Break up engine/events_3.asm

engine/events/checkforhiddenitems.asm

@@ -0,0 +1,85 @@
+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