From 85f9c258b578cd74af63e520bbec34e23fdb5bae Mon Sep 17 00:00:00 2001
From: xCrystal <rgr.crystal@gmail.com>
Date: Tue, 31 Oct 2023 16:02:37 +0100
Subject: [PATCH] Fix that CheckObjectCoveredByTextbox doesn't account for the
 background scroll (SCX/SCY) (#8)

---
 engine/overworld/map_objects.asm |  6 +-----
 home/menu.asm                    | 28 ++++++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/engine/overworld/map_objects.asm b/engine/overworld/map_objects.asm
index 6b6d18d0a..4f55f3320 100644
--- a/engine/overworld/map_objects.asm
+++ b/engine/overworld/map_objects.asm
@@ -2406,18 +2406,14 @@ CheckObjectCoveredByTextbox:
 	ldh a, [hCurSpriteYCoord]
 	add e
 	dec a
-	cp SCREEN_HEIGHT
-	jr nc, .ok9
 	ld b, a
 .next
 	ldh a, [hCurSpriteXCoord]
 	add d
 	dec a
-	cp SCREEN_WIDTH
-	jr nc, .ok8
 	ld c, a
 	push bc
-	call Coord2Tile
+	call ScrollAwareCoord2Tile
 	pop bc
 ; NPCs disappear if standing on tiles FIRST_REGULAR_TEXT_CHAR or above,
 ; since those IDs are for text characters and textbox frames.
diff --git a/home/menu.asm b/home/menu.asm
index 03f21caf0..36f28137e 100644
--- a/home/menu.asm
+++ b/home/menu.asm
@@ -257,6 +257,34 @@ ClearWholeMenuBox::
 	call ClearBox
 	ret
 
+ScrollAwareCoord2Tile::
+; Return the address of wTilemap(c, b) in hl relative to the background scroll in hSCX and hSCY.
+; c = c - [hSCX] / 8
+	ld a, [hSCX]
+	srl a
+	srl a
+	srl a
+	ld l, a
+	ld a, c
+	sub l
+	jr nc, .ok1
+	add BG_MAP_WIDTH
+.ok1
+	ld c, a
+; b = b - [hSCY] / 8
+	ld a, [hSCY]
+	srl a
+	srl a
+	srl a
+	ld l, a
+	ld a, b
+	sub l
+	jr nc, .ok2
+	add BG_MAP_HEIGHT
+.ok2
+	ld b, a
+	jr Coord2Tile
+
 MenuBoxCoord2Tile::
 	ld a, [wMenuBorderLeftCoord]
 	ld c, a