setwritemode

Syntax

#include <graphics.h>
void setwritemode(int mode);

Description

The following constants are defined:

COPY_PUT = 0      /* MOV */
XOR_PUT  = 1      /* XOR */

Each constant corresponds to a binary operation between each byte in the line and the corresponding bytes onscreen. COPY_PUT uses the assembly language MOV instruction, overwriting with the line whatever is on the screen. XOR_PUT uses the XOR command to combine the line with the screen. Two successive XOR commands will erase the line and restore the screen to its original appearance.

setwritemode currently works only with line, linerel, lineto, rectangle, and drawpoly.

Return Value

None.

See also

lineto

putimage

Example

/* setwritemode example */ 

#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>

int main()
{
   /* request autodetection */
   int gdriver = DETECT, gmode, errorcode;
   int xmax, ymax;

   /* 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 */
   }

   xmax = getmaxx();
   ymax = getmaxy();

   /* select XOR drawing mode */
   setwritemode(XOR_PUT);

   /* draw a line */
   line(0, 0, xmax, ymax);
   getch();

   /* erase the line by drawing over it */
   line(0, 0, xmax, ymax);
   getch();

   /* select overwrite drawing mode */
   setwritemode(COPY_PUT);

   /* draw a line */

   line(0, 0, xmax, ymax);

   /* clean up */
   getch();
   closegraph();
   return 0;
}