Correlation must be performed by all display drivers in page coordinates on fully clipped primitives. (Correlation is not required for hardcopy devices.) Correlating on areas is particularly complex because GreSetCurrentPosition and GreEndArea generate a closure line when the current position is not at the start of the current closed figure. This closure line can cause a correlation hit. Also, the area interior, itself, can cause a correlation hit that must be reported on the GreEndArea order.

The lines (arcs, full arcs, boxes, and fillets) defining the area boundary can cause a correlation hit if the area is specified with boundary. This hit must be reported when the function is issued.