函数名: clearviewport

功 能: 清除图形视区

用 法: void far clearviewport(void);

程序例:

#include <graphics.h>

#include <stdlib.h>

#include <stdio.h>

#include <conio.h>

#define CLIP_ON 1 /* activates clipping in viewport */

int main(void)

{

/* request auto detection */

int gdriver = DETECT, gmode, errorcode;

int 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\", grapherrormsg(errorcode));

printf("Press any key to halt:");

getch();

exit(1); /* terminate with an error code */

}

setcolor(getmaxcolor());

ht = textheight("W");

/* message in default full-screen viewport */

outtextxy(0, 0, "* <-- (0, 0) in default viewport");

/* create a smaller viewport */

setviewport(50, 50, getmaxx()-50, getmaxy()-50, CLIP_ON);

/* display some messages */

outtextxy(0, 0, "* <-- (0, 0) in smaller viewport");

outtextxy(0, 2*ht, "Press any key to clear viewport:");

/* wait for a key */

getch();

/* clear the viewport */

clearviewport();

/* output another message */

outtextxy(0, 0, "Press any key to quit:");

/* clean up */

getch();

closegraph();

return 0;

}