CPLOT, a Graphics Package for Tektronix terminals.

TitleCPLOT, a Graphics Package for Tektronix terminals.
Publication TypeSoftware
Year of Publication1979
AuthorsFreed, Adrian, Elsworthy Graeme, and Grevis Richard
PublisherAGSM released on magnetic tape as part of AUSAM release to AUUGN members

CPLOT contains a set of C procedures, designed to make interactive graphics programs easy to write and fast to run. This manual describes the "cplot" graphics library which was
designed with Tektronics terminals and the C language in mind. It is
now firmly based on the standard i/o library and uses it internally.


Unix edition 6 on PDP 11s

Full Text

CPLOT, a Graphics Package for Tektronix terminals.

by Graeme Elsworthy, Adrian Freed and Richard Grevis.

CPLOT contains a set of C procedures, designed to make interactive

graphics programs easy to write and fast to run.

1. Reference Manual

This manual describes the "cplot" graphics library which was

designed with Tektronics terminals and the C language in mind. It is

now firmly based on the standard i/o library and uses it internally.

1.1 Co‐ordinate Systems

Locations on the screen can be addressed absolutely or relatively in one

of two co‐ordinate systems; screen and user.

Screen co‐ordinates are those required by the Tektronix terminals

themselves. i.e.

0 <= x <= 1023,

0 <= y <= 780,

x and y integers.

User co‐ordinates are chosen by the user’s program itself, by calling

UWINDOW. UWINDOW, requires the upper and lower bounds of x and y, as floating

variables. Most calls consist of their base name prefixed by a ’u’ or an ’s’

(which indicate which co‐ordinate frame is to be used) and a suffix of an ’a’

or an ’r’ to indicate absolute or relative plotting mode respectively.

Arguments are float’s for calls to user co‐ordinate routines and int’s for

calls to screen routines.

1.2 Basic calls

INIT( OUTFILE ) required as first call to CPLOT to initialize terminal for

graphics. OUTFILE is a standard i/o file pointer where the plotting output is

to be put. Normally it would be "stdout". The screen is not erased.

FINISH() required as last call to CPLOT to set terminal for normal use.

ERASE() clears terminal screen.

HOME() puts the graphics cursor at top left of screen.

1.3 Defining the windows

SWINDOW( XLO, XHI, YLO, YHI ) defines the area of the screen to be used for


0 <= XLO < XHI <= 1023,

0 <= YLO < YHI <= 780,

XLO, XHI, YLO, YHI integers.

‐1 is returned on error and 0 if the window is valid.

UWINDOW( XLO, XHI, YLO, YHI ) defines user co‐ordinate system, which is a

window mapped onto the screen window.



XLO, XHI, YLO, YHI floating.

‐1 is returned if these conditions are not met, 0 if they are.

1.4 Graphics calls

[US]MOVE[AR]( X, Y ) moves cursor to X, Y.

[US]DRAW[AR]( X, Y ) draws a vector from current cursor position to X, Y,

leaving cursor at X, Y.

[US]DASH[AR]( X, Y, TYPE ) draws a dashed vector of the required type.

[US]POINT[AR]( X, Y ) puts a point at X, Y, leaving cursor at X, Y

1.5 Cursor Position

The following calls find the position of the virtual cursor in either

screen or user space. This is not necessarily the cursor’s physical position

on the screen, as the last vector may have been off the screen.

[US]WHERE( &X, &Y ) puts the user cursor position in float’s whose addresses

are given.

1.6 Cross‐hair Cursors

The following calls are available for use on terminals with cross‐hair


[US]CURSOR( &X, &Y ) puts cross‐hair cursors on screen and returns its co‐

ordinates, when a character is recieved.

The value of the function is the character that was typed. CURSOR() puts the

cross‐hair cursors on the terminal screen, but does not perform any read.

1.7 Status Enquiry

The following calls continuously return terminal status and current

cursor position without waiting for a user response.

[US]ENQ( &X, &Y ) enquiry. Returns the current cursor position and the

terminal status if the terminal supports the option.

1.8 Alpha‐numerics

The following calls can be used to conveniently intermix alphanumerics

and graphics.

ALPHA() puts terminal in alphanumeric mode. Only required if non‐CPLOT

alphanumerics is wanted.

[US]XPUTS[AR]( X, Y, &STRING ) prints STRING horizontally, starting at the

point X, Y. The graphics cursor is unchanged. [US]YPUTS[AR]( X, Y, &STRING )

prints STRING vertically downwards from X, Y.

1.9 Linking to the Library

CPLOT consists of a set of user calls for the functions described above,

which themselves call routines to do the basic terminal manipulation.

Although these support routines are available, it is strongly recommended that

they not be used.

Programs using the library must include the file "cplot.h" as some

routines are implemented as macros. This file also includes the standard i/o

library include file "stdio.h".

CPLOT is available as an object code library (the linker knows it

as ‐lt), which is linked to the users program in the usual way.

e.g cc prog.c ‐lt ‐lS

1.10 Library Modifications

This document and a source code listing of the library are available, but

the authors of the library would like to be advised of any modifications and

improvements that individual users might make, so that it can be continually

improved, for the benefit of all users.

A separate library of additional functions is being maintained, which

initially contains routines to draw circles, rectangles, triangles and arcs.

#include	<stdio.h>
FILE *debf;

/*			CPLOT,	A graphics package for Tektronix terminals.

				By Adrian Freed, Richard Grevis, and Graeme Elsworthy.

#define	FF	12
#define NUM_DASHES 10
#define	GS	29	/*	Graphics mode	*/
#define SYNC  026
#define US	31	/*	Alpha    mode	*/
#define MASK   037	/*	00011111	*/
#define ESC    033      /*	Control code preamble */
#define BELL	07
#define ENQUIRE	"\033\005"
#define BOTTOM	2,1
#define CURSORS	"\033\032"
#define CURSREAD "\033\032"

#define ALPHA 1
#define ONSCREEN	2
#define USER	4
#define SCREEN		010
#define	DASHMOVE	010000
#define	HIY	0040	/*   100000	*/
#define	LOY	0140	/*  1100000	*/
#define	HIX	0040	/*   100000	*/
#define	LOX	0100	/*  1000000	*/

#define	HOMEX	0
#define	HOMEY	767	/*	Home Co-ordinates	*/

#define	SXMAX	1023
#define	SYMAX	780	/*	Max. Screen positions	*/

#define	YCHSZ	22	/*	Character height	*/
#define XCHSZ	14	/*	Character width		*/

/*	TTY	masks	*/

#define	MAPCASE	04
#define	ECHO	010
#define	LFCR	020
#define	RAWMODE	040
#define	NLDELAY	01400
#define	FF1	040000

#define DEGTORAD 0.01745329

float g_xlo, g_ylo, g_xhi, g_yhi;	/*	User space descriptors	*/
int g_sxlo, g_sylo, g_sxhi, g_syhi;	/*	Screen descriptors	*/
float g_sxtrans, g_sytrans, g_uxtrans, g_uytrans;

int	g_spx, g_spy;	/*	Current screen position		*/	
int	g_sax, g_say;
float	g_px, g_py;		/*	Current user Co-ord. position	*/

int	g_sqx1, g_sqy1;	/*	First solved point	*/
int	g_sqx2, g_sqy2;	/*	Second solved point	*/

int	g_b1, g_b2, g_b3, g_b4;	/*	Bytes to be drawn	*/
int	g_nekmod;
int g_term;

** The global variables used with the dash line routines
int g_scan;
float g_dashbit ;
float g_xpos, g_ypos;
extern g_dashtable[NUM_DASHES][4];
float g_xold, g_yold;

FILE *g_out;
struct	g_ttystruct
	char ispeed, ospeed;
	char e, k;
	int mode;
} g_ttybuf, g_ttyb, g_outbuf;
int	g_syncs;

int	g_positioned;

float g_xsin, g_ysin, g_xcos, g_ycos;
float g_xscale, g_yscale;
int	g_status,g_last;

**	This structure allocates the bit representation
**	of a data word in the software character set.

struct	schar
	int vstat	:1;
	int deltax	:6;
	int deltay	:6;
#define		erase()		( g_put(ESC), g_put(FF),g_status =| ALPHA, g_status =& ~ONSCREEN )
#define		bell()		( g_alpha(), g_put( BELL ) )
#define		smovea(x,y)	( g_spx = (x), g_spy = (y), g_status =& ~(USER|ONSCREEN) )
#define		home()		smovea(HOMEX, HOMEY )
#define		syncs(x)	( g_syncs = (x) )
#define		sdrawr(x,y)	sdrawa( g_spx + (x), g_spy + (y) )
#define		sdashr(x,y,t)	sdasha( g_spx + (x), g_spy + (y) , (t))
#define		spointr(x,y)	spointa( g_spx + (x), g_spy + (y) )
#define		upointr( x,y ) 	( g_status & USER ) ?0: g_chtusr( g_spx, g_spy ), upointa( g_px+x, g_py+y )
#define		umovea(x,y)	( g_chtscr( g_px = (x), g_py = (y) ), g_status =| (USER), g_status =& ~ONSCREEN )
#define		udrawr(x,y)	( ( g_status & USER ) ?0:  g_chtusr( g_spx, g_spy ), udrawa(g_px + (x),g_py + (y)) )
#define		udashr(x,y,t)	( ( g_status & USER ) ?0:  g_chtusr( g_spx, g_spy ), udasha(g_px + (x),g_py + (y), (t)) )
#define		cursor()	( g_alpha(), fputs( CURSORS, stderr) )
#define		swhere(x,y)	( *(x) = g_spx, *(y) = g_spy )
#define		uwhere(x,y)	( (g_status & USER ) ?0: g_chtusr( g_spx, g_spy ), *(x) = g_px, *(y) = g_py )
#define		sxputsr(x,y,s)	sxputsa( g_spx + (x), g_spy + (y), s )
#define		uxputsr(x,y,s)	uxputsa( g_spx + (x), g_spy + (y), s )
#define		syputsr(x,y,s)	syputsa( g_spx + (x), g_spy + (y), s )
#define		uyputsr(x,y,s)	uyputsa( g_spx + (x), g_spy + (y), s )