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c:graphics.h:setactivepage

setactivepage

Syntax of setactivepage

#include <graphics.h>
void setactivepage(int page);
 

Description of setactivepage

setactivepage makes page the active graphics page. All subsequent
graphics output will be directed to that graphics page.
The active graphics page might not be the one you see onscreen, depending
on how many graphics pages are available on your system. Only the EGA,
VGA, and Hercules graphics cards support multiple pages.

Example of setactivepage

/* setactivepage example */
 
#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>
 
int main(void)
{
   /* select driver and mode that supports multiple pages */
   int gdriver = EGA, gmode = EGAHI, errorcode;
   int x, y, ht;
 
   /* 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 */
   }
 
   x = getmaxx() / 2;
   y = getmaxy() / 2;
   ht = textheight("W");
 
   /*  select the off screen page for drawing */
   setactivepage(1);
 
   /* draw a line on page #1 */
   line(0, 0, getmaxx(), getmaxy());
 
   /* output a message on page #1 */
   settextjustify(CENTER_TEXT, CENTER_TEXT);
   outtextxy(x, y, "This is page #1:");
   outtextxy(x, y+ht, "Press any key to halt:");
 
 
   /* select drawing to page #0 */
   setactivepage(0);
 
   /* output a message  on page #0 */
   outtextxy(x, y, "This is page #0.");
   outtextxy(x, y+ht, "Press any key to view page #1:");
   getch();
 
   /* select page #1 as the visible page */
   setvisualpage(1);
 
   /* clean up */
   getch();
   closegraph();
   return 0;
}

See also

output of setactivepage example

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c/graphics.h/setactivepage.txt · Last modified: 2015/05/06 23:06 (external edit)

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