Implement the engine to backup map objects when chaning maps (#32)

engine/board/menu.asm

@@ -89,6 +89,7 @@ BoardMenuScript::
 	end
 
 .EnterViewMapMode:
+	call BackupMapObjectsOnEnterViewMapMode
 	ld hl, wVramState
 	res 2, [hl]
 	ld a, BOARDEVENT_VIEW_MAP_MODE

engine/board/spaces.asm

@@ -269,6 +269,7 @@ PromptPlayerToChooseBranchDirection:
 	jp PlayClickSFX
 
 .EnterViewMapMode:
+	call BackupMapObjectsOnEnterViewMapMode
 	ld a, BOARDEVENT_VIEW_MAP_MODE
 	ldh [hCurBoardEvent], a
 	ld a, 100

engine/menus/save.asm

@@ -289,6 +289,7 @@ SaveGameData:
 	call SaveOptions
 	call SavePlayerData
 	call SavePokemonData
+	call SaveMapObjectsBackupsData
 	call SaveBox
 	call SaveChecksum
 	call ValidateBackupSave
@@ -446,6 +447,22 @@ SavePokemonData:
 	call CloseSRAM
 	ret
 
+SaveMapObjectsBackupsData:
+	ldh a, [rSVBK]
+	push af
+	ld a, BANK(wMapObjectsBackups)
+	ldh [rSVBK], a
+	ld a, BANK(sMapObjectsBackups)
+	call OpenSRAM
+	ld hl, wMapObjectsBackups
+	ld de, sMapObjectsBackups
+	ld bc, wMapObjectsBackupsEnd - wMapObjectsBackups
+	call CopyBytes
+	call CloseSRAM
+	pop af
+	ldh [rSVBK], a
+	ret
+
 SaveBox:
 	call GetBoxAddress
 	call SaveBoxAddress
@@ -526,6 +543,7 @@ TryLoadSaveFile:
 	jr nz, .backup
 	call LoadPlayerData
 	call LoadPokemonData
+	call LoadMapObjectsBackupsData
 	call LoadBox
 	farcall RestorePartyMonMail
 	call ValidateBackupSave
@@ -541,6 +559,7 @@ TryLoadSaveFile:
 	jr nz, .corrupt
 	call LoadBackupPlayerData
 	call LoadBackupPokemonData
+	call LoadMapObjectsBackupsData
 	call LoadBox
 	farcall RestorePartyMonMail
 	call ValidateSave
@@ -677,6 +696,22 @@ LoadPokemonData:
 	call CloseSRAM
 	ret
 
+LoadMapObjectsBackupsData:
+	ldh a, [rSVBK]
+	push af
+	ld a, BANK(wMapObjectsBackups)
+	ldh [rSVBK], a
+	ld a, BANK(sMapObjectsBackups)
+	call OpenSRAM
+	ld hl, sMapObjectsBackups
+	ld de, wMapObjectsBackups
+	ld bc, wMapObjectsBackupsEnd - wMapObjectsBackups
+	call CopyBytes
+	call CloseSRAM
+	pop af
+	ldh [rSVBK], a
+	ret
+
 LoadBox:
 	call GetBoxAddress
 	call LoadBoxAddress

engine/overworld/events.asm

@@ -135,7 +135,7 @@ CheckTrainerAndTalkerEvents:
 	bit 5, [hl]
 	ret
 
-; on enter overworld loop
+; on enter overworld loop (MAPSETUP_ENTERLEVEL or MAPSETUP_CONTINUE)
 StartMap:
 	xor a
 	ldh [hScriptVar], a
@@ -147,13 +147,39 @@ StartMap:
 	farcall InitCallReceiveDelay
 	call ClearJoypad
 
-; initialize board state
 	ld a, [hMapEntryMethod]
 	cp MAPSETUP_ENTERLEVEL
 	jr nz, .not_starting_level
+
+; initialize board state
 	xor a
 	ld [wCurTurn], a
 	ld [wCurSpace], a
+
+; initialize overworld state
+	ld hl, wNextWarp
+	xor a
+	ld [hli], a ; wNextWarp
+	ld [hli], a ; wNextMapGroup
+	ld [hli], a ; wNextMapNumber
+	ld [hli], a ; wPrevWarp
+	ld [hli], a ; wPrevMapGroup
+	ld [hl], a  ; wPrevMapNumber
+	ld a, BANK(wMapObjectsBackups)
+	ld [rSVBK], a
+	ld e, NUM_MAP_OBJECTS_BACKUPS
+	ld hl, wMapObjectsBackups
+	ld bc, wMap2ObjectsBackup - wMap1ObjectsBackup
+.loop
+	ld a, GROUP_N_A
+	ld [hl], a
+	add hl, bc
+	dec e
+	jr nz, .loop
+	ld [hl], $00 ; list terminator
+	ld a, 1
+	ld [rSVBK], a
+
 .not_starting_level
 	ld a, BOARDEVENT_DISPLAY_MENU
 	ldh [hCurBoardEvent], a

engine/overworld/warp_connection.asm

@@ -144,6 +144,7 @@ EnterMapConnection:
 	ld [wOverworldMapAnchor], a
 	ld a, h
 	ld [wOverworldMapAnchor + 1], a
+
 .done
 	scf
 	ret