From f1ba4dadeb1348ba59fbba20ff1314b863470231 Mon Sep 17 00:00:00 2001
From: Forest Belton <65484+forestbelton@users.noreply.github.com>
Date: Tue, 6 Jul 2021 21:33:42 -0400
Subject: [PATCH] Skip player update if the background is scrolling

---
 inc/util.inc | 9 +++++++++
 src/bg.s     | 9 +++++++++
 src/main.s   | 1 +
 src/player.s | 9 +++++++--
 4 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/inc/util.inc b/inc/util.inc
index 8c4a726..e40be8f 100644
--- a/inc/util.inc
+++ b/inc/util.inc
@@ -5,3 +5,12 @@ MACRO STORE16
     inc hl
     ld [hl], LOW(\1)
 ENDM
+
+; Stores an 8-bit value into memory
+; \1 Write address
+; \2 8-bit value
+MACRO SET8
+    ld h, HIGH(\1)
+    ld l, LOW(\1)
+    ld [hl], \2
+ENDM
diff --git a/src/bg.s b/src/bg.s
index 4bb1e29..3069a78 100644
--- a/src/bg.s
+++ b/src/bg.s
@@ -1,4 +1,6 @@
 INCLUDE "hardware.inc"
+INCLUDE "util.inc"
+
 INCLUDE "png/map/intro.inc"
 
 SECTION "BG Data", WRAM0
@@ -7,6 +9,8 @@ BG_COLLISION_DATA:: dw
 BG_MAP_WIDTH:: db
 BG_MAP_HEIGHT:: db
 
+BG_SCROLLING:: db
+
 SECTION "BG Code", ROM0
 
 MACRO update_map_info
@@ -24,6 +28,8 @@ MACRO update_map_info
 ENDM
 
 BG_Init::
+    SET8 BG_SCROLLING, 0
+
     ; copy map
     ld e, intro_HEIGHT
     ld bc, _SCRN0
@@ -58,3 +64,6 @@ BG_Init::
     update_map_info intro_COLLISION, intro_WIDTH, intro_HEIGHT
 
     ret
+
+BG_Update::
+    ret
diff --git a/src/main.s b/src/main.s
index 7cf5085..4e35120 100644
--- a/src/main.s
+++ b/src/main.s
@@ -53,6 +53,7 @@ start:
 
     call Keys_Update
     call Player_Update
+    call BG_Update
 
     ; wait for vblank
     halt
diff --git a/src/player.s b/src/player.s
index 96618f3..c66b742 100644
--- a/src/player.s
+++ b/src/player.s
@@ -60,10 +60,15 @@ Player_Init::
     ret
 
 Player_Update::
-    ld hl, keys
-    ld b, [hl]
+    ; suspend player state while map is scrolling
+    ld hl, BG_SCROLLING
+    ld a, [hl]
+    or a
+    ret nz
 
     ; check for jump
+    ld hl, keys
+    ld b, [hl]
     ld a, b
     and BTN_UP
     jr z, .jump_update_check