A Flutter package that provides smooth, animated scrolling for pointer-based input devices, such as mouse wheels and trackpads. It includes some widely used scroll animations that can be used out of the box, while also offering the flexibility to implement custom scroll animations.

Usage

To use this package, create an instance of AnimatedScrollController with your preferred ScrollAnimation factory, and pass it to your scrollable widget.

import 'package:flutter/material.dart';
import 'package:scroll_animator/scroll_animator.dart';

void main() => runApp(const ExampleApp());

class ExampleApp extends StatelessWidget {
  const ExampleApp({super.key});

  @override
  Widget build(final BuildContext context) => MaterialApp(
        home: Scaffold(
          appBar: AppBar(title: const Text('Scroll Animator Example')),
          body: _ScrollAnimatorExample(),
        ),
      );
}

class _ScrollAnimatorExample extends StatefulWidget {
  @override
  _ScrollAnimatorExampleState createState() => _ScrollAnimatorExampleState();
}

class _ScrollAnimatorExampleState extends State<_ScrollAnimatorExample> {
  late final ScrollController _scrollController;

  @override
  void initState() {
    super.initState();
    _scrollController = AnimatedScrollController(
      animationFactory: const ChromiumEaseInOut(),
    );
  }

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

  @override
  Widget build(final BuildContext context) => ListView.builder(
        controller: _scrollController,
        itemCount: 100,
        itemBuilder: (final context, final index) => ListTile(
          title: Text('Item $index'),
        ),
      );
}

Scroll animations

This package provides two built-in ScrollAnimation implementations, ported directly from Chromium along with their unit tests, so they should behave identically as in Chromium-based browsers.

ChromiumEaseInOut

This is the default scroll animation for most Chromium-based browsers, which is active when the #smooth-scrolling flag is enabled and #windows-scrolling-personality is disabled.

ChromiumImpulse

This is the default scroll animation for Microsoft Edge, but can also be enabled in other Chromium-based browsers by enabling both #smooth-scrolling and #windows-scrolling-personality flags.

Pointer precision

Trackpads typically provide precise and frequent scroll deltas, which often leads to the assumption that scroll smoothing isn't necessary. However, some trackpads can produce larger, less frequent deltas, similar to mouse wheels. Therefore, this package handles all scroll inputs without making assumptions based on the pointer type.

See this Chromium bug for discussion on this topic.