Rename App to Engine

lib/src/Engine.dart

@@ -0,0 +1,69 @@
+import 'dart:html' as html;
+
+import 'package:rules_of_living/src/Grid.dart';
+
+class Engine {
+  // Elapsed Time Counter - useful for Safety Timeout
+  Stopwatch _elapsed = new Stopwatch();
+
+  // Game Tick Rate - *does* impact game speed
+  int _MS_PER_STEP = 1000 ~/ 3;
+
+  // Max Frame (i.e. Rendering) rate - does *not* impact game speed
+  final int _MS_PER_FRAME = 1000 ~/ 30;
+
+  // ms stuck in updateloop after which game will declare itself unresponsive
+  final int SAFETY_TIMEOUT = 2000;
+
+  num _updateLag = 0.0;
+  num _drawLag = 0.0;
+
+  final html.CanvasElement canvas;
+  Grid grid = new Grid(100, 100);
+  bool running = false;
+
+  Engine(this.canvas) {
+    _elapsed.start();
+    grid.addPattern(amount: 15, dispersal: 5);
+  }
+
+  void reset() {
+    grid.reset();
+  }
+
+  void clear() {
+    grid = new Grid(100, 100);
+    running = false;
+  }
+
+  void process(num now) {
+    _drawLag += _elapsed.elapsedMilliseconds;
+    _updateLag += _elapsed.elapsedMilliseconds;
+    _elapsed.reset();
+
+    while (_updateLag >= _MS_PER_STEP) {
+      if (_elapsed.elapsedMilliseconds > SAFETY_TIMEOUT) {
+        // TODO stub - give warning etc when this occurs
+        print("ERROR STUCK IN UPDATE LOOP");
+        break;
+      }
+      if (running == true) update();
+      _updateLag -= _MS_PER_STEP;
+    }
+
+    if (_drawLag >= _MS_PER_FRAME) {
+      render(_updateLag / _MS_PER_STEP);
+      _drawLag = 0;
+    }
+  }
+
+  void update() {
+//    print("updating");
+    if(!grid.update()) running = false;
+  }
+
+  void render([num interp]) {
+//    print("rendering");
+    grid.render(canvas, interp);
+  }
+}