implementation of scanline fill for CC65 TGI.

tgi_fill.c

/**
 * screen_paint - Paint screen scanline_fill
 */
void _screen_paint(unsigned short x, unsigned short y)
{
  static unsigned short xStack[320];
  static unsigned char yStack[192];
  unsigned char stackentry = 1;
  unsigned char spanAbove, spanBelow;

  unsigned char oldColor = tgi_getpixel(x,y);

  if (oldColor == 1)
    return;

  do
    {
      while (x > 0 && tgi_getpixel(x-1,y) == oldColor)
        --x;

      spanAbove = spanBelow = false;
      while(tgi_getpixel(x,y) == oldColor)
        {
          tgi_setpixel(x,y);

          if (y < (191))
            {
              unsigned char belowColor = tgi_getpixel(x, y+1);
              if (!spanBelow  && belowColor == oldColor)
                {
                  xStack[stackentry]  = x;
                  yStack[stackentry]  = y+1;
                  ++stackentry;
                  spanBelow = true;
                }
              else if (spanBelow && belowColor != oldColor)
                spanBelow = false;
            }

          if (y > 0)
            {
              unsigned char aboveColor = tgi_getpixel(x, y-1);
              if (!spanAbove  && aboveColor == oldColor)
                {
                  xStack[stackentry]  = x;
                  yStack[stackentry]  = y-1;
                  ++stackentry;
                  spanAbove = true;
                }
              else if (spanAbove && aboveColor != oldColor)
                spanAbove = false;
            }

          ++x;
        }
      --stackentry;
      x = xStack[stackentry];
      y = yStack[stackentry];
    }
  while (stackentry);
}