Baby game

gameloop.dart

import 'dart:ui';

import 'package:flutter/cupertino.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/scheduler.dart';
import 'package:flutter/services.dart';

final entities = <Entity>[];

void main() {
  GameBinding();
}

class GameBinding extends BindingBase with SchedulerBinding, ServicesBinding {
  @override
  void initInstances() {
    super.initInstances();
    RawKeyboard.instance.addListener(pending.add);
    scheduleFrameCallback(gameLoop);
  }

  final pending = <RawKeyEvent>[];
  final entities = <Entity>[
    Entity(),
  ];


  void gameLoop(Duration duration) {
    var recorder = PictureRecorder();
    var canvas = Canvas(recorder);
    var playerMovement = normalizeEvents(pending);
    for (var i = 0; i < entities.length; i++) {
      var entity = entities[i];
      entity.move(playerMovement);
      entity.draw(canvas);
    }
    pending.clear();
    var picture = recorder.endRecording();
    var sceneBuilder = SceneBuilder();
    sceneBuilder.addPicture(Offset.zero, picture);
    window.render(sceneBuilder.build());
    scheduleFrameCallback(gameLoop);
  }
}

/// Normalize a stack of keyboard events into a single offset.
Offset normalizeEvents(List<RawKeyEvent> events) {
  var xOffset = 0.0;
  var yOffset = 0.0;
  for (var i = 0; i < events.length; i++) {
    var event = events[i];
    switch (event.logicalKey.keyId) {
      // A
      case 97:
        xOffset -= 5;
        break;
      // D
      case 100:
        xOffset += 5;
        break;
      // S
      case 115:
        yOffset += 5;
        break;
      // W
      case 119:
        yOffset -= 5;
        break;
    }
  }
  return Offset(xOffset, yOffset);
}

final paint = Paint()
  ..color = Color.fromRGBO(125, 125, 125, 1)
  ..style = PaintingStyle.fill;

class Entity {
  double xPosition = 0;
  double yPosition = 0;
  double zPosition = 0;
  double velocity = 1;
  bool isPlayer = true;

  void move(Offset offset) {
    if (!isPlayer) {
      return;
    }
    var dx = offset.dx;
    var dy = offset.dy;
    xPosition += dx;
    yPosition += dy;
  }

  void draw(Canvas canvas) {
    canvas.drawRect(Rect.fromLTWH(xPosition, yPosition, 25, 25), paint);
  }
}