gio$stdgraph

    This directory contains the source and executables for the STDGRAPH and
GKIDECODE graphics kernels.  The two kernels are implemented both as libraries
and as executable tasks.

	gkidecode	This kernel is used standalone to examine GKI
			metafiles.  The real work is done by the GKIPRINT
			library module in the GIO package.

	stdgraph	A graphics kernel for graphics terminals.  Implemented
			both as the library "libstdg.a" and as the kernel task
			STDGRAPH.  The library is required for this kernel to
			permit inclusion of the stdgraph kernel in the CL
			process.

Both kernels are available as CL callable tasks in the executable file
x_kernel.e.


GKIPRINT -- Graphics kernel for decoding metacode.  This graphics kernel
formats metacode instructions into readable form and prints them on the output
file.  The gkiprint kernel is useful for examining metafiles and for
debugging kernels which drive specific devices.  The driver consists of the
following procedures:

	     gkp_openws (devname, n, mode)
	    gkp_closews (devname, n)
	    gkp_mftitle (title, n)			**
	      gkp_clear (dummy)
	     gkp_cancel (dummy)
	      gkp_flush (dummy)
	   gkp_polyline (p, npts)
	 gkp_polymarker (p, npts)
	       gkp_text (x, y, text, n)
	   gkp_fillarea (p, npts)
       gkp_getcellarray (m, nx, ny, x1,y1, x2,y2)
       gkp_putcellarray (m, nx, ny, x1,y1, x2,y2)
	  gkp_setcursor (x, y, cursor)
	      gkp_plset (gki)
	      gkp_pmset (gki)
	      gkp_txset (gki)
	      gkp_faset (gki)
	  gkp_getcursor (cursor)
	     gkp_escape (fn, instruction, nwords)	**
	     gkp_setwcs (wcs, nwords)			**
	     gkp_getwcs (wcs, nwords)			**
	    gkp_unknown (gki)				**

A GKI driven device driver may implement any subset of these procedures.
The starred procedures should be omitted by most drivers.  In particular,
the SETWCS and GETWCS instructions are internal instructions which should
be ignored by ordinary device drivers.  The procedure names may be anything,
but the arguments lists must be as shown.  All coordinates are in GKI units,
0 to 32767.  Character strings are passed in ASCII, one character per metacode
word.  Whenever a GKI character string appears as an array argument in the
argument list of a procedure, the count N of the number of characters in the
string follows as the next argument.  GKI character strings are not EOS
delimited.  Polyline, polymarker, and fillarea data is passed as an array
of (x,y) points P, in GKI coordinates, defining the polyline or polygon to
be plotted.

One additional procedure, GKP_INSTALL, is called by the main program of the
graphics kernel task to install the debugging driver, i.e., to fill the DD
array with the entry point addresses of the driver procedures.  For a normal
driver this function is performed by a user supplied procedure named
GKOPEN (graphics kernel open).  The user supplied kernel procedures will
be called to execute each instruction as the instructions are decoded by the
main routine.  The user supplied procedure GKCLOSE will be called when
interpretation ends and the task is about to exit.

		 gkopen (dd)
		gkclose ()

Do not confuse GKOPEN and GKCLOSE, which open and close the graphics kernel,
with GKI_OPENWS and GKI_CLOSEWS, the metacode instructions used to direct
an opened kernel to open and close workstations.
