Atmos icon tweaks (#2874)

changes:

Airlock vents now use icon_states instead of atmos icon manager overlays.
Omni vents now use SSoverlay caching instead of atmos icon manager caching.
Added missing icon_states from #2812.

code/ATMOSPHERICS/components/binary_devices/dp_vent_pump.dm

@@ -59,23 +59,21 @@
 	if(!check_icon_cache())
 		return
 
-	overlays.Cut()
-
-	var/vent_icon = "vent"
+	var/istate = ""
 
 	var/turf/T = get_turf(src)
 	if(!istype(T))
 		return
 
 	if(!T.is_plating() && node1 && node2 && node1.level == 1 && node2.level == 1 && istype(node1, /obj/machinery/atmospherics/pipe) && istype(node2, /obj/machinery/atmospherics/pipe))
-		vent_icon += "h"
+		istate += "h"
 
 	if(!powered())
-		vent_icon += "off"
+		istate += "off"
 	else
-		vent_icon += "[use_power ? "[pump_direction ? "out" : "in"]" : "off"]"
+		istate += "[use_power ? "[pump_direction ? "out" : "in"]" : "off"]"
 
-	overlays += icon_manager.get_atmos_icon("device", , , vent_icon)
+	icon_state = istate
 
 /obj/machinery/atmospherics/binary/dp_vent_pump/update_underlays()
 	if(..())

code/ATMOSPHERICS/components/omni_devices/filter.dm

@@ -4,6 +4,7 @@
 /obj/machinery/atmospherics/omni/filter
 	name = "omni gas filter"
 	icon_state = "map_filter"
+	base_icon = "filter"
 
 	var/list/filters = new()
 	var/datum/omni_port/input

code/ATMOSPHERICS/components/omni_devices/mixer.dm

@@ -4,6 +4,7 @@
 /obj/machinery/atmospherics/omni/mixer
 	name = "omni gas mixer"
 	icon_state = "map_mixer"
+	base_icon = "mixer"
 
 	use_power = 1
 	idle_power_usage = 150		//internal circuitry, friction losses and stuff

code/ATMOSPHERICS/components/omni_devices/omni_base.dm

@@ -12,14 +12,16 @@
 	var/configuring = 0
 	//var/target_pressure = ONE_ATMOSPHERE	//a base type as abstract as this should NOT be making these kinds of assumptions
 
+	var/base_icon
+
 	var/tag_north = ATM_NONE
 	var/tag_south = ATM_NONE
 	var/tag_east = ATM_NONE
 	var/tag_west = ATM_NONE
 
-	var/overlays_on[5]
-	var/overlays_off[5]
-	var/overlays_error[2]
+	var/list/on_states = list()
+	var/list/off_states = list()
+
 	var/underlays_current[4]
 
 	var/list/ports = new()
@@ -44,20 +46,23 @@
 			initialize_directions |= d
 		ports += new_port
 
-	build_icons()
-
 /obj/machinery/atmospherics/omni/update_icon()
+	cut_overlays()
+	var/list/to_add = list(base_icon)
 	if(stat & NOPOWER)
-		overlays = overlays_off
+		to_add += off_states
 	else if(error_check())
-		overlays = overlays_error
+		to_add += "error"
+	else if (use_power)
+		to_add[1] = "[base_icon]_glow"
+		to_add += on_states
 	else
-		overlays = use_power ? (overlays_on) : (overlays_off)
+		to_add += off_states
+
+	add_overlay(to_add)
 
 	underlays = underlays_current
 
-	return
-
 /obj/machinery/atmospherics/omni/proc/error_check()
 	return
 
@@ -108,29 +113,12 @@
 	ui_interact(user)
 	return
 
-/obj/machinery/atmospherics/omni/proc/build_icons()
-	if(!check_icon_cache())
-		return
-
-	var/core_icon = null
-	if(istype(src, /obj/machinery/atmospherics/omni/mixer))
-		core_icon = "mixer"
-	else if(istype(src, /obj/machinery/atmospherics/omni/filter))
-		core_icon = "filter"
-	else
-		return
-
-	//directional icons are layers 1-4, with the core icon on layer 5
-	if(core_icon)
-		overlays_off[5] = icon_manager.get_atmos_icon("omni", , , core_icon)
-		overlays_on[5] = icon_manager.get_atmos_icon("omni", , , core_icon + "_glow")
-
-		overlays_error[1] = icon_manager.get_atmos_icon("omni", , , core_icon)
-		overlays_error[2] = icon_manager.get_atmos_icon("omni", , , "error")
-
 /obj/machinery/atmospherics/omni/proc/update_port_icons()
 	if(!check_icon_cache())
 		return
+	
+	on_states.Cut()
+	off_states.Cut()
 
 	for(var/datum/omni_port/P in ports)
 		if(P.update)
@@ -148,22 +136,19 @@
 			if(!ref_layer)
 				continue
 
-			var/list/port_icons = select_port_icons(P)
-			if(port_icons)
+			var/list/underlay_icon = select_port_icons(P)
+			if(underlay_icon)
 				if(P.node)
-					underlays_current[ref_layer] = port_icons["pipe_icon"]
+					underlays_current[ref_layer] = underlay_icon
 				else
 					underlays_current[ref_layer] = null
-				overlays_off[ref_layer] = port_icons["off_icon"]
-				overlays_on[ref_layer] = port_icons["on_icon"]
 			else
 				underlays_current[ref_layer] = null
-				overlays_off[ref_layer] = null
-				overlays_on[ref_layer] = null
 
 	update_icon()
 
-/obj/machinery/atmospherics/omni/proc/select_port_icons(var/datum/omni_port/P)
+// Assumes on_states and off_states have been cut if required.
+/obj/machinery/atmospherics/omni/proc/select_port_icons(datum/omni_port/P)
 	if(!istype(P))
 		return
 
@@ -182,21 +167,16 @@
 				ic_on += "_filter"
 				ic_off += "_out"
 
-		ic_on = icon_manager.get_atmos_icon("omni", , , ic_on)
-		ic_off = icon_manager.get_atmos_icon("omni", , , ic_off)
+		on_states += ic_on
+		off_states += ic_off
 
-		var/pipe_state
 		var/turf/T = get_turf(src)
 		if(!istype(T))
 			return
 		if(!T.is_plating() && istype(P.node, /obj/machinery/atmospherics/pipe) && P.node.level == 1 )
-			//pipe_state = icon_manager.get_atmos_icon("underlay_down", P.dir, color_cache_name(P.node))
-			pipe_state = icon_manager.get_atmos_icon("underlay", P.dir, color_cache_name(P.node), "down")
+			. = icon_manager.get_atmos_icon("underlay", P.dir, color_cache_name(P.node), "down")
 		else
-			//pipe_state = icon_manager.get_atmos_icon("underlay_intact", P.dir, color_cache_name(P.node))
-			pipe_state = icon_manager.get_atmos_icon("underlay", P.dir, color_cache_name(P.node), "intact")
-
-		return list("on_icon" = ic_on, "off_icon" = ic_off, "pipe_icon" = pipe_state)
+			. = icon_manager.get_atmos_icon("underlay", P.dir, color_cache_name(P.node), "intact")
 
 /obj/machinery/atmospherics/omni/update_underlays()
 	for(var/datum/omni_port/P in ports)