Flutter Inset Box Shadow

Flutter currently does not support the inset property for shadows. This type of shadow is for example used in Neumorphism.

This package extends BoxShadow and BoxDecoration to support the inset property.

Features

• All properties of BoxShadow are supported.
• If the property of a BoxShadow changes during a transition, we first make the old shadow disappear before making the new one appear.

Example

import 'package:flutter/material.dart' hide BoxDecoration, BoxShadow;
import 'package:flutter_inset_box_shadow/flutter_inset_box_shadow.dart';

void main() {
  runApp(const ExampleApp());
}

const primaryColor = Color(0xFFE0E0E0);

class ExampleApp extends StatelessWidget {
  const ExampleApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Example',
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        backgroundColor: primaryColor,
        body: Center(
          child: Container(
            width: 150,
            height: 150,
            decoration: BoxDecoration(
              borderRadius: BorderRadius.circular(50),
              color: primaryColor,
              boxShadow: const [
                BoxShadow(
                  offset: Offset(-20, -20),
                  blurRadius: 60,
                  color: Colors.white,
                  inset: true,
                ),
                BoxShadow(
                  offset: Offset(20, 20),
                  blurRadius: 60,
                  color: Color(0xFFBEBEBE),
                  inset: true,
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}

Usage

First, add the package:

flutter pub add flutter_inset_box_shadow

Then, import it as follows:

import 'package:flutter/material.dart' hide BoxDecoration, BoxShadow;
import 'package:flutter_inset_box_shadow/flutter_inset_box_shadow.dart';

It is necessary to hide BoxDecoration and BoxShadow because this library replaces them.

BoxShadow now has a boolean inset property, which is set to false by default.

return Container(
  decoration: BoxDecoration(
    boxShadow: [
      BoxShadow(
        blurRadius: 5,
        color: Colors.red,
      ),
      BoxShadow(
        offset: Offset(1, 2),
        blurRadius: 5,
        spreadRadius: 2,
        color: Colors.green,
        inset: true,
      ),
    ],
  ),
);

How does it work?

The algorithm used is the same as that of Blink, the Chromium rendering engine.

The idea is that we draw a rectangle hollowed out by another rounded rectangle inside, then we blur this hollowed rectangle.