Every Gantt abstract object is associated with a graphic representation composed of graphic objects of any subclass of IlvGraphic. When a line, node, subnode, or link is added to the Gantt chart, a default graphic representation provided by the Gantt library is used to display it.

To customize a Gantt chart, the user can define one graphic model for each abstract object to create its own graphic representation. Each time an instance of an abstract object for which the user has defined a graphic model is added to the chart, a copy of this model is made. The position and size of the resulting graphic object, that is, its bounding box, are computed by the Gantt chart according to their specific internal values. For example, the bounding box of nodes and subnodes depends on the maximum and minimum start and end-times.

The IlvGanttChart class provides member functions for setting and retrieving graphic models for lines, nodes, subnodes, and links:

See the example provided (Using the Gantt Chart Through Examples). In this example, the graphic model used to represent lines and nodes is an IlvGraphicSet, which is composed of two IlvMessageLabel objects.