At the beginning of DispCmds.h is an enumeration with entries for all the different DispCmd-derived classes. These names are used by the render routine in each DisplayDevice to determine what the commands are in a display list. When new drawing primitives are added, a new name should be put in this list, and that name should be specified in the DispCmd base class constructor.
Following this are enumerations describing the different types of spheres that may be drawn, and the different types of lines.