Computer dark visibility tweaks (#1829)

changes:

Holo-computers' displays now draw above the lighting layer, allowing them to be seen in the dark.
APCs' displays now draw above the lighting layer, allowing them to be seen in the dark.

code/modules/modular_computers/computers/modular_computer/power.dm

@@ -7,6 +7,9 @@
 			PRG.event_powerfailure(1)
 		shutdown_computer(0)
 
+	power_has_failed = TRUE
+	update_icon()
+
 // Tries to use power from battery. Passing 0 as parameter results in this proc returning whether battery is functional or not.
 /obj/item/modular_computer/proc/battery_power(var/power_usage = 0)
 	apc_powered = FALSE
@@ -38,14 +41,21 @@
 // Handles power-related things, such as battery interaction, recharging, shutdown when it's discharged
 /obj/item/modular_computer/proc/handle_power()
 	var/power_usage = screen_on ? base_active_power_usage : base_idle_power_usage
-	for(var/obj/item/weapon/computer_hardware/H in get_all_components())
-		if(H.enabled)
-			power_usage += H.power_usage
-	last_power_usage = power_usage
+	if (enabled)
+		for(var/obj/item/weapon/computer_hardware/H in get_all_components())
+			if(H.enabled)
+				power_usage += H.power_usage
+		last_power_usage = power_usage
 
 	// First tries to charge from an APC, if APC is unavailable switches to battery power. If neither works the computer fails.
 	if(apc_power(power_usage))
+		if (power_has_failed)
+			power_has_failed = FALSE
+			update_icon()
 		return
 	if(battery_power(power_usage))
+		if (power_has_failed)
+			power_has_failed = FALSE
+			update_icon()
 		return
-	power_failure()
+	power_failure()