[Port] Makes gravity event based, QOL additions as well as bugfixes regarding gravity

code/__DEFINES/dcs/signals/signals_movable.dm

@@ -69,8 +69,8 @@
 // /datum/element/movetype_handler signals
 /// Called when the floating anim has to be temporarily stopped and restarted later: (timer)
 #define COMSIG_PAUSE_FLOATING_ANIM "pause_floating_anim"
-/// From base of datum/element/movetype_handler/on_movement_type_trait_gain: (flag)
+/// From base of datum/element/movetype_handler/on_movement_type_trait_gain: (flag, old_movement_type)
 #define COMSIG_MOVETYPE_FLAG_ENABLED "movetype_flag_enabled"
-/// From base of datum/element/movetype_handler/on_movement_type_trait_loss: (flag)
+/// From base of datum/element/movetype_handler/on_movement_type_trait_loss: (flag, old_movement_type)
 #define COMSIG_MOVETYPE_FLAG_DISABLED "movetype_flag_disabled"
 

code/__DEFINES/flags.dm

@@ -141,6 +141,10 @@ GLOBAL_LIST_INIT(bitflags, list(1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 204
 #define FLOATING		(1<<3)
 #define PHASING			(1<<4)			//! When moving, will Bump()/Cross() everything, but won't be stopped.
 #define THROWN			(1<<5) //! while an atom is being thrown
+#define UPSIDE_DOWN 	(1<<6) /// The mob is walking on the ceiling. Or is generally just, upside down.
+
+/// Combination flag for movetypes which, for all intents and purposes, mean the mob is not touching the ground
+#define MOVETYPES_NOT_TOUCHING_GROUND (FLYING|FLOATING|UPSIDE_DOWN)
 
 //! ## Fire and Acid stuff, for resistance_flags
 #define LAVA_PROOF		(1<<0)

code/__DEFINES/gravity.dm

@@ -12,7 +12,18 @@
 /// Singularity is stage 6 (11x11)
 #define STAGE_SIX 11 //! From supermatter shard
 
-/// Anything above this is high gravity, anything below no grav until negative gravity
-#define STANDARD_GRAVITY 1
+/**
+ * The point where gravity is negative enough to pull you upwards.
+ * That means walking checks for a ceiling instead of a floor, and you can fall "upwards"
+ *
+ * This should only be possible on multi-z maps because it works like shit on maps that aren't.
+ */
+#define NEGATIVE_GRAVITY -1
+
+#define STANDARD_GRAVITY 1 //Anything above this is high gravity, anything below no grav until negative gravity
 /// The gravity strength threshold for high gravity damage.
-#define GRAVITY_DAMAGE_TRESHOLD 3
+#define GRAVITY_DAMAGE_THRESHOLD 3
+/// The scaling factor for high gravity damage.
+#define GRAVITY_DAMAGE_SCALING 0.5
+/// The maximum [BRUTE] damage a mob can take from high gravity per second.
+#define GRAVITY_DAMAGE_MAXIMUM 1.5

code/__DEFINES/traits/declarations.dm

@@ -317,4 +317,11 @@ Remember to update _globalvars/traits.dm if you're adding/removing/renaming trai
 /// The person with this trait always appears as 'unknown'.
 #define TRAIT_UNKNOWN "unknown"
 
+/// We are ignoring gravity
+#define TRAIT_IGNORING_GRAVITY "ignores_gravity"
+/// We have some form of forced gravity acting on us
+#define TRAIT_FORCED_GRAVITY "forced_gravity"
+#define TRAIT_MOVE_UPSIDE_DOWN "move_upside_down"
+#define TRAIT_NEGATES_GRAVITY "negates_gravity"
+
 // END TRAIT DEFINES

code/__DEFINES/traits/sources.dm

@@ -133,3 +133,6 @@
 #define NO_GRAVITY_TRAIT "no-gravity"
 #define LIFECANDLE_TRAIT "lifecandle"
 #define LEAPER_BUBBLE_TRAIT "leaper-bubble"
+#define NEGATIVE_GRAVITY_TRAIT "negative-gravity"
+/// Sources for TRAIT_IGNORING_GRAVITY
+#define IGNORING_GRAVITY_NEGATION "ignoring_gravity_negation"

code/_globalvars/bitfields.dm

@@ -153,7 +153,8 @@ DEFINE_BITFIELD(movement_type, list(
 	"FLYING" = FLYING,
 	"VENTCRAWLING" = VENTCRAWLING,
 	"FLOATING" = FLOATING,
-	"PHASING" = PHASING
+	"PHASING" = PHASING,
+	"UPSIDE_DOWN" = UPSIDE_DOWN,
 ))
 
 DEFINE_BITFIELD(mat_container_flags, list(

code/_globalvars/traits/_traits.dm

@@ -178,7 +178,11 @@ GLOBAL_LIST_INIT(traits_by_type, list(
 		"TRAIT_NORADDAMAGE" = TRAIT_NORADDAMAGE,
 		"TRAIT_MOBILE" = TRAIT_MOBILE,
 		"INSTANT_DO_AFTER" = INSTANT_DO_AFTER,
-		"TRAIT_UNKNOWN" = TRAIT_UNKNOWN
+		"TRAIT_UNKNOWN" = TRAIT_UNKNOWN,
+		"TRAIT_IGNORING_GRAVITY" = TRAIT_IGNORING_GRAVITY,
+		"TRAIT_FORCED_GRAVITY" = TRAIT_FORCED_GRAVITY,
+		"TRAIT_MOVE_UPSIDE_DOWN" = TRAIT_MOVE_UPSIDE_DOWN,
+		"TRAIT_NEGATES_GRAVITY" = TRAIT_NEGATES_GRAVITY
 	),
 	/obj/item/integrated_circuit = list(
 		"TRAIT_COMPONENT_MMI" = TRAIT_COMPONENT_MMI,

code/_onclick/hud/alert.dm

@@ -248,6 +248,11 @@ If you're feeling frisky, examine yourself and click the underlined item to pull
 		var/mob/living/carbon/M = usr
 		return M.help_shake_act(M)
 
+/atom/movable/screen/alert/negative
+	name = "Negative Gravity"
+	desc = "You're getting pulled upwards. While you won't have to worry about falling down anymore, you may accidentally fall upwards!"
+	icon_state = "negative"
+
 /atom/movable/screen/alert/weightless
 	name = "Weightless"
 	desc = "Gravity has ceased affecting you, and you're floating around aimlessly. You'll need something large and heavy, like a \

code/controllers/subsystem/mapping.dm

@@ -55,6 +55,10 @@ SUBSYSTEM_DEF(mapping)
 	var/datum/space_level/empty_space
 	var/num_of_res_levels = 1
 
+	///shows the default gravity value for each z level. recalculated when gravity generators change.
+	///List in the form: list(z level num = max generator gravity in that z level OR the gravity level trait)
+	var/list/gravity_by_z_level = list()
+
 /datum/controller/subsystem/mapping/PreInit()
 	..()
 #ifdef FORCE_MAP
@@ -126,6 +130,7 @@ SUBSYSTEM_DEF(mapping)
 	generate_station_area_list()
 	transit = add_new_zlevel("Transit/Reserved", list(ZTRAIT_RESERVED = TRUE))
 	initialize_reserved_level(transit.z_value)
+	calculate_default_z_level_gravities()
 	return SS_INIT_SUCCESS
 
 /datum/controller/subsystem/mapping/fire(resumed)
@@ -617,6 +622,9 @@ GLOBAL_LIST_EMPTY(the_station_areas)
 /// - Adds to z_list, and builds its area turfs
 /datum/controller/subsystem/mapping/proc/manage_z_level(datum/space_level/new_z, filled_with_space, contain_turfs = TRUE)
 	z_list += new_z
+
+	gravity_by_z_level.len += 1
+
 	if(contain_turfs)
 		build_area_turfs(new_z.z_value, filled_with_space)
 
@@ -632,6 +640,10 @@ GLOBAL_LIST_EMPTY(the_station_areas)
 		var/area/our_area = to_contain.loc
 		our_area.contained_turfs += to_contain
 
+/datum/controller/subsystem/mapping/proc/calculate_default_z_level_gravities()
+	for(var/z_level in 1 to length(z_list))
+		calculate_z_level_gravity(z_level)
+
 /datum/controller/subsystem/mapping/proc/generate_z_level_linkages()
 	for(var/z_level in 1 to length(z_list))
 		generate_linkages_for_z_level(z_level)
@@ -650,3 +662,16 @@ GLOBAL_LIST_EMPTY(the_station_areas)
 	multiz_levels[z_level] = new /list(LARGEST_Z_LEVEL_INDEX)
 	multiz_levels[z_level][Z_LEVEL_UP] = !!z_above
 	multiz_levels[z_level][Z_LEVEL_DOWN] = !!z_below
+
+/datum/controller/subsystem/mapping/proc/calculate_z_level_gravity(z_level_number)
+	if(!isnum(z_level_number) || z_level_number < 1)
+		return FALSE
+
+	var/max_gravity = 0
+
+	for(var/obj/machinery/gravity_generator/main/grav_gen as anything in GLOB.gravity_generators["[z_level_number]"])
+		max_gravity = max(grav_gen.setting, max_gravity)
+
+	max_gravity = max_gravity || level_trait(z_level_number, ZTRAIT_GRAVITY) || 0 //just to make sure no nulls
+	gravity_by_z_level[z_level_number] = max_gravity
+	return max_gravity

code/datums/components/caltrop.dm

@@ -55,7 +55,7 @@
 		if(!(flags & CALTROP_BYPASS_SHOES) && (H.shoes || feetCover))
 			return
 
-		if((H.movement_type & (FLYING|FLOATING)) || (H.body_position == LYING_DOWN)|| H.buckled)
+		if((H.movement_type & MOVETYPES_NOT_TOUCHING_GROUND) || (H.body_position == LYING_DOWN)|| H.buckled)
 			return
 
 		var/damage = rand(min_damage, max_damage)

code/datums/components/chasm.dm

@@ -69,7 +69,7 @@
 		return FALSE
 	if(!isliving(AM) && !isobj(AM))
 		return FALSE
-	if(is_type_in_typecache(AM, forbidden_types) || AM.throwing || (AM.movement_type & (FLOATING|FLYING)))
+	if(is_type_in_typecache(AM, forbidden_types) || AM.throwing || (AM.movement_type & MOVETYPES_NOT_TOUCHING_GROUND))
 		return FALSE
 	//Flies right over the chasm
 	if(ismob(AM))

code/datums/components/conveyor_movement.dm

@@ -24,7 +24,7 @@
 	source.delay = speed //We use the default delay
 	if(living_parent)
 		var/mob/living/moving_mob = parent
-		if((moving_mob.movement_type & (FLOATING|FLYING)) && !moving_mob.stat)
+		if((moving_mob.movement_type & MOVETYPES_NOT_TOUCHING_GROUND) && !moving_mob.stat)
 			return MOVELOOP_SKIP_STEP
 	var/atom/movable/moving_parent = parent
 	if(moving_parent.anchored || !moving_parent.has_gravity())

code/datums/components/slippery.dm

@@ -34,7 +34,7 @@
 	if(!isliving(arrived))
 		return
 	var/mob/living/victim = arrived
-	if(!(victim.movement_type & (FLOATING|FLYING)) && victim.slip(knockdown_time, parent, lube_flags, paralyze_time, force_drop_items) && callback)
+	if(!(victim.movement_type & MOVETYPES_NOT_TOUCHING_GROUND) && victim.slip(knockdown_time, parent, lube_flags, paralyze_time, force_drop_items) && callback)
 		callback.Invoke(victim)
 
 /datum/component/slippery/UnregisterFromParent()

code/datums/components/spikes.dm

@@ -58,7 +58,7 @@
 		if(ishuman(C))
 			var/mob/living/carbon/human/H = C
 			var/feetCover = (H.wear_suit && (H.wear_suit.body_parts_covered & FEET)) || (H.w_uniform && (H.w_uniform.body_parts_covered & FEET))
-			if((H.movement_type & (FLOATING|FLYING)) || H.body_position == LYING_DOWN || H.buckled || H.shoes || feetCover)
+			if((H.movement_type & MOVETYPES_NOT_TOUCHING_GROUND) || H.body_position == LYING_DOWN || H.buckled || H.shoes || feetCover)
 				prick(H, 0.5)
 			else
 				prick(H, 2)

code/datums/components/squashable.dm

@@ -53,7 +53,7 @@
 
 	if(isliving(crossing_movable))
 		var/mob/living/crossing_mob = crossing_movable
-		if(crossing_mob.mob_size > MOB_SIZE_SMALL && !(crossing_mob.movement_type & (FLOATING|FLYING)))
+		if(crossing_mob.mob_size > MOB_SIZE_SMALL && !(crossing_mob.movement_type & MOVETYPES_NOT_TOUCHING_GROUND))
 			if(HAS_TRAIT(crossing_mob, TRAIT_PACIFISM))
 				crossing_mob.visible_message("<span class='notice'>[crossing_mob] carefully steps over [parent_as_living].</span>", "<span class='notice'>You carefully step over [parent_as_living] to avoid hurting it.</span>")
 				return

code/datums/components/squeak.dm

@@ -94,7 +94,7 @@
 				return
 	if(istype(arrived, /obj/effect/dummy/phased_mob)) //don't squeek if they're in a phased/jaunting container.
 		return
-	if(arrived.movement_type & (FLYING|FLOATING) || !arrived.has_gravity())
+	if(arrived.movement_type & MOVETYPES_NOT_TOUCHING_GROUND || !arrived.has_gravity())
 		return
 	var/atom/current_parent = parent
 	if(isturf(current_parent?.loc))

code/datums/elements/forced_gravity.dm

@@ -4,29 +4,34 @@
 	var/gravity
 	var/ignore_space
 
-/datum/element/forced_gravity/Attach(datum/target, gravity=1, ignore_space=FALSE)
+/datum/element/forced_gravity/Attach(datum/target, gravity=1, ignore_space=FALSE, can_override = FALSE)
 	. = ..()
 	if(!isatom(target))
 		return ELEMENT_INCOMPATIBLE
 
 	src.gravity = gravity
 	src.ignore_space = ignore_space
 
-	RegisterSignal(target, COMSIG_ATOM_HAS_GRAVITY, PROC_REF(gravity_check))
+	RegisterSignal(target, COMSIG_ATOM_HAS_GRAVITY, PROC_REF(gravity_check), override = can_override)
 	if(isturf(target))
-		RegisterSignal(target, COMSIG_TURF_HAS_GRAVITY, PROC_REF(turf_gravity_check))
+		RegisterSignal(target, COMSIG_TURF_HAS_GRAVITY, PROC_REF(turf_gravity_check), override = can_override)
+
+	ADD_TRAIT(target, TRAIT_FORCED_GRAVITY, REF(src))
 
 /datum/element/forced_gravity/Detach(datum/source, force)
 	. = ..()
 	var/static/list/signals_b_gone = list(COMSIG_ATOM_HAS_GRAVITY, COMSIG_TURF_HAS_GRAVITY)
 	UnregisterSignal(source, signals_b_gone)
+	REMOVE_TRAIT(source, TRAIT_FORCED_GRAVITY, REF(src))
 
 /datum/element/forced_gravity/proc/gravity_check(datum/source, turf/location, list/gravs)
 	SIGNAL_HANDLER
-	if(!ignore_space && isspaceturf(location))
-		return
+	if(!ignore_space && location.force_no_gravity)
+		return FALSE
 	gravs += gravity
 
+	return TRUE
+
 /datum/element/forced_gravity/proc/turf_gravity_check(datum/source, atom/checker, list/gravs)
 	SIGNAL_HANDLER
-	return gravity_check(null, source, gravs)
+	gravity_check(null, source, gravs)

code/datums/elements/movetype_handler.dm

@@ -52,18 +52,24 @@
 	if(!(source.movement_type & (FLOATING|FLYING)) && (trait == TRAIT_MOVE_FLYING || trait == TRAIT_MOVE_FLOATING) && !paused_floating_anim_atoms[source] && !HAS_TRAIT(source, TRAIT_NO_FLOATING_ANIM))
 		DO_FLOATING_ANIM(source)
 	source.movement_type |= flag
-	SEND_SIGNAL(source, COMSIG_MOVETYPE_FLAG_ENABLED, flag)
+	if((trait == TRAIT_MOVE_FLYING || trait == TRAIT_MOVE_FLOATING) && !(source.movement_type & (FLOATING|FLYING)))
+		stop_floating(source)
+	SEND_SIGNAL(source, COMSIG_MOVETYPE_FLAG_DISABLED, flag)
 
 /// Called when a movement type trait is removed from the movable. Disables the relative bitflag if it wasn't there in the compile-time bitfield.
 /datum/element/movetype_handler/proc/on_movement_type_trait_loss(atom/movable/source, trait)
 	SIGNAL_HANDLER
 	var/flag = GLOB.movement_type_trait_to_flag[trait]
 	if(initial(source.movement_type) & flag)
 		return
+	var/old_state = source.movement_type
 	source.movement_type &= ~flag
-	if((trait == TRAIT_MOVE_FLYING || trait == TRAIT_MOVE_FLOATING) && !(source.movement_type & (FLOATING|FLYING)))
+	if((old_state & (FLOATING|FLYING)) && !(source.movement_type & (FLOATING|FLYING)))
 		stop_floating(source)
-	SEND_SIGNAL(source, COMSIG_MOVETYPE_FLAG_DISABLED, flag)
+		var/turf/pitfall = source.loc //Things that don't fly fall in open space.
+		if(istype(pitfall))
+			pitfall.zFall(source)
+	SEND_SIGNAL(source, COMSIG_MOVETYPE_FLAG_DISABLED, flag, old_state)
 
 /// Called when the TRAIT_NO_FLOATING_ANIM trait is added to the movable. Stops it from bobbing up and down.
 /datum/element/movetype_handler/proc/on_no_floating_anim_trait_gain(atom/movable/source, trait)

code/datums/proximity_monitor/fields/gravity.dm

@@ -9,7 +9,7 @@
 
 /datum/proximity_monitor/advanced/gravity/setup_field_turf(turf/T)
 	. = ..()
-	T.AddElement(/datum/element/forced_gravity, gravity_value)
+	T.AddElement(/datum/element/forced_gravity, gravity_value, can_override = TRUE)
 	modified_turfs[T] = gravity_value
 
 /datum/proximity_monitor/advanced/gravity/cleanup_field_turf(turf/T)

code/datums/weather/weather_types/floor_is_lava.dm

@@ -35,6 +35,6 @@
 		return
 	if(!L.client) //Only sentient people are going along with it!
 		return
-	if(L.movement_type & (FLOATING|FLYING))
+	if(L.movement_type & MOVETYPES_NOT_TOUCHING_GROUND)
 		return
 	L.adjustFireLoss(3)

code/game/atoms.dm

@@ -1897,6 +1897,12 @@ CREATION_TEST_IGNORE_SUBTYPES(/atom)
  * Sends signals [COMSIG_ATOM_HAS_GRAVITY] and [COMSIG_TURF_HAS_GRAVITY], both can force gravity with
  * the forced gravity var.
  *
+ * HEY JACKASS, LISTEN
+ * IF YOU ADD SOMETHING TO THIS PROC, MAKE SURE /mob/living ACCOUNTS FOR IT
+ *
+ * Living mobs treat gravity in an event based manner. We've decomposed this proc into different checks
+ * for them to use. If you add more to it, make sure you do that, or things will behave strangely
+ *
  * Gravity situations:
  * * No gravity if you're not in a turf
  * * No gravity if this atom is in is a space turf
@@ -1909,32 +1915,25 @@ CREATION_TEST_IGNORE_SUBTYPES(/atom)
 	if(!isturf(gravity_turf))
 		gravity_turf = get_turf(src)
 
-		if(!gravity_turf)
+		if(!gravity_turf)//no gravity in nullspace
 			return FALSE
 
 	var/list/forced_gravity = list()
 	SEND_SIGNAL(src, COMSIG_ATOM_HAS_GRAVITY, gravity_turf, forced_gravity)
-	if(!length(forced_gravity))
-		SEND_SIGNAL(gravity_turf, COMSIG_TURF_HAS_GRAVITY, src, forced_gravity)
+	SEND_SIGNAL(gravity_turf, COMSIG_TURF_HAS_GRAVITY, src, forced_gravity)
 	if(length(forced_gravity))
-		var/max_grav
-		for(var/i in forced_gravity)
-			max_grav = max(max_grav, i)
-		return max_grav
+		var/positive_grav = max(forced_gravity)
+		var/negative_grav = min(min(forced_gravity), 0) //negative grav needs to be below or equal to 0
 
-	if(!gravity_turf.check_gravity()) // Turf never has gravity
-		return FALSE
-	var/area/A = get_area(gravity_turf)
-	if(A.has_gravity) // Areas which always has gravity
-		return TRUE
-	else if(SSmapping.level_trait(gravity_turf.z, ZTRAIT_GRAVITY)) // If the z-level always has gravity
-		return TRUE
-	else if(GLOB.gravity_generators["[gravity_turf.get_virtual_z_level()]"]) // If there's a gravity generator on our z level
-		var/max_grav = 0
-		for(var/obj/machinery/gravity_generator/main/G in GLOB.gravity_generators["[gravity_turf.get_virtual_z_level()]"])
-			max_grav = max(G.setting,max_grav)
-		return max_grav
-	return FALSE
+		//our gravity is sum of the most massive positive and negative numbers returned by the signal
+		//so that adding two forced_gravity elements with an effect size of 1 each doesnt add to 2 gravity
+		//but negative force gravity effects can cancel out positive ones
+
+		return (positive_grav + negative_grav)
+
+	var/area/turf_area = gravity_turf.loc
+
+	return !gravity_turf.force_no_gravity && (SSmapping.gravity_by_z_level[gravity_turf.z] || turf_area.has_gravity)
 
 /*
 * Called when something made out of plasma is exposed to high temperatures.

code/game/objects/effects/mines.dm

@@ -125,7 +125,7 @@
 /obj/effect/mine/proc/on_entered(datum/source, atom/movable/AM)
 	SIGNAL_HANDLER
 
-	if(!isturf(loc) || AM.throwing || (AM.movement_type & (FLYING | FLOATING)) || !AM.has_gravity() || triggered)
+	if(!isturf(loc) || AM.throwing || (AM.movement_type & MOVETYPES_NOT_TOUCHING_GROUND) || !AM.has_gravity() || triggered)
 		return
 	if(ismob(AM))
 		checksmartmine(AM)