From: Lukas Krickl <lukas@krickl.dev>
Date: Wed, 3 Dec 2025 08:27:40 +0000 (+0100)
Subject: actor: Added left tile collision code
X-Git-Url: https://git.krickl.dev/?a=commitdiff_plain;h=62edddbd60d3908385f844d94b08acdcbe04c863;p=gbrg%2F.git

actor: Added left tile collision code
---

diff --git a/src/actor.s b/src/actor.s
index 796c39c..4157470 100644
--- a/src/actor.s
+++ b/src/actor.s
@@ -1,112 +1,35 @@
-	; fixes y position
-	; inputs:
-	;		a: direction
-	;	 hl: ptr to y pos
-	;	returns:
-	;		fixed y pos
-	;		a is unchanged
-	;	 hl: += 1
-	;		b: y pos adjusted / 16
-_act_test_col_y:
-	push af
-	and a, DIRUP
-	jr nz, @up REL
-	
-	pop af
-	push af
-	and a, DIRDOWN
-	jr nz, @down REL
-	
-	; no change
-	ld a, [hl+]
-	div16 a
-	ld b, a
-
-	pop af
-	ret
-@up:
-	ld a, [hl+]
-	div16 a
-	dec a
-	ld b, a
-
-	pop af
-	ret
-@down:
-	ld a, [hl+]
-	div16 a
-	inc a
-	ld b, a
-
-	pop af
-	ret
-	
-	; fixes x positions
-	; inputs:
-	;		a: direction
-	;		hl: ptr to x pos
-	;	returns:
-	;		fixed x pos
-	;		a is unchanged
-	;		c: x pos adjusted / 16
-_act_test_col_x:
-	push af
-
-	and a, DIRLEFT
-	jr nz, @left REL
-	
-	pop af
-	push af
-	and a, DIRRIGHT
-	jr nz, @right REL
-
-	; no change
-	ld a, [hl]
-	div16 a
-
-	ld c, a
-	pop af
-	ret
-@left:
-	ld a, [hl]
-	div16 a
-	dec a
-	ld c, a
-	
-	pop af
-	ret
-@right:
-	ld a, [hl]
-	div16 a
-	inc a
-	ld c, a
-
-	pop af
-	ret
 	
-	; stores current position in tmp_prev_pos
+	; stores current position in col_prev_pos
 	; inputs:
 	;		de: actor
 act_backup_pos:
 	ld hl, act_pos_y
 	add hl, de
 	ld a, [hl+]
-	ld [tmp_prev_pos], a ; y 
+	ld [col_prev_pos], a ; y 
 
 	ld a, [hl]
-	ld [tmp_prev_pos+1], a ; x
+	ld [col_prev_pos+1], a ; x
 	ret
 	
 	; restores prev x pos
 	; inputs:
 	;		de: actor
 act_rollback_pos_x:
+	ld hl, act_pos_x
+	add hl, de
+	ld a, [col_prev_pos+1]
+	ld [hl], a
 	ret
 
 	; restores prev y pos
 	; inputs:
 	;		de: actor
 act_rollback_pos_y:
+	ld hl, act_pos_y
+	add hl, de
+	ld a, [col_prev_pos]
+	ld [hl], a
 	ret
 	
 	; test collision based on an actor
@@ -114,9 +37,27 @@ act_rollback_pos_y:
 	;	inputs:
 	;		de: actor
 	;		col_point_xx: collision points
+	;  	col_direction: set to direction moved in
+	;		col_prev_pos: set to previous positions
 	; if collision occures rolls back to 
 	; previous position
 act_test_tile_collision:
+	ld a, [col_direction]
+	and a, DIRUP
+	call nz, _act_test_tile_up_collision
+
+	ld a, [col_direction]
+	and a, DIRDOWN
+	call nz, _act_test_tile_down_collision
+
+	ld a, [col_direction]
+	and a, DIRLEFT
+	call nz, _act_test_tile_left_collision
+
+	ld a, [col_direction]
+	and a, DIRRIGHT
+	call nz, _act_test_tile_right_collision
+
 
 	ld hl, act_pos_y
 	add hl, de
@@ -130,6 +71,68 @@ act_test_tile_collision:
 	and a, TF_WALL
 
 	ret
+	
+	; loads a collision point into bc
+	; inputs:
+	;		$1: point name
+	; returns:
+	;		b/c: y/x tile position
+#macro _act_tile_col_load_pt
+	ld a, [$1]
+	div16 a
+	ld b, a
+	ld a, [$1+1]
+	div16 a
+	ld c, a
+#endmacro
+	
+	; test direction routines:
+	;	preserve: de
+_act_test_tile_left_collision:
+	push de
+
+	; top left point
+	_act_tile_col_load_pt col_point_tl
+
+	call map_get_tile
+	ld de, t_flags
+	add hl, de
+	ld a, [hl]
+	and a, TF_WALL
+	jr nz, @collision REL
+
+	; bottom left point
+	_act_tile_col_load_pt col_point_bl
+
+	call map_get_tile
+	ld de, t_flags
+	add hl, de
+	ld a, [hl]
+	and a, TF_WALL
+	jr nz, @collision REL
+
+	pop de
+	ret
+@collision:
+	pop de
+	call act_rollback_pos_x
+	ret
+
+_act_test_tile_right_collision:
+	push de
+
+	pop de
+	ret
+
+_act_test_tile_up_collision:
+	push de
+	pop de
+	ret
+
+_act_test_tile_down_collision:
+	push de
+	pop de
+	ret
 
 	; update routines for each actor
 act_map_update_table:
diff --git a/src/player.s b/src/player.s
index de85d0c..6846e37 100644
--- a/src/player.s
+++ b/src/player.s
@@ -73,6 +73,9 @@ player_update:
 	; does not move out of bounds
 	; based on the last queued input
 player_handle_move:
+	xor a, a
+	ld [col_direction], a
+
 	ld b, BTNDOWN
 	input_held
 	jr z, @not_down REL
@@ -81,6 +84,10 @@ player_handle_move:
 		jr z, @not_down REL
 		inc a
 		ld [player+act_pos_y], a
+
+		ld a, [col_direction]
+		or a, DIRDOWN
+		ld [col_direction], a
 @not_down:
 
 	ld b, BTNUP
@@ -91,6 +98,10 @@ player_handle_move:
 		jr z, @not_up REL 
 		dec a
 		ld [player+act_pos_y], a
+
+		ld a, [col_direction]
+		or a, DIRUP
+		ld [col_direction], a
 @not_up:
 
 	ld b, BTNLEFT
@@ -101,6 +112,10 @@ player_handle_move:
 		jr z, @not_left REL
 		dec a
 		ld [player+act_pos_x], a
+
+		ld a, [col_direction]
+		or a, DIRLEFT
+		ld [col_direction], a
 @not_left:
 
 	ld b, BTNRIGHT
@@ -111,6 +126,10 @@ player_handle_move:
 		jr z, @not_right REL
 		inc a
 		ld [player+act_pos_x], a
+
+		ld a, [col_direction]
+		or a, DIRRIGHT
+		ld [col_direction], a
 @not_right:	
 	ret
 	
diff --git a/src/wram.s b/src/wram.s
index a75c721..bc45e76 100644
--- a/src/wram.s
+++ b/src/wram.s
@@ -96,9 +96,13 @@ col_point_tl: .adv 2
 col_point_tr: .adv 2
 col_point_bl: .adv 2
 col_point_br: .adv 2
+	; direction the movement is happening 
+	; in. this is required so that the collision code
+	; can handle pushbacks in case of wall collision
+col_direction: .adv 2
 	
 	; y/x previous position
-tmp_prev_pos: .adv 2
+col_prev_pos: .adv 2
 	
 	
 	; space for 4 tile ids