Generalised Drawing Primitive

Although at present GKS defines only six types of graphics primitives, the standard allows for these to be augmented within particular implementations by using Generalised Drawing Primitives (GDPs). Thus, the Generalised Drawing Primitive may be thought of as a 'standard way to be non-standard', and in fact a mechanism exists for implementors of GKS to register GDPs with the International Standards Organization group responsible for GKS. The intention is that these registered GDPs will be incorporated as new primitives within future revisions of the standard. However, note that the use of GDPs may make programs non-portable to other GKS implementations. On the other hand, they do permit the GKS driver to make use of special hardware features, circle drawing for example, if these features are available.

GKSGRAL supports 6 GDPs:

1. Circle
2. Circular Arc
3. Ellipse
4. Elliptical Arc
5. Bezier Curve defined by Bezier Polygon
6. Cubic Curve defined by Interpolation Points

CALL GGDP(N, PXA, PYA, PRIMID, IDR, DATREC)