worn overlays proc sends a signal (tgstation#73101)

what the title says, it sends the list of overlays to be edited and some
other stuff
makes modsuits use this

code/__DEFINES/dcs/signals/signals_object.dm

@@ -155,6 +155,8 @@
 	#define COMPONENT_OFFER_TAKE_INTERRUPT (1<<0)
 /// sent from obj/effect/attackby(): (/obj/effect/hit_effect, /mob/living/attacker, params)
 #define COMSIG_ITEM_ATTACK_EFFECT "item_effect_attacked"
+/// Called by /obj/item/proc/worn_overlays(list/overlays, mutable_appearance/standing, isinhands, icon_file)
+#define COMSIG_ITEM_GET_WORN_OVERLAYS "item_get_worn_overlays"
 
 ///from base of [/obj/item/proc/tool_check_callback]: (mob/living/user)
 #define COMSIG_TOOL_IN_USE "tool_in_use"

code/modules/mob/living/carbon/carbon_update_icons.dm

@@ -453,10 +453,9 @@
 	RETURN_TYPE(/list)
 
 	. = list()
-	if(!blocks_emissive)
-		return
-
-	. += emissive_blocker(standing.icon, standing.icon_state, src, alpha = standing.alpha)
+	if(blocks_emissive)
+		. += emissive_blocker(standing.icon, standing.icon_state, src, alpha = standing.alpha)
+	SEND_SIGNAL(src, COMSIG_ITEM_GET_WORN_OVERLAYS, ., standing, isinhands, icon_file)
 
 ///Checks to see if any bodyparts need to be redrawn, then does so. update_limb_data = TRUE redraws the limbs to conform to the owner.
 /mob/living/carbon/proc/update_body_parts(update_limb_data)

code/modules/mod/mod_control.dm

@@ -433,14 +433,6 @@
 		retract(null, part)
 	return ..()
 
-/obj/item/mod/control/worn_overlays(mutable_appearance/standing, isinhands = FALSE, icon_file)
-	. = ..()
-	for(var/obj/item/mod/module/module as anything in modules)
-		var/list/module_icons = module.generate_worn_overlay(standing)
-		if(!length(module_icons))
-			continue
-		. += module_icons
-
 /obj/item/mod/control/update_icon_state()
 	icon_state = "[skin]-[base_icon_state][active ? "-sealed" : ""]"
 	return ..()
@@ -553,6 +545,7 @@
 	modules += new_module
 	complexity += new_module.complexity
 	new_module.mod = src
+	new_module.RegisterSignal(src, COMSIG_ITEM_GET_WORN_OVERLAYS, TYPE_PROC_REF(/obj/item/mod/module, add_module_overlay))
 	new_module.on_install()
 	if(wearer)
 		new_module.on_equip()
@@ -571,6 +564,7 @@
 		old_module.on_suit_deactivation(deleting = deleting)
 		if(old_module.active)
 			old_module.on_deactivation(display_message = !deleting, deleting = deleting)
+	old_module.UnregisterSignal(src, COMSIG_ITEM_GET_WORN_OVERLAYS)
 	old_module.on_uninstall(deleting = deleting)
 	QDEL_LIST_ASSOC_VAL(old_module.pinned_to)
 	old_module.mod = null

code/modules/mod/modules/_module.dm

@@ -264,6 +264,12 @@
 		device = null
 		qdel(src)
 
+/// Adds the worn overlays to the suit.
+/obj/item/mod/module/proc/add_module_overlay(obj/item/source, list/overlays, mutable_appearance/standing, isinhands, icon_file)
+	SIGNAL_HANDLER
+
+	overlays += generate_worn_overlay(standing)
+
 /// Generates an icon to be used for the suit's worn overlays
 /obj/item/mod/module/proc/generate_worn_overlay(mutable_appearance/standing)
 	. = list()