Scene graph

When building an application in Famous, much of your work will deal with managing and manipulating a data structure called the scene graph. Understanding the scene graph is essential to understanding Famous as a whole.

Note: These concepts become more concrete in the displaying content guide.

What is a scene graph?

Think of the scene graph as a family tree of display elements. Each element in the tree is a node. Each node can have zero or more children and at most one parent. You can think of all the descendents of a node as being grouped together.

scene graph

The scene graph represents the structure of your application. Whereas in HTML, sub-elements are represented with tag nesting, in Famous, sub-elements are represented as child nodes. Here's a visualization of how a scene graph structure might relate to an application's UI:

scene graph and layout

In this illustration, we see a simple application compared to its scene-graph representation. The top-level of the application is the root node. It has three children: header, content area, footer. Meanwhile, the content area itself has three children: the items.

Creating a scene graph

In your Famous code, we create a scene graph by spawning nodes from your application's main scene, and then adding children to them. To create the above scene graph in Famous code, we could write the following:

var FamousEngine = require('famous/core/FamousEngine');

// Initialize the FamousEngine to start the rendering process

// Create a scene for the FamousEngine to render
var scene = FamousEngine.createScene();
var appNode = scene.addChild();
var headerNode = appNode.addChild();
var contentNode = appNode.addChild();
var footerNode = appNode.addChild();
var itemNode1 = contentNode.addChild();
var itemNode2 = contentNode.addChild();
var itemNode3 = contentNode.addChild();

Rendering the scene graph

We've learned that a scene graph gives us our application's structure --- but how do we display it? The scene graph by itself isn't enough. As we'll see in the next section, to actually display content, we'll need to decorate our nodes with components.