It depends how you want to do this. The logical way would be to add variables to the rec.
like if your layers are ground, mask, animation, fringe; add groundtileset, masktileset, animationtileset, fringetileset.
This is how Elysium does it, you can rip some of thier code if you must..
OR
calculate how many tiles are in your tileset. Then when drawing, if the number is over that many tiles, subtract it, and go to the next tileset. This will cause less packetlag, but more ingame drawing lag. I suggest the first way, though if you optimize the second (only convert after you get the packet) it will be slightly better. But not noticeably. Do the first way
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