Itemfinder routines and labels.

1 files changed, 83 insertions, 0 deletions

diff --git a/engine/events/checkforhiddenitems.asm b/engine/events/checkforhiddenitems.asm
new file mode 100644
index 00000000..c71bd290
--- /dev/null
+++ b/engine/events/checkforhiddenitems.asm
@@ -0,0 +1,83 @@
+CheckForHiddenItems:
+; 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
+	ld [wBuffer1], a
+; Get the coordinate of the bottom right corner of the screen, and load it in wBuffer3/wBuffer4.
+	ld a, [wXCoord]
+	add SCREEN_WIDTH / 4
+	ld [wBuffer4], a
+	ld a, [wYCoord]
+	add SCREEN_HEIGHT / 4
+	ld [wBuffer3], a
+; Get the pointer for the first bg_event in the map...
+	ld hl, wCurMapBGEventsPointer
+	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, [wCurMapBGEventCount]
+	and a
+	jr z, .nobgeventitems
+; For i = 1:wCurMapBGEventCount...
+.loop
+; Store the counter in wBuffer2, and store the bg_event pointer in the stack.
+	ld [wBuffer2], 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, [wBuffer3]
+	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, [wBuffer4]
+	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, [wBuffer1]
+	call GetFarHalfword
+	ld a, [wBuffer1]
+	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 pointer and increment it by the length of a bg_event.
+	pop hl
+	ld bc, BG_EVENT_SIZE
+	add hl, bc
+; Restore the BG event counter and decrement it.  If it hits zero, there are no hidden items in range.
+	ld a, [wBuffer2]
+	dec a
+	jr nz, .loop
+
+.nobgeventitems
+	xor a
+	ret
+
+.itemnearby
+	pop hl
+	scf
+	ret
+
+.GetFarByte:
+	ld a, [wBuffer1]
+	call GetFarByte
+	inc hl
+	ret