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int xsize, ysize;
int x, scan, w, xstart;
static int sizes[4] = {32, 64, 64, 128};
unsigned which;
unsigned char *where, *scrolls, *tiles, *tile_line;
int xoff, yoff, xoff_mask;
int xscroll, yscroll;
#if PLANE == 0
// Plane 0 is only where the window isn't
// This should make Herzog Zwei split screen work perfectly, and clean
// up those little glitches on Sonic 3's level select.
if(reg[18] & 0x80) // Window goes down, plane 0 goes up! :)
{
if((line>>3) >= (reg[18]&0x1f)) return;
} else { // Window goes up, plane 0 goes down
if((line>>3) < (reg[18]&0x1f)) return;
}
#endif
xsize = sizes[ reg[16] & 3] << 1;
ysize = sizes[(reg[16] >> 4) & 3];
#if PLANE == 0
yscroll = get_word(vsram);
scrolls = vram + ((reg[13]<<10) & 0xfc00);
tiles = vram + (reg[ 2]<<10);
#else // PLANE == 1
yscroll = get_word(vsram+2);
scrolls = vram + ((reg[13]<<10) & 0xfc00) + 2;
tiles = vram + (reg[ 4]<<13);
#endif
// Interlace?
if(reg[12] & 2)
yscroll >>= 1;
// Offset for the line
yscroll += line;
// Wide or narrow?
if(reg[12] & 1)
{
w = 40; xstart = -8;
} else {
w = 32; xstart = 24;
}
// How do we horizontal offset?
switch(reg[11] & 3)
{
case 2: // per tile
scrolls += (line & ~7) << 2;
break;
case 3: // per line
scrolls += line << 2;
break;
default:
break;
}
xscroll = get_word(scrolls);
xoff_mask = xsize - 1;
yoff = (yscroll>>3) & (ysize - 1);
xoff = ((-(xscroll>>3) - 1)<<1) & xoff_mask;
tile_line = tiles + xsize * yoff;
scan = yscroll & 7;
where = dest + (xstart + (xscroll & 7)) * Bpp;
for(x = -1; x < w; ++x)
{
#if PLANE == 0
if(reg[17] & 0x80) // Don't draw where the window will be
{
if(x >= ((reg[17]&0x1f) << 1)) goto skip;
} else {
// + 1 so scroll layers in Sonic look right
if((x + 1) < ((reg[17]&0x1f) << 1)) goto skip;
}
#endif
which = get_word(tile_line + xoff);
#if (FRONT == 0) && (PLANE == 1)
draw_tile_solid(which, scan, where);
#elif FRONT == 1
if(which >> 15) draw_tile(which, scan, where);
#else
if(!(which >> 15)) draw_tile(which, scan, where);
#endif
#if PLANE == 0
skip:
#endif
where += Bpp_times8;
xoff = (xoff + 2) & xoff_mask;
}
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