As a general rule, you create your prototypes in Views Studio and then use them in your application. The following section explains the C++ API that you use to add prototypes to your application and how to manipulate these prototypes.

The following items are described in this section:

To make sure that your application is linked with the necessary library packages, you must first include the header files corresponding to the graphic objects, the accessors (subclasses of IlvUserAccessor), and the interactors used in the prototypes that you will load.

To include all the predefined accessor classes, use the header file <ILVHOME>/include/ilviews/protos/allaccs.h.

Here is a typical set of header files to include in order to build an application that can load prototypes containing any type of graphic object:

You may also want to add the following header files:

If you know in advance the Prototypes that you will use, you can reduce the size of your application by including only the necessary header files instead of allaccs.h, graphics.h, and gadgets.h.

To compile applications that use the prototypes package, you must compile them with the library ilvproto. This library also requires the following libraries: ilvgrapher, ilvmgr, and the usual Views libraries for your platform. The ilvgdpro library may be needed for applications that use old features of prototypes.

To load a.ilv file containing prototype instances, you simply use the read or readFile methods of IlvManager or IlvContainer:

All the prototypes used in the file will be loaded automatically from their prototype libraries. Prototype libraries are searched for in the file system using the display path. For example, if the panel contains prototypes from a prototype library called mylib located in /usr/home/yourdir/protolibs/mylib.ipl, you should include /usr/home/yourdir/protolibs/ in your ILVPATH environment variable.

To allow handling of groups in a container or manager, the IlvGroupHolder class provides all the necessary interface. Instances of the IlvGroupHolder class are automatically attached to containers or managers containing prototype instances. This class provides the methods for adding, removing, and retrieving groups (and thus prototype instances). You can retrieve the group holder attached to a container, manager, or graphic holder with the global methods:

You may need to create instances of your prototypes by coding. To create instances of your prototypes, you must first load them. You can load a whole prototype library and then load one or more of the prototypes it contains. To do this, create an instance of the IlvProtoLibrary class and call its load method:

If you want to load a prototype library that is not located in the display path, you can specify the directory where the library is located in the call to the constructor:

Once you have loaded a prototype library, you can retrieve all its prototypes or a particular prototype with the following methods:

or:

The array returned by the getPrototypes method is allocated with the new[] operator and must be released with the delete[] operator when it is no longer needed.

Alternatively, you can load each prototype individually with the global function IlvLoadPrototype:

The first argument specifies the name of the prototype library and the name of the prototype (separated by a period). The second argument is the instance of IlvDisplay that your application has created. The prototype library file and the prototype files are searched for in the file system using the display path.

To create an instance of a prototype, use the clone method:

The argument of the clone method is the name of the new instance. You can pass 0, which means that a name is generated automatically.

Instances of the IlvGroupHolder class are automatically attached to containers or managers containing prototype instances. This class provides the methods for adding, removing, and retrieving groups (and thus prototype instances).

To add the new prototype instance to a manager or a container, you can use the addGroup methods of the IlvGroupHolder attached to manager/container classes:

Alternatively, you can create an IlvProtoGraphic object and directly place it in the manager.

Often, you will set the position of the prototype instance when you add it to a manager or container. You can do this by either:

To remove a prototype instance from its container or its manager, you can use the removeGroup methods of the IlvGroupHolder class:

You can also remove its embedding IlvProtoGraphic from its container or manager:

To completely delete a prototype instance, simply call the delete operator. You can also delete its encapsulating protoGraphic.

To get all the groups contained in a manager or container, use the getGroups method of its attached group holder:

To retrieve a group by its name, use the getGroup method:

This method returns 0 if the specified group does not exist.

Prototype instances are manipulated through a uniform API based on named attributes (also called properties or accessors). This API is the same as the one provided by the class IlvGraphic and basically consists of the IlvGraphic::changeValue and IlvGraphic::queryValue methods.

A named attribute is represented by an instance of the IlvValue class and is defined by the following:

The type of the value is set automatically by the IlvValue class. You use constructors to initialize values of predefined types (such as IlInt, const char*, IlvColor*, and so on). You can also change a value using the assignment operator = or by casting an IlvValue to a predefined type. The IlvValue class handles all conversions automatically. For more details, see the IlvValue class in the Views Reference Manual.

To set a value for a prototype instance, you must create an IlvValue and call the IlvGraphic::changeValue method:

You do not need to create a new IlvValue every time you want to change a value. You can use an existing IlvValue and change its data with the assignment operator:

You can set several values in a single call. To do this, you must create and initialize an array of IlvValue objects and call the changeValues method. The following example shows how to set the position of an object in a single call:

To retrieve a value, use the queryValue method:

The queryValue method takes an IlvValue reference as parameter. The IlvValue must be initialized with the name of the value to retrieve. The queryValue method stores the retrieved value in its argument and returns a reference to it. In the example, assigning the result of queryValue to the integer variable x calls the IlvValue to the IlInt cast operator.

To retrieve several values in a single call, create an array of IlvValue objects and call the queryValues method:

The IlvValue class converts values automatically as required. This means that you do not need to know the exact type of a value that you set or retrieve. For example, you could set the position of an object using a string value as follows:

Conversely, when you retrieve a value, you can convert it to the type you need as follows:

A prototype and its instances have three kinds or attributes: user-defined attributes, predefined attributes, and sub-attributes.

The user-defined attributes are the attributes defined by the accessors that you attached to the prototype when you designed it in Views Studio. They vary from one prototype to another. The effect of setting or retrieving a user-defined attribute is determined by the accessor objects that compose it.

For example, suppose that you have created a prototype representing a thermometer. You defined a temperature attribute by adding a reference accessor that maps the temperature to the value attribute of a gauge. To change the temperature displayed by an instance of your prototype, use the changeValue method as follows:

The predefined attributes of a group let you modify or retrieve common properties that all prototypes have, such as the position, the size, the visibility, and so on.

Most predefined attributes take effect only when a group is added to a manager or a container, but they can be set before that. They are stored in the graphic node but only take effect when the group is added.

The predefined attributes are listed in Predefined Attributes of Prototypes and Prototype Instances.

The sub-attributes of prototypes let you directly access the attributes of the objects contained in your prototypes. The names of sub-attributes are built by concatenating the path of the object and the attribute name. The components of a sub-attribute name are separated by a period. For example, if your prototype contains an IlvLabel named title, you can set or retrieve its label using the attribute name title.label.

All the predefined properties listed in Predefined Attributes of Prototypes and Prototype Instances can also be accessed for a particular graphic node.