Fixes turf_decal layering

code/__DEFINES/layers.dm

@@ -13,6 +13,7 @@
 //#define TURF_LAYER 2 //For easy recordkeeping; this is a byond define
 #define MID_TURF_LAYER 2.02
 #define HIGH_TURF_LAYER 2.03
+#define TURF_DECAL_LAYER 2.039 //Makes turf decals appear in DM how they will look inworld.
 #define ABOVE_OPEN_TURF_LAYER 2.04
 #define CLOSED_TURF_LAYER 2.05
 #define BULLET_HOLE_LAYER 2.06
@@ -20,7 +21,6 @@
 #define LATTICE_LAYER 2.2
 #define DISPOSAL_PIPE_LAYER 2.3
 #define GAS_PIPE_HIDDEN_LAYER 2.35
-#define TURF_DECAL_LAYER 2.39
 #define WIRE_LAYER 2.4
 #define WIRE_TERMINAL_LAYER 2.45
 #define GAS_SCRUBBER_LAYER 2.46

code/datums/components/decal.dm

@@ -0,0 +1,53 @@
+/datum/component/decal
+	dupe_mode = COMPONENT_DUPE_ALLOWED
+
+	var/cleanable
+	var/mutable_appearance/pic
+
+/datum/component/decal/Initialize(_icon, _icon_state, _dir, _cleanable=CLEAN_GOD, _color, _layer=TURF_LAYER)
+	if(!isatom(parent) || !_icon || !_icon_state)
+		. = COMPONENT_INCOMPATIBLE
+		CRASH("A turf decal was applied incorrectly to [parent.type]: icon:[_icon ? _icon : "none"] icon_state:[_icon_state ? _icon_state : "none"]")
+
+	// It has to be made from an image or dir breaks because of a byond bug
+	var/temp_image = image(_icon, null, _icon_state, _layer, _dir)
+	pic = new(temp_image)
+	pic.color = _color
+
+	cleanable = _cleanable
+
+	apply()
+
+	if(_dir) // If no dir is assigned at start then it follows the atom's dir
+		RegisterSignal(COMSIG_ATOM_DIR_CHANGE, .proc/rotate_react)
+	if(_cleanable)
+		RegisterSignal(COMSIG_COMPONENT_CLEAN_ACT, .proc/clean_react)
+
+/datum/component/decal/Destroy()
+	remove()
+	return ..()
+
+/datum/component/decal/OnTransfer(atom/thing)
+	remove()
+	remove(thing)
+	apply(thing)
+
+/datum/component/decal/proc/apply(atom/thing)
+	var/atom/master = thing || parent
+	master.add_overlay(pic, TRUE)
+
+/datum/component/decal/proc/remove(atom/thing)
+	var/atom/master = thing || parent
+	master.cut_overlay(pic, TRUE)
+
+/datum/component/decal/proc/rotate_react(old_dir, new_dir)
+	if(old_dir == new_dir)
+		return
+	remove()
+	var/rotation = SimplifyDegrees(dir2angle(new_dir)-dir2angle(old_dir))
+	pic.dir = turn(pic.dir, rotation)
+	apply()
+
+/datum/component/decal/proc/clean_react(strength)
+	if(strength >= cleanable)
+		qdel(src)

code/game/objects/effects/decals/decal.dm

@@ -20,6 +20,7 @@
 /obj/effect/turf_decal
 	icon = 'icons/turf/decals.dmi'
 	icon_state = "warningline"
+	layer = TURF_DECAL_LAYER
 
 /obj/effect/turf_decal/Initialize()
 	..()

code/game/turfs/simulated/walls.dm

@@ -29,12 +29,12 @@
 
 	var/static/list/dent_decal_list = list(
 	WALL_DENT_HIT = list(
-	mutable_appearance('icons/effects/effects.dmi', "impact1", TURF_DECAL_LAYER),
-	mutable_appearance('icons/effects/effects.dmi', "impact2", TURF_DECAL_LAYER),
-	mutable_appearance('icons/effects/effects.dmi', "impact3", TURF_DECAL_LAYER)
+	mutable_appearance('icons/effects/effects.dmi', "impact1", BULLET_HOLE_LAYER),
+	mutable_appearance('icons/effects/effects.dmi', "impact2", BULLET_HOLE_LAYER),
+	mutable_appearance('icons/effects/effects.dmi', "impact3", BULLET_HOLE_LAYER)
 	),
 	WALL_DENT_SHOT = list(
-	mutable_appearance('icons/effects/effects.dmi', "bullet_hole", TURF_DECAL_LAYER)
+	mutable_appearance('icons/effects/effects.dmi', "bullet_hole", BULLET_HOLE_LAYER)
 	)
 	)