Removing priority overlays, update_icon() splitup for guns.

code/game/objects/items/grenades/plastic.dm

@@ -60,7 +60,8 @@
 	if(target)
 		if(!QDELETED(target))
 			location = get_turf(target)
-			target.cut_overlay(plastic_overlay, TRUE)
+			target.cut_overlay(plastic_overlay)
+			UnregisterSignal(target, COMSIG_ATOM_UPDATE_OVERLAYS, .proc/add_plastic_overlay)
 			if(!ismob(target) || full_damage_on_mobs)
 				target.ex_act(EXPLODE_HEAVY, target)
 	else
@@ -126,13 +127,17 @@
 				I.embedding["embed_chance"] = 0
 				I.updateEmbedding()
 
-		target.add_overlay(plastic_overlay, TRUE)
+		RegisterSignal(target, COMSIG_ATOM_UPDATE_OVERLAYS, .proc/add_plastic_overlay)
+		target.update_icon()
 		if(!nadeassembly)
 			to_chat(user, "<span class='notice'>You plant the bomb. Timer counting down from [det_time].</span>")
 			addtimer(CALLBACK(src, .proc/prime), det_time*10)
 		else
 			qdel(src)	//How?
 
+/obj/item/grenade/plastic/proc/add_plastic_overlay(atom/source, list/overlay_list)
+	overlay_list += plastic_overlay
+
 /obj/item/grenade/plastic/proc/shout_syndicate_crap(mob/M)
 	if(!M)
 		return

code/game/objects/obj_defense.dm

@@ -186,7 +186,7 @@ GLOBAL_DATUM_INIT(acid_overlay, /mutable_appearance, mutable_appearance('icons/e
 
 		if(!acid_level)
 			SSacid.processing[src] = src
-			add_overlay(GLOB.acid_overlay, TRUE)
+			update_icon()
 		var/acid_cap = acidpwr * 300 //so we cannot use huge amounts of weak acids to do as well as strong acids.
 		if(acid_level < acid_cap)
 			acid_level = min(acid_level + acidpwr * acid_volume, acid_cap)
@@ -224,7 +224,7 @@ GLOBAL_DATUM_INIT(acid_overlay, /mutable_appearance, mutable_appearance('icons/e
 	if(!(resistance_flags & ON_FIRE) && (resistance_flags & FLAMMABLE))
 		resistance_flags |= ON_FIRE
 		SSfire_burning.processing[src] = src
-		add_overlay(GLOB.fire_overlay, TRUE)
+		update_icon()
 		return 1
 
 //called when the obj is destroyed by fire
@@ -236,7 +236,7 @@ GLOBAL_DATUM_INIT(acid_overlay, /mutable_appearance, mutable_appearance('icons/e
 /obj/proc/extinguish()
 	if(resistance_flags & ON_FIRE)
 		resistance_flags &= ~ON_FIRE
-		cut_overlay(GLOB.fire_overlay, TRUE)
+		update_icon()
 		SSfire_burning.processing -= src
 
 /obj/zap_act(power, zap_flags, shocked_targets)

code/game/objects/objs.dm

@@ -317,6 +317,13 @@
 	icon_state = unique_reskin[choice]
 	to_chat(M, "[src] is now skinned as '[choice]'.")
 
+/obj/update_overlays()
+	. = ..()
+	if(acid_level)
+		. += GLOB.acid_overlay
+	if(resistance_flags & ON_FIRE)
+		. += GLOB.fire_overlay
+
 //Called when the object is constructed by an autolathe
 //Has a reference to the autolathe so you can do !!FUN!! things with hacked lathes
 /obj/proc/autolathe_crafted(obj/machinery/autolathe/A)