packages/flutter/lib/src/material/scrollbar.dart - mirrors/flutter - Git at Google

 // Copyright 2014 The Flutter 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:flutter/cupertino.dart';
 import 'package:flutter/gestures.dart';

 import 'color_scheme.dart';
 import 'material_state.dart';
 import 'scrollbar_theme.dart';
 import 'theme.dart';

 const double _kScrollbarThickness = 8.0;
 const double _kScrollbarThicknessWithTrack = 12.0;
 const double _kScrollbarMargin = 2.0;
 const double _kScrollbarMinLength = 48.0;
 const Radius _kScrollbarRadius = Radius.circular(8.0);
 const Duration _kScrollbarFadeDuration = Duration(milliseconds: 300);
 const Duration _kScrollbarTimeToFade = Duration(milliseconds: 600);

 /// A Material Design scrollbar.
 ///
 /// To add a scrollbar to a [ScrollView], wrap the scroll view
 /// widget in a [Scrollbar] widget.
 ///
 /// {@macro flutter.widgets.Scrollbar}
 ///
 /// Dynamically changes to an iOS style scrollbar that looks like
 /// [CupertinoScrollbar] on the iOS platform.
 ///
 /// The color of the Scrollbar will change when dragged. A hover animation is
 /// also triggered when used on web and desktop platforms. A scrollbar track
 /// can also been drawn when triggered by a hover event, which is controlled by
 /// [showTrackOnHover]. The thickness of the track and scrollbar thumb will
 /// become larger when hovering, unless overridden by [hoverThickness].
 ///
 /// {@tool dartpad}
 /// This sample shows a [Scrollbar] that executes a fade animation as scrolling occurs.
 /// The Scrollbar will fade into view as the user scrolls, and fade out when scrolling stops.
 ///
 /// ** See code in examples/api/lib/material/scrollbar/scrollbar.0.dart **
 /// {@end-tool}
 ///
 /// {@tool dartpad}
 /// When isAlwaysShown is true, the scrollbar thumb will remain visible without the
 /// fade animation. This requires that a ScrollController is provided to controller,
 /// or that the PrimaryScrollController is available.
 ///
 /// ** See code in examples/api/lib/material/scrollbar/scrollbar.1.dart **
 /// {@end-tool}
 ///
 /// See also:
 ///
 ///  * [RawScrollbar], a basic scrollbar that fades in and out, extended
 ///    by this class to add more animations and behaviors.
 ///  * [ScrollbarTheme], which configures the Scrollbar's appearance.
 ///  * [CupertinoScrollbar], an iOS style scrollbar.
 ///  * [ListView], which displays a linear, scrollable list of children.
 ///  * [GridView], which displays a 2 dimensional, scrollable array of children.
 class Scrollbar extends StatelessWidget {
   /// Creates a material design scrollbar that by default will connect to the
   /// closest Scrollable descendant of [child].
   ///
   /// The [child] should be a source of [ScrollNotification] notifications,
   /// typically a [Scrollable] widget.
   ///
   /// If the [controller] is null, the default behavior is to
   /// enable scrollbar dragging using the [PrimaryScrollController].
   ///
   /// When null, [thickness] defaults to 8.0 pixels on desktop and web, and 4.0
   /// pixels when on mobile platforms. A null [radius] will result in a default
   /// of an 8.0 pixel circular radius about the corners of the scrollbar thumb,
   /// except for when executing on [TargetPlatform.android], which will render the
   /// thumb without a radius.
   const Scrollbar({
     Key? key,
     required this.child,
     this.controller,
     this.isAlwaysShown,
     this.showTrackOnHover,
     this.hoverThickness,
     this.thickness,
     this.radius,
     this.notificationPredicate,
     this.interactive,
     this.scrollbarOrientation,
   }) : super(key: key);

   /// {@macro flutter.widgets.Scrollbar.child}
   final Widget child;

   /// {@macro flutter.widgets.Scrollbar.controller}
   final ScrollController? controller;

   /// {@macro flutter.widgets.Scrollbar.isAlwaysShown}
   final bool? isAlwaysShown;

   /// Controls if the track will show on hover and remain, including during drag.
   ///
   /// If this property is null, then [ScrollbarThemeData.showTrackOnHover] of
   /// [ThemeData.scrollbarTheme] is used. If that is also null, the default value
   /// is false.
   final bool? showTrackOnHover;

   /// The thickness of the scrollbar when a hover state is active and
   /// [showTrackOnHover] is true.
   ///
   /// If this property is null, then [ScrollbarThemeData.thickness] of
   /// [ThemeData.scrollbarTheme] is used to resolve a thickness. If that is also
   /// null, the default value is 12.0 pixels.
   final double? hoverThickness;

   /// The thickness of the scrollbar in the cross axis of the scrollable.
   ///
   /// If null, the default value is platform dependent. On [TargetPlatform.android],
   /// the default thickness is 4.0 pixels. On [TargetPlatform.iOS],
   /// [CupertinoScrollbar.defaultThickness] is used. The remaining platforms have a
   /// default thickness of 8.0 pixels.
   final double? thickness;

   /// The [Radius] of the scrollbar thumb's rounded rectangle corners.
   ///
   /// If null, the default value is platform dependent. On [TargetPlatform.android],
   /// no radius is applied to the scrollbar thumb. On [TargetPlatform.iOS],
   /// [CupertinoScrollbar.defaultRadius] is used. The remaining platforms have a
   /// default [Radius.circular] of 8.0 pixels.
   final Radius? radius;

   /// {@macro flutter.widgets.Scrollbar.interactive}
   final bool? interactive;

   /// {@macro flutter.widgets.Scrollbar.notificationPredicate}
   final ScrollNotificationPredicate? notificationPredicate;

   /// {@macro flutter.widgets.Scrollbar.scrollbarOrientation}
   final ScrollbarOrientation? scrollbarOrientation;

   @override
   Widget build(BuildContext context) {
     if (Theme.of(context).platform == TargetPlatform.iOS) {
       return CupertinoScrollbar(
         isAlwaysShown: isAlwaysShown ?? false,
         thickness: thickness ?? CupertinoScrollbar.defaultThickness,
         thicknessWhileDragging: thickness ?? CupertinoScrollbar.defaultThicknessWhileDragging,
         radius: radius ?? CupertinoScrollbar.defaultRadius,
         radiusWhileDragging: radius ?? CupertinoScrollbar.defaultRadiusWhileDragging,
         controller: controller,
         notificationPredicate: notificationPredicate,
         scrollbarOrientation: scrollbarOrientation,
         child: child,
       );
     }
     return _MaterialScrollbar(
       controller: controller,
       isAlwaysShown: isAlwaysShown,
       showTrackOnHover: showTrackOnHover,
       hoverThickness: hoverThickness,
       thickness: thickness,
       radius: radius,
       notificationPredicate: notificationPredicate,
       interactive: interactive,
       scrollbarOrientation: scrollbarOrientation,
       child: child,
     );
   }
 }

 class _MaterialScrollbar extends RawScrollbar {
   const _MaterialScrollbar({
     Key? key,
     required Widget child,
     ScrollController? controller,
     bool? isAlwaysShown,
     this.showTrackOnHover,
     this.hoverThickness,
     double? thickness,
     Radius? radius,
     ScrollNotificationPredicate? notificationPredicate,
     bool? interactive,
     ScrollbarOrientation? scrollbarOrientation,
   }) : super(
          key: key,
          child: child,
          controller: controller,
          isAlwaysShown: isAlwaysShown,
          thickness: thickness,
          radius: radius,
          fadeDuration: _kScrollbarFadeDuration,
          timeToFade: _kScrollbarTimeToFade,
          pressDuration: Duration.zero,
          notificationPredicate: notificationPredicate ?? defaultScrollNotificationPredicate,
          interactive: interactive,
          scrollbarOrientation: scrollbarOrientation,
        );

   final bool? showTrackOnHover;
   final double? hoverThickness;

   @override
   _MaterialScrollbarState createState() => _MaterialScrollbarState();
 }

 class _MaterialScrollbarState extends RawScrollbarState<_MaterialScrollbar> {
   late AnimationController _hoverAnimationController;
   bool _dragIsActive = false;
   bool _hoverIsActive = false;
   late ColorScheme _colorScheme;
   late ScrollbarThemeData _scrollbarTheme;
   // On Android, scrollbars should match native appearance.
   late bool _useAndroidScrollbar;

   @override
   bool get showScrollbar => widget.isAlwaysShown ?? _scrollbarTheme.isAlwaysShown ?? false;

   @override
   bool get enableGestures => widget.interactive ?? _scrollbarTheme.interactive ?? !_useAndroidScrollbar;

   bool get _showTrackOnHover => widget.showTrackOnHover ?? _scrollbarTheme.showTrackOnHover ?? false;

   Set<MaterialState> get _states => <MaterialState>{
     if (_dragIsActive) MaterialState.dragged,
     if (_hoverIsActive) MaterialState.hovered,
   };

   MaterialStateProperty<Color> get _thumbColor {
     final Color onSurface = _colorScheme.onSurface;
     final Brightness brightness = _colorScheme.brightness;
     late Color dragColor;
     late Color hoverColor;
     late Color idleColor;
     switch (brightness) {
       case Brightness.light:
         dragColor = onSurface.withOpacity(0.6);
         hoverColor = onSurface.withOpacity(0.5);
         idleColor = _useAndroidScrollbar
           ? Theme.of(context).highlightColor.withOpacity(1.0)
           : onSurface.withOpacity(0.1);
         break;
       case Brightness.dark:
         dragColor = onSurface.withOpacity(0.75);
         hoverColor = onSurface.withOpacity(0.65);
         idleColor = _useAndroidScrollbar
           ? Theme.of(context).highlightColor.withOpacity(1.0)
           : onSurface.withOpacity(0.3);
         break;
     }

     return MaterialStateProperty.resolveWith((Set<MaterialState> states) {
       if (states.contains(MaterialState.dragged))
         return _scrollbarTheme.thumbColor?.resolve(states) ?? dragColor;

       // If the track is visible, the thumb color hover animation is ignored and
       // changes immediately.
       if (states.contains(MaterialState.hovered) && _showTrackOnHover)
         return _scrollbarTheme.thumbColor?.resolve(states) ?? hoverColor;

       return Color.lerp(
         _scrollbarTheme.thumbColor?.resolve(states) ?? idleColor,
         _scrollbarTheme.thumbColor?.resolve(states) ?? hoverColor,
         _hoverAnimationController.value,
       )!;
     });
   }

   MaterialStateProperty<Color> get _trackColor {
     final Color onSurface = _colorScheme.onSurface;
     final Brightness brightness = _colorScheme.brightness;
     return MaterialStateProperty.resolveWith((Set<MaterialState> states) {
       if (states.contains(MaterialState.hovered) && _showTrackOnHover) {
         return _scrollbarTheme.trackColor?.resolve(states)
           ?? (brightness == Brightness.light
             ? onSurface.withOpacity(0.03)
             : onSurface.withOpacity(0.05));
       }
       return const Color(0x00000000);
     });
   }

   MaterialStateProperty<Color> get _trackBorderColor {
     final Color onSurface = _colorScheme.onSurface;
     final Brightness brightness = _colorScheme.brightness;
     return MaterialStateProperty.resolveWith((Set<MaterialState> states) {
       if (states.contains(MaterialState.hovered) && _showTrackOnHover) {
         return _scrollbarTheme.trackBorderColor?.resolve(states)
           ?? (brightness == Brightness.light
             ? onSurface.withOpacity(0.1)
             : onSurface.withOpacity(0.25));
       }
       return const Color(0x00000000);
     });
   }

   MaterialStateProperty<double> get _thickness {
     return MaterialStateProperty.resolveWith((Set<MaterialState> states) {
       if (states.contains(MaterialState.hovered) && _showTrackOnHover)
         return widget.hoverThickness
           ?? _scrollbarTheme.thickness?.resolve(states)
           ?? _kScrollbarThicknessWithTrack;
       // The default scrollbar thickness is smaller on mobile.
       return widget.thickness
         ?? _scrollbarTheme.thickness?.resolve(states)
         ?? (_kScrollbarThickness / (_useAndroidScrollbar ? 2 : 1));
     });
   }

   @override
   void initState() {
     super.initState();
     _hoverAnimationController = AnimationController(
       vsync: this,
       duration: const Duration(milliseconds: 200),
     );
     _hoverAnimationController.addListener(() {
       updateScrollbarPainter();
     });
   }

   @override
   void didChangeDependencies() {
     final ThemeData theme = Theme.of(context);
     _colorScheme = theme.colorScheme;
     _scrollbarTheme = theme.scrollbarTheme;
     switch (theme.platform) {
       case TargetPlatform.android:
         _useAndroidScrollbar = true;
         break;
       case TargetPlatform.iOS:
       case TargetPlatform.linux:
       case TargetPlatform.fuchsia:
       case TargetPlatform.macOS:
       case TargetPlatform.windows:
         _useAndroidScrollbar = false;
         break;
     }
     super.didChangeDependencies();
   }

   @override
   void updateScrollbarPainter() {
     scrollbarPainter
       ..color = _thumbColor.resolve(_states)
       ..trackColor = _trackColor.resolve(_states)
       ..trackBorderColor = _trackBorderColor.resolve(_states)
       ..textDirection = Directionality.of(context)
       ..thickness = _thickness.resolve(_states)
       ..radius = widget.radius ?? _scrollbarTheme.radius ?? (_useAndroidScrollbar ? null : _kScrollbarRadius)
       ..crossAxisMargin = _scrollbarTheme.crossAxisMargin ?? (_useAndroidScrollbar ? 0.0 : _kScrollbarMargin)
       ..mainAxisMargin = _scrollbarTheme.mainAxisMargin ?? 0.0
       ..minLength = _scrollbarTheme.minThumbLength ?? _kScrollbarMinLength
       ..padding = MediaQuery.of(context).padding
       ..scrollbarOrientation = widget.scrollbarOrientation;
   }

   @override
   void handleThumbPressStart(Offset localPosition) {
     super.handleThumbPressStart(localPosition);
     setState(() { _dragIsActive = true; });
   }

   @override
   void handleThumbPressEnd(Offset localPosition, Velocity velocity) {
     super.handleThumbPressEnd(localPosition, velocity);
     setState(() { _dragIsActive = false; });
   }

   @override
   void handleHover(PointerHoverEvent event) {
     super.handleHover(event);
     // Check if the position of the pointer falls over the painted scrollbar
     if (isPointerOverScrollbar(event.position, event.kind, forHover: true)) {
       // Pointer is hovering over the scrollbar
       setState(() { _hoverIsActive = true; });
       _hoverAnimationController.forward();
     } else if (_hoverIsActive) {
       // Pointer was, but is no longer over painted scrollbar.
       setState(() { _hoverIsActive = false; });
       _hoverAnimationController.reverse();
     }
   }

   @override
   void handleHoverExit(PointerExitEvent event) {
     super.handleHoverExit(event);
     setState(() { _hoverIsActive = false; });
     _hoverAnimationController.reverse();
   }

   @override
   void dispose() {
     _hoverAnimationController.dispose();
     super.dispose();
   }
 }
	// Copyright 2014 The Flutter 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:flutter/cupertino.dart';
	import 'package:flutter/gestures.dart';

	import 'color_scheme.dart';
	import 'material_state.dart';
	import 'scrollbar_theme.dart';
	import 'theme.dart';

	const double _kScrollbarThickness = 8.0;
	const double _kScrollbarThicknessWithTrack = 12.0;
	const double _kScrollbarMargin = 2.0;
	const double _kScrollbarMinLength = 48.0;
	const Radius _kScrollbarRadius = Radius.circular(8.0);
	const Duration _kScrollbarFadeDuration = Duration(milliseconds: 300);
	const Duration _kScrollbarTimeToFade = Duration(milliseconds: 600);

	/// A Material Design scrollbar.
	///
	/// To add a scrollbar to a [ScrollView], wrap the scroll view
	/// widget in a [Scrollbar] widget.
	///
	/// {@macro flutter.widgets.Scrollbar}
	///
	/// Dynamically changes to an iOS style scrollbar that looks like
	/// [CupertinoScrollbar] on the iOS platform.
	///
	/// The color of the Scrollbar will change when dragged. A hover animation is
	/// also triggered when used on web and desktop platforms. A scrollbar track
	/// can also been drawn when triggered by a hover event, which is controlled by
	/// [showTrackOnHover]. The thickness of the track and scrollbar thumb will
	/// become larger when hovering, unless overridden by [hoverThickness].
	///
	/// {@tool dartpad}
	/// This sample shows a [Scrollbar] that executes a fade animation as scrolling occurs.
	/// The Scrollbar will fade into view as the user scrolls, and fade out when scrolling stops.
	///
	/// See code in examples/api/lib/material/scrollbar/scrollbar.0.dart
	/// {@end-tool}
	///
	/// {@tool dartpad}
	/// When isAlwaysShown is true, the scrollbar thumb will remain visible without the
	/// fade animation. This requires that a ScrollController is provided to controller,
	/// or that the PrimaryScrollController is available.
	///
	/// See code in examples/api/lib/material/scrollbar/scrollbar.1.dart
	/// {@end-tool}
	///
	/// See also:
	///
	/// * [RawScrollbar], a basic scrollbar that fades in and out, extended
	/// by this class to add more animations and behaviors.
	/// * [ScrollbarTheme], which configures the Scrollbar's appearance.
	/// * [CupertinoScrollbar], an iOS style scrollbar.
	/// * [ListView], which displays a linear, scrollable list of children.
	/// * [GridView], which displays a 2 dimensional, scrollable array of children.
	class Scrollbar extends StatelessWidget {
	/// Creates a material design scrollbar that by default will connect to the
	/// closest Scrollable descendant of [child].
	///
	/// The [child] should be a source of [ScrollNotification] notifications,
	/// typically a [Scrollable] widget.
	///
	/// If the [controller] is null, the default behavior is to
	/// enable scrollbar dragging using the [PrimaryScrollController].
	///
	/// When null, [thickness] defaults to 8.0 pixels on desktop and web, and 4.0
	/// pixels when on mobile platforms. A null [radius] will result in a default
	/// of an 8.0 pixel circular radius about the corners of the scrollbar thumb,
	/// except for when executing on [TargetPlatform.android], which will render the
	/// thumb without a radius.
	const Scrollbar({
	Key? key,
	required this.child,
	this.controller,
	this.isAlwaysShown,
	this.showTrackOnHover,
	this.hoverThickness,
	this.thickness,
	this.radius,
	this.notificationPredicate,
	this.interactive,
	this.scrollbarOrientation,
	}) : super(key: key);

	/// {@macro flutter.widgets.Scrollbar.child}
	final Widget child;

	/// {@macro flutter.widgets.Scrollbar.controller}
	final ScrollController? controller;

	/// {@macro flutter.widgets.Scrollbar.isAlwaysShown}
	final bool? isAlwaysShown;

	/// Controls if the track will show on hover and remain, including during drag.
	///
	/// If this property is null, then [ScrollbarThemeData.showTrackOnHover] of
	/// [ThemeData.scrollbarTheme] is used. If that is also null, the default value
	/// is false.
	final bool? showTrackOnHover;

	/// The thickness of the scrollbar when a hover state is active and
	/// [showTrackOnHover] is true.
	///
	/// If this property is null, then [ScrollbarThemeData.thickness] of
	/// [ThemeData.scrollbarTheme] is used to resolve a thickness. If that is also
	/// null, the default value is 12.0 pixels.
	final double? hoverThickness;

	/// The thickness of the scrollbar in the cross axis of the scrollable.
	///
	/// If null, the default value is platform dependent. On [TargetPlatform.android],
	/// the default thickness is 4.0 pixels. On [TargetPlatform.iOS],
	/// [CupertinoScrollbar.defaultThickness] is used. The remaining platforms have a
	/// default thickness of 8.0 pixels.
	final double? thickness;

	/// The [Radius] of the scrollbar thumb's rounded rectangle corners.
	///
	/// If null, the default value is platform dependent. On [TargetPlatform.android],
	/// no radius is applied to the scrollbar thumb. On [TargetPlatform.iOS],
	/// [CupertinoScrollbar.defaultRadius] is used. The remaining platforms have a
	/// default [Radius.circular] of 8.0 pixels.
	final Radius? radius;

	/// {@macro flutter.widgets.Scrollbar.interactive}
	final bool? interactive;

	/// {@macro flutter.widgets.Scrollbar.notificationPredicate}
	final ScrollNotificationPredicate? notificationPredicate;

	/// {@macro flutter.widgets.Scrollbar.scrollbarOrientation}
	final ScrollbarOrientation? scrollbarOrientation;

	@override
	Widget build(BuildContext context) {
	if (Theme.of(context).platform == TargetPlatform.iOS) {
	return CupertinoScrollbar(
	isAlwaysShown: isAlwaysShown ?? false,
	thickness: thickness ?? CupertinoScrollbar.defaultThickness,
	thicknessWhileDragging: thickness ?? CupertinoScrollbar.defaultThicknessWhileDragging,
	radius: radius ?? CupertinoScrollbar.defaultRadius,
	radiusWhileDragging: radius ?? CupertinoScrollbar.defaultRadiusWhileDragging,
	controller: controller,
	notificationPredicate: notificationPredicate,
	scrollbarOrientation: scrollbarOrientation,
	child: child,
	);
	}
	return _MaterialScrollbar(
	controller: controller,
	isAlwaysShown: isAlwaysShown,
	showTrackOnHover: showTrackOnHover,
	hoverThickness: hoverThickness,
	thickness: thickness,
	radius: radius,
	notificationPredicate: notificationPredicate,
	interactive: interactive,
	scrollbarOrientation: scrollbarOrientation,
	child: child,
	);
	}
	}

	class _MaterialScrollbar extends RawScrollbar {
	const _MaterialScrollbar({
	Key? key,
	required Widget child,
	ScrollController? controller,
	bool? isAlwaysShown,
	this.showTrackOnHover,
	this.hoverThickness,
	double? thickness,
	Radius? radius,
	ScrollNotificationPredicate? notificationPredicate,
	bool? interactive,
	ScrollbarOrientation? scrollbarOrientation,
	}) : super(
	key: key,
	child: child,
	controller: controller,
	isAlwaysShown: isAlwaysShown,
	thickness: thickness,
	radius: radius,
	fadeDuration: _kScrollbarFadeDuration,
	timeToFade: _kScrollbarTimeToFade,
	pressDuration: Duration.zero,
	notificationPredicate: notificationPredicate ?? defaultScrollNotificationPredicate,
	interactive: interactive,
	scrollbarOrientation: scrollbarOrientation,
	);

	final bool? showTrackOnHover;
	final double? hoverThickness;

	@override
	_MaterialScrollbarState createState() => _MaterialScrollbarState();
	}

	class _MaterialScrollbarState extends RawScrollbarState<_MaterialScrollbar> {
	late AnimationController _hoverAnimationController;
	bool _dragIsActive = false;
	bool _hoverIsActive = false;
	late ColorScheme _colorScheme;
	late ScrollbarThemeData _scrollbarTheme;
	// On Android, scrollbars should match native appearance.
	late bool _useAndroidScrollbar;

	@override
	bool get showScrollbar => widget.isAlwaysShown ?? _scrollbarTheme.isAlwaysShown ?? false;

	@override
	bool get enableGestures => widget.interactive ?? _scrollbarTheme.interactive ?? !_useAndroidScrollbar;

	bool get _showTrackOnHover => widget.showTrackOnHover ?? _scrollbarTheme.showTrackOnHover ?? false;

	Set<MaterialState> get _states => <MaterialState>{
	if (_dragIsActive) MaterialState.dragged,
	if (_hoverIsActive) MaterialState.hovered,
	};

	MaterialStateProperty<Color> get _thumbColor {
	final Color onSurface = _colorScheme.onSurface;
	final Brightness brightness = _colorScheme.brightness;
	late Color dragColor;
	late Color hoverColor;
	late Color idleColor;
	switch (brightness) {
	case Brightness.light:
	dragColor = onSurface.withOpacity(0.6);
	hoverColor = onSurface.withOpacity(0.5);
	idleColor = _useAndroidScrollbar
	? Theme.of(context).highlightColor.withOpacity(1.0)
	: onSurface.withOpacity(0.1);
	break;
	case Brightness.dark:
	dragColor = onSurface.withOpacity(0.75);
	hoverColor = onSurface.withOpacity(0.65);
	idleColor = _useAndroidScrollbar
	? Theme.of(context).highlightColor.withOpacity(1.0)
	: onSurface.withOpacity(0.3);
	break;
	}

	return MaterialStateProperty.resolveWith((Set<MaterialState> states) {
	if (states.contains(MaterialState.dragged))
	return _scrollbarTheme.thumbColor?.resolve(states) ?? dragColor;

	// If the track is visible, the thumb color hover animation is ignored and
	// changes immediately.
	if (states.contains(MaterialState.hovered) && _showTrackOnHover)
	return _scrollbarTheme.thumbColor?.resolve(states) ?? hoverColor;

	return Color.lerp(
	_scrollbarTheme.thumbColor?.resolve(states) ?? idleColor,
	_scrollbarTheme.thumbColor?.resolve(states) ?? hoverColor,
	_hoverAnimationController.value,
	)!;
	});
	}

	MaterialStateProperty<Color> get _trackColor {
	final Color onSurface = _colorScheme.onSurface;
	final Brightness brightness = _colorScheme.brightness;
	return MaterialStateProperty.resolveWith((Set<MaterialState> states) {
	if (states.contains(MaterialState.hovered) && _showTrackOnHover) {
	return _scrollbarTheme.trackColor?.resolve(states)
	?? (brightness == Brightness.light
	? onSurface.withOpacity(0.03)
	: onSurface.withOpacity(0.05));
	}
	return const Color(0x00000000);
	});
	}

	MaterialStateProperty<Color> get _trackBorderColor {
	final Color onSurface = _colorScheme.onSurface;
	final Brightness brightness = _colorScheme.brightness;
	return MaterialStateProperty.resolveWith((Set<MaterialState> states) {
	if (states.contains(MaterialState.hovered) && _showTrackOnHover) {
	return _scrollbarTheme.trackBorderColor?.resolve(states)
	?? (brightness == Brightness.light
	? onSurface.withOpacity(0.1)
	: onSurface.withOpacity(0.25));
	}
	return const Color(0x00000000);
	});
	}

	MaterialStateProperty<double> get _thickness {
	return MaterialStateProperty.resolveWith((Set<MaterialState> states) {
	if (states.contains(MaterialState.hovered) && _showTrackOnHover)
	return widget.hoverThickness
	?? _scrollbarTheme.thickness?.resolve(states)
	?? _kScrollbarThicknessWithTrack;
	// The default scrollbar thickness is smaller on mobile.
	return widget.thickness
	?? _scrollbarTheme.thickness?.resolve(states)
	?? (_kScrollbarThickness / (_useAndroidScrollbar ? 2 : 1));
	});
	}

	@override
	void initState() {
	super.initState();
	_hoverAnimationController = AnimationController(
	vsync: this,
	duration: const Duration(milliseconds: 200),
	);
	_hoverAnimationController.addListener(() {
	updateScrollbarPainter();
	});
	}

	@override
	void didChangeDependencies() {
	final ThemeData theme = Theme.of(context);
	_colorScheme = theme.colorScheme;
	_scrollbarTheme = theme.scrollbarTheme;
	switch (theme.platform) {
	case TargetPlatform.android:
	_useAndroidScrollbar = true;
	break;
	case TargetPlatform.iOS:
	case TargetPlatform.linux:
	case TargetPlatform.fuchsia:
	case TargetPlatform.macOS:
	case TargetPlatform.windows:
	_useAndroidScrollbar = false;
	break;
	}
	super.didChangeDependencies();
	}

	@override
	void updateScrollbarPainter() {
	scrollbarPainter
	..color = _thumbColor.resolve(_states)
	..trackColor = _trackColor.resolve(_states)
	..trackBorderColor = _trackBorderColor.resolve(_states)
	..textDirection = Directionality.of(context)
	..thickness = _thickness.resolve(_states)
	..radius = widget.radius ?? _scrollbarTheme.radius ?? (_useAndroidScrollbar ? null : _kScrollbarRadius)
	..crossAxisMargin = _scrollbarTheme.crossAxisMargin ?? (_useAndroidScrollbar ? 0.0 : _kScrollbarMargin)
	..mainAxisMargin = _scrollbarTheme.mainAxisMargin ?? 0.0
	..minLength = _scrollbarTheme.minThumbLength ?? _kScrollbarMinLength
	..padding = MediaQuery.of(context).padding
	..scrollbarOrientation = widget.scrollbarOrientation;
	}

	@override
	void handleThumbPressStart(Offset localPosition) {
	super.handleThumbPressStart(localPosition);
	setState(() { _dragIsActive = true; });
	}

	@override
	void handleThumbPressEnd(Offset localPosition, Velocity velocity) {
	super.handleThumbPressEnd(localPosition, velocity);
	setState(() { _dragIsActive = false; });
	}

	@override
	void handleHover(PointerHoverEvent event) {
	super.handleHover(event);
	// Check if the position of the pointer falls over the painted scrollbar
	if (isPointerOverScrollbar(event.position, event.kind, forHover: true)) {
	// Pointer is hovering over the scrollbar
	setState(() { _hoverIsActive = true; });
	_hoverAnimationController.forward();
	} else if (_hoverIsActive) {
	// Pointer was, but is no longer over painted scrollbar.
	setState(() { _hoverIsActive = false; });
	_hoverAnimationController.reverse();
	}
	}

	@override
	void handleHoverExit(PointerExitEvent event) {
	super.handleHoverExit(event);
	setState(() { _hoverIsActive = false; });
	_hoverAnimationController.reverse();
	}

	@override
	void dispose() {
	_hoverAnimationController.dispose();
	super.dispose();
	}
	}