pokecrystal-board/engine/events/checkforhiddenitems.asm
2018-01-11 23:50:44 -05:00

86 lines
2.0 KiB
NASM

CheckForHiddenItems: ; b8172
; Checks to see if there are hidden items on the screen that have not yet been found. If it finds one, returns carry.
call GetMapScriptHeaderBank
ld [Buffer1], a
; Get the coordinate of the bottom right corner of the screen, and load it in Buffer3/Buffer4.
ld a, [XCoord]
add SCREEN_WIDTH / 4
ld [Buffer4], a
ld a, [YCoord]
add SCREEN_HEIGHT / 4
ld [Buffer3], a
; Get the pointer for the first BG event header in the map...
ld hl, wCurrMapBGEventHeaderPointer
ld a, [hli]
ld h, [hl]
ld l, a
; ... before even checking to see if there are any BG events on this map.
ld a, [wCurrMapBGEventCount]
and a
jr z, .nobgeventitems
; For i = 1:wCurrMapBGEventCount...
.loop
; Store the counter in Buffer2, and store the BG event header pointer in the stack.
ld [Buffer2], a
push hl
; Get the Y coordinate of the BG event.
call .GetFarByte
ld e, a
; Is the Y coordinate of the BG event on the screen? If not, go to the next BG event.
ld a, [Buffer3]
sub e
jr c, .next
cp SCREEN_HEIGHT / 2
jr nc, .next
; Is the X coordinate of the BG event on the screen? If not, go to the next BG event.
call .GetFarByte
ld d, a
ld a, [Buffer4]
sub d
jr c, .next
cp SCREEN_WIDTH / 2
jr nc, .next
; Is this BG event a hidden item? If not, go to the next BG event.
call .GetFarByte
cp BGEVENT_ITEM
jr nz, .next
; Has this item already been found? If not, set off the Itemfinder.
ld a, [Buffer1]
call GetFarHalfword
ld a, [Buffer1]
call GetFarHalfword
ld d, h
ld e, l
ld b, CHECK_FLAG
call EventFlagAction
ld a, c
and a
jr z, .itemnearby
.next
; Restore the BG event header pointer and increment it by the length of a BG event header.
pop hl
ld bc, 5
add hl, bc
; Restore the BG event counter and decrement it. If it hits zero, there are no hidden items in range.
ld a, [Buffer2]
dec a
jr nz, .loop
.nobgeventitems
xor a
ret
.itemnearby
pop hl
scf
ret
; b81e2
.GetFarByte: ; b81e2
ld a, [Buffer1]
call GetFarByte
inc hl
ret
; b81ea