SceneManager provides a central management system for all objects in the scene graph (see the DisplayObject section on The Scene Graph). Any object that derives from DisplayObject will be automatically registered and unregistered with the SceneManager as it is added and removed as a child node in the graph. That is, DisplayObject instances that are diconnected from the root node of the Scene are not registered with SceneManager and will not be accessible via its query methods.
bo-X provides a simple, yet powerful query languages called boQL (awesome name, right?) based on a number of existing graph languages including e4x, css, and xpath to name a few.
After all, what's the power of a scene graph when there is no way to query it?
boQL queries are made up of simple match statements, separated by a search depth operator which defines whether the match statement should be executed at a shallow or recursive level. This is best explained by a few examples.
Suppose, for DisplayObjects with names "a", ... "z", the following scene graph:
"a" -> "b" -> ... -> "z"
That is, a is parent to b is parent to c-- and so on down the line. Suppose we would like a reference to g. With boQL, there are a number of ways to accomplish this:
// specify an explicit path to g
var g = SceneManager.find("a.b.c.d.e.f.g");
// specify any part of the path, using .. to specify recursion
var g = SceneManager.find("a..e..g");
var g = SceneManager.find("..g");
This form of boQL matches DisplayObject instances by name, but boQL also supports matching by arbitrary DisplayObject properties by using the @ symbol.
Here are a few examples:
// find all visible DisplayObjects that are below b in the graph
var visibleElements = SceneManager.find("..b..(@visible==true)");
// find all DisplayObjects with alpha less than 1
var alphaElements = SceneManager.find("..(@alpha<1)")
// find all immediate children of a with id greater than or equal to 10
var objects - SceneManager.find("a.(@id>=10)");
Every DisplayObject has an integral id unique across all DisplayObject instances, accessible via DisplayObject::getUniqueId(). The SceneManager has a constant time lookup by id for all DisplayObject instances.