//See ::/Demo/Lectures/GraphicsCPULoad.HC
U8 rev[256],    //The VGA bits are bwd

image[640*480/8];       //We need read-modify write.
//0xA0000 alias memory can't be read.

U0 MGInit()
{
  I64 i,j;
  MemSet(image,0,sizeof(image));
  MemSet(rev,0,sizeof(rev));
  for (i=0; i<256; i++)
    for (j=0; j<8; j++)
      if (Bt(&i,j))
        Bts(&rev[i],7-j);
}

U0 MGUpdate()
{//Copy image to VGA memory
//For better performance we could only write what's changed.
  //0xA0000 alias is slower than normal RAM.
  OutU8(VGAP_IDX,VGAR_MAP_MASK);
  OutU8(VGAP_DATA,0xF);//All color planes at once -- Black and White
  MemCpy(text.vga_alias,image,sizeof(image)); //Alias of 0xA0000
}

U0 MGPlot(I64 x,I64 y)
{
  if (0<=x<640 && 0<=y<480)
    Bts(image,y*640+x^7);
}

U0 MGHLine(I64 x1,I64 x2,I64 y)
{//Warning!  No clipping
//For performance, we do as many whole-bytes as possible.
  U8 *ptr;
  I64 i,w,leading,trailing,whole_bytes;
  if (x2<x1) SwapI64(&x1,&x2);
  ptr=image+y*640/8+x1>>3;
  w=x2-x1+1;
  leading =8-x1&7;
  trailing=(x2+1)&7;
  if (leading+trailing>w)
    *ptr|=rev[(0xFF00>>leading&(0x00FF<<trailing)>>8)];
  else
  {
    whole_bytes=(w-leading-trailing)>>3;
    if (leading)
      *ptr++|=rev[(0xFF00>>leading)&0xFF];
    for (i=0; i<whole_bytes; i++)
      *ptr++=0xFF;
    if (trailing)
      *ptr++|=rev[(0x00FF<<trailing)>>8];
  }
}

U0 MGLine(I64 x1,I64 y1,I64 x2,I64 y2)
{//Warning!  No clipping
  I64 dx=x2-x1,dy=y2-y1;
  x1<<=32;
  x2<<=32;
  y1<<=32;
  y2<<=32;
  if (AbsI64(dx)>AbsI64(dy))
  {
    dy=dy<<32/AbsI64(dx);
    dx=SignI64(dx)<<32;
    while (x1!=x2)
    {
      MGPlot(x1.i32[1],y1.i32[1]);
      x1+=dx;
      y1+=dy;
    }
  }
  else
  {
    dx=dx<<32/AbsI64(dy);
    dy=SignI64(dy)<<32;
    while (y1!=y2)
    {
      MGPlot(x1.i32[1],y1.i32[1]);
      x1+=dx;
      y1+=dy;
    }
  }
  MGPlot(x1.i32[1],y1.i32[1]);
}

U0 MGCircle(I64 x,I64 y,F64 r)
{
  F64 s,c,x1,y1,x2,y2;
  I64 len;
  if (r<0) return;
  x1=r;
  y1=0;
  c=Cos(1/r);
  s=Sin(1/r);
  len=2*r*pi;
  MGPlot(x+x1,y+y1);
  while (len-->=0)
  {
    //m1@a1 * m2@a2     = m1*m2@(arg1+arg2)
    //(x1+y1i)*(x2+y2i) = x1*x2+(x1*y1+x2*y2)i-y1*y2
    // meti=mCos(t)+imSin(t)
    x2=x1;
    y2=y1;
    x1=c*x2-s*y2;
    y1=s*x2+c*y2;
    MGPlot(x+x1,y+y1);
  }
}


U0 MiniGrLibDemo()
{
  I64 i;
  MGInit;
  for (i=0; i<100; i++)
    MGHLine(200+i,400+i,300+i);
  for (i=0; i<500; i+=10)
    MGLine(i,0,0,480-i);
  for (i=0; i<300; i+=4)
    MGCircle(200,100+i,i);
  MGUpdate;
  Busy(1500000);
  /*
  We are returning graphics to normal operations under TempleOS.
  It is not normal to by-pass the TempleOS graphcis routines.
  The TempleOS graphics don't know VGA has changed.
  This bit tells TempleOS to update whole scrn.
  */
  //<CTRL-ALT-v> will flush scrn VGA cache.
  VGAFlush;
}

MiniGrLibDemo;

//See RawPutChar() for text.
//See ::/Demo/Lectures/ScrnMemory.HC for color.
//See ::/Demo/Lectures/GraphicsCPULoad.HC.