From 56f61d2296adac1e5f20be2c9bf10931bee6e634 Mon Sep 17 00:00:00 2001
From: Ccomp5950 <Ccomp5950@gmail.com>
Date: Fri, 14 Feb 2014 02:33:28 -0600
Subject: [PATCH] Code effeciency project:  Canister icon updates

Before:  If a canister is hooked up to a connector port it's icons were being deleted and recreated every tick.

After:  We store an update_flag that is a bitfield of the current icon and overlay states, and created a proc to check if it should change.  If not, we don't mess with icons.  Real simple.
---
 code/game/machinery/atmoalter/canister.dm | 67 +++++++++++++++++------
 1 file changed, 51 insertions(+), 16 deletions(-)

diff --git a/code/game/machinery/atmoalter/canister.dm b/code/game/machinery/atmoalter/canister.dm
index 35e96899ea1..627886ec5c5 100644
--- a/code/game/machinery/atmoalter/canister.dm
+++ b/code/game/machinery/atmoalter/canister.dm
@@ -17,6 +17,7 @@
 	volume = 1000
 	use_power = 0
 	var/release_log = ""
+	var/update_flag = 0
 
 /obj/machinery/portable_atmospherics/canister/sleeping_agent
 	name = "Canister: \[N2O\]"
@@ -49,30 +50,64 @@
 	canister_color = "grey"
 	can_label = 0
 
+/obj/machinery/portable_atmospherics/canister/proc/check_change()
+	var/old_flag = update_flag
+	update_flag = 0
+	if(holding)
+		update_flag |= 1
+	if(connected_port)
+		update_flag |= 2
+
+	var/tank_pressure = air_contents.return_pressure()
+	if(tank_pressure < 10)
+		update_flag |= 4
+	else if(tank_pressure < ONE_ATMOSPHERE)
+		update_flag |= 8
+	else if(tank_pressure < 15*ONE_ATMOSPHERE)
+		update_flag |= 16
+	else
+		update_flag |= 32
+
+	if(update_flag == old_flag)
+		return 1
+	else
+		return 0
+
 /obj/machinery/portable_atmospherics/canister/update_icon()
-	src.overlays = 0
+/*
+update_flag
+1 = holding
+2 = connected_port
+4 = tank_pressure < 10
+8 = tank_pressure < ONE_ATMOS
+16 = tank_pressure < 15*ONE_ATMOS
+32 = tank_pressure go boom.
+*/
 
 	if (src.destroyed)
+		src.overlays = 0
 		src.icon_state = text("[]-1", src.canister_color)
 
-	else
+	if(icon_state != "[canister_color]") 
 		icon_state = "[canister_color]"
-		if(holding)
-			overlays += "can-open"
+	
+	if(check_change()) //Returns 1 if no change needed to icons.
+		return
 
-		if(connected_port)
-			overlays += "can-connector"
+	src.overlays = 0
 
-		var/tank_pressure = air_contents.return_pressure()
-
-		if (tank_pressure < 10)
-			overlays += image('icons/obj/atmos.dmi', "can-o0")
-		else if (tank_pressure < ONE_ATMOSPHERE)
-			overlays += image('icons/obj/atmos.dmi', "can-o1")
-		else if (tank_pressure < 15*ONE_ATMOSPHERE)
-			overlays += image('icons/obj/atmos.dmi', "can-o2")
-		else
-			overlays += image('icons/obj/atmos.dmi', "can-o3")
+	if(update_flag & 1)
+		overlays += "can-open"
+	if(update_flag & 2)
+		overlays += "can-connector"
+	if(update_flag & 4)
+		overlays += "can-o0"
+	if(update_flag & 8)
+		overlays += "can-o1"
+	else if(update_flag & 16)
+		overlays += "can-o2"
+	else if(update_flag & 32)
+		overlays += "can-o3"
 	return
 
 /obj/machinery/portable_atmospherics/canister/temperature_expose(datum/gas_mixture/air, exposed_temperature, exposed_volume)