Port transitions.dart to fn3

packages/flutter/lib/src/fn3/transitions.dart

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:sky/animation.dart';
+import 'package:sky/src/fn3/basic.dart';
+import 'package:sky/src/fn3/framework.dart';
+import 'package:vector_math/vector_math.dart';
+
+export 'package:sky/animation.dart' show Direction;
+
+// TODO(abarth): TransitionProxy
+
+abstract class TransitionComponent extends StatefulComponent {
+  TransitionComponent({
+    Key key,
+    this.performance
+  }) : super(key: key) {
+    assert(performance != null);
+  }
+
+  final WatchableAnimationPerformance performance;
+
+  Widget build(BuildContext context);
+
+  TransitionComponentState createState() => new TransitionComponentState(this);
+}
+
+class TransitionComponentState extends ComponentState<TransitionComponent> {
+  TransitionComponentState(TransitionComponent config) : super(config) {
+    config.performance.addListener(_performanceChanged);
+  }
+
+  void didUpdateConfig(TransitionComponent oldConfig) {
+    if (config.performance != oldConfig.performance) {
+      oldConfig.performance.removeListener(_performanceChanged);
+      config.performance.addListener(_performanceChanged);
+    }
+  }
+
+  void dispose() {
+    config.performance.removeListener(_performanceChanged);
+  }
+
+  void _performanceChanged() {
+    setState(() {
+      // The performance's state is our build state, and it changed already.
+    });
+  }
+
+  Widget build(BuildContext context) {
+    return config.build(context);
+  }
+}
+
+abstract class TransitionWithChild extends TransitionComponent {
+  TransitionWithChild({
+    Key key,
+    this.child,
+    WatchableAnimationPerformance performance
+  }) : super(key: key, performance: performance);
+
+  final Widget child;
+
+  Widget build(BuildContext context) => buildWithChild(context, child);
+
+  Widget buildWithChild(BuildContext context, Widget child);
+}
+
+class SlideTransition extends TransitionWithChild {
+  SlideTransition({
+    Key key,
+    this.position,
+    WatchableAnimationPerformance performance,
+    Widget child
+  }) : super(key: key,
+             performance: performance,
+             child: child);
+
+  final AnimatedValue<Point> position;
+
+  Widget buildWithChild(BuildContext context, Widget child) {
+    performance.updateVariable(position);
+    Matrix4 transform = new Matrix4.identity()
+      ..translate(position.value.x, position.value.y);
+    return new Transform(transform: transform, child: child);
+  }
+}
+
+class FadeTransition extends TransitionWithChild {
+  FadeTransition({
+    Key key,
+    this.opacity,
+    WatchableAnimationPerformance performance,
+    Widget child
+  }) : super(key: key,
+             performance: performance,
+             child: child);
+
+  final AnimatedValue<double> opacity;
+
+  Widget buildWithChild(BuildContext context, Widget child) {
+    performance.updateVariable(opacity);
+    return new Opacity(opacity: opacity.value, child: child);
+  }
+}
+
+class ColorTransition extends TransitionWithChild {
+  ColorTransition({
+    Key key,
+    this.color,
+    WatchableAnimationPerformance performance,
+    Widget child
+  }) : super(key: key,
+             performance: performance,
+             child: child);
+
+  final AnimatedColorValue color;
+
+  Widget buildWithChild(BuildContext context, Widget child) {
+    performance.updateVariable(color);
+    return new DecoratedBox(
+      decoration: new BoxDecoration(backgroundColor: color.value),
+      child: child
+    );
+  }
+}
+
+class SquashTransition extends TransitionWithChild {
+  SquashTransition({
+    Key key,
+    this.width,
+    this.height,
+    WatchableAnimationPerformance performance,
+    Widget child
+  }) : super(key: key,
+             performance: performance,
+             child: child);
+
+  final AnimatedValue<double> width;
+  final AnimatedValue<double> height;
+
+  Widget buildWithChild(BuildContext context, Widget child) {
+    if (width != null)
+      performance.updateVariable(width);
+    if (height != null)
+      performance.updateVariable(height);
+    return new SizedBox(width: width?.value, height: height?.value, child: child);
+  }
+}
+
+typedef Widget BuilderFunction(BuildContext context);
+
+class BuilderTransition extends TransitionComponent {
+  BuilderTransition({
+    Key key,
+    this.variables,
+    this.builder,
+    WatchableAnimationPerformance performance
+  }) : super(key: key,
+             performance: performance);
+
+  final List<AnimatedValue> variables;
+  final BuilderFunction builder;
+
+  Widget build(BuildContext context) {
+    for (int i = 0; i < variables.length; ++i)
+      performance.updateVariable(variables[i]);
+    return builder(context);
+  }
+}