Working with the Textport

GL provides subroutines both to set up a textport, a window associated with a graphics application shell, and to turn it on and off. The textport subroutine allocates an area of the screen for a textport, and the parameters specify the screen coordinates for the textport. The syntax is as follows:

void textport(Screencoord left, Screencoord right,
              Screencoord bottom, Screencoord top

The tpon subroutine brings the textport to the front of any windows that conceal it so that character strings can be drawn into it. The tpoff subroutine pushes the textport behind all other windows. When the textport is off, it is not visible on the screen, and character strings cannot be written into it. The syntax for the tpon and tpoff subroutines is as follows:

void tpon()

void tpoff()

List of GL Textport Subroutines