/* * File: graphics.c * Last modified on Thu Sep 16 09:34:19 1993 by eroberts * ----------------------------------------------------- * Implements the graphics.h interface to generate a * PostScript file.  PostScript is a registered trademark * of the Adobe Systems Incorporated. *//* * General implementation notes * ---------------------------- * This implementation of the graphics.h interface does not * actually do any display but instead writes a PostScript * file containing commands that would generate the picture. * The advantage of this implementation is portability, since * it contains no code that depends on graphics primitives * for a particular platform. * * The code for this implementation is for the most part * straightforward, because all of the graphics primitives * have simple PostScript equivalents.  The only hard part * is making sure that the end of the file is correct when * the file is closed, usually via the exit call.  To print * the page, the showpage command must occur at the end of * the file, but the graphics package does not get control * at that point.  To avoid the problem, each call to this * package writes a legal trailer to the file.  Thus, the * invariant after each call to any of these functions is * that the PostScript file is complete.  Before writing * new data, these functions back up the file pointer over * the old trailer and begin rewriting from that point. */#include <stdio.h>#include <math.h>#include "genlib.h"#include "graphics.h"/* * Constants: WindowHeight, WindowWidth * ------------------------------------ * These constants are the values returned by GetWindowHeight * and GetWindowWidth.  The assumption here is that output is * being directed to an 8.5 x 11 page. */#define WindowHeight 11.0#define WindowWidth   8.5/* * Constant: PSFileName * -------------------- * The name of the PostScript output file. */#define PSFileName "graphics.ps"/* * Private variables * ----------------- * initialized    Set to TRUE when InitGraphics is called. * psfile         The file stream used for PostScript. * cx, cy         The current x, y positions. * nextWrite      The file index for the next PostScript *                command (see the general notes above). */static bool initialized = FALSE;static FILE *psfile;static double cx, cy;static long nextWrite;/* Private function prototypes */static void InitCheck(void);static void WritePostScriptHeader(void);static void WritePostScriptTrailer(void);static void ResetFilePointer(void);static double Pts(double inches);static double Radians(double degrees);/* Public functions */void InitGraphics(void){    if (initialized) fclose(psfile);    psfile = fopen(PSFileName, "w");    WritePostScriptHeader();    WritePostScriptTrailer();    cx = cy = 0;    initialized = TRUE;}void MovePen(double x, double y){    InitCheck();    cx = x;    cy = y;}void DrawLine(double dx, double dy){    InitCheck();    ResetFilePointer();    fprintf(psfile, "newpath %g %g moveto", Pts(cx), Pts(cy));    fprintf(psfile, " %g %g rlineto stroke\n", Pts(dx), Pts(dy));    cx += dx;    cy += dy;    WritePostScriptTrailer();}void DrawArc(double r, double start, double sweep){    double x, y;    InitCheck();    x = cx + r * cos(Radians(start + 180));    y = cy + r * sin(Radians(start + 180));    ResetFilePointer();    fprintf(psfile, "newpath %g %g %g", Pts(x), Pts(y), Pts(r));    fprintf(psfile, " %g %g", start, start + sweep);    fprintf(psfile, " %s stroke\n", (sweep < 0) ? "arcn" : "arc");    WritePostScriptTrailer();    cx = x + r * cos(Radians(start + sweep));    cy = y + r * sin(Radians(start + sweep));}double GetWindowWidth(void){    InitCheck();    return (WindowWidth);}double GetWindowHeight(void){    InitCheck();    return (WindowHeight);}double GetCurrentX(void){    InitCheck();    return (cx);}double GetCurrentY(void){    InitCheck();    return (cy);}/* Private functions */static void InitCheck(void){    if (!initialized) Error("InitGraphics has not been called");}static void WritePostScriptHeader(void){    fprintf(psfile, "%%!PS-Adobe-1.0\n");    fprintf(psfile, "%%%%Title: graphics window\n");    fprintf(psfile, "%%%%Pages: 1\n");    fprintf(psfile, "%%%%EndComments\n");}static void WritePostScriptTrailer(void){    nextWrite = ftell(psfile);    fprintf(psfile, "showpage\n");}static void ResetFilePointer(void){    fseek(psfile, nextWrite, 0);}static double Pts(double inches){    return (72 * inches);}static double Radians(double degrees){    return (degrees / 180 * 3.1415926535);}