The following program uses VioGetPhysBuf (and can therefore only be run in
a full-screen session) to draw a series of circles,  then rotates the
palette to produce a hypnotic effect (do not use under the influence of
recreational drugs :-).

It was compiled with IBM cset++ thus:

    icc /G4 /Q /Smes /W3 /Kb+ /O /Gs /Gm circ_fs.c

I was not able to get the program to function properly when compiled with
Borland/2 or Watcom 32bit (works ok Watcom 16bit).

When I get around to it,  I plan to try to write the same program as a PM
program,  and as a DIVE program,  unless someone else wants to...

 #define INCL_NOPMAPI
 #define INCL_VIO
 #define INCL_DOS
 #include 
 #include 
 #include 
 #include 
 #include 
 #include 
 #include 
 #include 
 //icc /G4 /Q /Smes /W3 /Kb+ /O /Oi20 /Gs /Gm circ_fs.c
 //p.fitzsimmons 3/95


 #define SIZEX 320
 #define SIZEY 200
 #define ORIGINX (SIZEX/2)
 #define ORIGINY (SIZEY/2)

 #define squared(n)  ((n) * (n))
 #define point(x, y)  pchScreen[ (unsigned) ((y) * SIZEX + x)]


 // circle with origin (h,k) and radius r:  r^2 = (x-h)^2 + (y-k)^2

 void circles(UCHAR *pchScreen)
 {
     int x, y, r;

     for(x=0; x=0; i--){     // rotate old values
         pal[(i+1) * 3 + 0] = pal[i*3 + 0];
         pal[(i+1) * 3 + 1] = pal[i*3 + 1];
         pal[(i+1) * 3 + 2] = pal[i*3 + 2];
     }
     pal[0] = r;     // add new value
     pal[1] = g;
     pal[2] = b;

     switch(ch){
         case 0: b = newcolor(&bdir, b, &ch); break;
         case 2: g = newcolor(&gdir, g, &ch); break;
         case 1: r = newcolor(&rdir, r, &ch); break;
     }

     rc = VioSetState(&vcr, 0);
     if(rc){
         printf( "SYS%04u: Error setting palette registers.\n", rc);
         exit(1);
     }
 }

 static void setmode(void)
 {
     VIOMODEINFO vi;
     USHORT rc;

     vi.cb = sizeof(vi);
     VioGetMode(&vi, 0);
     vi.fbType = 3;
     vi.color  = 8;
     vi.col    = 40;
     vi.row    = 25;
     vi.hres   = SIZEX;
     vi.vres   = SIZEY;
     if( 0 != (rc = VioSetMode(&vi, 0))){
         printf("SYS%04u: Could not set video mode to 320x200x256", rc);
         exit(1);
     }
 }

 void thread2(void *arg)
 {
     unsigned i=0;
     DosSetPriority(PRTYS_PROCESS, PRTYC_IDLETIME, 1, 0);
     for(;;){
         rotate(0);
         if(!(i++ % 2))   // sleep every other loop
             DosSleep(1);
     }
 }


 int main(void)
 {
     VIOPHYSBUF viopb;
     PCH    pchScreen;
     USHORT fStatus;

     srand(time(NULL) % 0x8000);
     setmode();
     viopb.pBuf = (PBYTE) 0xA0000L;
     viopb.cb = 64000L;
     VioScrLock(LOCKIO_WAIT, (PBYTE) &fStatus, 0);
     VioGetPhysBuf(&viopb, 0);
     pchScreen = MAKEP(viopb.asel[0], 0);
     _fmemset(pchScreen, 0, (size_t)viopb.cb);
     circles(pchScreen);
     VioScrUnLock(0);
     rotate(1);
     DosSleep(100L);     // pause for effect
     _beginthread(thread2, NULL, 0x2000, NULL);
     getch();
     return 0;
 }


--- Maximus/2 2.02p1