firstcx(t.x/tiles_per_chunk), lastcx((t.x + t.w - 1)/tiles_per_chunk), lastcy((t.y + t.h - 1)/tiles_per_chunk), curcy(t.y/tiles_per_chunk)
firstcx(t.x/c_tiles_per_chunk), lastcx((t.x + t.w - 1)/c_tiles_per_chunk), lastcy((t.y + t.h - 1)/c_tiles_per_chunk), curcy(t.y/c_tiles_per_chunk)
	Chunk_intersect_iterator(Rectangle t) : tiles(t),		  firstcx(t.x/tiles_per_chunk),		  lastcx((t.x + t.w - 1)/tiles_per_chunk),		  lastcy((t.y + t.h - 1)/tiles_per_chunk),		  curcy(t.y/tiles_per_chunk)		{		curcx = firstcx;		if (t.x <= 0 || t.y <= 0)			{		// Empty to begin with.			curcx = lastcx + 1;			curcy = lastcy + 1;			}		}