Makes the shuttle code a little bit more robust by removing a snowflake loop (#2559)

code/modules/shuttle/on_move.dm

@@ -4,15 +4,17 @@ All ShuttleMove procs go here
 
 /************************************Base procs************************************/
 
-// Called on every turf in the shuttle region, return false if it doesn't want to move
-/turf/proc/fromShuttleMove(turf/newT, turf_type, baseturf_type)
-	if(type == turf_type && baseturf == baseturf_type)
-		return FALSE
-	return TRUE
+// Called on every turf in the shuttle region, returns a bitflag for allowed movements of that turf
+// returns the new move_mode (based on the old)
+/turf/proc/fromShuttleMove(turf/newT, turf_type, list/baseturf_cache, move_mode)
+	if(!(move_mode & MOVE_AREA) || (istype(src, turf_type) && baseturf_cache[baseturf]))
+		return move_mode
+	return move_mode | MOVE_TURF | MOVE_CONTENTS
 
 // Called from the new turf before anything has been moved
 // Only gets called if fromShuttleMove returns true first
-/turf/proc/toShuttleMove(turf/oldT, shuttle_dir)
+// returns the new move_mode (based on the old)
+/turf/proc/toShuttleMove(turf/oldT, shuttle_dir, move_mode)
 	for(var/i in contents)
 		var/atom/movable/thing = i
 		if(ismob(thing))
@@ -38,7 +40,7 @@ All ShuttleMove procs go here
 			else
 				qdel(thing)
 
-	return TRUE
+	return move_mode
 
 // Called on the old turf to move the turf data
 /turf/proc/onShuttleMove(turf/newT, turf_type, baseturf_type, rotation, list/movement_force, move_dir)
@@ -73,9 +75,9 @@ All ShuttleMove procs go here
 /////////////////////////////////////////////////////////////////////////////////////
 
 // Called on every atom in shuttle turf contents before anything has been moved
-// Return true if it should be moved regardless of turf being moved
-/atom/movable/proc/beforeShuttleMove(turf/newT, rotation)
-	return FALSE
+// returns the new move_mode (based on the old)
+/atom/movable/proc/beforeShuttleMove(turf/newT, rotation, move_mode)
+	return move_mode
 
 // Called on atoms to move the atom to the new location
 /atom/movable/proc/onShuttleMove(turf/newT, turf/oldT, rotation, list/movement_force, move_dir, old_dock)
@@ -102,13 +104,16 @@ All ShuttleMove procs go here
 /////////////////////////////////////////////////////////////////////////////////////
 
 // Called on areas before anything has been moved
-/area/proc/beforeShuttleMove()
-	return TRUE
+// returns the new move_mode (based on the old)
+/area/proc/beforeShuttleMove(list/shuttle_areas)
+	if(!shuttle_areas[src])
+		return NONE
+	return MOVE_AREA
 
 // Called on areas to move their turf between areas
 /area/proc/onShuttleMove(turf/oldT, turf/newT, area/underlying_old_area)
 	if(newT == oldT) // In case of in place shuttle rotation shenanigans.
-		return
+		return TRUE
 
 	contents -= oldT
 	underlying_old_area.contents += oldT
@@ -117,7 +122,7 @@ All ShuttleMove procs go here
 
 	var/area/old_dest_area = newT.loc
 	parallax_movedir = old_dest_area.parallax_movedir
-	
+
 	old_dest_area.contents -= newT
 	contents += newT
 	newT.change_area(old_dest_area, src)
@@ -160,9 +165,11 @@ All ShuttleMove procs go here
 	SSair.add_to_active(src, TRUE)
 	SSair.add_to_active(oldT, TRUE)
 
+/************************************Area move procs************************************/
+
 /************************************Machinery move procs************************************/
 
-/obj/machinery/door/airlock/beforeShuttleMove(turf/newT, rotation)
+/obj/machinery/door/airlock/beforeShuttleMove(turf/newT, rotation, move_mode)
 	. = ..()
 	shuttledocked = 0
 	for(var/obj/machinery/door/airlock/A in range(1, src))
@@ -176,11 +183,11 @@ All ShuttleMove procs go here
 	for(var/obj/machinery/door/airlock/A in range(1, src))
 		A.shuttledocked = 1
 
-/obj/machinery/camera/beforeShuttleMove(turf/newT, rotation)
+/obj/machinery/camera/beforeShuttleMove(turf/newT, rotation, move_mode)
 	. = ..()
 	GLOB.cameranet.removeCamera(src)
 	GLOB.cameranet.updateChunk()
-	return TRUE
+	. |= MOVE_CONTENTS
 
 /obj/machinery/camera/afterShuttleMove(list/movement_force, shuttle_dir, shuttle_preferred_direction, move_dir)
 	. = ..()
@@ -207,7 +214,7 @@ All ShuttleMove procs go here
 	if(z == ZLEVEL_MINING) //Avoids double logging and landing on other Z-levels due to badminnery
 		SSblackbox.add_details("colonies_dropped", "[x]|[y]|[z]") //Number of times a base has been dropped!
 
-/obj/machinery/gravity_generator/main/beforeShuttleMove(turf/newT, rotation)
+/obj/machinery/gravity_generator/main/beforeShuttleMove(turf/newT, rotation, move_mode)
 	. = ..()
 	on = FALSE
 	update_list()
@@ -218,9 +225,9 @@ All ShuttleMove procs go here
 		on = TRUE
 	update_list()
 
-/obj/machinery/thruster/beforeShuttleMove(turf/newT, rotation)
+/obj/machinery/thruster/beforeShuttleMove(turf/newT, rotation, move_mode)
 	. = ..()
-	. = TRUE
+	. |= MOVE_CONTENTS
 
 //Properly updates pipes on shuttle movement
 /obj/machinery/atmospherics/shuttleRotate(rotation)
@@ -271,7 +278,7 @@ All ShuttleMove procs go here
 	var/turf/T = loc
 	hide(T.intact)
 
-/obj/machinery/navbeacon/beforeShuttleMove(turf/newT, rotation)
+/obj/machinery/navbeacon/beforeShuttleMove(turf/newT, rotation, move_mode)
 	. = ..()
 	GLOB.navbeacons["[z]"] -= src
 	GLOB.deliverybeacons -= src
@@ -333,13 +340,13 @@ All ShuttleMove procs go here
 
 /************************************Structure move procs************************************/
 
-/obj/structure/grille/beforeShuttleMove(turf/newT, rotation)
+/obj/structure/grille/beforeShuttleMove(turf/newT, rotation, move_mode)
 	. = ..()
-	. = TRUE
+	. |= MOVE_CONTENTS
 
-/obj/structure/lattice/beforeShuttleMove(turf/newT, rotation)
+/obj/structure/lattice/beforeShuttleMove(turf/newT, rotation, move_mode)
 	. = ..()
-	. = TRUE
+	. |= MOVE_CONTENTS
 
 /obj/structure/disposalpipe/afterShuttleMove(list/movement_force, shuttle_dir, shuttle_preferred_direction, move_dir)
 	. = ..()
@@ -350,6 +357,11 @@ All ShuttleMove procs go here
 	var/turf/T = loc
 	if(level==1)
 		hide(T.intact)
+		
+/obj/structure/shuttle/beforeShuttleMove(turf/newT, rotation, move_mode)
+	. = ..()
+	. |= MOVE_CONTENTS
+
 
 /************************************Misc move procs************************************/
 
@@ -371,4 +383,4 @@ All ShuttleMove procs go here
 
 /obj/effect/abstract/proximity_checker/onShuttleMove(turf/newT, turf/oldT, rotation, list/movement_force, move_dir, old_dock)
 	//timer so it only happens once
-	addtimer(CALLBACK(monitor, /datum/proximity_monitor/proc/SetRange, monitor.current_range, TRUE), 0, TIMER_UNIQUE)
+	addtimer(CALLBACK(monitor, /datum/proximity_monitor/proc/SetRange, monitor.current_range, TRUE), 0, TIMER_UNIQUE)