Canvas.drawVertices does not use anti-aliasing

[NWalker1208]

The drawVertices method does not use any anti-aliasing, even when it is enabled in the Paint settings.

Steps to Reproduce

1. Draw a set of vertices with drawVertices.
2. Draw the same set using drawPath with Path.addPolygon.
3. Use the same Paint for both methods.

Expected results:
Both drawings should be anti-aliased.

Actual results:
The drawing of drawVertices is not anti-aliased.

Logs

flutter analyze

Analyzing vertices_test...
No issues found! (ran in 2.1s)

flutter doctor -v

[√] Flutter (Channel dev, 2.1.0-10.0.pre, on Microsoft Windows [Version 10.0.19042.844], locale en-US)
    • Flutter version 2.1.0-10.0.pre at d:\Developer\flutter
    • Framework revision cc9b78fc5c (8 days ago), 2021-02-25 13:26:03 -0800
    • Engine revision a252ec09b7
    • Dart version 2.13.0 (build 2.13.0-77.0.dev)

[√] Android toolchain - develop for Android devices (Android SDK version 30.0.1)
    • Android SDK at D:\Developer\Android\SDK
    • Platform android-30, build-tools 30.0.1
    • ANDROID_SDK_ROOT = D:\Developer\Android\SDK
    • Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b01)
    • All Android licenses accepted.

[√] Chrome - develop for the web
    • Chrome at C:\Program Files (x86)\Google\Chrome\Application\chrome.exe

[√] Visual Studio - develop for Windows (Visual Studio Community 2019 16.8.5)
    • Visual Studio at C:\Program Files (x86)\Microsoft Visual Studio\2019\Community
    • Visual Studio Community 2019 version 16.8.31005.135
    • Windows 10 SDK version 10.0.18362.0

[√] Android Studio (version 4.1.0)
    • Android Studio at C:\Program Files\Android\Android Studio
    • Flutter plugin can be installed from:
       https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
       https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b01)

[√] VS Code, 64-bit edition (version 1.52.1)
    • VS Code at C:\Program Files\Microsoft VS Code
    • Flutter extension version 3.19.0

[√] Connected device (3 available)
    • Windows (desktop) • windows • windows-x64    • Microsoft Windows [Version 10.0.19042.844]
    • Chrome (web)      • chrome  • web-javascript • Google Chrome 89.0.4389.72
    • Edge (web)        • edge    • web-javascript • Microsoft Edge 88.0.705.81

• No issues found!

Sample Code

import 'dart:math';
import 'dart:ui';

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

enum PaintMethod {
  /// Path uses Path.addPolygon to draw a path.
  path,

  /// Vertices uses the drawVertices method. No anti-aliasing is applied.
  vertices,
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Vertex Test',
      theme: ThemeData(primarySwatch: Colors.blue),
      home: MyHomePage(
        shape: [
          /// Creates a 15 sided polygon
          for (int i = 0; i < 16; i++)
            Offset(50, 50) + Offset.fromDirection(2 * pi * (i / 15), 30),
        ],
      ),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key? key, this.shape = const []}) : super(key: key);

  /// The shape to be painted.
  final List<Offset> shape;

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

class _MyHomePageState extends State<MyHomePage> {
  /// The method to use when painting.
  PaintMethod method = PaintMethod.path;

  void setMethod(PaintMethod value) => setState(() => method = value);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Vertex Test'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Expanded(
              child: CustomPaint(
                painter: VertexPainter(widget.shape, method),
                child: Container(),
              ),
            ),
            Row(
              children: [
                Radio<PaintMethod>(
                  value: PaintMethod.path,
                  groupValue: method,
                  onChanged: (v) => setMethod(v!),
                ),
                Expanded(child: Text('Path')),
                Radio<PaintMethod>(
                  value: PaintMethod.vertices,
                  groupValue: method,
                  onChanged: (v) => setMethod(v!),
                ),
                Expanded(child: Text('Vertices')),
              ],
            )
          ],
        ),
      ),
    );
  }
}

class VertexPainter extends CustomPainter {
  const VertexPainter(this.positions, this.method);

  /// Positions should be between (0,0) and (100,100)
  final List<Offset> positions;

  /// The method to use when painting
  final PaintMethod method;

  @override
  void paint(Canvas canvas, Size size) {
    canvas.save();
    canvas.scale(size.width / 100, size.height / 100);
    final paint = Paint()
      ..color = Colors.red
      ..style = PaintingStyle.fill
      ..isAntiAlias = true;

    switch (method) {
      case PaintMethod.path:
        canvas.drawPath(Path()..addPolygon(positions, false), paint);
        break;
      case PaintMethod.vertices:
        canvas.drawVertices(
          Vertices(VertexMode.triangleFan, positions),
          BlendMode.srcOver,
          paint,
        );
    }
    canvas.restore();
  }

  @override
  bool shouldRepaint(VertexPainter old) =>
      old.positions != positions || old.method != method;
}

Screenshots

These screenshots are from the sample code above.

Full Drawing

drawPath	drawVertices

Cropped

drawPath	drawVertices

[darshankawar]

flutter doctor -v

[✓] Flutter (Channel stable, 2.0.1, on Mac OS X 10.15.4 19E2269 darwin-x64,
    locale en-GB)
    • Flutter version 2.0.1 at /Users/dhs/documents/Fluttersdk/flutter
    • Framework revision c5a4b4029c (4 days ago), 2021-03-04 09:47:48 -0800
    • Engine revision 40441def69
    • Dart version 2.12.0

[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.0)
    • Android SDK at /Users/dhs/Library/Android/sdk
    • Platform android-30, build-tools 30.0.0
    • Java binary at: /Applications/Android
      Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build
      1.8.0_242-release-1644-b3-6915495)
    • All Android licenses accepted.

[!] Xcode - develop for iOS and macOS
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 12.3, Build version 12C33
    ! CocoaPods 1.9.3 out of date (1.10.0 is recommended).
        CocoaPods is used to retrieve the iOS and macOS platform side's plugin
        code that responds to your plugin usage on the Dart side.
        Without CocoaPods, plugins will not work on iOS or macOS.
        For more info, see https://flutter.dev/platform-plugins
      To upgrade see
      https://guides.cocoapods.org/using/getting-started.html#installation for
      instructions.

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 4.1)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build
      1.8.0_242-release-1644-b3-6915495)

[✓] VS Code (version 1.54.1)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.18.1

[✓] Connected device (3 available)
    • SM A260G (mobile) • 5200763ebcfa861f • android-arm    • Android 8.1.0 (API
      27)
    • macOS (desktop)   • macos            • darwin-x64     • Mac OS X 10.15.4
      19E2269 darwin-x64
    • Chrome (web)      • chrome           • web-javascript • Google Chrome
      88.0.4324.192

! Doctor found issues in 1 category.