#include <graphics.h>
int textwidth(char *textstring);
 

The graphics function textwidth takes the string length, current font
size, and multiplication factor, and determines the width of textstring
in pixels.
This function is useful for computing viewport widths, sizing a title to
make it fit on a graph or in a box, and so on.
Use textwidth to compute the width of strings, instead of doing the
computations manually. When you use this function, no source code
modifications have to be made when different fonts are selected.

/* textwidth example */
 
#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>
 
int main(void)
{
   /* request autodetection */
   int gdriver = DETECT, gmode, errorcode;
   int x = 0, y = 0;
   int i;
   char msg[80];
 
   /* initialize graphics and local variables */
   initgraph(&gdriver, &gmode, "");
 
   /* read result of initialization */
   errorcode = graphresult();
   if (errorcode != grOk) {  /* an error occurred */
printf("Graphics error: %s\n", grapherrormsg(errorcode));
 
printf("Press any key to halt:");
getch();
exit(1);   /* terminate with an error code */
   }
 
   y = getmaxy() / 2;
   settextjustify(LEFT_TEXT, CENTER_TEXT);
   for (i = 1; i < 11; i++) {
/* select the text style, direction, and size */
settextstyle(TRIPLEX_FONT, HORIZ_DIR, i);
 
/* create a message string */
sprintf(msg, "Size: %d", i);
 
/* output the message */
outtextxy(x, y, msg);
 
/* advance to the end of the text */
 
x += textwidth(msg);
   }
 
   /* clean up */
   getch();
   closegraph();
   return 0;
}

gettextsettings outtext outtextxy settextstyle textheight

  no output of example at the moment
  do not hesitate and add it...