Use can_atmos_pass to reduce proc-calls in c_airblock()

- Add additional can_atmos_pass value ATMOS_PASS_PROC which indicates custom behavior requiring calling the CanZASPass proc.
  - The benefit being for the other three values we DON'T need to call CanZASPass at all!  We already know the behavior without the overhead of a proc call.
  - Obviously any atom with can_atmos_pass = ATMOS_PASS_PROC cannot now call ..() in CanZASPass() since the default behavior would be to (recursively) call CanZASPass()
  - This required re-numbering the constants, so I also fixed all code that assumed particular values for the constants.
- Switched all types which overrode CanZASPass with custom logic to be can_atmos_pass = ATMOS_PASS_PROC
- Changed /turf/c_airblock() to skip calling /atom/movable/c_airblock() for the three can_atmos_pass values that don't require calling the proc.

code/ZAS/Atom.dm

@@ -16,11 +16,19 @@
 // Inputs: The turf the airflow is from, which may not be the same as loc. is_zone is for conditionally disallowing merging.
 // Outputs: Boolean if airflow can pass.
 /atom/proc/CanZASPass(turf/T, is_zone)
+	// Behaviors defined here so when people directly call c_airblock it will still obey can_atmos_pass
 	switch(can_atmos_pass)
+		if(ATMOS_PASS_YES)
+			return TRUE
+		if(ATMOS_PASS_NO)
+			return FALSE
 		if(ATMOS_PASS_DENSITY)
 			return !density
+		if(ATMOS_PASS_PROC)
+			// Cowardly refuse to recursively self-call CanZASPass. The hero BYOND needs?
+			CRASH("can_atmos_pass = ATMOS_PASS_PROC but CanZASPass not overridden on [src] ([type])")
 		else
-			return can_atmos_pass
+			CRASH("Invalid can_atmos_pass = [can_atmos_pass] on [src] ([type])")
 
 /turf/CanPass(atom/movable/mover, turf/target)
 	if(!target) return FALSE
@@ -87,6 +95,15 @@ turf/c_airblock(turf/other)
 	var/result = 0
 	for(var/mm in contents)
 		var/atom/movable/M = mm
-		result |= M.c_airblock(other)
+		switch(M.can_atmos_pass)
+			if(ATMOS_PASS_YES)
+				continue
+			if(ATMOS_PASS_NO)
+				return BLOCKED
+			if(ATMOS_PASS_DENSITY)
+				if(density)
+					return BLOCKED
+			if(ATMOS_PASS_PROC)
+				result |= M.c_airblock(other)
 		if(result == BLOCKED) return BLOCKED
 	return result

code/__defines/ZAS.dm

@@ -4,3 +4,10 @@
 #define BLOCKED 3		// Blocked, zone boundaries will not cross even if opened.
 
 #define ZONE_MIN_SIZE 14 // Zones with less than this many turfs will always merge, even if the connection is not direct
+
+// Used for quickly making certain things allow airflow or not.
+// More complicated, conditional airflow should override CanZASPass().
+#define ATMOS_PASS_YES			1	// Always blocks air and zones.
+#define ATMOS_PASS_NO			2	// Never blocks air or zones.
+#define ATMOS_PASS_DENSITY		3	// Blocks air and zones if density = 1, allows both if density = 0
+#define ATMOS_PASS_PROC			4	// Call CanZASPass() using c_airblock

code/__defines/atmos.dm

@@ -94,9 +94,3 @@
 #define ATMOSTANK_CO2           25000 // CO2 and PH are not critically important for station, only for toxins and alternative coolants, no need to store a lot of those.
 #define ATMOSTANK_PHORON        25000
 #define ATMOSTANK_NITROUSOXIDE  10000 // N2O doesn't have a real useful use, i guess it's on station just to allow refilling of sec's riot control canisters?
-
-// Used for quickly making certain things allow airflow or not.
-// More complicated, conditional airflow should override CanZASPass().
-#define ATMOS_PASS_YES		1
-#define ATMOS_PASS_NO		0
-#define ATMOS_PASS_DENSITY	-1 // Just checks density.

code/game/machinery/doors/door.dm

@@ -9,7 +9,7 @@
 	anchored = 1
 	opacity = 1
 	density = 1
-	can_atmos_pass = ATMOS_PASS_DENSITY
+	can_atmos_pass = ATMOS_PASS_PROC
 	layer = DOOR_OPEN_LAYER
 	var/open_layer = DOOR_OPEN_LAYER
 	var/closed_layer = DOOR_CLOSED_LAYER
@@ -157,8 +157,8 @@
 
 /obj/machinery/door/CanZASPass(turf/T, is_zone)
 	if(is_zone)
-		return !block_air_zones
+		return !block_air_zones // Block merging unless block_air_zones = 0
-	return ..()
+	return !density // Block airflow unless density = 0
 
 /obj/machinery/door/proc/bumpopen(mob/user as mob)
 	if(operating)	return

code/game/machinery/doors/windowdoor.dm

@@ -14,6 +14,7 @@
 	opacity = 0
 	var/obj/item/weapon/airlock_electronics/electronics = null
 	explosion_resistance = 5
+	can_atmos_pass = ATMOS_PASS_PROC
 	air_properties_vary_with_direction = 1
 
 /obj/machinery/door/window/New()
@@ -95,7 +96,7 @@
 	if(get_dir(T, loc) == turn(dir, 180))
 		if(is_zone) // No merging allowed.
 			return FALSE
-		return ..() // Air can flow if open (density == FALSE).
+		return !density  // Air can flow if open (density == FALSE).
 	return TRUE // Windoors don't block if not facing the right way.
 
 /obj/machinery/door/window/CheckExit(atom/movable/mover as mob|obj, turf/target as turf)

code/game/objects/effects/zone_divider.dm

@@ -7,6 +7,7 @@
 	anchored = 1
 	density = 0
 	opacity = 0
+	can_atmos_pass = ATMOS_PASS_PROC
 
 /obj/effect/zone_divider/CanZASPass(turf/T, is_zone)
  	// Special case to prevent us from being part of a zone during the first air master tick.

code/game/objects/structures/window.dm

@@ -3,7 +3,7 @@
 	desc = "A window."
 	icon = 'icons/obj/structures_vr.dmi' // VOREStation Edit - New icons
 	density = 1
-	can_atmos_pass = ATMOS_PASS_DENSITY
+	can_atmos_pass = ATMOS_PASS_PROC
 	w_class = ITEMSIZE_NORMAL
 
 	layer = WINDOW_LAYER

code/modules/mob/living/living_movement.dm

@@ -8,10 +8,6 @@
 		return !P.can_hit_target(src, P.permutated, src == P.original, TRUE)
 	return (!mover.density || !density || lying)
 
-// There is no need to override this if you're just going to unconditionally return TRUE.  Set can_atmos_pass instead.
-///mob/CanZASPass(turf/T, is_zone)
-//	return TRUE
-
 /mob/living/SelfMove(turf/n, direct)
 	// If on walk intent, don't willingly step into hazardous tiles.
 	// Unless the walker is confused.

code/modules/power/turbine.dm

@@ -28,6 +28,7 @@
 	icon_state = "compressor"
 	anchored = TRUE
 	density = TRUE
+	can_atmos_pass = ATMOS_PASS_PROC
 	circuit = /obj/item/weapon/circuitboard/machine/power_compressor
 	var/obj/machinery/power/turbine/turbine
 	var/datum/gas_mixture/gas_contained