Nodes

Nodes

Nodes are the core engine entities. Nodes can:

• Be drawn on the screen.
• Contain other nodes.
• Have hierarchical transformations (from parent to children).
• Get input routed.
• Schedule actions and/or tasks.

The core node is cc.node.Node. Unlike as in V3 API, a Node object by default can draw itself as a solid color. Nodes receive a RenderingContext object as draw method parameter which allows for arbitrary rendering like stroking, pattern, images, tinting, etc. See (RenderingContext)[RenderingContext] for more information. It is expected the developer will overwrite draw( ctx ) method instead of subclassing to create a new Node type.

Nodes by default have no input enabled. Mouse/touch events won't be routed to a node unless the method enabledEvents is called, regardless the developer has registered any touch/mouse callback function. See (Input)[Input] for more info.

Nodes have identification capabilities. You can setTag a node, or setName. Since nodes can contain other nodes, the method enumerateChildren(pattern) matches to node names and invokes a callback for node name match. The enumeration can be recursive and have a directory like structure.

A Node can schedule an undefined amount of Action objects as well as tasks on itself. Actions and tasks will be applied in a timely manner.

Visually, nodes can have three different attributes:

• Color. Which tints images and solid colors. setColor()
• Alpha. Which modifies node's transparency. Transparency can be cascaded, meaning the transparency can propagate down the node's hierarchy. setAlpha() or setOpacity.
• Alpha blend. Which modifies blending parameters (affects how colos compose when mixed). setBlendFunc( src, dst) or setCompositeOperation( cc.render.CompositeOperation ).

Finally, nodes can have a transformation applied. For example, they can be rotated, scaled and/or translated. Other types of nodes (like sprites) can be for example flipped. The V4 implementation offers two different transformation anchors:

• position anchor, which affects how nodes are placed on the screen.
• transformation anchor, which affects how nodes are rotated and/or scaled. These transformations apply hierarchically. For example a node translated will affect all its children position. Methods like rotate(r), scale(x,y), x, y, rotation, scaleX, scaleY, etc. will affect a lazily calculated local and global transformation matrices.