Chapter 7, “Customizing a Chart,” describes a number of ways in which the appearance or behavior of Objective Chart can be modified. These methods generally involved setting various style flags or specifying various parameters. In this chapter, techniques that involve subclassing the Objective Chart classes and overriding virtual functions are discussed.

The Objective Chart classes include a number of undefined, virtual functions that handle the processing of custom graph and axis types. These functions allow you, the developer, to design completely new graph or axis types that you can reuse and share with your colleagues.

In practice, the complete definition of a new graph or axis type requires modification of a number of functions in several different classes. Therefore, we first consider the case in which the standard behavior is close to what is needed. We just need to create a special set of axis labels or modify the way the data items are drawn slightly.