Ports some hud and update_icon code updates.

code/game/machinery/buttons.dm

@@ -38,21 +38,22 @@
 			board.one_access = 1
 			board.accesses = req_one_access
 
-
-/obj/machinery/button/update_icon()
-	cut_overlays()
+/obj/machinery/button/update_icon_state()
 	if(panel_open)
 		icon_state = "button-open"
-		if(device)
-			add_overlay("button-device")
-		if(board)
-			add_overlay("button-board")
-
+	else if(stat & (NOPOWER|BROKEN))
+		icon_state = "[skin]-p"
 	else
-		if(stat & (NOPOWER|BROKEN))
-			icon_state = "[skin]-p"
-		else
-			icon_state = skin
+		icon_state = skin
+
+/obj/machinery/button/update_overlays()
+	. = ..()
+	if(!panel_open)
+		return
+	if(device)
+		. += "button-device"
+	if(board)
+		. += "button-board"
 
 /obj/machinery/button/attackby(obj/item/W, mob/user, params)
 	if(istype(W, /obj/item/screwdriver))
@@ -168,7 +169,7 @@
 	if(device)
 		device.pulsed()
 
-	addtimer(CALLBACK(src, .proc/update_icon), 15)
+	addtimer(CALLBACK(src, /atom/.proc/update_icon), 15)
 
 /obj/machinery/button/power_change()
 	..()

code/game/machinery/camera/camera.dm

@@ -292,7 +292,7 @@
 			new /obj/item/stack/cable_coil(loc, 2)
 	qdel(src)
 
-/obj/machinery/camera/update_icon()
+/obj/machinery/camera/update_icon_state()
 	if(!status)
 		icon_state = "[initial(icon_state)]1"
 	else if (stat & EMPED)

code/game/machinery/defibrillator_mount.dm

@@ -38,17 +38,21 @@
 		defib.cell.give(180) //90% efficiency, slightly better than the cell charger's 87.5%
 		update_icon()
 
-/obj/machinery/defibrillator_mount/update_icon()
-	cut_overlays()
-	if(defib)
-		add_overlay("defib")
-		if(defib.powered)
-			add_overlay(defib.safety ? "online" : "emagged")
-			var/ratio = defib.cell.charge / defib.cell.maxcharge
-			ratio = CEILING(ratio * 4, 1) * 25
-			add_overlay("charge[ratio]")
-		if(clamps_locked)
-			add_overlay("clamps")
+/obj/machinery/defibrillator_mount/update_overlays()
+	. = ..()
+	if(!defib)
+		return
+
+	. += "defib"
+
+	if(defib.powered)
+		. += (defib.safety ? "online" : "emagged")
+		var/ratio = defib.cell.charge / defib.cell.maxcharge
+		ratio = CEILING(ratio * 4, 1) * 25
+		. += "charge[ratio]"
+
+	if(clamps_locked)
+		. += "clamps"
 
 /obj/machinery/defibrillator_mount/get_cell()
 	if(defib)