From 897a0ff92b25d73114fcf338071bff2fd10d15d6 Mon Sep 17 00:00:00 2001
From: Lukas Krickl <lukas@krickl.dev>
Date: Tue, 12 Aug 2025 20:36:57 +0200
Subject: [PATCH] objanim: Added framework for makign door animations more
 generic

---
 src/objanim.s | 61 +++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 44 insertions(+), 17 deletions(-)

diff --git a/src/objanim.s b/src/objanim.s
index 516c756..bce08f6 100644
--- a/src/objanim.s
+++ b/src/objanim.s
@@ -59,16 +59,56 @@ objanim_door_open:
 	ld [gameplay_flags], a
 
 	ret
+	
+	; down animation
+objanim_door_open_down_fn:
+	ld a, [objanim+obja_timer] ; read timer before calling handler
+	push af
+	call objanim_door_open_generic_fn
+
+	pop af
+	push bc ; save next state
+	; hl = oam ptr
+	inc hl ; skip obj1 y
+
+	; adjust x position based on timer
+	; offset position by counter 
+	sra a
+	ld b, a
+	ld a, [hl]
+	sub a, b
+	; wirte adjusted obj1 x 
+	ld [hl+], a ; hl = obj1 tile
+
+	inc hl ; skip obj1 tile
+	inc hl ; skip obj1 flags
+	inc hl ; skip obj2 y 
+	
+	; hl = obj2 x 
+	ld a, [hl]
+	add a, b
+	; write adjusted obj2 x
+	ld [hl+], a
+	
+	pop bc ; restore next state
+	ret
 
 	; state function for door opening animation
-	; down
+	; is called by more specific functions that take this base setup
+	; and set the right tiles and animations after
 	; inputs:
 	;		de: objanim
-objanim_door_open_down_fn:
+	;	returns:
+	;		hl: first object used
+	;				the objects are guaranteed to be consecutive
+	;				and 2 objects will have been reserved
+	;		bc: next state
+objanim_door_open_generic_fn:
 #define TMP_Y, scratch
 #define TMP_X, scratch+1
 
 	call load_unit_obj
+	push hl
 	ld de, objanim+st_size
 	call load_scroll
 
@@ -86,13 +126,6 @@ objanim_door_open_down_fn:
 	ld a, [de] ; a = x position
 	tile_to_scrn OBJ_OFF_X, c 
 	ld [TMP_X], a
-	; offset position by counter 
-	push af
-	ld a, [objanim+obja_timer]
-	sra a
-	ld b, a
-	pop af
-	sub a, b
 	ld [hl+], a
 
 	
@@ -114,13 +147,6 @@ objanim_door_open_down_fn:
 	; set x pos
 	ld a, [TMP_X]
 	add a, 8 ; move over a tile
-	; offset position by counter
-	push af
-	ld a, [objanim+obja_timer]
-	sra a
-	ld b, a
-	pop af
-	add a, b
 	ld [hl+], a
 	
 	; tile 
@@ -130,7 +156,8 @@ objanim_door_open_down_fn:
 	; flags
 	xor a, a
 	ld [hl], a
-
+	
+	pop hl ; restore object ptr used == return value
 	; check if we are done
 	ld a, [objanim+obja_timer]
 	inc a
-- 
2.30.2