browserloops-examples/lib/game/Game.dart

import 'dart:html';

import 'dart:math';

typedef void gridIterator(int x, int y);

class Game {
  List<List<Color>> grid;
  CanvasElement canvas;
  Random rng = new Random();

  double _oscill = 0.1;
  bool _oscillDir = true; // oscillate upwards (true) or downwards (false)
  double _OSCILLSPEED = 0.1;
  bool _fwd = true;

  Game(CanvasElement this.canvas) {
    grid = _buildGrid(5, 5, new Color(255, 0, 255));
  }

  // In-World Logic Updates
  void update([num dt]) {
    int ry = rng.nextInt(grid.length);
    grid[ry][rng.nextInt(grid[ry].length)] = new Color(rng.nextInt(255), rng.nextInt(255), rng.nextInt(255));
  }

  // Render Pipeline
  void draw([num interp]) {
    CanvasRenderingContext2D ctx = this.canvas.context2D;

    int brickW = (canvas.width ~/ grid[0].length);
    int brickH = (canvas.height ~/ grid.length);

    ctx.clearRect(0, 0, canvas.width, canvas.height);
    _grid_foreach((x, y) {
        Color col = _oscillate(grid[y][x]);
        ctx.setFillColorRgb(col.r, col.g, col.b);
        ctx.fillRect(x*brickW, y*brickH, brickW, brickH);
    });
  }

  // Slightly oscillating colors to highlight rendering updates
  Color _oscillate(Color col) {
    if(_oscill >= 50.0 || _oscill <= -50.0) {
      _oscillDir = !_oscillDir;
      _oscill = max( min(_oscill, 49.0), -49.0);
    }
    else _oscillDir == true ? _oscill += _OSCILLSPEED : _oscill -= _OSCILLSPEED;

    int o = _oscill.toInt();
    return new Color(col.r + o, col.g + o, col.b + o);
  }

  void _grid_foreach(gridIterator fun) {
    for (int y = 0; y < grid.length; y++) {
      for (int x = 0; x < grid[y].length; x++) {
        fun(x, y);
      }
    }
  }

  List<List<Color>> _buildGrid(int w, int h, Color col) {
    List<List<Color>> grid = new List(h);
    for (int y = 0; y < h; y++) {
      grid[y] = new List(w);
      for (int x = 0; x < w; x++) {
        grid[y][x] = col;
      }
    }
    return grid;
  }
}

class Color {
  final int r;
  final int g;
  final int b;

  const Color(this.r, this.g, this.b);
}