A binning free list. Binning is important to avoid sifting through lots of small strips when allocating many texture items.
A texture allocator using the guillotine algorithm with the rectangle merge improvement. See sections 2.2 and 2.2.5 in "A Thousand Ways to Pack the Bin - A Practical Approach to Two- Dimensional Rectangle Bin Packing":
The minimum number of pixels on each side that we require for rects to be classified as "large" within the free list.
The minimum number of pixels on each side that we require for rects to be classified as "medium" within the free list.