flame/lib/game.dart

import 'dart:ui';
import 'dart:typed_data';

abstract class Game {

  void update(double t);

  void render(Canvas canvas);

  start() {
    var previous = Duration.ZERO;

    window.onBeginFrame = (now) {
      var recorder = new PictureRecorder();
      var canvas = new Canvas(recorder, new Rect.fromLTWH(
          0.0, 0.0, window.physicalSize.width, window.physicalSize.height));

      Duration delta = now - previous;
      if (previous == Duration.ZERO) {
        delta = Duration.ZERO;
      }
      previous = now;

      var t = delta.inMicroseconds / Duration.MICROSECONDS_PER_SECOND;

      update(t);
      render(canvas);

      var deviceTransform = new Float64List(16)
        ..[0] = 1.0 // window.devicePixelRatio
        ..[5] = 1.0 // window.devicePixelRatio
        ..[10] = 1.0
        ..[15] = 1.0;

      var builder = new SceneBuilder()
        ..pushTransform(deviceTransform)
        ..addPicture(Offset.zero, recorder.endRecording())
        ..pop();

      window.render(builder.build());
      window.scheduleFrame();
    };

    window.scheduleFrame();
  }
}