#include <go32.h>
#include <dpmi.h>
#include <pc.h>
#include <sys/movedata.h>
#include <sys/farptr.h>



static inline void vgamode(int n){
 __dpmi_regs r;
 r.x.ax=n;
 __dpmi_int(0x10,&r);
}


/* switch to mode 13h when program starts */
__attribute__((constructor))
void grafixinit(){
 vgamode(0x13);
}


/* switch back to mode 3 and kill sound when program exits */
__attribute__((destructor))
void grafixend(){
 vgamode(3);
 nosound();
}


static inline void vsync(){
 /* wait until any previous retrace has ended */
 do{}while(inportb(0x3DA) & 8);

 /* wait until a new retrace has just begun */
 do{}while(!(inportb(0x3DA) & 8));
}


/* sets a color 0..255 in the palette with rgb values 0,,63 */
static inline void setcolor(const unsigned char n,const unsigned char r,const unsigned char g,const unsigned char b){
 outportb(0x3C8,n);
 outportb(0x3C9,r);
 outportb(0x3C9,g);
 outportb(0x3C9,b);
}


/* set pixel */
static inline void pset(const unsigned x,const unsigned y,const unsigned char color){
 if(x<320&&y<200)
  _farpokeb(_dos_ds, 0xA0000+x+((y<<8)+(y<<6)), color);
}


/* sets 2 pixels at once, color is 2 bytes */
static inline void psetw(const unsigned x,const unsigned y,const unsigned short color){
 if(x<319&&y<200)
  _farpokew(_dos_ds, 0xA0000+x+((y<<8)+(y<<6)), color);
}


/* sets 4 pixels at once, color is 4 bytes */
static inline void psetl(const unsigned x,const unsigned y,const unsigned long color){
 if(x<317&&y<200)
  _farpokel(_dos_ds, 0xA0000+x+((y<<8)+(y<<6)), color);
}

Provides the basics for mode 13h

vga mode 13h for djgpp

C