c语言中 函数名: clearviewport(), 功 能: 清除图形视区 具体怎么用?

clearviewport
函数名: clearviewport
功 能: 清除图形视区
用 法: void far clearviewport(void);
程序例:

#include
#include
#include
#include

#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\n", 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 *