Subsysteming Attempt 2...?

code/__DEFINES/MC.dm

@@ -1,4 +1,5 @@
 #define MC_TICK_CHECK ((TICK_USAGE > Master.current_ticklimit || src.state != SS_RUNNING) ? pause() : 0)
+#define MC_PAUSE_IF_TRUE(value) (value ? pause() : 0)
 
 #define MC_TICK_REMAINING_MS ((Master.current_ticklimit - TICK_USAGE) * world.tick_lag)
 
@@ -117,3 +118,15 @@
 }\
 /datum/controller/subsystem/verb_manager/##X/fire() {..() /*just so it shows up on the profiler*/} \
 /datum/controller/subsystem/verb_manager/##X
+
+//If you use this, MAKE SURE that all shared data and calls in Fire() are on the main subsystem, otherwise, the background subsystem will do nothing.
+#define BACKGROUND_SUBSYSTEM_DEF(X) /datum/controller/subsystem/##X/background/New(){\
+	PreInit();\
+	ss_id="background_[#X]";\
+}\
+/datum/controller/subsystem/##X/background/fire() {\
+	if(SS##X.can_fire) { ..() }\
+}\
+/datum/controller/subsystem/##X/background/Recover(){}\
+/datum/controller/subsystem/##X/background/flags=SS_BACKGROUND|SS_NO_INIT;\
+/datum/controller/subsystem/##X/background

code/__DEFINES/dcs/signals/signals.dm

@@ -216,7 +216,7 @@
 #define COMSIG_ATOM_SET_OPACITY "atom_set_opacity"
 
 /// from base of /atom/movable/proc/on_virtual_z_change():  (new_virtual_z, old_virtual_z)
-#define COMSIG_ATOM_VIRTUAL_Z_CHANGE "atom_virtual_z_change"
+#define COMSIG_MOVABLE_VIRTUAL_Z_CHANGE "atom_virtual_z_change"
 
 //from base of atom/movable/on_enter_storage(): (datum/component/storage/concrete/master_storage)
 #define COMSIG_STORAGE_ENTERED "storage_entered"

code/__DEFINES/dcs/signals/signals_vlevels.dm

@@ -0,0 +1,2 @@
+/// Sent when the vlevel is clearing itself, so spawners and such stop spawning, etc. in /datum/virtual_level/clear_reservation(): ()
+#define COMSIG_VLEVEL_CLEARING "vlevel_clearing"

code/__DEFINES/maps.dm

@@ -103,6 +103,23 @@ require only minor tweaks.
 
 
 ///Map generation defines
+
+// These are used by SSmap_gen to run the phases of map generation in order.
+// As they are numeric, they can also be used to estimate the progress a map
+// has made towards generating, even in a queue.
+#define MAPGEN_PHASE_GENERATE 0
+#define MAPGEN_PHASE_AFTERCHANGE 1
+#define MAPGEN_PHASE_RUIN_PLACE 2
+#define MAPGEN_PHASE_RUIN_PLACING 3
+#define MAPGEN_PHASE_POPULATE 4
+#define MAPGEN_PHASE_FINISHED 5
+
+// Map generation priorities. Lower numbers are higher priority
+// as they are inserted at earlier positions in the queue.
+#define MAPGEN_PRIORITY_HIGH 1
+#define MAPGEN_PRIORITY_MED 2
+#define MAPGEN_PRIORITY_LOW 3
+
 #define BIOME_LOWEST_HUMIDITY "biome_lowest_humidity"
 #define BIOME_LOW_HUMIDITY "biome_low_humidity"
 #define BIOME_MEDIUM_HUMIDITY "biome_medium_humidity"

code/__DEFINES/subsystems.dm

@@ -141,7 +141,8 @@
 #define INIT_ORDER_XKEYSCORE -10
 #define INIT_ORDER_STICKY_BAN -10
 #define INIT_ORDER_LIGHTING -20
-#define INIT_ORDER_SHUTTLE -21
+#define INIT_ORDER_MAP_GEN -21
+#define INIT_ORDER_SHUTTLE -22
 #define INIT_ORDER_OVERMAP -25
 #define INIT_ORDER_PATH -50
 #define INIT_ORDER_DISCORD -60
@@ -161,17 +162,19 @@
 #define FIRE_PRIORITY_VIS 10
 #define FIRE_PRIORITY_AMBIENCE 10
 #define FIRE_PRIORITY_GARBAGE 15
+#define FIRE_PRIORITY_MAP_GEN_BACKGROUND 17
 #define FIRE_PRIORITY_WET_FLOORS 20
 #define FIRE_PRIORITY_AIR 20
 #define FIRE_PRIORITY_NPC 20
+#define FIRE_PRIORITY_MAP_GEN 20
 #define FIRE_PRIORITY_PROCESS 25
 #define FIRE_PRIORITY_THROWING 25
 #define FIRE_PRIORITY_SPACEDRIFT 30
-#define FIRE_PRIOTITY_SMOOTHING 35
+#define FIRE_PRIORITY_SMOOTHING 35
 #define FIRE_PRIORITY_NETWORKS 40
 #define FIRE_PRIORITY_OBJ 40
 #define FIRE_PRIORITY_ACID 40
-#define FIRE_PRIOTITY_BURNING 40
+#define FIRE_PRIORITY_BURNING 40
 #define FIRE_PRIORITY_DEFAULT 50
 #define FIRE_PRIORITY_PARALLAX 65
 #define FIRE_PRIORITY_INSTRUMENTS 80