Fix flickering with item menu

color/refreshmaps.asm

@@ -133,17 +133,33 @@ ENDR
 	ld bc, -$c0
 	add hl,bc
 
-; BEGIN loading palettes
+; BEGIN loading palette maps
 
 	ld a,1
 	ld [rVBK],a
 	inc a
 	ld [rSVBK],a
 
+	; Skip palette update if the pre-vblank routine updated a different portion of
+	; the window... I guess this can happen due to lag? If this is omitted, there's
+	; corruption when scrolling throw the item menu.
+	ld a,[W2_PreVBlankWindowPortion]
+	inc a
+	cp $03
+	jr nz,.checkPortion
+	xor a
+.checkPortion
+	ld b,a
+	ld a,[H_AUTOBGTRANSFERPORTION]
+	cp b
+	jr nz,.palettesDone
+
+	; Always update if using tile-based palettes
 	ld a,[W2_TileBasedPalettes]
 	and a
 	jr nz,.continue
 
+	; If using static palettes, we can check whether that's been updated
 	ld a,[W2_StaticPaletteMapChanged_vbl]
 	and a
 	jr z, .palettesDone

color/vblank.asm

@@ -142,7 +142,14 @@ RefreshWindowPalettesPreVBlank:
 	and a
 	ret z
 
+	ld a,[rSVBK]
+	ld b,a
+	ld a,$02
+	ld [rSVBK],a
+	push bc ; Push last wram bank
+
 	ld a,[H_AUTOBGTRANSFERPORTION]
+	ld [W2_PreVBlankWindowPortion],a
 	and a
 	jr z,.firstThird
 	dec a
@@ -161,12 +168,6 @@ RefreshWindowPalettesPreVBlank:
 
 ; BEGIN loading palettes
 
-	ld a,[rSVBK]
-	ld b,a
-	ld a,$02
-	ld [rSVBK],a
-	push bc ; Push last wram bank
-
 	ld hl, W2_ScreenPalettesBuffer
 
 	ld b,6
@@ -175,8 +176,8 @@ RefreshWindowPalettesPreVBlank:
 	and a
 	jr nz,.tileBasedPalettes
 
-; TODO: delete this?
 .staticMapPalettes:	; Palettes are loaded from a 20x18 grid of palettes
+	; If the window transfer destination changed, we'll need to rewrite everything
 	ld a,[W2_LastAutoCopyDest]
 	ld b,a
 	ld a,[H_AUTOBGTRANSFERDEST+1]

color/wram.asm

@@ -14,7 +14,7 @@ W2_TilesetPaletteMap	EQU $d200
 W2_SpritePaletteMap		EQU $d400
 
 ; Palette calculations for wTileMap are stored here before vblank.
-W2_ScreenPalettesBuffer	EQU $d500 ; 32x6 bytes (DMA-able), $d500-$d5c0
+W2_ScreenPalettesBuffer        EQU $d500 ; 32x6 bytes (DMA-able), $d500-$d5c0
 
 W2_TownMapLoaded               EQU $d700
 W2_TileBasedPalettes           EQU $d701
@@ -30,10 +30,14 @@ W2_SprPaletteDataModified      EQU $d785
 ; actual-vblank routines.
 W2_StaticPaletteMapChanged_vbl EQU $d786
 
+; Former value of [H_AUTOBGTRANSFERDEST+1]. Should be $98 or $9c.
 W2_LastAutoCopyDest            EQU $d787
 
 W2_ForceBGPUpdate              EQU $d788
-W2_ForceOBPUpdate             EQU $d789
+W2_ForceOBPUpdate              EQU $d789
+
+; The value of H_AUTOBGTRANSFERPORTION that the pre-vblank routine operated with
+W2_PreVBlankWindowPortion      EQU $d78a
 
 ; In bank 1, the stack starts at $dfff. So, that's also the stack here when bank 2 is
 ; loaded. Don't use anything too close to there.