Linking Application Objects to Prototypes

Once you have defined your prototypes and your panels, you may want to connect these to real application data and processes defined in C++.

There are three methods available to link prototypes to application objects, depending on the type of interface you want to produce:

• When the display is graphics-rich but represents only a few application objects and values, you may want to link the application objects by directly feeding values to the prototype instances of a given panel.

This is typically used in static synoptic displays composed of only predefined graphic components. It is convenient to use feed values directly when the application is not expecting user input to modify application values through a prototype instance. The base_feed sample in <ILVHOME>/samples/protos shows how to use this approach for a simple control panel.

• To build WYSIWYG, direct-manipulation application object editors, you may want to use an IlvGroupMediator. With this class, you can link an application object to a given IlvGroup (or prototype instance) in a panel, allowing interactive editing of its attributes. A group mediator allows you to bind and unbind application objects dynamically to a given prototype that serves as an editor for the object.

A typical application of this type is a WYSIWYG inspector such as the Guides inspector in Prototypes Studio. The inspector sample in <ILVHOME>/samples/protos is an example of this kind of editor. It shows how to build a 2D transformation matrix editor controlling the viewpoint of a view interactively.

• To create many instances of a prototype dynamically, with each instance linked to a given application object, you should use an IlvProtoMediator. This class instantiates the prototype and links it to an application object of a given class as it is created. This allows clear separation of interface design from the application design, each being able to evolve separately from a commonly agreed upon application interface.

A typical application of this type allows you to view panels where many objects of many classes are represented and edited at the same time. Each application class is linked to a prototype and each instance of the class to an instance of the prototype.

Cartographic displays and all graph displays are examples of applications that can benefit from prototypes using IlvProtoMediators. <ILVHOME>/samples/protos/interact_synoptic is an example of this type of application, showing a very simple air-traffic simulator, where each flight and each airport are represented by prototype instances. The simulator only deals with changing the attributes of the flight, whereas the prototypes can be incrementally refined in the drawing editor to present the best display.