dart_ui_isolate 1.0.0

Allows running `dart:ui` in an isolate.

dart_ui_isolate

This plugin let you run dart:ui in an isolate.

See this issue: https://github.com/flutter/flutter/issues/10647

Inspired by flutter_isolate, this plugin uses multiple FlutterEngine instances.

DartUiIsolate API

	Android	iOS	Description
DartUiIsolate.spawn()	✅	✅	spawns a new DartUiIsolate
isolate.pause()	✅	✅	pauses the isolate
isolate.resume()	✅	✅	resumes the isolate
isolate.kill()	✅	✅	kills the an isolate
flutterCompute()	✅	✅	runs code in compute callback

Usage

To spawn a DartUiIsolate, call the spawn() method, or the flutterCompute() method.

Killing

DartUiIsolates require explict termination with kill().

DartUiIsolates are backed by a platform specific 'view', so the event loop does not automatically terminate when there is no more work left.

Compute Callback

To use an isolate for a single task (like the Flutter compute method), use flutterCompute:

@pragma('vm:entry-point')
Future<int> expensiveWork(int arg) async {
  int result;
  // lots of calculations
  return result;
}

Future<int> doExpensiveWorkInBackground() async {
  return await flutterCompute(expensiveWork, arg);
}

Isolate Entry Point

The isolate entrypoint must be a top-level function, or a class static method.

The isolate entrypoint must decorated with @pragma('vm:entry-point'). Otherwise the app will crash in release mode.

MacOS: Due to limitations on macOS, the enty point must be in /lib/main.dart.

Top-Level Entry Point:

@pragma('vm:entry-point')
void topLevelFunction(Map<String, dynamic> args) {
  // performs work in an isolate
}

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  @override
  void initState() {
    DartUiIsolate.spawn(topLevelFunction, {});
    super.initState();
  }

  Widget build(BuildContext context) {
    return Container();
  }
}

Class Static Entry Point:

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  
  @pragma('vm:entry-point')
  static void topLevelFunction(Map<String, dynamic> args) {
    // performs work in an isolate
  }

  @override
  void initState() {
    DartUiIsolate.spawn(_MyAppState.staticMethod, {});
    super.initState();
  }

  Widget build(BuildContext context) {
    return Container();
  }
}

A class-level method will not work and will throw an Exception:

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {

  
  void classMethod(Map<String, dynamic> args) {
    // don't do this!
  }

  @override
  void initState() {
    // this will throw NoSuchMethodError: The method 'toRawHandle' was called on null.
    DartUiIsolate.spawn(classMethod, {}); 
    super.initState();
  }
  Widget build(BuildContext context) {
    return Container();
  }
}