Fixes turf_decal layering

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)