Implement Surf technique, avoid facing-tile events when player has yet to STEP_TURN or while not in BOARDEVENT_HANDLE_BOARD [bugfix to previous two commits] (#34)

new tile permission SPACE_TILE added, which acts as WATER_TILE while on PLAYER_SURF or PLAYER_SURF_PIKA state, as LAND_TILE otherwise

engine/events/overworld.asm

@@ -408,6 +408,16 @@ SurfFunction:
 	ld a, $80
 	ret
 
+SurfAutoScript::
+	readmem wSurfingPlayerState
+	writevar VAR_MOVEMENT
+	special UpdatePlayerSprite
+	special PlayMapMusic
+; step into the water (slow_step DIR, step_end)
+	special SurfStartStep
+	applymovement PLAYER, wMovementBuffer
+	end
+
 SurfFromMenuScript:
 	special UpdateTimePals
 
@@ -456,7 +466,7 @@ GetSurfType:
 	ld a, PLAYER_SURF
 	ret
 
-CheckDirection:
+CheckDirection::
 ; Return carry if a tile permission prevents you
 ; from moving in the direction you're facing.
 

engine/overworld/events.asm

@@ -641,9 +641,23 @@ SetMinTwoStepWildEncounterCooldown: ; unreferenced
 	ret
 
 CheckFacingTileEvent:
+; no tile events if not in BOARDEVENT_HANDLE_BOARD (e.g. after player lands in space)
 	ldh a, [hCurBoardEvent]
-	cp BOARDEVENT_VIEW_MAP_MODE
+	cp BOARDEVENT_HANDLE_BOARD
+	jr nz, .NoAction
+
+; no facing-tile events until player has turned to the walking direction.
+; if the player has to perform a STEP_TURN first, the facing tile is not the right one.
+	ld a, [wWalkingDirection]
+	cp STANDING
 	jr z, .NoAction
+	ld e, a
+	ld a, [wPlayerDirection]
+	rrca
+	rrca
+	maskbits NUM_DIRECTIONS
+	cp e
+	jr nz, .NoAction
 
 	call .TryObjectEvent
 	jr c, .Action
@@ -729,6 +743,33 @@ CheckFacingTileEvent:
 	ret ; c
 
 .TryTileCollisionEvent:
+	call GetFacingTileCoord
+	ld [wFacingTileID], a
+
+;; Surf
+; Don't surf if already surfing.
+	ld a, [wPlayerState]
+	cp PLAYER_SURF_PIKA
+	jr z, .next_event_1
+	cp PLAYER_SURF
+	jr z, .next_event_1
+
+; Must be facing water.
+	ld a, [wFacingTileID]
+	call GetTileCollision
+	cp WATER_TILE
+	jr nz, .next_event_1
+
+	ld a, PLAYER_SURF
+	ld [wSurfingPlayerState], a
+
+	ld a, BANK(SurfAutoScript)
+	ld hl, SurfAutoScript
+	call CallScript
+	ret ; c
+
+.next_event_1
+.no_event
 	xor a
 	ret ; nc
 

engine/overworld/player_movement.asm

@@ -929,6 +929,8 @@ ENDM
 	call GetTileCollision
 	and a ; LAND_TILE
 	ret z
+	cp SPACE_TILE
+	ret z
 	scf
 	ret
 
@@ -939,6 +941,10 @@ ENDM
 	call GetTileCollision
 	cp WATER_TILE
 	jr z, .Water
+	; because this is called during PLAYER_SURF or PLAYER_SURF_PIKA state,
+	; SPACE_TILE is considered still water. Do not stop surfing on a space tile.
+	cp SPACE_TILE
+	jr z, .Water
 
 ; Can walk back onto land from water.
 	and a ; LAND_TILE