The GPORTSTK subroutine is a graphical call that stacks the viewport defined by the matrix viewport onto the current viewport; that is, the new viewport is defined relative to the current viewport. This call is part of the traditional graphics subsystem, which is no longer being developed.

The viewport argument is a numeric matrix or literal defined in normalized coordinates of the form

{minimum-x minimum-y maximum-x maximum-y}

This graphics command uses world coordinates. An example of a valid statement follows:

call gportstk({5 5 95 95});