From 58a2afc01f8ef64b8f92c5c26e05d3e54adf64f6 Mon Sep 17 00:00:00 2001
From: Lukas Krickl <lukas@krickl.dev>
Date: Wed, 4 Dec 2024 08:11:11 +0100
Subject: [PATCH] WIP: reworking room flag access

---
 src/collision.s | 42 +-----------------------------------------
 src/macros.inc  | 10 ++++++++++
 src/map.s       | 45 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 56 insertions(+), 41 deletions(-)

diff --git a/src/collision.s b/src/collision.s
index 5d84f71..4ecd53c 100644
--- a/src/collision.s
+++ b/src/collision.s
@@ -35,8 +35,6 @@ collision_player:
   col_head 1
   col_point 0, 0
 
-collision_tile_lut:
-  .rep cti, ROOM_H, 1, .db cti * ROOM_W 
 
   ; checks an entire collision table based on an original point
   ; and a ptr to a collision point table
@@ -108,45 +106,7 @@ collision_tile_table_check:
   ;   a = 0 -> no collision
   ;   a = 1 -> collision
 collision_tile:
-  ; y pos / 16 -> tile pos
-  srl d ; / 2
-  srl d ; / 4
-  srl d ; / 8
-  srl d ; / 16
-
-  ; x pos / 16 -> tile pos 
-  srl e ; / 2
-  srl e ; / 4
-  srl e ; / 8
-  srl e ; / 16
-  ld a, e ; a = x pos
-
-  ld e, d
-  ld d, 0 ; de = y position now
-
-  ; -> now convert position to 
-  ; map flag index using a simple lut
-  ; for y position + x
-  ld hl, collision_tile_lut
-  add hl, de ; hl + y offset 
-  ; hl = row ptr
-  ld e, a ; e = x pos
-  ld a, [hl] ; a = map flags row offset 
-  add a, e ; row + x = position of tile in map 
-
-  push af
-
-  ld hl, curr_room_flags ; hl = flags for currently loaded room 
-  ld a, [hl+] ; load curr room flags ptr
-  ld e, a 
-  ld a, [hl]
-  ld d, a ; de = flags pointer 
-
-  pop af
-  ld h, 0
-  ld l, a ; hl = tile offset 
-  add hl, de ; hl + de 
-
+  call room_get_flag_ptr
   ; hl = current tile flags 
 
   ld a, [hl] ; load flags
diff --git a/src/macros.inc b/src/macros.inc
index a0fd3c8..91a04e9 100644
--- a/src/macros.inc
+++ b/src/macros.inc
@@ -73,4 +73,14 @@
   ld e, a 
   add hl, de ; hl = correct tile index 
   ld a, [hl]
+#endmacro
+
+  ; divides a regiser by 16
+  ; inputs:
+  ;   $1: the register 
+#macro div16 
+  srl $1 ; / 2
+  srl $1 ; / 4
+  srl $1 ; / 8
+  srl $1 ; / 16
 #endmacro 
diff --git a/src/map.s b/src/map.s
index 41acf89..d6e4409 100644
--- a/src/map.s
+++ b/src/map.s
@@ -195,6 +195,51 @@ room_draw:
 
   ret
 
+room_tile_lut:
+  .rep cti, ROOM_H, 1, .db cti * ROOM_W 
+
+  ; loads the flag pointer for a position into hl
+  ; inputs:
+  ;   de: y/x
+  ; returns:
+  ;   hl: pointer to flag at position y/x 
+  ; uses:
+  ;   de, hl, a
+room_get_flag_ptr:
+  ; y pos / 16 -> tile pos
+  div16 d
+
+  ; x pos / 16 -> tile pos 
+  div16 e
+  ld a, e ; a = x pos
+
+  ld e, d
+  ld d, 0 ; de = y position now
+
+  ; -> now convert position to 
+  ; map flag index using a simple lut
+  ; for y position + x
+  ld hl, room_tile_lut
+  add hl, de ; hl + y offset 
+  ; hl = row ptr
+  ld e, a ; e = x pos
+  ld a, [hl] ; a = map flags row offset 
+  add a, e ; row + x = position of tile in map 
+
+  push af
+
+  ld hl, curr_room_flags ; hl = flags for currently loaded room 
+  ld a, [hl+] ; load curr room flags ptr
+  ld e, a 
+  ld a, [hl]
+  ld d, a ; de = flags pointer 
+
+  pop af
+  ld h, 0
+  ld l, a ; hl = tile offset 
+  add hl, de ; hl + de 
+  ret
+
   ; sets a tile position flag
   ; as a flag  
   ; for actor -> actor collision detection 
-- 
2.30.2