The IlvManager class provides a wide range of interactors that are used to create objects and change their shape. The IlvGrapher class contains specific interactors designed to create new nodes and links and change the way they are connected:

The IlvGraphSelectInteractor class derives from the IlvSelectInteractor class. It contains additional member functions used to manage the drawing of ghost images for links attached to nodes that are moved or enlarged. This class has the following constructor:

This constructor initializes a new instance of the IlvGraphSelectInteractor class that lets you select individual objects or groups of objects in the view view connected to the manager manager. This manager is assumed to be an instance of the IlvGrapher class.

The IlvMakeNodeInteractor class is the base class for interactors that allow the user to interactively create nodes in a grapher. Instances of this class must be attached to a grapher and one of its connected views, as shown here:

To create a node, drag a rectangular region in the working view. There are two ways to specify what type of graphic object is created:

The grapher library provides predefined subclasses of IlvMakeNodeInteractor:

The IlvMakeLinkInteractor class is the base class for interactors that allow the user to interactively connect nodes in a grapher. Its constructor is as follows:

The oriented parameter specifies whether created links are oriented. An example of how to create an interactor of this type and connect it to a grapher and one of its view is presented here:

To connect two nodes, perform the following steps:

You can control which node is valid by overloading the IlvMakeLinkInteractor::acceptFrom and IlvMakeLinkInteractor::acceptTo methods. There are two ways of specifying what type of link should be created:

The Grapher library provides several predefined subclasses of IlvMakeLinkInteractor:

The IlvMakePolyLinkInteractor class is a special kind of interactor that does not derive from IlvMakeLinkInteractor.

This interactor is used to create links whose intermediate points can be explicitly defined. It lets you control the shape drawn by the user by means of the IlvMakePolyLinkInteractor::accept method:

By overloading this method, you can add specific constraints on the position of the intermediate points of the link. Once these points have been defined, the link is created with the IlvMakePolyLinkInteractor::makeLink method, which must be defined in subclasses to return the appropriate link instance. The grapher library provides one predefined subclass, IlvMakePolylineLinkInteractor, which is used to create links of the IlvPolylineLinkImage type.

The IlvPinEditorInteractor class lets the user interactively edit the connection pins of a grapher node. When this interactor is active, selecting a node will highlight its connection pins, as shown in Figure 2.11:

Once a grapher node is selected, you can:

When a link is selected, its selection object draws handles that you can use to change its shape or edit the way it is connected. Figure 2.12 shows a link that has been selected:

An end point handle can be dragged to:

The intermediate point handles can be used to edit the shape of the link. The kind of interaction allowed by these handles depends on the kind of link being edited.