Remove OverscrollIndicator (#8134)

This feature is wired in differently in the new scrolling world.

packages/flutter/lib/material.dart

@@ -57,7 +57,6 @@ export 'src/material/list.dart';
 export 'src/material/list_item.dart';
 export 'src/material/material.dart';
 export 'src/material/mergeable_material.dart';
-export 'src/material/overscroll_indicator.dart';
 export 'src/material/page.dart';
 export 'src/material/paginated_data_table.dart';
 export 'src/material/popup_menu.dart';

packages/flutter/lib/src/material/app.dart

@@ -8,7 +8,6 @@ import 'package:flutter/widgets.dart';
 
 import 'arc.dart';
 import 'colors.dart';
-import 'overscroll_indicator.dart';
 import 'page.dart';
 import 'theme.dart';
 
@@ -190,30 +189,6 @@ class _ScrollLikeMountainViewDelegate extends ScrollConfigurationDelegate {
   @override
   ExtentScrollBehavior createScrollBehavior() => new OverscrollWhenScrollableBehavior(platform: TargetPlatform.android);
 
-  ScrollableEdge _overscrollIndicatorEdge(ScrollableEdge edge) {
-    switch (edge) {
-      case ScrollableEdge.leading:
-        return ScrollableEdge.trailing;
-      case ScrollableEdge.trailing:
-        return ScrollableEdge.leading;
-      case ScrollableEdge.both:
-        return ScrollableEdge.none;
-      case ScrollableEdge.none:
-        return ScrollableEdge.both;
-    }
-    return ScrollableEdge.both;
-  }
-
-  @override
-  Widget wrapScrollWidget(BuildContext context, Widget scrollWidget) {
-    // Only introduce an overscroll indicator for the edges of the scrollable
-    // that aren't already clamped.
-    return new OverscrollIndicator(
-      edge: _overscrollIndicatorEdge(ClampOverscrolls.of(context)?.edge),
-      child: scrollWidget
-    );
-  }
-
   @override
   bool updateShouldNotify(ScrollConfigurationDelegate old) => false;
 }

packages/flutter/lib/src/material/overscroll_indicator.dart

-// Copyright 2016 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.
-
-////////////////////////////////////////////////////////////////////////////////
-// DELETE THIS FILE WHEN REMOVING LEGACY SCROLLING CODE
-////////////////////////////////////////////////////////////////////////////////
-
-import 'dart:async' show Timer;
-import 'dart:math' as math;
-
-import 'package:flutter/foundation.dart';
-import 'package:flutter/widgets.dart';
-
-import 'theme.dart';
-
-const double _kMinIndicatorExtent = 0.0;
-const double _kMaxIndicatorExtent = 64.0;
-const double _kMinIndicatorOpacity = 0.0;
-const double _kMaxIndicatorOpacity = 0.25;
-
-final Tween<double> _kIndicatorOpacity = new Tween<double>(begin: 0.0, end: 0.3);
-
-// If an overscroll gesture lasts longer than this the hide timer will
-// cause the indicator to fade-out.
-const Duration _kTimeoutDuration = const Duration(milliseconds: 500);
-
-// Fade-out duration if the fade-out was triggered by the timer.
-const Duration _kTimeoutHideDuration = const Duration(milliseconds: 2000);
-
-// Fade-out duration if the fade-out was triggered by an input gesture.
-const Duration _kNormalHideDuration = const Duration(milliseconds: 600);
-
-
-class _Painter extends CustomPainter {
-  _Painter({
-    this.scrollDirection,
-    this.extent, // Indicator width or height, per scrollDirection.
-    this.dragPosition,
-    this.isLeading, // Similarly true if the indicator appears at the top/left.
-    this.color
-  });
-
-  // See EdgeEffect setSize() in https://github.com/android
-  static final double _kSizeToRadius = 0.75 / math.sin(math.PI / 6.0);
-
-  final Axis scrollDirection;
-  final double extent;
-  final bool isLeading;
-  final Color color;
-  final Point dragPosition;
-
-  void paintIndicator(Canvas canvas, Size size) {
-    final Paint paint = new Paint()..color = color;
-    final double width = size.width;
-    final double height = size.height;
-
-    switch (scrollDirection) {
-      case Axis.vertical:
-        final double radius = width * _kSizeToRadius;
-        final double centerX = width / 2.0;
-        final double centerY = isLeading ? extent - radius : height - extent + radius;
-        final double eventX = dragPosition?.x ?? 0.0;
-        final double biasX = (0.5 - (1.0 - eventX / width)) * centerX;
-        canvas.drawCircle(new Point(centerX + biasX, centerY), radius, paint);
-        break;
-      case Axis.horizontal:
-        final double radius = height * _kSizeToRadius;
-        final double centerX = isLeading ? extent - radius : width - extent + radius;
-        final double centerY = height / 2.0;
-        final double eventY = dragPosition?.y ?? 0.0;
-        final double biasY = (0.5 - (1.0 - eventY / height)) * centerY;
-        canvas.drawCircle(new Point(centerX, centerY + biasY), radius, paint);
-        break;
-    }
-  }
-
-  @override
-  void paint(Canvas canvas, Size size) {
-    if (color.alpha == 0 || size.isEmpty)
-      return;
-    paintIndicator(canvas, size);
-  }
-
-  @override
-  bool shouldRepaint(_Painter oldPainter) {
-    return oldPainter.scrollDirection != scrollDirection
-      || oldPainter.extent != extent
-      || oldPainter.isLeading != isLeading
-      || oldPainter.color != color;
-  }
-}
-
-/// When the child's Scrollable descendant overscrolls, displays a
-/// a translucent arc over the affected edge of the child.
-/// If the OverscrollIndicator's child has more than one Scrollable descendant
-/// the scrollableKey parameter can be used to identify the one to track.
-class OverscrollIndicator extends StatefulWidget {
-  /// Creates an overscroll indicator.
-  ///
-  /// The [child] argument must not be null.
-  OverscrollIndicator({
-    Key key,
-    this.scrollableKey,
-    this.edge: ScrollableEdge.both,
-    @required this.child,
-  }) : super(key: key) {
-    assert(child != null);
-    assert(edge != null);
-  }
-
-  /// Identifies the [Scrollable] descendant of child that the overscroll
-  /// indicator will track. Can be null if there's only one [Scrollable]
-  /// descendant.
-  final Key scrollableKey;
-
-  /// Where the overscroll indicator should appear.
-  final ScrollableEdge edge;
-
-  /// The overscroll indicator will be stacked on top of this child. The
-  /// indicator will appear when child's [Scrollable] descendant is
-  /// over-scrolled.
-  final Widget child;
-
-  @override
-  _OverscrollIndicatorState createState() => new _OverscrollIndicatorState();
-}
-
-class _OverscrollIndicatorState extends State<OverscrollIndicator> with SingleTickerProviderStateMixin {
-
-  AnimationController _extentAnimation;
-  bool _scrollUnderway = false;
-  Timer _hideTimer;
-  Axis _scrollDirection;
-  double _scrollOffset;
-  double _minScrollOffset;
-  double _maxScrollOffset;
-  Point _dragPosition;
-
-  @override
-  void initState() {
-    super.initState();
-    _extentAnimation = new AnimationController(
-      lowerBound: _kMinIndicatorExtent,
-      upperBound: _kMaxIndicatorExtent,
-      duration: _kNormalHideDuration,
-      vsync: this,
-    );
-  }
-
-  void _hide([Duration duration=_kTimeoutHideDuration]) {
-    _scrollUnderway = false;
-    _hideTimer?.cancel();
-    _hideTimer = null;
-    if (!_extentAnimation.isAnimating) {
-      _extentAnimation.duration = duration;
-      _extentAnimation.reverse();
-    }
-  }
-
-  void _updateState(ScrollableState scrollable) {
-    if (scrollable.scrollBehavior is! ExtentScrollBehavior)
-      return;
-    final ExtentScrollBehavior scrollBehavior = scrollable.scrollBehavior;
-    _scrollDirection = scrollable.config.scrollDirection;
-    _scrollOffset = scrollable.virtualScrollOffset;
-    _minScrollOffset = scrollBehavior.minScrollOffset;
-    _maxScrollOffset = scrollBehavior.maxScrollOffset;
-  }
-
-  void _onScrollStarted(ScrollableState scrollable) {
-    assert(_scrollUnderway == false);
-    _scrollUnderway = true;
-    _updateState(scrollable);
-  }
-
-  void _onScrollUpdated(ScrollableState scrollable, DragUpdateDetails details) {
-    if (!_scrollUnderway) // The hide timer has run.
-      return;
-
-    final double value = scrollable.virtualScrollOffset;
-    if (_isOverscroll(value)) {
-      _refreshHideTimer();
-      // Hide the indicator as soon as user starts scrolling in the reverse direction of overscroll.
-      if (_isReverseScroll(value)) {
-        _hide(_kNormalHideDuration);
-      } else if (_isMatchingOverscrollEdge(value)) {
-        // Changing the animation's value causes an implicit setState().
-        _dragPosition = details?.globalPosition ?? Point.origin;
-        _extentAnimation.value = value < _minScrollOffset ? _minScrollOffset - value : value - _maxScrollOffset;
-      } else {
-        _hide(_kNormalHideDuration);
-      }
-    }
-    _updateState(scrollable);
-  }
-
-  void _onScrollEnded(ScrollableState scrollable) {
-    if (!_scrollUnderway) // The hide timer has run.
-      return;
-
-    _updateState(scrollable);
-    _hide(_kNormalHideDuration);
-  }
-
-  void _refreshHideTimer() {
-    _hideTimer?.cancel();
-    _hideTimer = new Timer(_kTimeoutDuration, _hide);
-  }
-
-  bool _isOverscroll(double scrollOffset) {
-    return (scrollOffset < _minScrollOffset || scrollOffset > _maxScrollOffset) &&
-      ((scrollOffset - _scrollOffset).abs() > kPixelScrollTolerance.distance);
-  }
-
-  bool _isMatchingOverscrollEdge(double scrollOffset) {
-    switch (config.edge) {
-      case ScrollableEdge.both:
-        return true;
-      case ScrollableEdge.leading:
-        return scrollOffset < _minScrollOffset;
-      case ScrollableEdge.trailing:
-        return scrollOffset > _maxScrollOffset;
-      case ScrollableEdge.none:
-        return false;
-    }
-    return false;
-  }
-
-  bool _isReverseScroll(double scrollOffset) {
-    final double delta = _scrollOffset - scrollOffset;
-    return scrollOffset < _minScrollOffset ? delta < 0.0 : delta > 0.0;
-  }
-
-  bool _handleScrollNotification(ScrollNotification notification) {
-    if (config.scrollableKey == null) {
-        if (notification.depth != 0)
-          return false;
-    } else if (config.scrollableKey != notification.scrollable.config.key) {
-      return false;
-    }
-
-    final ScrollableState scrollable = notification.scrollable;
-    switch (notification.kind) {
-      case ScrollNotificationKind.started:
-        _onScrollStarted(scrollable);
-        break;
-      case ScrollNotificationKind.updated:
-        _onScrollUpdated(scrollable, notification.dragUpdateDetails);
-        break;
-      case ScrollNotificationKind.ended:
-        _onScrollEnded(scrollable);
-        break;
-    }
-    return false;
-  }
-
-  @override
-  void dispose() {
-    _hideTimer?.cancel();
-    _hideTimer = null;
-    _extentAnimation.dispose();
-    super.dispose();
-  }
-
-  Color get _indicatorColor {
-    final Color accentColor = Theme.of(context).accentColor.withOpacity(0.35);
-    final double t = (_extentAnimation.value - _kMinIndicatorExtent) / (_kMaxIndicatorExtent - _kMinIndicatorExtent);
-    return accentColor.withOpacity(_kIndicatorOpacity.lerp(Curves.easeIn.transform(t)));
-  }
-
-  @override
-  Widget build(BuildContext context) {
-    return new NotificationListener<ScrollNotification>(
-      onNotification: _handleScrollNotification,
-      child: new AnimatedBuilder(
-        animation: _extentAnimation,
-        builder: (BuildContext context, Widget child) {
-          // We keep the same widget hierarchy here, even when we're not
-          // painting anything, to avoid rebuilding the children.
-          return new CustomPaint(
-            foregroundPainter: _scrollDirection == null ? null : new _Painter(
-              scrollDirection: _scrollDirection,
-              extent: _extentAnimation.value,
-              dragPosition: _dragPosition,
-              isLeading: _scrollOffset < _minScrollOffset,
-              color: _indicatorColor
-            ),
-            child: child
-          );
-        },
-        child: new ClampOverscrolls.inherit(
-          context: context,
-          edge: config.edge,
-          child: config.child,
-        )
-      )
-    );
-  }
-}