为图形输出设置当前视口

[c]代码库

#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; 

   /* 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()); 

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

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