The format is almost identical to CL2, except it uses the frame header
to store frame width and height instead of 5 32-line offsets.
This means we always have access to frame dimensions, so we can use it
as an on-disk format for our graphics as well.
Additionally, we may be able to optimize the rendering even more
in the future now that we have guaranteed knowledge of frame dimensions.
Convert CEL files to CL2 at load time. CL2 format is more efficient and is about as fast to render.
CEL vs CL2 sizes, on dLvl 5: https://gist.github.com/glebm/9bbdd76962abcd4fd2405ecd3379af97
Memory:
* Peak memory (while loading): -300 KiB
* Memory in-game (dLvl5): -700 KiB
* RG99 binary size: -15 KiB (1333096 -> 1317192)
Performance on rg99:
* On average, -1 FPS in town.
* Same FPS in dungeon (20 FPS on dLvl 1).
Makes `CelSprite` unowned and adds a new `OwnedCelSprite` class for
owned sprites.
This clarifies ownership and makes the code cleaner in a number of
places.
Additionally, because the `CelSprite` class is now tiny (1 less
pointer), we can pass it by-value instead of by-reference, removing a
pointer indirection in the rendering functions.
Gleb Mazovetskiy