Overworld HUD implementation (#15)

engine/overworld/events.asm

@@ -126,7 +126,9 @@ EnterMap:
 	ld [wPoisonStepCount], a
 .dontresetpoison
 
-	call EnableOverworldWindowHUD
+	call ConstructOverworldHUDTilemap
+	call TransferOverworldHUDToBGMap
+	call EnableOverworldHUD
 
 	xor a ; end map entry
 	ldh [hMapEntryMethod], a

engine/overworld/init_map.asm

@@ -25,17 +25,20 @@ ReanchorBGMap_NoOAMUpdate::
 	xor a
 	ldh [hLCDCPointer], a
 	ldh [hBGMapMode], a
+	; prepare vBGMap1/vBGMap3 to be displayed while vBGMap0/vBGMap2 is reanchored.
+	; draw screen at wTilemap and wAttrmap and then transfer it.
 	ld a, $90
 	ldh [hWY], a
 	call LoadScreenTilemapAndAttrmapPals
+	call LoadWindowHUD
 	ld a, HIGH(vBGMap1)
 	call .LoadBGMapAddrIntoHRAM
 	call HDMATransferTilemapAndAttrmap_OpenAndCloseMenu
 	farcall ApplyPals
 	ld a, TRUE
 	ldh [hCGBPalUpdate], a
-	; display window while BG map is reanchored.
-	; disable LCD interrupt to prevent cropping the window due to hWindowHUD
+	; display window using vBGMap1/vBGMap3 while vBGMap0/vBGMap2 is reanchored.
+	; disable LCD interrupt to prevent cropping the window if window HUD is active
 	; (caller must re-enable when window is hidden again).
 	xor a
 	ldh [rSTAT], a

engine/overworld/load_screen_tilemap.asm

@@ -33,4 +33,5 @@ _LoadScreenTilemap::
 .carry
 	dec b
 	jr nz, .loop
+
 	ret

engine/overworld/scripting.asm

@@ -1165,7 +1165,7 @@ Script_loadtrainer:
 	ret
 
 Script_startbattle:
-	call DisableWindowHUD
+	call DisableOverworldHUD
 	call BufferScreen
 	predef StartBattle
 	ld a, [wBattleResult]

engine/overworld/warp_connection.asm

@@ -1,5 +1,4 @@
 HandleNewMap:
-	call ClearUnusedMapBuffer
 	call ResetMapBufferEventFlags
 	call ResetFlashIfOutOfCave
 	call GetCurrentMapSceneID