Fixes matrix transformations in sprites

sky/examples/game/lib/transform_node.dart

-part of sprites;
-
-double degrees2radians(double degrees) => degrees * Math.PI/180.8;
-
-double radians2degrees(double radians) => radians * 180.0/Math.PI;
-
-class TransformNode {
-
-  // Member variables
-
-  SpriteBox _spriteBox;
-  TransformNode _parent;
-
-  Vector2 _position;
-  double _rotation;
-  
-  bool _isMatrixDirty;
-  Matrix3 _transform;
-  Matrix3 _pivotTransform;
-  
-  double _width;
-  double _height;
-
-  double _scaleX;
-  double _scaleY;
-  
-  Vector2 _pivot;
-
-  bool visible;
-
-  double _zPosition;
-  int _addedOrder;
-  int _childrenLastAddedOrder;
-  bool _childrenNeedSorting;
-
-  List<TransformNode>_children;
-
-  // Constructors
-  
-  TransformNode() {
-    _width = 0.0;
-    _height = 0.0;
-    _rotation = 0.0;
-    _pivot = new Vector2(0.0, 0.0);
-    _position = new Vector2(0.0, 0.0);
-    _scaleX = _scaleY = 1.0;
-    _isMatrixDirty = false;
-    _transform = new Matrix3.identity();
-    _pivotTransform = new Matrix3.identity();
-    _children = [];
-    _childrenNeedSorting = false;
-    _childrenLastAddedOrder = 0;
-    visible = true;
-  }
-
-  // Property setters and getters
-
-  SpriteBox get spriteBox => _spriteBox;
-
-  TransformNode get parent => _parent;
-  
-  double get rotation => _rotation;
-  
-  void set rotation(double rotation) {
-    _rotation = rotation;
-    _isMatrixDirty = true;
-  }
-
-  Vector2 get position => _position;
-  
-  void set position(Vector2 position) {
-    _position = position;
-    _isMatrixDirty = true;
-  }
-  
-  double get width => _width;
-  
-  void set width(double width) {
-    _width = width;
-    _isMatrixDirty = true;
-  }
-  
-  double get height => _height;
-    
-  void set height(double height) {
-    _height = height;
-    _isMatrixDirty = true;
-  }
-  
-  Vector2 get pivot => _pivot;
-  
-  void set pivot(Vector2 pivot) {
-    _pivot = pivot;
-    _isMatrixDirty = true;
-  }
-
-  double get zPosition => _zPosition;
-
-  void set zPosition(double zPosition) {
-    _zPosition = zPosition;
-    if (_parent != null) {
-      _parent._childrenNeedSorting = true;
-    }
-  }
-
-  double get scale {
-    assert(_scaleX == _scaleY);
-    return _scaleX;
-  }
-
-  void set scale(double scale) {
-    _scaleX = _scaleY = scale;
-    _isMatrixDirty = true;
-  }
-
-  List<TransformNode> get children => _children;
-
-  // Adding and removing children
-
-  void addChild(TransformNode child) {
-    assert(child._parent == null);
-
-    _childrenNeedSorting = true;
-    _children.add(child);
-    child._parent = this;
-    child._spriteBox = this._spriteBox;
-    _childrenLastAddedOrder += 1;
-    child._addedOrder = _childrenLastAddedOrder;
-  }
-
-  void removeChild(TransformNode child) {
-    if (_children.remove(child)) {
-      child._parent = null;
-      child._spriteBox = null;
-    }
-  }
-
-  void removeFromParent() {
-    assert(_parent != null);
-    _parent.removeFromParent();
-  }
-
-  void removeAllChildren() {
-    for (TransformNode child in _children) {
-      child._parent = null;
-      child._spriteBox = null;
-    }
-    _children = [];
-    _childrenNeedSorting = false;
-  }
-
-  // Calculating the transformation matrix
-  
-  Matrix3 get transformMatrix {
-    if (!_isMatrixDirty) {
-      return _transform;
-    }
-   
-    Vector2 pivotInPoints = new Vector2(_width * _pivot[0], _height * _pivot[1]);
-    
-    double cx, sx, cy, sy;
-    
-    if (_rotation == 0) {
-      cx = 1.0;
-      sx = 0.0;
-      cy = 1.0;
-      sy = 0.0;
-    }
-    else {
-      double radiansX = degrees2radians(_rotation);
-      double radiansY = degrees2radians(_rotation);
-      
-      cx = Math.cos(radiansX);
-      sx = Math.sin(radiansX);
-      cy = Math.cos(radiansY);
-      sy = Math.sin(radiansY);
-    }
-    
-    // TODO: Add support for scale
-    double scaleX = 1.0;
-    double scaleY = 1.0;
-    
-    // Create transformation matrix for scale, position and rotation
-    _transform.setValues(cy * scaleX, sy * scaleX, 0.0,
-               -sx * scaleY, cx * scaleY, 0.0,
-               _position[0], _position[1], 1.0);
-    
-    if (_pivot.x != 0 || _pivot.y != 0) {
-      _pivotTransform.setValues(1.0, 0.0, 0.0, 0.0, 1.0, 0.0, pivotInPoints[0], pivotInPoints[1], 1.0);
-      _transform.multiply(_pivotTransform);
-    }
-    
-    return _transform;
-  }
-
-  // Rendering
-  
-  void visit(PictureRecorder canvas) {
-    if (!visible) return;
-
-    prePaint(canvas);
-    paint(canvas);
-    visitChildren(canvas);
-    postPaint(canvas);
-  }
-  
-  void prePaint(PictureRecorder canvas) {
-    canvas.save();
-    
-    canvas.translate(_position[0], _position[1]);
-    canvas.rotate(degrees2radians(_rotation));
-    canvas.scale(_scaleX, _scaleY);
-    canvas.translate(-_width*_pivot[0], -_height*_pivot[1]);
-    
-    // TODO: Use transformation matrix instead of individual calls
-//    List<double> matrix = [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0];
-//    this.transformMatrix.copyIntoArray(matrix);
-//    canvas.concat(matrix);
-  }
-  
-  void paint(PictureRecorder canvas) {
-    
-  }
- 
-  void visitChildren(PictureRecorder canvas) {
-    // Sort children primarily by zPosition, secondarily by added order
-    if (_childrenNeedSorting) {
-      _children.sort((TransformNode a, TransformNode b) {
-        if (a._zPosition == b._zPosition) {
-          return b._addedOrder - a._addedOrder;
-        }
-        else if (a._zPosition > b._zPosition) {
-          return 1;
-        }
-        else {
-          return -1;
-        }
-      });
-      _childrenNeedSorting = false;
-    }
-
-    // Visit each child
-    _children.forEach((child) => child.visit(canvas));
-  }
-  
-  void postPaint(PictureRecorder canvas) {
-    canvas.restore();
-  }
-
-  // Receiving update calls
-
-  void update(double dt) {
-
-  }
-}