[Cupertino] Add Scrollbar

Runtime/cupertino/scrollbar.cs

+using System;
+using Unity.UIWidgets.animation;
+using Unity.UIWidgets.async;
+using Unity.UIWidgets.foundation;
+using Unity.UIWidgets.ui;
+using Unity.UIWidgets.widgets;
+
+namespace Unity.UIWidgets.cupertino {
+    public class CupertinoScrollbarUtils {
+        public static Color _kScrollbarColor = new Color(0x99777777);
+        public static float _kScrollbarThickness = 2.5f;
+        public static float _kScrollbarMainAxisMargin = 4.0f;
+        public static float _kScrollbarCrossAxisMargin = 2.5f;
+        public static float _kScrollbarMinLength = 36.0f;
+        public static float _kScrollbarMinOverscrollLength = 8.0f;
+        public static Radius _kScrollbarRadius = Radius.circular(1.25f);
+        public static TimeSpan _kScrollbarTimeToFade = new TimeSpan(0, 0, 0, 0, 50);
+        public static TimeSpan _kScrollbarFadeDuration = new TimeSpan(0, 0, 0, 0, 250);
+    }
+
+    public class CupertinoScrollbar : StatefulWidget {
+        public CupertinoScrollbar(
+            Widget child,
+            Key key = null
+        ) : base(key: key) {
+            this.child = child;
+        }
+
+        public readonly Widget child;
+
+        public override State createState() => new _CupertinoScrollbarState();
+    }
+
+    class _CupertinoScrollbarState : TickerProviderStateMixin<CupertinoScrollbar> {
+        ScrollbarPainter _painter;
+        TextDirection _textDirection;
+        AnimationController _fadeoutAnimationController;
+        Animation<float> _fadeoutOpacityAnimation;
+        Timer _fadeoutTimer;
+
+        public override void initState() {
+            base.initState();
+            this._fadeoutAnimationController = new AnimationController(
+                vsync: this,
+                duration: CupertinoScrollbarUtils._kScrollbarFadeDuration
+            );
+            this._fadeoutOpacityAnimation = new CurvedAnimation(
+                parent: this._fadeoutAnimationController,
+                curve: Curves.fastOutSlowIn
+            );
+        }
+
+
+        public override void didChangeDependencies() {
+            base.didChangeDependencies();
+            this._textDirection = Directionality.of(this.context);
+            this._painter = this._buildCupertinoScrollbarPainter();
+        }
+
+        ScrollbarPainter _buildCupertinoScrollbarPainter() {
+            return new ScrollbarPainter(
+                color: CupertinoScrollbarUtils._kScrollbarColor,
+                textDirection: this._textDirection,
+                thickness: CupertinoScrollbarUtils._kScrollbarThickness,
+                fadeoutOpacityAnimation: this._fadeoutOpacityAnimation,
+                mainAxisMargin: CupertinoScrollbarUtils._kScrollbarMainAxisMargin,
+                crossAxisMargin: CupertinoScrollbarUtils._kScrollbarCrossAxisMargin,
+                radius: CupertinoScrollbarUtils._kScrollbarRadius,
+                minLength: CupertinoScrollbarUtils._kScrollbarMinLength,
+                minOverscrollLength: CupertinoScrollbarUtils._kScrollbarMinOverscrollLength
+            );
+        }
+
+        bool _handleScrollNotification(ScrollNotification notification) {
+            if (notification is ScrollUpdateNotification ||
+                notification is OverscrollNotification) {
+                if (this._fadeoutAnimationController.status != AnimationStatus.forward) {
+                    this._fadeoutAnimationController.forward();
+                }
+
+                this._fadeoutTimer?.cancel();
+                this._painter.update(notification.metrics, notification.metrics.axisDirection);
+            }
+            else if (notification is ScrollEndNotification) {
+                this._fadeoutTimer?.cancel();
+                this._fadeoutTimer = Window.instance.run(CupertinoScrollbarUtils._kScrollbarTimeToFade, () => {
+                    this._fadeoutAnimationController.reverse();
+                    this._fadeoutTimer = null;
+                });
+            }
+
+            return false;
+        }
+
+
+        public override void dispose() {
+            this._fadeoutAnimationController.dispose();
+            this._fadeoutTimer?.cancel();
+            this._painter.dispose();
+            base.dispose();
+        }
+
+
+        public override Widget build(BuildContext context) {
+            return new NotificationListener<ScrollNotification>(
+                onNotification: this._handleScrollNotification,
+                child: new RepaintBoundary(
+                    child: new CustomPaint(
+                        foregroundPainter: this._painter,
+                        child: new RepaintBoundary(
+                            child: this.widget.child
+                        )
+                    )
+                )
+            );
+        }
+    }
+}

Runtime/cupertino/scrollbar.cs.meta

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