Foam can pass through tables and computers and grilles (#89636)

code/__DEFINES/traits/declarations.dm

@@ -582,6 +582,8 @@ Remember to update _globalvars/traits.dm if you're adding/removing/renaming trai
 
 /// Does the mob ignore elevation? (e.g. xeno larvas on hiding)
 #define TRAIT_IGNORE_ELEVATION "ignore_elevation"
+/// Is the mob currently elevated? (eg standing on a table)
+#define TRAIT_MOB_ELEVATED "mob_elevated"
 
 /// Prevents you from twohanding weapons.
 #define TRAIT_NO_TWOHANDING "no_twohanding"
@@ -1096,6 +1098,8 @@ Remember to update _globalvars/traits.dm if you're adding/removing/renaming trai
 #define TRAIT_NO_MIRROR_REFLECTION "no_mirror_reflection"
 /// If this movable is currently treading in a turf with the immerse element.
 #define TRAIT_IMMERSED "immersed"
+/// From [/datum/element/elevation] for purpose of checking if the object causes things in its turf to become elevated
+#define TRAIT_ELEVATING_OBJECT "elevating_object"
 /// From [/datum/element/elevation_core] for purpose of checking if the turf has the trait from an instance of the element
 #define TRAIT_ELEVATED_TURF "elevated_turf"
 /**

code/_globalvars/traits/_traits.dm

@@ -19,6 +19,7 @@ GLOBAL_LIST_INIT(traits_by_type, list(
 		"TRAIT_DO_NOT_SPLASH" = TRAIT_DO_NOT_SPLASH,
 		"TRAIT_DRIED" = TRAIT_DRIED,
 		"TRAIT_DRYABLE" = TRAIT_DRYABLE,
+		"TRAIT_ELEVATING_OBJECT" = TRAIT_ELEVATING_OBJECT,
 		"TRAIT_FISHING_SPOT" = TRAIT_FISHING_SPOT,
 		"TRAIT_FOOD_CHEF_MADE" = TRAIT_FOOD_CHEF_MADE,
 		"TRAIT_FOOD_FRIED" = TRAIT_FOOD_FRIED,
@@ -355,6 +356,7 @@ GLOBAL_LIST_INIT(traits_by_type, list(
 		"TRAIT_MOB_BREEDER" = TRAIT_MOB_BREEDER,
 		"TRAIT_MOB_CAN_DIG" = TRAIT_MOB_CAN_DIG,
 		"TRAIT_MOB_EATER" = TRAIT_MOB_EATER,
+		"TRAIT_MOB_ELEVATED" = TRAIT_MOB_ELEVATED,
 		"TRAIT_MOB_HATCHED" = TRAIT_MOB_HATCHED,
 		"TRAIT_MOB_HIDE_HAPPINESS" = TRAIT_MOB_HIDE_HAPPINESS,
 		"TRAIT_MOB_MERGE_STACKS" = TRAIT_MOB_MERGE_STACKS,

code/datums/elements/elevation.dm

@@ -13,6 +13,8 @@
 	if(!isatom(target) || isarea(target))
 		return ELEMENT_INCOMPATIBLE
 
+	ADD_TRAIT(target, TRAIT_ELEVATING_OBJECT, ref(src))
+
 	src.pixel_shift = pixel_shift
 
 	if(ismovable(target))
@@ -29,6 +31,7 @@
 
 /datum/element/elevation/Detach(atom/movable/source)
 	unregister_turf(source, source.loc)
+	REMOVE_TRAIT(source, TRAIT_ELEVATING_OBJECT, ref(src))
 	return ..()
 
 /datum/element/elevation/proc/reset_elevation(turf/target)
@@ -175,6 +178,7 @@
 	// we want to avoid accidentally double-elevating anything they're buckled to (namely vehicles)
 	if(target.has_offset(source = ELEVATION_SOURCE(src)))
 		return
+	ADD_TRAIT(target, TRAIT_MOB_ELEVATED, ELEVATION_SOURCE(src))
 	// We are buckled to something
 	if(target.buckled)
 		// We are buckled to a vehicle, so it also must be elevated
@@ -190,6 +194,7 @@
 
 /// Reverts elevation of the mob.
 /datum/element/elevation_core/proc/deelevate_mob(mob/living/target, elevate_time = ELEVATE_TIME)
+	REMOVE_TRAIT(target, TRAIT_MOB_ELEVATED, ELEVATION_SOURCE(src))
 	target.remove_offsets(ELEVATION_SOURCE(src), animate = elevate_time > 0)
 	if(isvehicle(target.buckled))
 		animate(target.buckled, pixel_z = -pixel_shift, time = elevate_time, flags = ANIMATION_RELATIVE|ANIMATION_PARALLEL)

code/game/objects/effects/effect_system/fluid_spread/effects_foam.dm

@@ -39,6 +39,8 @@
 	. = ..()
 	if(slippery_foam)
 		AddComponent(/datum/component/slippery, 100)
+	if(HAS_TRAIT(loc, TRAIT_ELEVATED_TURF))
+		layer = WATER_LEVEL_LAYER
 	create_reagents(1000, REAGENT_HOLDER_INSTANT_REACT)
 	playsound(src, 'sound/effects/bubbles/bubbles2.ogg', 80, TRUE, -3)
 	AddElement(/datum/element/atmos_sensitive, mapload)
@@ -96,10 +98,14 @@
 				continue
 			if(turf_location.underfloor_accessibility < UNDERFLOOR_INTERACTABLE && HAS_TRAIT(object, TRAIT_T_RAY_VISIBLE))
 				continue
+			if (HAS_TRAIT(loc, TRAIT_ELEVATED_TURF) && !HAS_TRAIT(object, TRAIT_ELEVATING_OBJECT))
+				continue // Do expose tables, don't expose items on tables
 			reagents.expose(object, VAPOR, fraction)
 
 	var/hit = 0
 	for(var/mob/living/foamer in loc)
+		if (HAS_TRAIT(foamer, TRAIT_MOB_ELEVATED))
+			continue
 		hit += foam_mob(foamer, seconds_per_tick)
 	if(hit)
 		lifetime += ds_seconds_per_tick //this is so the decrease from mobs hit and the natural decrease don't cumulate.
@@ -137,6 +143,7 @@
 		return FALSE
 
 	var/datum/can_pass_info/info = new(no_id = TRUE)
+	info.pass_flags = PASSTABLE | PASSGRILLE | PASSMACHINE | PASSSTRUCTURE
 	for(var/iter_dir in GLOB.cardinals)
 		var/turf/spread_turf = get_step(src, iter_dir)
 		if(spread_turf?.density || spread_turf.LinkBlockedWithAccess(spread_turf, info))
@@ -149,6 +156,8 @@
 			continue
 
 		for(var/mob/living/foaming in spread_turf)
+			if (HAS_TRAIT(foaming, TRAIT_MOB_ELEVATED))
+				continue
 			foam_mob(foaming, seconds_per_tick)
 
 		var/obj/effect/particle_effect/fluid/foam/spread_foam = new type(spread_turf, group, src)