adds a helper for updating one piece of clothing depending on its slot (#66191)

you can now run the proc update_clothing to use the slot_flags of an item to properly update a mob's icons
this is used by spraycans coloring an item, instead of running regenerate_icons

less weighty than regenerate_icons form of updating an item that you dont really know where is.
lets us support modsuits worn on stuff that isnt the back in the future

code/game/objects/items/crayons.dm

@@ -771,12 +771,13 @@
 				return FALSE
 
 			target.add_atom_colour(paint_color, WASHABLE_COLOUR_PRIORITY)
-			if(isliving(target.loc))
+			if(isitem(target) && isliving(target.loc))
+				var/obj/item/target_item = target
 				var/mob/living/holder = target.loc
-				if(holder.is_holding(target))
+				if(holder.is_holding(target_item))
 					holder.update_inv_hands()
 				else
-					holder.regenerate_icons()
+					holder.update_clothing(target_item.slot_flags)
 			SEND_SIGNAL(target, COMSIG_OBJ_PAINTED, color_is_dark)
 		. = use_charges(user, 2, requires_full = FALSE)
 		reagents.trans_to(target, ., volume_multiplier, transfered_by = user, methods = VAPOR)

code/modules/mob/living/carbon/human/human_update_icons.dm

@@ -100,6 +100,40 @@ There are several things that need to be remembered:
 		//damage overlays
 		update_damage_overlays()
 
+/mob/living/carbon/human/update_clothing(slot_flags)
+	if(slot_flags & ITEM_SLOT_BACK)
+		update_inv_back()
+	if(slot_flags & ITEM_SLOT_MASK)
+		update_inv_wear_mask()
+	if(slot_flags & ITEM_SLOT_NECK)
+		update_inv_neck()
+	if(slot_flags & ITEM_SLOT_HANDCUFFED)
+		update_inv_handcuffed()
+	if(slot_flags & ITEM_SLOT_LEGCUFFED)
+		update_inv_legcuffed()
+	if(slot_flags & ITEM_SLOT_BELT)
+		update_inv_belt()
+	if(slot_flags & ITEM_SLOT_ID)
+		update_inv_wear_id()
+	if(slot_flags & ITEM_SLOT_EARS)
+		update_inv_ears()
+	if(slot_flags & ITEM_SLOT_EYES)
+		update_inv_glasses()
+	if(slot_flags & ITEM_SLOT_GLOVES)
+		update_inv_gloves()
+	if(slot_flags & ITEM_SLOT_HEAD)
+		update_inv_head()
+	if(slot_flags & ITEM_SLOT_FEET)
+		update_inv_shoes()
+	if(slot_flags & ITEM_SLOT_OCLOTHING)
+		update_inv_wear_suit()
+	if(slot_flags & ITEM_SLOT_ICLOTHING)
+		update_inv_w_uniform()
+	if(slot_flags & ITEM_SLOT_SUITSTORE)
+		update_inv_s_store()
+	if(slot_flags & ITEM_SLOT_LPOCKET || slot_flags & ITEM_SLOT_RPOCKET)
+		update_inv_pockets()
+
 /* --------------------------------------- */
 //vvvvvv UPDATE_INV PROCS vvvvvv
 

code/modules/mob/mob_update_icons.dm

@@ -4,6 +4,9 @@
 /mob/proc/regenerate_icons() //TODO: phase this out completely if possible
 	return
 
+/mob/proc/update_clothing(slot_flags)
+	return
+
 /mob/proc/update_icons()
 	return