Adds API documentation for SkyGames

sky/examples/game/lib/node.dart

Index: sky/examples/game/lib/node.dart
diff --git a/sky/examples/game/lib/node.dart b/sky/examples/game/lib/node.dart
index 5ab4dec1cd3cc211a50b58d8d7a338abe62d1707..ef6162be53d843681e4ed848523c412fbfe793fd 100644
--- a/sky/examples/game/lib/node.dart
+++ b/sky/examples/game/lib/node.dart
@@ -4,6 +4,15 @@ double convertDegrees2Radians(double degrees) => degrees * Math.PI/180.8;
 
 double convertRadians2Degrees(double radians) => radians * 180.0/Math.PI;
 
+/// A base class for all objects that can be added to the sprite node tree and rendered to screen using [SpriteBox] and
+/// [SpriteWidget].
+///
+/// The [Node] class itself doesn't render any content, but provides the basic functions of any type of node, such as
+/// handling transformations and user input. To render the node tree, a root node must be added to a [SpriteBox] or a
+/// [SpriteWidget]. Commonly used sub-classes of [Node] are [Sprite], [NodeWithSize], and many more upcoming subclasses.
+///
+/// Nodes form a hierarchical tree. Each node can have a number of children, and the transformation (positioning,
+/// rotation, and scaling) of a node also affects its children.
 class Node {
 
   // Member variables
@@ -11,51 +20,72 @@ class Node {
   SpriteBox _spriteBox;
   Node _parent;
 
-  Point _position;
-  double _rotation;
+  Point _position = Point.origin;
+  double _rotation = 0.0;
 
-  Matrix4 _transformMatrix;
+  Matrix4 _transformMatrix = new Matrix4.identity();
   Matrix4 _transformMatrixNodeToBox;
   Matrix4 _transformMatrixBoxToNode;
 
-  double _scaleX;
-  double _scaleY;
+  double _scaleX = 1.0;
+  double _scaleY = 1.0;
 
-  bool visible;
+  /// The visibility of this node and its children.
+  bool visible = true;
 
-  double _zPosition;
+  double _zPosition = 0.0;
   int _addedOrder;
-  int _childrenLastAddedOrder;
-  bool _childrenNeedSorting;
-
+  int _childrenLastAddedOrder = 0;
+  bool _childrenNeedSorting = false;
+
+  /// Decides if the node and its children is currently paused.
+  ///
+  /// A paused node will not receive any input events, update calls, or run any animations.
+  ///
+  ///     myNodeTree.paused = true;
   bool paused = false;
 
   bool _userInteractionEnabled = false;
+
+  /// If set to true the node will receive multiple pointers, otherwise it will only receive events the first pointer.
+  ///
+  /// This property is only meaningful if [userInteractionEnabled] is set to true. Default value is false.
+  ///
+  ///     class MyCustomNode extends Node {
+  ///       handleMultiplePointers = true;
+  ///     }
   bool handleMultiplePointers = false;
   int _handlingPointer;
 
-  List<Node>_children;
+  List<Node>_children = [];
 
   // Constructors
-  
+
+  /// Creates a new [Node] without any transformation.
+  ///
+  ///     var myNode = new Node();
   Node() {
-    _rotation = 0.0;
-    _position = Point.origin;
-    _scaleX = _scaleY = 1.0;
-    _transformMatrix = new Matrix4.identity();
-    _children = [];
-    _childrenNeedSorting = false;
-    _childrenLastAddedOrder = 0;
-    _zPosition = 0.0;
-    visible = true;
   }
 
   // Property setters and getters
 
+  /// The [SpriteBox] this node is added to, or null if it's not currently added to a [SpriteBox].
+  ///
+  /// For most applications it's not necessary to access the [SpriteBox] directly.
+  ///
+  ///     // Get the transformMode of the sprite box
+  ///     var transformMode = myNode.spriteBox.transformMode;
   SpriteBox get spriteBox => _spriteBox;
 
+  /// The parent of this node, or null if it doesn't have a parent.
+  ///
+  ///     // Hide the parent
+  ///     myNode.parent.visible = false;
   Node get parent => _parent;
-  
+
+  /// The rotation of this node in degrees.
+  ///
+  ///     myNode.rotation = 45.0;
   double get rotation => _rotation;
   
   void set rotation(double rotation) {
@@ -64,6 +94,9 @@ class Node {
     _invalidateTransformMatrix();
   }
 
+  /// The position of this node relative to its parent.
+  ///
+  ///     myNode.position = new Point(42.0, 42.0);
   Point get position => _position;
   
   void set position(Point position) {
@@ -72,6 +105,14 @@ class Node {
     _invalidateTransformMatrix();
   }
 
+  /// The draw order of this node compared to its parent and its siblings.
+  ///
+  /// By default nodes are drawn in the order that they have been added to a parent. To override this behavior the
+  /// [zPosition] property can be used. A higher value of this property will force the node to be drawn in front of
+  /// siblings that have a lower value. If a negative value is used the node will be drawn behind its parent.
+  ///
+  ///     nodeInFront.zPosition = 1.0;
+  ///     nodeBehind.zPosition = -1.0;
   double get zPosition => _zPosition;
 
   void set zPosition(double zPosition) {
@@ -82,6 +123,11 @@ class Node {
     }
   }
 
+  /// The scale of this node relative its parent.
+  ///
+  /// The [scale] property is only valid if [scaleX] and [scaleY] are equal values.
+  ///
+  ///     myNode.scale = 5.0;
   double get scale {
     assert(_scaleX == _scaleY);
     return _scaleX;
@@ -93,6 +139,9 @@ class Node {
     _invalidateTransformMatrix();
   }
 
+  /// The horizontal scale of this node relative its parent.
+  ///
+  ///     myNode.scaleX = 5.0;
   double get scaleX => _scaleX;
 
   void set scaleX(double scaleX) {
@@ -101,6 +150,9 @@ class Node {
     _invalidateTransformMatrix();
   }
 
+  /// The vertical scale of this node relative its parent.
+  ///
+  ///     myNode.scaleY = 5.0;
   double get scaleY => _scaleY;
 
   void set scaleY(double scaleY) {
@@ -109,6 +161,14 @@ class Node {
     _invalidateTransformMatrix();
   }
 
+  /// A list of the children of this node.
+  ///
+  /// This list should only be modified by using the [addChild] and [removeChild] methods.
+  ///
+  ///     // Iterate over a nodes children
+  ///     for (Node child in myNode.children) {
+  ///       // Do something with the child
+  ///     }
   List<Node> get children {
     _sortChildren();
     return _children;
@@ -116,6 +176,11 @@ class Node {
 
   // Adding and removing children
 
+  /// Adds a child to this node.
+  ///
+  /// The same node cannot be added to multiple nodes.
+  ///
+  ///     addChild(new Sprite(myImage));
   void addChild(Node child) {
     assert(child != null);
     assert(child._parent == null);
@@ -129,6 +194,9 @@ class Node {
     if (_spriteBox != null) _spriteBox._eventTargets = null;
   }
 
+  /// Removes a child from this node.
+  ///
+  ///     removeChild(myChildNode);
   void removeChild(Node child) {
     assert(child != null);
     if (_children.remove(child)) {
@@ -138,11 +206,17 @@ class Node {
     }
   }
 
+  /// Removes this node from its parent node.
+  ///
+  ///     removeFromParent();
   void removeFromParent() {
     assert(_parent != null);
     _parent.removeChild(this);
   }
 
+  /// Removes all children of this node.
+  ///
+  ///     removeAllChildren();
   void removeAllChildren() {
     for (Node child in _children) {
       child._parent = null;
@@ -172,7 +246,12 @@ class Node {
   }
 
   // Calculating the transformation matrix
-  
+
+  /// The transformMatrix describes the transformation from the node's parent.
+  ///
+  /// You cannot set the transformMatrix directly, instead use the position, rotation and scale properties.
+  ///
+  ///     Matrix4 matrix = myNode.transformMatrix;
   Matrix4 get transformMatrix {
     if (_transformMatrix != null) {
       return _transformMatrix;
@@ -251,6 +330,12 @@ class Node {
     return _transformMatrixBoxToNode;
   }
 
+  /// Converts a point from the coordinate system of the [SpriteBox] to the local coordinate system of the node.
+  ///
+  /// This method is particularly useful when handling pointer events and need the pointers position in a local
+  /// coordinate space.
+  ///
+  ///     Point localPoint = myNode.convertPointToNodeSpace(pointInBoxCoordinates);
   Point convertPointToNodeSpace(Point boxPoint) {
     assert(boxPoint != null);
     assert(_spriteBox != null);
@@ -259,6 +344,9 @@ class Node {
     return new Point(v[0], v[1]);
   }
 
+  /// Converts a point from the local coordinate system of the node to the coordinate system of the [SpriteBox].
+  ///
+  ///     Point pointInBoxCoordinates = myNode.convertPointToBoxSpace(localPoint);
   Point convertPointToBoxSpace(Point nodePoint) {
     assert(nodePoint != null);
     assert(_spriteBox != null);
@@ -267,6 +355,9 @@ class Node {
     return new Point(v[0], v[1]);
   }
 
+  /// Converts a [point] from another [node]s coordinate system into the local coordinate system of this node.
+  ///
+  ///     Point pointInNodeASpace = nodeA.convertPointFromNode(pointInNodeBSpace, nodeB);
   Point convertPointFromNode(Point point, Node node) {
     assert(node != null);
     assert(point != null);
@@ -281,8 +372,23 @@ class Node {
 
   // Hit test
 
-  bool isPointInside(Point nodePoint) {
-    assert(nodePoint != null);
+  /// Returns true if the [point] is inside the node, the [point] is in the local coordinate system of the node.
+  ///
+  ///     myNode.isPointInside(localPoint);
+  ///
+  /// [NodeWithSize] provides a basic bounding box check for this method, if you require a more detailed check this
+  /// method can be overridden.
+  ///
+  ///     bool isPointInside (Point nodePoint) {
+  ///       double minX = -size.width * pivot.x;
+  ///       double minY = -size.height * pivot.y;
+  ///       double maxX = minX + size.width;
+  ///       double maxY = minY + size.height;
+  ///       return (nodePoint.x >= minX && nodePoint.x < maxX &&
+  ///       nodePoint.y >= minY && nodePoint.y < maxY);
+  ///     }
+  bool isPointInside(Point point) {
+    assert(point != null);
 
     return false;
   }
@@ -304,7 +410,23 @@ class Node {
     // Get the transformation matrix and apply transform
     canvas.concat(transformMatrix.storage);
   }
-  
+
+  /// Paints this node to the canvas.
+  ///
+  /// Subclasses, such as [Sprite], override this method to do the actual painting of the node. To do custom
+  /// drawing override this method and make calls to the [canvas] object. All drawing is done in the node's local
+  /// coordinate system, relative to the node's position. If you want to make the drawing relative to the node's
+  /// bounding box's origin, override [NodeWithSize] and call the applyTransformForPivot method before making calls for
+  /// drawing.
+  ///
+  ///     void paint(PictureRecorder canvas) {
+  ///       canvas.save();
+  ///       applyTransformForPivot(canvas);

[Hixie, 2015/06/22 17:08:42]

note that save/transform/restore is expensive (expensive enough that we do
translate/-translate for most widgets, and are considering even removing that
where we can).

+  ///
+  ///       // Do painting here
+  ///
+  ///       canvas.restore();
+  ///     }
   void paint(PictureRecorder canvas) {
   }
  
@@ -339,14 +461,35 @@ class Node {
 
   // Receiving update calls
 
+  /// Called before a frame is drawn.
+  ///
+  /// Override this method to do any updates to the node or node tree before it's drawn to screen.
+  ///
+  ///     // Make the node rotate at a fixed speed
+  ///     void update(double dt) {
+  ///       rotation = rotation * 10.0 * dt;
+  ///     }
   void update(double dt) {
   }
 
+  /// Called whenever the [SpriteBox] is modified or resized, or if the device is rotated.
+  ///
+  /// Override this method to do any updates that may be necessary to correctly display the node or node tree with the
+  /// new layout of the [SpriteBox].
+  ///
+  ///     void spriteBoxPerformedLayout() {
+  ///       // Move some stuff around here
+  ///     }
   void spriteBoxPerformedLayout() {
   }
 
   // Handling user interaction
 
+  /// The node will receive user interactions, such as pointer (touch or mouse) events.
+  ///
+  ///     class MyCustomNode extends NodeWithSize {
+  ///       userInteractionEnabled = true;
+  ///     }
   bool get userInteractionEnabled => _userInteractionEnabled;
 
   void set userInteractionEnabled(bool userInteractionEnabled) {
@@ -354,6 +497,33 @@ class Node {
     if (_spriteBox != null) _spriteBox._eventTargets = null;
   }
 
+  /// Handles an event, such as a pointer (touch or mouse) event.
+  ///
+  /// Override this method to handle events. The node will only receive events if the [userInteractionEnabled] property
+  /// is set to true and the [isPointInside] method returns true for the position of the pointer down event (default
+  /// behavior provided by [NodeWithSize]). Unless [handleMultiplePointers] is set to true, the node will only receive
+  /// events for the first pointer that is down.
+  ///
+  /// Return true if the node has consumed the event, if an event is consumed it will not be passed on to nodes behind
+  /// the current node.
+  ///
+  ///     // MyTouchySprite gets transparent when we touch it
+  ///     class MyTouchySprite extends Sprite {
+  ///
+  ///       MyTouchySprite(Image img) : super (img) {
+  ///         userInteractionEnabled = true;
+  ///       }
+  ///
+  ///       bool handleEvent(SpriteBoxEvent event) {
+  ///         if (event.type == 'pointerdown) {
+  ///           opacity = 0.5;
+  ///         }
+  ///         else if (event.type == 'pointerup') {
+  ///           opacity = 1.0;
+  ///         }
+  ///         return true;
+  ///       }
+  ///     }
   bool handleEvent(SpriteBoxEvent event) {
     return false;
   }