Use Ozzie's new panning friction simulation (Resolves #6) (#17)

Author: matthew-carroll

.run/Page List - Old Velocity (debug).run.xml

@@ -4,4 +4,4 @@ export 'src/page_list_viewport.dart';
 export 'src/page_list_performance_optimizer.dart';
 export 'src/logging.dart';
 
-export 'src/deprecated_gestures.dart';
+export 'src/page_list_viewport_gestures.dart';

example/lib/main_list_old_velocity.dart

@@ -1042,259 +1042,6 @@ class ViewportPageParentData extends ContainerBoxParentData<RenderBox> with Cont
   }
 }
 
-/// Controls a [PageListViewportController] with scale gestures to pan and zoom the
-/// associated [PageListViewport].
-class PageListViewportGestures extends StatefulWidget {
-  const PageListViewportGestures({
-    Key? key,
-    required this.controller,
-    this.onTapUp,
-    this.onLongPressStart,
-    this.onLongPressMoveUpdate,
-    this.onLongPressEnd,
-    this.onDoubleTapDown,
-    this.onDoubleTap,
-    this.onDoubleTapCancel,
-    this.panAndZoomPointerDevices = const {
-      PointerDeviceKind.mouse,
-      PointerDeviceKind.trackpad,
-      PointerDeviceKind.touch,
-    },
-    this.clock = const Clock(),
-    required this.child,
-  }) : super(key: key);
-
-  final PageListViewportController controller;
-
-  // All of these methods were added because our client needs to
-  // respond to them, and we internally respond to other gestures.
-  // Flutter won't let gestures pass from parent to child, so we're
-  // forced to expose all of these callbacks so that our client can
-  // hook into them.
-  final void Function(TapUpDetails)? onTapUp;
-  final void Function(LongPressStartDetails)? onLongPressStart;
-  final void Function(LongPressMoveUpdateDetails)? onLongPressMoveUpdate;
-  final void Function(LongPressEndDetails)? onLongPressEnd;
-  final void Function(TapDownDetails)? onDoubleTapDown;
-  final void Function()? onDoubleTap;
-  final void Function()? onDoubleTapCancel;
-
-  final Set<PointerDeviceKind> panAndZoomPointerDevices;
-
-  /// Reports the time, so that the gesture system can track how much
-  /// time has passed.
-  ///
-  /// [clock] is configurable so that a fake version can be injected
-  /// in tests.
-  final Clock clock;
-
-  final Widget child;
-
-  @override
-  State<PageListViewportGestures> createState() => _PageListViewportGesturesState();
-}
-
-class _PageListViewportGesturesState extends State<PageListViewportGestures> with TickerProviderStateMixin {
-  bool _isPanningEnabled = true;
-  bool _isPanning = false;
-
-  late PanAndScaleVelocityTracker _panAndScaleVelocityTracker;
-  double? _startContentScale;
-  Offset? _startOffset;
-  int? _endTimeInMillis;
-  late Ticker _ticker;
-
-  @override
-  void initState() {
-    super.initState();
-    _panAndScaleVelocityTracker = PanAndScaleVelocityTracker(clock: widget.clock);
-    _ticker = createTicker(_onFrictionTick);
-  }
-
-  @override
-  void dispose() {
-    _ticker.dispose();
-    super.dispose();
-  }
-
-  void _onPointerDown(PointerDownEvent event) {
-    if (event.kind == PointerDeviceKind.stylus) {
-      _isPanningEnabled = false;
-    }
-
-    // Stop any on-going friction simulation.
-    _stopMomentum();
-  }
-
-  void _onPointerUp(PointerUpEvent event) {
-    _isPanningEnabled = true;
-  }
-
-  void _onPointerCancel(PointerCancelEvent event) {
-    _isPanningEnabled = true;
-  }
-
-  void _onScaleStart(ScaleStartDetails details) {
-    PageListViewportLogs.pagesListGestures.finer("onScaleStart()");
-    if (!_isPanningEnabled) {
-      // The user is interacting with a stylus. We don't want to pan
-      // or scale with a stylus.
-      return;
-    }
-
-    _isPanning = true;
-
-    final timeSinceLastGesture = _endTimeInMillis != null ? _timeSinceEndOfLastGesture : null;
-    _startContentScale = widget.controller.scale;
-    _startOffset = widget.controller.origin;
-
-    _panAndScaleVelocityTracker.onScaleStart(details);
-
-    if ((timeSinceLastGesture == null || timeSinceLastGesture > const Duration(milliseconds: 30))) {
-      // We've started a new gesture after a reasonable period of time since the
-      // last gesture. Stop any momentum from the last gesture.
-      _stopMomentum();
-    }
-  }
-
-  void _onScaleUpdate(ScaleUpdateDetails details) {
-    PageListViewportLogs.pagesList
-        .finer("onScaleUpdate() - new focal point ${details.focalPoint}, focal delta: ${details.focalPointDelta}");
-    if (!_isPanning) {
-      // The user is interacting with a stylus. We don't want to pan
-      // or scale with a stylus.
-      return;
-    }
-
-    if (!_isPanningEnabled) {
-      PageListViewportLogs.pagesListGestures.finer("Started panning when the stylus was down. Resetting transform to:");
-      PageListViewportLogs.pagesListGestures.finer(" - origin: ${widget.controller.origin}");
-      PageListViewportLogs.pagesListGestures.finer(" - scale: ${widget.controller.scale}");
-
-      _isPanning = false;
-
-      // When this condition is triggered, _startOffset and _startContentScale
-      // should be non-null. But sometimes they are null. I don't know why. When that
-      // happens, return.
-      if (_startOffset == null || _startContentScale == null) {
-        return;
-      }
-
-      widget.controller
-        ..setScale(_startContentScale!, details.focalPoint)
-        ..translate(_startOffset! - widget.controller.origin);
-      return;
-    }
-
-    _panAndScaleVelocityTracker.onScaleUpdate(details);
-
-    widget.controller //
-      ..setScale(details.scale * _startContentScale!, details.localFocalPoint)
-      ..translate(details.focalPointDelta);
-    PageListViewportLogs.pagesListGestures
-        .finer("New origin: ${widget.controller.origin}, scale: ${widget.controller.scale}");
-  }
-
-  void _onScaleEnd(ScaleEndDetails details) {
-    PageListViewportLogs.pagesListGestures.finer("onScaleEnd()");
-    if (!_isPanning) {
-      return;
-    }
-
-    _panAndScaleVelocityTracker.onScaleEnd(details);
-
-    if (details.pointerCount == 0) {
-      _startMomentum();
-      _isPanning = false;
-    }
-  }
-
-  Duration get _timeSinceEndOfLastGesture => Duration(milliseconds: widget.clock.millis - _endTimeInMillis!);
-
-  void _startMomentum() {
-    PageListViewportLogs.pagesListGestures.fine("Starting momentum...");
-    final velocity = _panAndScaleVelocityTracker.velocity;
-    PageListViewportLogs.pagesListGestures.fine("Starting momentum with velocity: $velocity");
-
-    _velocity = velocity;
-
-    if (!_ticker.isTicking) {
-      _lastTime = Duration.zero;
-      _ticker.start();
-    }
-  }
-
-  void _stopMomentum() {
-    if (_ticker.isTicking) {
-      _ticker.stop();
-    }
-  }
-
-  Duration _lastTime = Duration.zero;
-  Offset _velocity = Offset.zero;
-  void _onFrictionTick(Duration elapsedTime) {
-    if (elapsedTime == Duration.zero) {
-      return;
-    }
-
-    final dt = elapsedTime - _lastTime;
-    _lastTime = elapsedTime;
-    final secondsFraction = dt.inMilliseconds / 1000;
-    final dp = _velocity * secondsFraction;
-    final originBeforeDelta = widget.controller.origin;
-    final newOrigin = widget.controller.origin + dp;
-    final translate = newOrigin - originBeforeDelta;
-
-    final direction = Offset.fromDirection(_velocity.direction);
-
-    // We want:
-    // - a decay of 3% when moving very fast (less drag when flinging fast)
-    // - a decay of 6% when moving slowly (more drag when coming to rest)
-    final velocityIntensity = math.pow((_velocity.distance / kMaxFlingVelocity).clamp(0.0, 1.0), 1 / 4.0).toDouble();
-    final drag = lerpDouble(0.06, 0.03, velocityIntensity)!;
-    _velocity = _velocity - (direction * _velocity.distance * drag);
-
-    PageListViewportLogs.pagesListGestures
-        .finest("Friction tick. Time: ${elapsedTime.inMilliseconds}ms. Velocity: $_velocity. Movement: $translate");
-
-    widget.controller.translate(translate);
-
-    PageListViewportLogs.pagesListGestures.finest("New origin: $newOrigin");
-
-    // If the viewport hit a wall, or if the simulations are done, stop
-    // ticking.
-    if (translate.distance < 0.5) {
-      _ticker.stop();
-    }
-  }
-
-  @override
-  Widget build(BuildContext context) {
-    return Listener(
-      // Listen for finger-down in a Listener so that we have zero
-      // latency when stopping a friction simulation. Also, track when
-      // a stylus is used, so we can prevent panning.
-      onPointerDown: _onPointerDown,
-      onPointerUp: _onPointerUp,
-      onPointerCancel: _onPointerCancel,
-      child: GestureDetector(
-        onTapUp: widget.onTapUp,
-        onLongPressStart: widget.onLongPressStart,
-        onLongPressMoveUpdate: widget.onLongPressMoveUpdate,
-        onLongPressEnd: widget.onLongPressEnd,
-        onDoubleTapDown: widget.onDoubleTapDown,
-        onDoubleTap: widget.onDoubleTap,
-        onDoubleTapCancel: widget.onDoubleTapCancel,
-        onScaleStart: _onScaleStart,
-        onScaleUpdate: _onScaleUpdate,
-        onScaleEnd: _onScaleEnd,
-        supportedDevices: widget.panAndZoomPointerDevices,
-        child: widget.child,
-      ),
-    );
-  }
-}
-
 /// Tracks scale gesture events and calculates a velocity based on those
 /// events.
 ///