From 5a5b143bbc41cbfd77abc7f6ed7d4c93fc345f81 Mon Sep 17 00:00:00 2001
From: Dave VanEe <dave.vanee@gmail.com>
Date: Tue, 1 Mar 2022 07:10:18 -0800
Subject: [PATCH] Ensure OAM is fully initialized at startup

---
 src/header.asm | 51 +++++++++++++++++++++++++++-----------------------
 1 file changed, 28 insertions(+), 23 deletions(-)

diff --git a/src/header.asm b/src/header.asm
index 88c8436..944989d 100644
--- a/src/header.asm
+++ b/src/header.asm
@@ -86,15 +86,41 @@ Reset::
     ld      a, WY_START
     ldh     [rWY], a
 
-    ; Initialize variables
-    xor     a
+    ; Position sprite to overlap (R)
+    ld      de, SpriteAnimationPath
+    ld      hl, wShadowOAM
+    ld      a, SPRITE_Y_COORD
+    ld      [hli], a
+    ld      a, [de]
+    ld      [hli], a
+    ld      a, SPRITE_TILE_ID
+    ld      [hli], a
+    ld      a, e
+    ldh     [hSpriteLowByte], a
+
+    ; Clear remaining wShadowOAM
+    ld      a, c    ; zero from MemcpySmall
+    ld      c, OAM_COUNT * sizeof_OAM_ATTRS - 3
+    rst     MemsetSmall
+
+    ; Take advantate of trailing A==0 to initialize a few vars
     ldh     [hSCYCache], a
     ldh     [hFrameCounterLogo], a
+
+    ; Set object palette for effect
+    dec     a   ; $FF
+    ldh     [rOBP0], a
+
+    ; Initialize aditional variables
     ld      a, SPLIT_LINE+1
     ldh     [hResumeLY], a
     ld      a, LOW(SplitAnimationPath)
     ldh     [hSplitLowByte], a
 
+    ; Ensure OAM is initialized before sprites are enabled
+    ld      a, HIGH(wShadowOAM)
+    call    hOAMDMA
+
     ; Enable window/objects safely
 :   ldh     a, [rSTAT]
     and     STATF_BUSY
@@ -110,27 +136,6 @@ Reset::
     ld      c, 6
     call    LCDMemsetSmallFromB
 
-    ; Position sprite to overlap (R)
-    ld      de, SpriteAnimationPath
-    ld      hl, wShadowOAM
-    ld      a, SPRITE_Y_COORD
-    ld      [hli], a
-    ld      a, [de]
-    ld      [hli], a
-    ld      a, SPRITE_TILE_ID
-    ld      [hli], a
-    ld      a, e
-    ldh     [hSpriteLowByte], a
-
-    ; Clear remaining wShadowOAM
-    ld      a, c    ; zero from MemcpySmall
-    ld      c, OAM_COUNT * sizeof_OAM_ATTRS - 3
-    rst     MemsetSmall
-
-    ; Set object palette for effect
-    dec     a   ; $FF
-    ldh     [rOBP0], a
-
     ; Animate!
     ld      b, SPLIT_LINE
     ld      h, d