[MIRROR] A comprehensive refactor / cleanup of bullet_hit and `on_h…

…it` to cut out a single bad species / mob proc [MDB IGNORE] (#24430)

* A comprehensive refactor / cleanup of `bullet_hit` and `on_hit` to cut out a single bad species / mob proc (#79024)

## About The Pull Request

- Refactored `bullet_act`. Adds `should_call_parent` and refactors
associated children to support that.
   - Fixes silicons sparking off when hit by disabler fire.
- Desnowflakes firing range target integrity and cleans up its
bullet-hole code a bit.
- Cleans up changeling tentacle code a fair bit and fixes it not taking
off throw mode if you fail to catch something.
   - The Sleeping Carp deflection is now signalized
- Nightmare projectile dodging is now signalized and sourced from the
Nightmare's brain rather than species
- Refactored how cardboard cutouts get knocked over to be less
snowflaked / use integrity
- Also adds projectile `on_hit` `should_call_parent` and cleans up a bit
of that, particularly their arguments.
- On hit arguments were passed wrong this entire time, it's a good thing
nothing relied on that.

## Why It's Good For The Game

This is cringe.

https://github.com/tgstation/tgstation/blob/1863eb2cd82e7cee4fdfff37b42d3fd0c7edd797/code/modules/mob/living/carbon/human/_species.dm#L1430-L1442

Bullets should overall act more consistent across mob types and objects.

## Changelog

:cl: Melbert
fix: Silicons don't spark when shot by disablers
fix: Changelings who fail to catch something with a tencacle will have
throw mode disabled automatically
fix: Fixes occasions where you can reflect with Sleeping Carp when you
shouldn't be able to
fix: Fixes some projectiles causing like 20x less eye blur than they
should be
refactor: Refactored bullet-mob interactions
refactor: Nightmare "shadow dodge" projectile ability is now sourced
from their brain
/:cl:

* A comprehensive refactor / cleanup of `bullet_hit` and `on_hit` to cut out a single bad species / mob proc

* Modular changes

---------

Co-authored-by: MrMelbert <[email protected]>
Co-authored-by: Giz <[email protected]>

code/__DEFINES/dcs/signals/signals_atom/signals_atom_x_act.dm

@@ -15,6 +15,14 @@
 ///from base of atom/fire_act(): (exposed_temperature, exposed_volume)
 #define COMSIG_ATOM_FIRE_ACT "atom_fire_act"
 ///from base of atom/bullet_act(): (/obj/projectile, def_zone)
+#define COMSIG_ATOM_PRE_BULLET_ACT "pre_atom_bullet_act"
+	/// All this does is prevent default bullet on_hit from being called, [BULLET_ACT_HIT] being return is implied
+	#define COMPONENT_BULLET_ACTED (1<<0)
+	/// Forces bullet act to return [BULLET_ACT_BLOCK], takes priority over above
+	#define COMPONENT_BULLET_BLOCKED (1<<1)
+	/// Forces bullet act to return [BULLET_ACT_FORCE_PIERCE], takes priority over above
+	#define COMPONENT_BULLET_PIERCED (1<<2)
+///from base of atom/bullet_act(): (/obj/projectile, def_zone)
 #define COMSIG_ATOM_BULLET_ACT "atom_bullet_act"
 ///from base of atom/CheckParts(): (list/parts_list, datum/crafting_recipe/R)
 #define COMSIG_ATOM_CHECKPARTS "atom_checkparts"

code/datums/components/singularity.dm

@@ -101,7 +101,7 @@
 	)
 	AddComponent(/datum/component/connect_loc_behalf, parent, loc_connections)
 
-	RegisterSignal(parent, COMSIG_ATOM_BULLET_ACT, PROC_REF(consume_bullets))
+	RegisterSignal(parent, COMSIG_ATOM_PRE_BULLET_ACT, PROC_REF(consume_bullets))
 
 	if (notify_admins)
 		admin_investigate_setup()
@@ -127,7 +127,7 @@
 		COMSIG_ATOM_ATTACK_PAW,
 		COMSIG_ATOM_BLOB_ACT,
 		COMSIG_ATOM_BSA_BEAM,
-		COMSIG_ATOM_BULLET_ACT,
+		COMSIG_ATOM_PRE_BULLET_ACT,
 		COMSIG_ATOM_BUMPED,
 		COMSIG_MOVABLE_PRE_MOVE,
 		COMSIG_ATOM_ATTACKBY,
@@ -180,6 +180,7 @@
 	SIGNAL_HANDLER
 
 	qdel(projectile)
+	return COMPONENT_BULLET_BLOCKED
 
 /// Calls singularity_act on the thing passed, usually destroying the object
 /datum/component/singularity/proc/default_singularity_act(atom/thing)

code/datums/martial/_martial.dm

@@ -101,7 +101,3 @@
 	if(help_verb)
 		remove_verb(holder_living, help_verb)
 	return
-
-///Gets called when a projectile hits the owner. Returning anything other than BULLET_ACT_HIT will stop the projectile from hitting the mob.
-/datum/martial_art/proc/on_projectile_hit(mob/living/attacker, obj/projectile/P, def_zone)
-	return BULLET_ACT_HIT

code/datums/martial/sleeping_carp.dm

@@ -15,11 +15,13 @@
 		return
 	target.add_traits(list(TRAIT_NOGUNS, TRAIT_HARDLY_WOUNDED, TRAIT_NODISMEMBER), SLEEPING_CARP_TRAIT)
 	RegisterSignal(target, COMSIG_ATOM_ATTACKBY, PROC_REF(on_attackby))
+	RegisterSignal(target, COMSIG_ATOM_PRE_BULLET_ACT, PROC_REF(hit_by_projectile))
 	target.faction |= FACTION_CARP //:D
 
 /datum/martial_art/the_sleeping_carp/on_remove(mob/living/target)
 	target.remove_traits(list(TRAIT_NOGUNS, TRAIT_HARDLY_WOUNDED, TRAIT_NODISMEMBER), SLEEPING_CARP_TRAIT)
 	UnregisterSignal(target, COMSIG_ATOM_ATTACKBY)
+	UnregisterSignal(target, COMSIG_ATOM_PRE_BULLET_ACT)
 	target.faction -= FACTION_CARP //:(
 	. = ..()
 
@@ -113,6 +115,8 @@
 	return ..()
 
 /datum/martial_art/the_sleeping_carp/proc/can_deflect(mob/living/carp_user)
+	if(!can_use(carp_user) || !carp_user.throw_mode)
+		return FALSE
 	if(carp_user.incapacitated(IGNORE_GRAB)) //NO STUN
 		return FALSE
 	if(!(carp_user.mobility_flags & MOBILITY_USE)) //NO UNABLE TO USE
@@ -124,17 +128,20 @@
 		return FALSE
 	return TRUE
 
-/datum/martial_art/the_sleeping_carp/on_projectile_hit(mob/living/carp_user, obj/projectile/P, def_zone)
-	. = ..()
+/datum/martial_art/the_sleeping_carp/proc/hit_by_projectile(mob/living/carp_user, obj/projectile/hitting_projectile, def_zone)
+	SIGNAL_HANDLER
+
 	if(!can_deflect(carp_user))
-		return BULLET_ACT_HIT
-	if(carp_user.throw_mode)
-		carp_user.visible_message(span_danger("[carp_user] effortlessly swats the projectile aside! They can block bullets with their bare hands!"), span_userdanger("You deflect the projectile!"))
-		playsound(get_turf(carp_user), pick('sound/weapons/bulletflyby.ogg', 'sound/weapons/bulletflyby2.ogg', 'sound/weapons/bulletflyby3.ogg'), 75, TRUE)
-		P.firer = carp_user
-		P.set_angle(rand(0, 360))//SHING
-		return BULLET_ACT_FORCE_PIERCE
-	return BULLET_ACT_HIT
+		return NONE
+
+	carp_user.visible_message(
+		span_danger("[carp_user] effortlessly swats [hitting_projectile] aside! [carp_user.p_They()] can block bullets with [carp_user.p_their()] bare hands!"),
+		span_userdanger("You deflect [hitting_projectile]!"),
+	)
+	playsound(carp_user, pick('sound/weapons/bulletflyby.ogg', 'sound/weapons/bulletflyby2.ogg', 'sound/weapons/bulletflyby3.ogg'), 75, TRUE)
+	hitting_projectile.firer = carp_user
+	hitting_projectile.set_angle(rand(0, 360))//SHING
+	return COMPONENT_BULLET_PIERCED
 
 ///Signal from getting attacked with an item, for a special interaction with touch spells
 /datum/martial_art/the_sleeping_carp/proc/on_attackby(mob/living/carp_user, obj/item/attack_weapon, mob/attacker, params)

code/game/atom_defense.dm

@@ -151,4 +151,6 @@
 
 /// A cut-out proc for [/atom/proc/bullet_act] so living mobs can have their own armor behavior checks without causing issues with needing their own on_hit call
 /atom/proc/check_projectile_armor(def_zone, obj/projectile/impacting_projectile, is_silent)
+	if(uses_integrity)
+		return clamp(PENETRATE_ARMOUR(get_armor_rating(impacting_projectile.armor_flag), impacting_projectile.armour_penetration), 0, 100)
 	return 0

code/game/atoms.dm

@@ -586,19 +586,33 @@
 /**
  * React to a hit by a projectile object
  *
- * Default behaviour is to send the [COMSIG_ATOM_BULLET_ACT] and then call [on_hit][/obj/projectile/proc/on_hit] on the projectile.
- *
  * @params
- * hitting_projectile - projectile
- * def_zone - zone hit
- * piercing_hit - is this hit piercing or normal?
+ * * hitting_projectile - projectile
+ * * def_zone - zone hit
+ * * piercing_hit - is this hit piercing or normal?
  */
 /atom/proc/bullet_act(obj/projectile/hitting_projectile, def_zone, piercing_hit = FALSE)
+	SHOULD_CALL_PARENT(TRUE)
+
+	var/sigreturn = SEND_SIGNAL(src, COMSIG_ATOM_PRE_BULLET_ACT, hitting_projectile, def_zone)
+	if(sigreturn & COMPONENT_BULLET_PIERCED)
+		return BULLET_ACT_FORCE_PIERCE
+	if(sigreturn & COMPONENT_BULLET_BLOCKED)
+		return BULLET_ACT_BLOCK
+	if(sigreturn & COMPONENT_BULLET_ACTED)
+		return BULLET_ACT_HIT
+
 	SEND_SIGNAL(src, COMSIG_ATOM_BULLET_ACT, hitting_projectile, def_zone)
-	// This armor check only matters for the visuals and messages in on_hit(), it's not actually used to reduce damage since
-	// only living mobs use armor to reduce damage, but on_hit() is going to need the value no matter what is shot.
-	var/visual_armor_check = check_projectile_armor(def_zone, hitting_projectile)
-	. = hitting_projectile.on_hit(src, visual_armor_check, def_zone, piercing_hit)
+	if(QDELETED(hitting_projectile)) // Signal deleted it?
+		return BULLET_ACT_BLOCK
+
+	return hitting_projectile.on_hit(
+		target = src,
+		// This armor check only matters for the visuals and messages in on_hit(), it's not actually used to reduce damage since
+		// only living mobs use armor to reduce damage, but on_hit() is going to need the value no matter what is shot.
+		blocked = check_projectile_armor(def_zone, hitting_projectile),
+		pierce_hit = piercing_hit,
+	)
 
 ///Return true if we're inside the passed in atom
 /atom/proc/in_contents_of(container)//can take class or object instance as argument

code/game/objects/effects/phased_mob.dm

@@ -61,7 +61,8 @@
 /obj/effect/dummy/phased_mob/ex_act()
 	return FALSE
 
-/obj/effect/dummy/phased_mob/bullet_act(blah)
+/obj/effect/dummy/phased_mob/bullet_act(obj/projectile/hitting_projectile, def_zone, piercing_hit = FALSE)
+	SHOULD_CALL_PARENT(FALSE)
 	return BULLET_ACT_FORCE_PIERCE
 
 /obj/effect/dummy/phased_mob/relaymove(mob/living/user, direction)

code/game/objects/items/cardboard_cutouts.dm

@@ -6,6 +6,7 @@
 	icon_state = "cutout_basic"
 	w_class = WEIGHT_CLASS_BULKY
 	resistance_flags = FLAMMABLE
+	obj_flags = CAN_BE_HIT
 	item_flags = NO_PIXEL_RANDOM_DROP
 	/// If the cutout is pushed over and has to be righted
 	var/pushed_over = FALSE
@@ -35,7 +36,7 @@
 
 //ATTACK HAND IGNORING PARENT RETURN VALUE
 /obj/item/cardboard_cutout/attack_hand(mob/living/user, list/modifiers)
-	if(!user.combat_mode || pushed_over)
+	if(!user.combat_mode || pushed_over || !isturf(loc))
 		return ..()
 	user.visible_message(span_warning("[user] pushes over [src]!"), span_danger("You push over [src]!"))
 	playsound(src, 'sound/weapons/genhit.ogg', 50, TRUE)
@@ -60,32 +61,20 @@
 /obj/item/cardboard_cutout/attackby(obj/item/I, mob/living/user, params)
 	if(istype(I, /obj/item/toy/crayon))
 		change_appearance(I, user)
-		return
-	// Why yes, this does closely resemble mob and object attack code.
-	if(I.item_flags & NOBLUDGEON)
-		return
-	if(!I.force)
-		playsound(loc, 'sound/weapons/tap.ogg', get_clamped_volume(), TRUE, -1)
-	else if(I.hitsound)
-		playsound(loc, I.hitsound, get_clamped_volume(), TRUE, -1)
-
-	user.changeNext_move(CLICK_CD_MELEE)
-	user.do_attack_animation(src)
-
-	if(I.force)
-		user.visible_message(span_danger("[user] hits [src] with [I]!"), \
-			span_danger("You hit [src] with [I]!"))
-		if(prob(I.force))
-			push_over()
-
-/obj/item/cardboard_cutout/bullet_act(obj/projectile/P, def_zone, piercing_hit = FALSE)
-	if(istype(P, /obj/projectile/bullet))
-		P.on_hit(src, 0, piercing_hit)
-	visible_message(span_danger("[src] is hit by [P]!"))
-	playsound(src, 'sound/weapons/slice.ogg', 50, TRUE)
-	if(prob(P.damage))
+		return TRUE
+
+	return ..()
+
+/obj/item/cardboard_cutout/take_damage(damage_amount, damage_type, damage_flag, sound_effect, attack_dir, armour_penetration)
+	. = ..()
+	var/damage_sustained = . || 0
+	if((damage_flag == BULLET || damage_flag == MELEE) && (damage_type == BRUTE) && prob(damage_sustained))
 		push_over()
-	return BULLET_ACT_HIT
+
+/obj/item/cardboard_cutout/deconstruct(disassembled)
+	if(!(flags_1 & (HOLOGRAM_1|NODECONSTRUCT_1)))
+		new /obj/item/stack/sheet/cardboard(loc, 1)
+	return ..()
 
 /proc/get_cardboard_cutout_instance(datum/cardboard_cutout/cardboard_cutout)
 	ASSERT(ispath(cardboard_cutout), "[cardboard_cutout] is not a path of /datum/cardboard_cutout")

code/game/objects/items/crayons.dm

@@ -815,7 +815,8 @@
 			carbon_target.set_eye_blur_if_lower(6 SECONDS)
 			carbon_target.adjust_temp_blindness(2 SECONDS)
 		if(carbon_target.get_eye_protection() <= 0) // no eye protection? ARGH IT BURNS. Warning: don't add a stun here. It's a roundstart item with some quirks.
-			carbon_target.apply_effects(eyeblur = 5, jitter = 10)
+			carbon_target.adjust_jitter(1 SECONDS)
+			carbon_target.adjust_eye_blur(0.5 SECONDS)
 			flash_color(carbon_target, flash_color=paint_color, flash_time=40)
 		if(ishuman(carbon_target) && actually_paints)
 			var/mob/living/carbon/human/human_target = carbon_target

code/game/objects/items/melee/misc.dm

@@ -235,6 +235,7 @@
 	shard.countdown = null
 	START_PROCESSING(SSobj, src)
 	visible_message(span_warning("[src] appears, balanced ever so perfectly on its hilt. This isn't ominous at all."))
+	RegisterSignal(src, COMSIG_ATOM_PRE_BULLET_ACT, PROC_REF(eat_bullets))
 
 /obj/item/melee/supermatter_sword/process()
 	if(balanced || throwing || ismob(src.loc) || isnull(src.loc))
@@ -283,11 +284,16 @@
 	consume_everything()
 	return TRUE
 
-/obj/item/melee/supermatter_sword/bullet_act(obj/projectile/projectile)
-	visible_message(span_danger("[projectile] smacks into [src] and rapidly flashes to ash."),\
-	span_hear("You hear a loud crack as you are washed with a wave of heat."))
-	consume_everything(projectile)
-	return BULLET_ACT_HIT
+/obj/item/melee/supermatter_sword/proc/eat_bullets(datum/source, obj/projectile/hitting_projectile)
+	SIGNAL_HANDLER
+
+	visible_message(
+		span_danger("[hitting_projectile] smacks into [source] and rapidly flashes to ash."),
+		null,
+		span_hear("You hear a loud crack as you are washed with a wave of heat."),
+	)
+	consume_everything(hitting_projectile)
+	return COMPONENT_BULLET_BLOCKED
 
 /obj/item/melee/supermatter_sword/suicide_act(mob/living/user)
 	user.visible_message(span_suicide("[user] touches [src]'s blade. It looks like [user.p_theyre()] tired of waiting for the radiation to kill [user.p_them()]!"))

code/game/objects/items/shooting_range.dm

@@ -4,73 +4,84 @@
 	icon = 'icons/obj/structures.dmi'
 	icon_state = "target_h"
 	density = FALSE
-	var/hp = 1800
+	max_integrity = 1800
+	item_flags = CAN_BE_HIT
 	/// Lazylist to keep track of bullet-hole overlays.
 	var/list/bullethole_overlays
 
-/obj/item/target/welder_act(mob/living/user, obj/item/I)
-	..()
-	if(I.use_tool(src, user, 0, volume=40))
-		for (var/bullethole in bullethole_overlays)
-			cut_overlay(bullethole)
-		bullethole_overlays = null
-		to_chat(user, span_notice("You slice off [src]'s uneven chunks of aluminium and scorch marks."))
+/obj/item/target/welder_act(mob/living/user, obj/item/tool)
+	if(tool.use_tool(src, user, 0 SECONDS, volume = 40))
+		LAZYNULL(bullethole_overlays)
+		balloon_alert(user, "target repaired")
+		update_appearance(UPDATE_OVERLAYS)
 	return TRUE
 
+/obj/item/target/update_overlays()
+	. = ..()
+	. |= bullethole_overlays
+
+/obj/item/target/bullet_act(obj/projectile/hitting_projectile, def_zone, piercing_hit = FALSE)
+	if(prob(25))
+		return ..() // RNG change to just not leave a mark, like walls
+	if(length(overlays) > 35)
+		return ..() // Too many bullets, we're done here
+
+	// Projectiles which do not deal damage will not leave dent / scorch mark graphics.
+	// However we snowflake some projectiles to leave them anyway, because they're appropriate.
+	var/static/list/always_leave_marks
+	if(isnull(always_leave_marks))
+		always_leave_marks = typecacheof(list(
+			/obj/projectile/beam/practice,
+			/obj/projectile/beam/laser/carbine/practice,
+		))
+
+	var/is_invalid_damage = hitting_projectile.damage_type != BRUTE && hitting_projectile.damage_type != BURN
+	var/is_safe = !hitting_projectile.is_hostile_projectile()
+	var/is_generic_projectile = !is_type_in_typecache(hitting_projectile, always_leave_marks)
+	if(is_generic_projectile && (is_invalid_damage || is_safe))
+		return ..() // Don't bother unless it's real shit
+
+	var/p_x = hitting_projectile.p_x + pick(0, 0, 0, 0, 0, -1, 1) // really ugly way of coding "sometimes offset p_x!"
+	var/p_y = hitting_projectile.p_y + pick(0, 0, 0, 0, 0, -1, 1)
+	var/icon/our_icon = icon(icon, icon_state)
+	if(!our_icon.GetPixel(p_x, p_y) || hitting_projectile.original != src)
+		return BULLET_ACT_FORCE_PIERCE // We, "missed", I guess?
+
+	. = ..()
+	if(. != BULLET_ACT_HIT)
+		return
+
+	var/image/bullet_hole = image('icons/effects/effects.dmi', "dent", OBJ_LAYER + 0.5)
+	bullet_hole.pixel_x = p_x - 1 //offset correction
+	bullet_hole.pixel_y = p_y - 1
+	if(hitting_projectile.damage_type != BRUTE)
+		bullet_hole.setDir(pick(GLOB.cardinals))// random scorch design
+		if(hitting_projectile.damage < 20 && is_generic_projectile)
+			bullet_hole.icon_state = "light_scorch"
+		else
+			bullet_hole.icon_state = "scorch"
+
+	LAZYADD(bullethole_overlays, bullet_hole)
+	update_appearance(UPDATE_OVERLAYS)
+
 /obj/item/target/syndicate
 	icon_state = "target_s"
 	desc = "A shooting target that looks like syndicate scum."
-	hp = 2600
+	max_integrity = 2600
 
 /obj/item/target/alien
 	icon_state = "target_q"
 	desc = "A shooting target that looks like a xenomorphic alien."
-	hp = 2350
+	max_integrity = 2350
 
 /obj/item/target/alien/anchored
 	anchored = TRUE
 
 /obj/item/target/clown
 	icon_state = "target_c"
 	desc = "A shooting target that looks like a useless clown."
-	hp = 2000
-
-#define DECALTYPE_SCORCH 1
-#define DECALTYPE_BULLET 2
+	max_integrity = 2000
 
 /obj/item/target/clown/bullet_act(obj/projectile/P)
 	. = ..()
-	playsound(src.loc, 'sound/items/bikehorn.ogg', 50, TRUE)
-
-/obj/item/target/bullet_act(obj/projectile/P)
-	if(istype(P, /obj/projectile/bullet)) // If it's a foam dart, don't bother with any of this other shit
-		return P.on_hit(src, 0)
-	var/p_x = P.p_x + pick(0,0,0,0,0,-1,1) // really ugly way of coding "sometimes offset P.p_x!"
-	var/p_y = P.p_y + pick(0,0,0,0,0,-1,1)
-	var/decaltype = DECALTYPE_SCORCH
-	if(istype(P, /obj/projectile/bullet))
-		decaltype = DECALTYPE_BULLET
-	var/icon/C = icon(icon,icon_state)
-	if(C.GetPixel(p_x, p_y) && P.original == src && overlays.len <= 35) // if the located pixel isn't blank (null)
-		hp -= P.damage
-		if(hp <= 0)
-			visible_message(span_danger("[src] breaks into tiny pieces and collapses!"))
-			qdel(src)
-		var/image/bullet_hole = image('icons/effects/effects.dmi', "scorch", OBJ_LAYER + 0.5)
-		bullet_hole.pixel_x = p_x - 1 //offset correction
-		bullet_hole.pixel_y = p_y - 1
-		if(decaltype == DECALTYPE_SCORCH)
-			bullet_hole.setDir(pick(NORTH,SOUTH,EAST,WEST))// random scorch design
-			if(P.damage >= 20 || istype(P, /obj/projectile/beam/practice))
-				bullet_hole.setDir(pick(NORTH,SOUTH,EAST,WEST))
-			else
-				bullet_hole.icon_state = "light_scorch"
-		else
-			bullet_hole.icon_state = "dent"
-		LAZYADD(bullethole_overlays, bullet_hole)
-		add_overlay(bullet_hole)
-		return BULLET_ACT_HIT
-	return BULLET_ACT_FORCE_PIERCE
-
-#undef DECALTYPE_SCORCH
-#undef DECALTYPE_BULLET
+	playsound(src, 'sound/items/bikehorn.ogg', 50, TRUE)