From 29f42778dda50d3391deeb4687cfb429fe4b3252 Mon Sep 17 00:00:00 2001
From: Tkdrg <tkdrg@users.noreply.github.com>
Date: Sat, 24 Oct 2015 13:55:58 -0300
Subject: [PATCH] Improves performance of set_airlock_overlays

They will now only update when they actually change. On my testing, this
made performance improve about 3-15 times, depending on the use case.

I could have made this a loop if I turned the overlays into a list with
defines but I was lazy and this copy-paste is probably slightly faster
than a list as well (despite being harder to read and to maintain).
---
 code/game/machinery/doors/airlock.dm | 39 +++++++++++++++++++++++-----
 1 file changed, 32 insertions(+), 7 deletions(-)

diff --git a/code/game/machinery/doors/airlock.dm b/code/game/machinery/doors/airlock.dm
index c3d7449b657..47859e4bb5a 100644
--- a/code/game/machinery/doors/airlock.dm
+++ b/code/game/machinery/doors/airlock.dm
@@ -58,6 +58,13 @@ var/list/airlock_overlays = list()
 	var/airlock_material = null //material of inner filling; if its an airlock with glass, this should be set to "glass"
 	var/overlays_file = 'icons/obj/doors/airlocks/station/overlays.dmi'
 
+	var/image/old_frame_overlay //keep those in order to prevent unnecessary updating
+	var/image/old_filling_overlay
+	var/image/old_lights_overlay
+	var/image/old_panel_overlay
+	var/image/old_weld_overlay
+	var/image/old_sparks_overlay
+
 	explosion_block = 1
 
 /obj/machinery/door/airlock/New()
@@ -312,13 +319,31 @@ About the new airlock wires panel:
 			if(p_open)
 				panel_overlay = get_airlock_overlay("panel_opening", overlays_file)
 
-	overlays.Cut()
-	overlays += frame_overlay
-	overlays += filling_overlay
-	overlays += lights_overlay
-	overlays += panel_overlay
-	overlays += weld_overlay
-	overlays += sparks_overlay
+	//doesn't use overlays.Cut() for performance reasons
+	if(frame_overlay != old_frame_overlay)
+		overlays -= old_frame_overlay
+		overlays += frame_overlay
+		old_frame_overlay = frame_overlay
+	if(filling_overlay != old_filling_overlay)
+		overlays -= old_filling_overlay
+		overlays += filling_overlay
+		old_filling_overlay = filling_overlay
+	if(lights_overlay != old_lights_overlay)
+		overlays -= old_lights_overlay
+		overlays += lights_overlay
+		old_lights_overlay = lights_overlay
+	if(panel_overlay != old_panel_overlay)
+		overlays -= old_panel_overlay
+		overlays += panel_overlay
+		old_panel_overlay = panel_overlay
+	if(weld_overlay != old_weld_overlay)
+		overlays -= old_weld_overlay
+		overlays += weld_overlay
+		old_weld_overlay = weld_overlay
+	if(sparks_overlay != old_sparks_overlay)
+		overlays -= old_sparks_overlay
+		overlays += sparks_overlay
+		old_sparks_overlay = sparks_overlay
 
 /proc/get_airlock_overlay(icon_state, icon_file)
 	var/iconkey = "[icon_state][icon_file]"