14 KiB
Design Flaws
These are parts of the code that do not work incorrectly, like bugs and glitches, but that clearly exist just to work around a problem. In other words, with a slightly different design, the code would not need to exist at all. Design flaws may be exceptions to a usual rule, such as "tables of pointers in different banks use dba" (one exception, and another) or "graphics used as a unit are stored and loaded contiguously" (a notable exception).
Contents
- Pic banks are offset by
PICS_FIX PokemonPicPointersandUnownPicPointersare assumed to start at the same address- Footprints are split into top and bottom halves
ITEM_C3andITEM_DCbreak up the continuous sequence of TM items- Pokédex entry banks are derived from their species IDs
- Identical sine wave code and data is repeated five times
GetForestTreeFrameworks, but it's still bad
Pic banks are offset by PICS_FIX
data/pokemon/pic_pointers.asm, data/pokemon/unown_pic_pointers.asm, and data/trainers/pic_pointers.asm all have to use dba_pic instead of dba. This is a macro in macros/data.asm that offsets banks by PICS_FIX:
dba_pic: MACRO ; dbw bank, address
db BANK(\1) - PICS_FIX
dw \1
ENDM
The offset is translated into a correct bank by FixPicBank in engine/gfx/load_pics.asm:
FixPicBank:
; This is a thing for some reason.
PICS_FIX EQU $36
GLOBAL PICS_FIX
push hl
push bc
sub BANK("Pics 1") - PICS_FIX
ld c, a
ld b, 0
ld hl, .PicsBanks
add hl, bc
ld a, [hl]
pop bc
pop hl
ret
.PicsBanks:
db BANK("Pics 1") ; BANK("Pics 1") + 0
db BANK("Pics 2") ; BANK("Pics 1") + 1
db BANK("Pics 3") ; BANK("Pics 1") + 2
db BANK("Pics 4") ; BANK("Pics 1") + 3
db BANK("Pics 5") ; BANK("Pics 1") + 4
db BANK("Pics 6") ; BANK("Pics 1") + 5
db BANK("Pics 7") ; BANK("Pics 1") + 6
db BANK("Pics 8") ; BANK("Pics 1") + 7
db BANK("Pics 9") ; BANK("Pics 1") + 8
db BANK("Pics 10") ; BANK("Pics 1") + 9
db BANK("Pics 11") ; BANK("Pics 1") + 10
db BANK("Pics 12") ; BANK("Pics 1") + 11
db BANK("Pics 13") ; BANK("Pics 1") + 12
db BANK("Pics 14") ; BANK("Pics 1") + 13
db BANK("Pics 15") ; BANK("Pics 1") + 14
db BANK("Pics 16") ; BANK("Pics 1") + 15
db BANK("Pics 17") ; BANK("Pics 1") + 16
db BANK("Pics 18") ; BANK("Pics 1") + 17
db BANK("Pics 19") ; BANK("Pics 1") + 18
db BANK("Pics 20") ; BANK("Pics 1") + 19
db BANK("Pics 21") ; BANK("Pics 1") + 20
db BANK("Pics 22") ; BANK("Pics 1") + 21
db BANK("Pics 23") ; BANK("Pics 1") + 22
db BANK("Pics 24") ; BANK("Pics 1") + 23
Fix: Use dba instead of dba_pic, delete FixPicBank, and remove all four calls to FixPicBank.
PokemonPicPointers and UnownPicPointers are assumed to start at the same address
In gfx/pics.asm:
; PokemonPicPointers and UnownPicPointers are assumed to start at the same
; address, but in different banks. This is enforced in pokecrystal.link.
SECTION "Pic Pointers", ROMX
INCLUDE "data/pokemon/pic_pointers.asm"
SECTION "Unown Pic Pointers", ROMX
INCLUDE "data/pokemon/unown_pic_pointers.asm"
In pokecrystal.link:
ROMX $48
org $4000
"Pic Pointers"
"Pics 1"
ROMX $49
org $4000
"Unown Pic Pointers"
"Pics 2"
Two routines in engine/gfx/load_pics.asm make this assumption; GetFrontpicPointer:
ld a, [wCurPartySpecies]
cp UNOWN
jr z, .unown
ld a, [wCurPartySpecies]
ld d, BANK(PokemonPicPointers)
jr .ok
.unown
ld a, [wUnownLetter]
ld d, BANK(UnownPicPointers)
.ok
ld hl, PokemonPicPointers ; UnownPicPointers
dec a
ld bc, 6
call AddNTimes
And GetMonBackpic:
; These are assumed to be at the same address in their respective banks.
ld hl, PokemonPicPointers ; UnownPicPointers
ld a, b
ld d, BANK(PokemonPicPointers)
cp UNOWN
jr nz, .ok
ld a, c
ld d, BANK(UnownPicPointers)
.ok
dec a
ld bc, 6
call AddNTimes
Fix:
Don't enforce org $4000 in pokecrystal.link.
Modify GetFrontpicPointer:
ld a, [wCurPartySpecies]
cp UNOWN
jr z, .unown
ld a, [wCurPartySpecies]
ld hl, PokemonPicPointers
ld d, BANK(PokemonPicPointers)
jr .ok
.unown
ld a, [wUnownLetter]
ld hl, UnownPicPointers
ld d, BANK(UnownPicPointers)
.ok
dec a
ld bc, 6
call AddNTimes
And GetMonBackpic:
ld a, b
ld hl, PokemonPicPointers
ld d, BANK(PokemonPicPointers)
cp UNOWN
jr nz, .ok
ld a, c
ld hl, UnownPicPointers
ld d, BANK(UnownPicPointers)
.ok
dec a
ld bc, 6
call AddNTimes
Footprints are split into top and bottom halves
; Footprints are 2x2 tiles each, but are stored as a 16x64-tile image
; (32 rows of 8 footprints per row).
; That means there's a row of the top two tiles for eight footprints,
; then a row of the bottom two tiles for those eight footprints.
; These macros help extract the first and the last two tiles, respectively.
footprint_top EQUS "0, 2 * LEN_1BPP_TILE"
footprint_bottom EQUS "2 * LEN_1BPP_TILE, 2 * LEN_1BPP_TILE"
; Entries correspond to Pokémon species, two apiece, 8 tops then 8 bottoms
; 001-008 top halves
INCBIN "gfx/footprints/bulbasaur.1bpp", footprint_top
INCBIN "gfx/footprints/ivysaur.1bpp", footprint_top
INCBIN "gfx/footprints/venusaur.1bpp", footprint_top
INCBIN "gfx/footprints/charmander.1bpp", footprint_top
INCBIN "gfx/footprints/charmeleon.1bpp", footprint_top
INCBIN "gfx/footprints/charizard.1bpp", footprint_top
INCBIN "gfx/footprints/squirtle.1bpp", footprint_top
INCBIN "gfx/footprints/wartortle.1bpp", footprint_top
; 001-008 bottom halves
INCBIN "gfx/footprints/bulbasaur.1bpp", footprint_bottom
INCBIN "gfx/footprints/ivysaur.1bpp", footprint_bottom
INCBIN "gfx/footprints/venusaur.1bpp", footprint_bottom
INCBIN "gfx/footprints/charmander.1bpp", footprint_bottom
INCBIN "gfx/footprints/charmeleon.1bpp", footprint_bottom
INCBIN "gfx/footprints/charizard.1bpp", footprint_bottom
INCBIN "gfx/footprints/squirtle.1bpp", footprint_bottom
INCBIN "gfx/footprints/wartortle.1bpp", footprint_bottom
...
Pokedex_LoadAnyFootprint in engine/pokedex/pokedex.asm:
push hl
ld e, l
ld d, h
ld hl, vTiles2 tile $62
lb bc, BANK(Footprints), 2
call Request1bpp
pop hl
; Whoever was editing footprints forgot to fix their
; tile editor. Now each bottom half is 8 tiles off.
ld de, 8 tiles
add hl, de
ld e, l
ld d, h
ld hl, vTiles2 tile $64
lb bc, BANK(Footprints), 2
call Request1bpp
Fix:
Store footprints contiguously:
INCBIN "gfx/footprints/bulbasaur.1bpp"
INCBIN "gfx/footprints/ivysaur.1bpp"
INCBIN "gfx/footprints/venusaur.1bpp"
INCBIN "gfx/footprints/charmander.1bpp"
INCBIN "gfx/footprints/charmeleon.1bpp"
INCBIN "gfx/footprints/charizard.1bpp"
INCBIN "gfx/footprints/squirtle.1bpp"
INCBIN "gfx/footprints/wartortle.1bpp"
...
Modify Pokedex_LoadAnyFootprint:
ld e, l
ld d, h
ld hl, vTiles2 tile $62
lb bc, BANK(Footprints), 4
call Request1bpp
ITEM_C3 and ITEM_DC break up the continuous sequence of TM items
constants/item_constants.asm defined the 50 TMs in order with add_tm, but ITEM_C3 and ITEM_DC break up that sequence.
add_tm DYNAMICPUNCH ; bf
...
add_tm ROLLOUT ; c2
const ITEM_C3 ; c3
add_tm ROAR ; c4
...
add_tm DIG ; db
const ITEM_DC ; dc
add_tm PSYCHIC_M ; dd
...
add_tm NIGHTMARE ; f2
NUM_TMS = const_value - TM01 - 2 ; discount ITEM_C3 and ITEM_DC
GetTMHMNumber and GetNumberedTMHM in engine/items/items.asm have to compensate for this:
GetTMHMNumber::
; Return the number of a TM/HM by item id c.
ld a, c
; Skip any dummy items.
cp ITEM_C3 ; TM04-05
jr c, .done
cp ITEM_DC ; TM28-29
jr c, .skip
dec a
.skip
dec a
.done
sub TM01
inc a
ld c, a
ret
GetNumberedTMHM:
; Return the item id of a TM/HM by number c.
ld a, c
; Skip any gaps.
cp ITEM_C3 - (TM01 - 1)
jr c, .done
cp ITEM_DC - (TM01 - 1) - 1
jr c, .skip_one
.skip_two
inc a
.skip_one
inc a
.done
add TM01
dec a
ld c, a
ret
Fix:
Move ITEM_C3 and ITEM_DC above all the TMs in every table of item data.
Modify engine/items/items.asm:
GetTMHMNumber::
; Return the number of a TM/HM by item id c.
ld a, c
sub TM01
inc a
ld c, a
ret
GetNumberedTMHM:
; Return the item id of a TM/HM by number c.
ld a, c
add TM01
dec a
ld c, a
ret
Pokédex entry banks are derived from their species IDs
PokedexDataPointerTable in data/pokemon/dex_entry_pointers.asm is a table of dw, not dba, yet there are four banks used for Pokédex entries. The correct bank is derived from the species ID at the beginning of each Pokémon's base stats. (This is the only use the base stat species ID has.)
Three separate routines do the same derivation; GetDexEntryPointer in engine/pokedex/pokedex_2.asm:
GetDexEntryPointer:
; return dex entry pointer b:de
push hl
ld hl, PokedexDataPointerTable
ld a, b
dec a
ld d, 0
ld e, a
add hl, de
add hl, de
ld e, [hl]
inc hl
ld d, [hl]
push de
rlca
rlca
maskbits NUM_DEX_ENTRY_BANKS
ld hl, .PokedexEntryBanks
ld d, 0
ld e, a
add hl, de
ld b, [hl]
pop de
pop hl
ret
.PokedexEntryBanks:
db BANK("Pokedex Entries 001-064")
db BANK("Pokedex Entries 065-128")
db BANK("Pokedex Entries 129-192")
db BANK("Pokedex Entries 193-251")
GetPokedexEntryBank in engine/items/item_effects.asm:
GetPokedexEntryBank:
push hl
push de
ld a, [wEnemyMonSpecies]
rlca
rlca
maskbits NUM_DEX_ENTRY_BANKS
ld hl, .PokedexEntryBanks
ld d, 0
ld e, a
add hl, de
ld a, [hl]
pop de
pop hl
ret
.PokedexEntryBanks:
db BANK("Pokedex Entries 001-064")
db BANK("Pokedex Entries 065-128")
db BANK("Pokedex Entries 129-192")
db BANK("Pokedex Entries 193-251")
And PokedexShow_GetDexEntryBank in engine/pokegear/radio.asm:
PokedexShow_GetDexEntryBank:
push hl
push de
ld a, [wCurPartySpecies]
dec a
rlca
rlca
maskbits NUM_DEX_ENTRY_BANKS
ld hl, .PokedexEntryBanks
ld d, 0
ld e, a
add hl, de
ld a, [hl]
pop de
pop hl
ret
.PokedexEntryBanks:
db BANK("Pokedex Entries 001-064")
db BANK("Pokedex Entries 065-128")
db BANK("Pokedex Entries 129-192")
db BANK("Pokedex Entries 193-251")
Fix: Use dba instead of dw in PokedexDataPointerTable, and modify the code that accesses it to match.
Identical sine wave code and data is repeated five times
_Sine in engine/math/sine.asm:
_Sine::
; a = d * sin(e * pi/32)
ld a, e
calc_sine_wave
Sprites_Cosine and Sprites_Sine in engine/gfx/sprites.asm:
Sprites_Cosine:
; a = d * cos(a * pi/32)
add %010000 ; cos(x) = sin(x + pi/2)
; fallthrough
Sprites_Sine:
; a = d * sin(a * pi/32)
calc_sine_wave
BattleAnim_Cosine and BattleAnim_Sine in engine/battle_anims/functions.asm:
BattleAnim_Cosine:
; a = d * cos(a * pi/32)
add %010000 ; cos(x) = sin(x + pi/2)
; fallthrough
BattleAnim_Sine:
; a = d * sin(a * pi/32)
calc_sine_wave BattleAnimSineWave
...
BattleAnimSineWave:
sine_table 32
StartTrainerBattle_DrawSineWave in engine/battle/battle_transition.asm:
StartTrainerBattle_DrawSineWave:
calc_sine_wave
And CelebiEvent_Cosine in engine/events/celebi.asm:
CelebiEvent_Cosine:
; a = d * cos(a * pi/32)
add %010000 ; cos(x) = sin(x + pi/2)
calc_sine_wave
They all rely on calc_sine_wave in macros/code.asm:
calc_sine_wave: MACRO
; input: a = a signed 6-bit value
; output: a = d * sin(a * pi/32)
and %111111
cp %100000
jr nc, .negative\@
call .apply\@
ld a, h
ret
.negative\@
and %011111
call .apply\@
ld a, h
xor $ff
inc a
ret
.apply\@
ld e, a
ld a, d
ld d, 0
if _NARG == 1
ld hl, \1
else
ld hl, .sinetable\@
endc
add hl, de
add hl, de
ld e, [hl]
inc hl
ld d, [hl]
ld hl, 0
.multiply\@ ; factor amplitude
srl a
jr nc, .even\@
add hl, de
.even\@
sla e
rl d
and a
jr nz, .multiply\@
ret
if _NARG == 0
.sinetable\@
sine_table 32
endc
ENDM
And on sine_table in macros/data.asm:
sine_table: MACRO
; \1 samples of sin(x) from x=0 to x<32768 (pi radians)
x = 0
rept \1
dw (sin(x) + (sin(x) & $ff)) >> 8 ; round up
x = x + DIV(32768, \1) ; a circle has 65536 "degrees"
endr
ENDM
Fix: Edit home/sine.asm to contain a single copy of the (co)sine code in bank 0, and call it from those five sites.
GetForestTreeFrame works, but it's still bad
In engine/tilesets/tileset_anims.asm:
GetForestTreeFrame:
; Return 0 if a is even, or 2 if odd.
and a
jr z, .even
cp 1
jr z, .odd
cp 2
jr z, .even
cp 3
jr z, .odd
cp 4
jr z, .even
cp 5
jr z, .odd
cp 6
jr z, .even
.odd
ld a, 2
scf
ret
.even
xor a
ret
Fix:
GetForestTreeFrame:
; Return 0 if a is even, or 2 if odd.
and 1
add a
ret