatefulWidget> ? state as RebuildCountingState<StatefulWidget> : null;
+
   @override
   State<StatefulWidget> createState() => state; // ignore: no_logic_in_create_state, this test predates the lint
 }
 
-abstract class _TestAnimatedWidgetState extends State<TestAnimatedWidget> {
+abstract class _TestAnimatedWidgetState extends RebuildCountingState<TestAnimatedWidget> {
   bool toggle = false;
   final Widget child = const Placeholder();
   final Duration duration = animationDuration;
@@ -444,6 +587,7 @@ abstract class _TestAnimatedWidgetState extends State<TestAnimatedWidget> {
 
   @override
   Widget build(BuildContext context) {
+    builds++;
     final Widget animatedWidget = getAnimatedWidget();
 
     return Stack(
@@ -516,6 +660,30 @@ class _TestAnimatedPositionedDirectionalWidgetState extends _TestAnimatedWidgetS
   }
 }
 
+class _TestAnimatedScaleWidgetState extends _TestAnimatedWidgetState {
+  @override
+  Widget getAnimatedWidget() {
+    return AnimatedScale(
+      duration: duration,
+      onEnd: widget.callback,
+      scale: toggle ? 2.0 : 1.0,
+      child: child,
+    );
+  }
+}
+
+class _TestAnimatedRotationWidgetState extends _TestAnimatedWidgetState {
+  @override
+  Widget getAnimatedWidget() {
+    return AnimatedRotation(
+      duration: duration,
+      onEnd: widget.callback,
+      turns: toggle ? 1.5 : 0.0,
+      child: child,
+    );
+  }
+}
+
 class _TestAnimatedOpacityWidgetState extends _TestAnimatedWidgetState {
   @override
   Widget getAnimatedWidget() {
@@ -541,6 +709,7 @@ class _TestSliverAnimatedOpacityWidgetState extends _TestAnimatedWidgetState {
 
   @override
   Widget build(BuildContext context) {
+    builds++;
     final Widget animatedWidget = getAnimatedWidget();
 
     return Material(