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8 ECMAScript Bindings normative
Requirements Class
http:www.opengis.netspecarml2.0reqscripting
Target Type Software Implementation
The following section describes the scripting part of ARML 2.0. Throughout this section, an WebIDL translation of the object model is introduced to define ECMAScript bindings and a JSON serialization
of the ARML 2.0 object model.
ARML provides ECMAScript the standardized version of JavaScript bindings to allow the dynamic access and modification of objects in the AR scene, as well as event handlers to react on user input.
In addition to the XML serialization, each class defined in ARML also has a JSON serialization, which is used to access and modify the properties of the objects in the scene.
Implementations are encouraged to support ARMLs ECMAScript bindings to allow the developer dynamic access to the scene. However, if ECMAScript bindings cannot be provided for whatever
reason, the implementation must clearly state that only the descriptive ARML specification is supported.
8.1 Accessing ARElements and Modifying the Scene
Implementations must ensure that an arml object is injected into the ECMAScript runtime context on startup. This object is the root node for any scripting operations on the AR scene and serves as the
namespace for the objects defined in ARML 2.0.
Requirement
http:www.opengis.netspecarml2.0reqscriptinggeneralarml_injection On startup, the arml object shall be injected into the ECMAScript runtime.
In addition to serving as the namespace, arml has the following properties and methods:
module arml { readonly attribute ARElement[] arElements;
ARElement getARElementByIdString id; void addToSceneARElement element;
void removeFromSceneARElement element; void addEventListenerString type, EventListener listener;
void removeEventListenerString type, EventListener listener; ... all interface objects from below
}
getARElementByIdString id returns the object having its id property set to the passed String. In case no such object exists, or id is
empty, the call returns null.
addToSceneARElement element adds the given element to the AR scene
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removeFromSceneARElement element removes the given element from the AR scene
8.2 Object Creation and Property Access
Each concrete subclass of ARElement has its own constructor. To make an object accessible in the scene, arml.addToSceneelement must be invoked first, only then is the element accessible via
arml.getARElementByIdelement.id.
Requirement
http:www.opengis.netspecarml2.0reqscriptinggeneralobject_access After an ARElement was added to the scene either through descriptive definition or by calling
arml.addToScene, its ECMAScript representation is accessible through arml.getARElementById with the id of the ARElement as parameter.
An implementation must ensure that properties set in the descriptive spec are always in sync with the matching properties in the scripting spec. For example, if the following feature is defined in the
declarative spec:
Feature id=empireStateBuilding nameThe Empire State Buildingname
enabledtrueenabled anchors
... anchors
Tracker
Then the implementation shall ensure that the following object is accessible:
var empireState = arml.getARElementByIdempireStateBuilding;
Furthermore, the implementation shall ensure that the object stored in empireState has its properties set to the following values:
empireState = { id : empireStateBuilding,
name : The Empire State Building, enabled : true,
anchors : [ ... the array of Anchors defined for the Feature
] }
The properties of empireState can now be accessed and modified using empireState.name etc.
Requirement
http:www.opengis.netspecarml2.0reqscriptinggeneralsynchronization An implementation shall ensure that properties set in the descriptive spec are always in sync with the
matching properties in the scripting spec.
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8.3 Object and Constructor Definitions
