Objects

Objects and Widgets are actually one and the same thing. The origin of this misnomer goes back to the very early days of TULIP. Objects were the software counterpart of the physical tangible object being placed on the table. The term Widget was only introduced at a later stage when the development team introduced the separation of functional behaviour and visual representation. Even though no longer appropriate, the objects tag and its object children stuck around and were kept for reasons of backward compatibility.

Type

The mandatory <type> tag allows specifying the kind of widget to be instantiated. Widgets are identified by their Java Class name. For instance, the following snippet would specify to use a widget defined by the Java SelectorWidget class:

<type>SelectorWidget</type> 

Name

The optional <name> tag allows specifying a given name for the widget.

<name>Vehicle Euro Class</name> 

Handles

Each physical object relies on a fiducial marker to a.) identify the object via the identifier the marker represents and b.) to detect its position and orientation on the tangible table. Currently, widgets bear only one single marker, but for the sake of flexibility, you may specify multiple markers should the necessity arise. Each marker definition requires its own <handle> tag definition within the overall <handles> group of tags. The following snippet assigns the id 30 to the enclosing widget definition:

<handles>
    <handle>30</handle>
</handles>

Multiple Instances

The TUIO (Tangible User-interface Input/Output) protocol that TULIP uses to capture what's happening on the tangible table, supports multiple instances of widgets with the same ID. The protocol relies on a SessionID attribute to distinguish between markers having the same ObjectID. The optional <multipleInstances> tag allows flagging a widget as a potential candidate to appear multiple times on the table. It is important to note that we have implemented the basic mechanisms for retrieving and managing the SessionID attribute, however, TULIP currently doesn't fully exploit this, thus, multiple instances currently isn't fully supported.

Tangible

All object definitions are by default considered to be tangible, meaning they can be manipulated by the user who can drop them on the table, move them around and ultimately lift them from the table. All those actions will be reflected the corresponding widget. The optional <tangible> flag gives designers the possibility to disengage widget state from user action by specifying false as a value. Non tangible objects will always appear on their designated stage (see <stageId> tag) at their pre-defined position (see <stagePosition> tag).

StageId

The optional <stageId> tag determines on which stage the widget will appear. If not specified, the widget will appear on the stage representing the tangible table itself, which by definition has the <stageId> 0 (zero). When specified, it is important to make sure the referenced stage was previously declared at Scenario level in the <StageSet> section.

Stage Position

The optional <stagePosition> tag determines the spatial position of the widget on the given stage. The spatial position is expressed as a point following the TULIP convention. Have a look at the section about common point properties for more information about how to define a point in TULIP scenarios.

Interactions

Interactions give authors the possibility to react to selected user interactions. Please have a look at the dedicated section about Interactions for a more detailed description.

Coronas

As already mentioned earlier in this section, Widgets define the functional behavior of the tangible object, e.g. selecting an option, setting a value, zooming and so on. However, a Widget usually also requires a visual representation of itself, either promoting its function or for displaying possible choices to the user, for instance in the case of selector widget. Visual representation are handled by dedicated objects called Coronas. The <coronas> tag groups individual <corona> definitions for a given Widget. Coronas will be covered separately.