pokecrystal/engine/events/checkforhiddenitems.asm

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CheckForHiddenItems:
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; Checks to see if there are hidden items on the screen that have not yet been found. If it finds one, returns carry.
call GetMapScriptsBank
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ld [wCurMapScriptBank], a
; Get the coordinate of the bottom right corner of the screen, and load it in wBottomRightYCoord/wBottomRightXCoord.
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ld a, [wXCoord]
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add SCREEN_WIDTH / 4
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ld [wBottomRightXCoord], a
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ld a, [wYCoord]
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add SCREEN_HEIGHT / 4
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ld [wBottomRightYCoord], a
; Get the pointer for the first bg_event in the map...
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ld hl, wCurMapBGEventsPointer
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ld a, [hli]
ld h, [hl]
ld l, a
; ... before even checking to see if there are any BG events on this map.
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ld a, [wCurMapBGEventCount]
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and a
jr z, .nobgeventitems
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; For i = 1:wCurMapBGEventCount...
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.loop
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; Store the counter in wRemainingBGEventCount, and store the bg_event pointer in the stack.
ld [wRemainingBGEventCount], a
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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.
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ld a, [wBottomRightYCoord]
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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
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ld a, [wBottomRightXCoord]
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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.
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ld a, [wCurMapScriptBank]
call GetFarWord
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ld a, [wCurMapScriptBank]
call GetFarWord
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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 pointer and increment it by the length of a bg_event.
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pop hl
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ld bc, BG_EVENT_SIZE
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add hl, bc
; Restore the BG event counter and decrement it. If it hits zero, there are no hidden items in range.
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ld a, [wRemainingBGEventCount]
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dec a
jr nz, .loop
.nobgeventitems
xor a
ret
.itemnearby
pop hl
scf
ret
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.GetFarByte:
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ld a, [wCurMapScriptBank]
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call GetFarByte
inc hl
ret