A region can only be selected by one DC at a time. As soon as a region is selected, operations that reference its handle are invalid. The coordinates of the region are in device coordinates within the DC. Clipping is inclusive at the left and bottom boundaries, exclusive at the right and top boundaries. Functions that modify the clipping region also modify the region when its handle is returned by a subsequent GreSelectClipRegion.

GreSelectClipRegion passes the handle of the previously selected clip region back to the calling routine at the location addressed by phrgnOld. If this handle is not NULL, the calling routine is responsible for deleting the previous clip region. If the default clip region is in use when GreSelectClipRegion is called, a null region handle is returned.

Note: The clip region should be deleted whether it was created explicitly, or in a call to GreIntersectClipRectangle or GreExcludeClipRectangle.