path: root/engine/overworld/map_sprites.asm

; Loads tile patterns for map's sprites.
; For outside maps, it loads one of several fixed sets of sprites.
; For inside maps, it loads each sprite picture ID used in the map header.
; This is also called after displaying text because loading
; text tile patterns overwrites half of the sprite tile pattern data.
; Note on notation:
; x#SPRITESTATEDATA1_* and x#SPRITESTATEDATA2_* are used to denote wSpriteStateData1 and
; wSpriteStateData2 sprite slot, respectively, within loops. The X is the loop index.
; If there is an inner loop, Y is the inner loop index, i.e. y#SPRITESTATEDATA1_* and
; y#SPRITESTATEDATA2_* denote fields of the sprite slots iterated over in the inner loop.
_InitMapSprites::
	call InitOutsideMapSprites
	ret c ; return if the map is an outside map (already handled by above call)
; if the map is an inside map (i.e. mapID >= $25)
	call LoadSpriteSetFromMapHeader
	call LoadMapSpriteTilePatterns
	call Func_14150
	ret

; Loads sprite set for outside maps (cities and routes) and sets VRAM slots.
; sets carry if the map is a city or route, unsets carry if not
InitOutsideMapSprites:
	ld a, [wCurMap]
	cp FIRST_INDOOR_MAP ; is the map a city or a route?
	ret nc ; if not, return
	call GetSplitMapSpriteSetID
; if so, choose the appropriate one
	ld b, a ; b = spriteSetID
	ld a, [wFontLoaded]
	bit 0, a ; reloading upper half of tile patterns after displaying text?
	jr nz, .loadSpriteSet ; if so, forcibly reload the sprite set
	ld a, [wSpriteSetID]
	cp b ; has the sprite set ID changed?
	jr z, .skipLoadingSpriteSet ; if not, don't load it again
.loadSpriteSet
	ld a, b
	ld [wSpriteSetID], a
	dec a
	ld c, a
	ld b, 0
	ld a, (wSpriteSetID - wSpriteSet)
	ld hl, SpriteSets
	call AddNTimes ; get sprite set offset
	ld de, wSpriteSet
	ld bc, (wSpriteSetID - wSpriteSet)
	call CopyData ; copy it to wSpriteSet
	call LoadMapSpriteTilePatterns
.skipLoadingSpriteSet
	call Func_14150
	scf
	ret

LoadSpriteSetFromMapHeader:
; This loop stores the correct VRAM tile pattern slots according the sprite
; data from the map's header. Since the VRAM tile pattern slots are filled in
; the order of the sprite set, in order to find the VRAM tile pattern slot
; for a sprite slot, the picture ID for the sprite is looked up within the
; sprite set. The index of the picture ID within the sprite set plus two
; (since the Red sprite always has the first VRAM tile pattern slot and the
; Pikachu sprite reserves the second slot) is the VRAM tile pattern slot.
	ld hl, wSpriteSet
	ld bc, (wSpriteSetID - wSpriteSet)
	xor a
	call FillMemory
	ld a, SPRITE_PIKACHU ; load Pikachu separately
	ld [wSpriteSet], a
	ld hl, wSprite01StateData1
	ld a, 14
.storeVRAMSlotsLoop
	push af
	ld a, [hl] ; [x#SPRITESTATEDATA1_PICTUREID] (zero if sprite slot is not used)
	and a ; is the sprite slot used?
	jr z, .continue ; if the sprite slot is not used
	ld c, a
	call CheckForFourTileSprite ; is this a four tile sprite?
	jr nc, .isFourTileSprite
; loop through the space reserved for four tile picture IDs
	ld de, wSpriteSet + 9
	ld b, 2
	call CheckIfPictureIDAlreadyLoaded
	jr .continue

.isFourTileSprite
; loop through the space reserved for regular picture IDs
	ld de, wSpriteSet
	ld b, 9
	call CheckIfPictureIDAlreadyLoaded
.continue
	ld de, wSprite02StateData1 - wSprite01StateData1
	add hl, de
	pop af
	dec a
	jr nz, .storeVRAMSlotsLoop
	ret

CheckIfPictureIDAlreadyLoaded:
; Check if the current picture ID has already had its tile patterns loaded.
; This done by looping through the previous sprite slots and seeing if any of
; their picture ID's match that of the current sprite slot.
.loop
	ld a, [de]
	and a ; is sprite set slot not taken up yet?
	jr z, .spriteSlotNotTaken ; if so, load it as it signifies we've reached
	                          ; the end of data for the last sprite set

	cp c  ; is the tile pattern already loaded?
	ret z ; don't redundantly load
	dec b ; have we reached the end of the sprite set?
	jr z, .spriteNotAlreadyLoaded ; if so, we're done here
	inc de
	jr .loop

.spriteSlotNotTaken
	ld a, c
	ld [de], a
	ret
.spriteNotAlreadyLoaded
	scf
	ret

CheckForFourTileSprite:
; Checks for a sprite added in yellow
; Returns no carry if the sprite is Pikachu, as its sprite is handled separately
; Else, returns carry if the sprite uses 4 tiles
	cp SPRITE_PIKACHU       ; is this the Pikachu Sprite?
	ret z                   ; return if yes

	cp FIRST_STILL_SPRITE   ; is this a four tile sprite?
	jr nc, .notYellowSprite ; set carry if yes
; regular sprite
	and a
	ret

.notYellowSprite
	scf
	ret

LoadMapSpriteTilePatterns:
	ld a, 0
.loop
	ldh [hVRAMSlot], a
	cp 9
	jr nc, .fourTileSprite
	call LoadStillTilePattern
	call LoadWalkingTilePattern
	jr .continue

.fourTileSprite
	call LoadStillTilePattern
.continue
	ldh a, [hVRAMSlot]
	inc a
	cp 11
	jr nz, .loop
	ret

ReloadWalkingTilePatterns:
	xor a
.loop
	ldh [hVRAMSlot], a
	cp 9
	jr nc, .fourTileSprite
	call LoadWalkingTilePattern
.fourTileSprite
	ldh a, [hVRAMSlot]
	inc a
	cp 11
	jr nz, .loop
	ret

LoadStillTilePattern:
	ld a, [wFontLoaded]
	bit 0, a ; reloading upper half of tile patterns after displaying text?
	ret nz ; if so, skip loading data into the lower half
	call ReadSpriteSheetData
	ret nc
	call GetSpriteVRAMAddress
	call CopyVideoDataAlternate ; new yellow function
	ret

LoadWalkingTilePattern:
	call ReadSpriteSheetData
	ret nc
	ld hl, $c0
	add hl, de
	ld d, h
	ld e, l
	call GetSpriteVRAMAddress
	set 3, h ; add $800 to hl
	call CopyVideoDataAlternate
	ret

GetSpriteVRAMAddress:
	push bc
	ldh a, [hVRAMSlot]
	ld c, a
	ld b, 0
	ld hl, SpriteVRAMAddresses
	add hl, bc
	add hl, bc
	ld a, [hli]
	ld h, [hl]
	ld l, a
	pop bc
	ret

SpriteVRAMAddresses:
; Equivalent to multiplying $C0 (number of bytes in 12 tiles) times the VRAM
; slot and adding the result to $8000 (the VRAM base address).
	dw vChars0 + $0c0
	dw vChars0 + $180
	dw vChars0 + $240
	dw vChars0 + $300
	dw vChars0 + $3c0
	dw vChars0 + $480
	dw vChars0 + $540
	dw vChars0 + $600
	dw vChars0 + $6c0
	dw vChars0 + $780 ; 4-tile sprites
	dw vChars0 + $7c0 ; 4-tile sprites

ReadSpriteSheetData:
	ldh a, [hVRAMSlot]
	ld e, a
	ld d, 0
	ld hl, wSpriteSet
	add hl, de
	ld a, [hl]
	and a
	ret z

	dec a
	ld l, a
	ld h, 0
	add hl, hl
	add hl, hl
	ld de, SpriteSheetPointerTable
	add hl, de
	ld e, [hl]
	inc hl
	ld d, [hl]
	inc hl
	ld c, [hl]
	swap c ; get the number of tiles, not the raw byte length
		   ; this is because of the use of CopyVideoDataAlternate
	inc hl
	ld b, [hl]
	inc hl
	scf
	ret

Func_14150:
	ld a, $1
	ld [wSpritePlayerStateData2ImageBaseOffset], a ; vram slot for player
	ld a, $2
	ld [wSpritePikachuStateData2ImageBaseOffset], a ; vram slot for Pikachu
	ld a, $e
	ld hl, wSprite01StateData1
.loop
	ldh [hVRAMSlot], a ; store current sprite set slot as a counter
	ld a, [hl] ; [x#SPRITESTATEDATA1_PICTUREID]
	and a ; is the sprite unused?
	jr z, .spriteUnused
	call Func_14179
	push hl
	ld de, (wSpritePlayerStateData2ImageBaseOffset) - (wSpriteStateData1) ; $10e
	add hl, de ; [x#SPRITESTATEDATA2_IMAGEBASEOFFSET]
	ld [hl], a ; write offset
	pop hl
.spriteUnused
	ld de, wSprite02StateData1 - wSprite01StateData1
	add hl, de
	ldh a, [hVRAMSlot]
	dec a
	jr nz, .loop
	ret

Func_14179:
	push de
	push bc
	ld c, a  ; c = picture ID
	ld b, 11
	ld de, wSpriteSet
.findSpriteImageBaseOffsetLoop
	ld a, [de] ; a = sprite set picture ID
	cp c ; have we found a match?
	jr z, .foundSpritePictureID ; if so, get the sprite image base offset and return
	inc de
	dec b ; have we looped through all entries in wSpriteSet?
	jr nz, .findSpriteImageBaseOffsetLoop ; continue looping if not
	ld a, $1 ; assume slot one if this ever happens
	jr .done
.foundSpritePictureID
	ld a, 13
	sub b ; get sprite image base offset
.done
	pop bc
	pop de
	ret

GetSplitMapSpriteSetID:
	ld e, a
	ld d, 0
	ld hl, MapSpriteSets
	add hl, de
	ld a, [hl] ; a = spriteSetID
	cp $f0 ; does the map have 2 sprite sets?
	ret c
; Chooses the correct sprite set ID depending on the player's position within
; the map for maps with two sprite sets.
	cp $f8
	jr z, .route20
	ld hl, SplitMapSpriteSets
	and $0f
	dec a
	add a
	add a
	add l
	ld l, a
	jr nc, .noCarry
	inc h
.noCarry
	ld a, [hli] ; determines whether the map is split East/West or North/South
	cp $01
	ld a, [hli] ; position of dividing line
	ld b, a
	jr z, .eastWestDivide
.northSouthDivide
	ld a, [wYCoord]
	jr .compareCoord
.eastWestDivide
	ld a, [wXCoord]
.compareCoord
	cp b
	jr c, .loadSpriteSetID
; if in the East side or South side
	inc hl
.loadSpriteSetID
	ld a, [hl]
	ret
; Uses sprite set $01 for West side and $0A for East side.
; Route 20 is a special case because the two map sections have a more complex
; shape instead of the map simply being split horizontally or vertically.
.route20
	ld hl, wXCoord
	ld a, [hl]
	cp $2b
	ld a, $01
	ret c
	ld a, [hl]
	cp $3e
	ld a, $0a
	ret nc
	ld a, [hl]
	cp $37
	ld b, $08
	jr nc, .next
	ld b, $0d
.next
	ld a, [wYCoord]
	cp b
	ld a, $0a
	ret c
	ld a, $01
	ret

INCLUDE "data/maps/sprite_sets.asm"

INCLUDE "data/sprites/sprites.asm"