samples/pop_pop_win: now based on StageXL

samples/pop_pop_win/lib/src/canvas/board_element.dart

-part of pop_pop_win.canvas;
-
-class BoardElement extends ParentThing {
-  Array2d<SquareElement> _elements;
-
-  BoardElement(): super(0, 0) {
-    cacheEnabled = true;
-  }
-
-  int get visualChildCount {
-    if (_elements == null) {
-      return 0;
-    } else {
-      return _elements.length;
-    }
-  }
-
-  Thing getVisualChild(int index) {
-    return _elements[index];
-  }
-
-  void update() {
-    if (_game == null) {
-      _elements = null;
-    } else if(_elementsNeedUpdate) {
-      _elements = new Array2d<SquareElement>(
-          _game.field.width, _game.field.height);
-
-      for (int i = 0; i < _elements.length; i++) {
-        final coords = _elements.getCoordinate(i);
-        final se = new SquareElement(coords.item1, coords.item2);
-        se.registerParent(this);
-
-        _gameElement.wireSquareMouseEvent(se);
-
-        // position the square
-        final etx = se.addTransform();
-        etx.setToTranslation(coords.item1 * SquareElement._size,
-            coords.item2 * SquareElement._size);
-
-        _elements[i] = se;
-      }
-
-      size = new Size(_game.field.width * SquareElement._size,
-          _game.field.height * SquareElement._size);
-    }
-    super.update();
-  }
-
-  GameElement get _gameElement => (parent as CanvasThing).parent;
-
-  Game get _game => _gameElement._game;
-
-  bool get _elementsNeedUpdate {
-    assert(_game != null);
-    return _elements == null ||
-        _elements.width != _game.field.width ||
-        _elements.height != _game.field.height;
-  }
-
-  TextureData get _textureData => _gameElement._textureData;
-
-}