Adds a HUD icon for crit marines for vampire lurker (#6314)

# About the pull request
Adds an HUD icon for marines that can be headbited for vampire
This was comically complicated to add
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# Explain why it's good for the game
Rather than having to spam headbite 20 times until someone is actually
unconcious, adds a neat HUD icon.
# Testing Photographs and Procedure
<details>
<summary>Screenshots & Videos</summary>

Put screenshots and videos here with an empty line between the
screenshots and the `<details>` tags.

</details>


# Changelog
:cl:
qol: Added an hud icon for vampires that lets them know when an enemy
can be executed.
/:cl:

---------

Co-authored-by: harryob <[email protected]>

code/__DEFINES/mob_hud.dm

@@ -13,6 +13,7 @@
 #define XENO_HOSTILE_SLOW "13" // xeno-inflicted slow. used by a bunch of MOBA xenos stuff
 #define XENO_HOSTILE_TAG "14" // dancer prae 'tag'
 #define XENO_HOSTILE_FREEZE "15" // Any xeno-inflifcted root
+#define XENO_EXECUTE "28" // Execute thershold, vampire
 
 #define HEALTH_HUD_XENO "16" // health HUD for xenos
 #define PLASMA_HUD "17" // indicates the plasma level of xenos.
@@ -45,6 +46,7 @@
 #define MOB_HUD_FACTION_PMC 15
 #define MOB_HUD_HUNTER 16
 #define MOB_HUD_HUNTER_CLAN 17
+#define MOB_HUD_EXECUTE 18
 
 //for SL/FTL/LZ targeting on locator huds
 #define TRACKER_SL "track_sl"

code/datums/mob_hud.dm

@@ -18,7 +18,8 @@ GLOBAL_LIST_INIT_TYPED(huds, /datum/mob_hud, list(
 	MOB_HUD_FACTION_CLF = new /datum/mob_hud/faction/clf(),
 	MOB_HUD_FACTION_PMC = new /datum/mob_hud/faction/pmc(),
 	MOB_HUD_HUNTER = new /datum/mob_hud/hunter_hud(),
-	MOB_HUD_HUNTER_CLAN = new /datum/mob_hud/hunter_clan()
+	MOB_HUD_HUNTER_CLAN = new /datum/mob_hud/hunter_clan(),
+	MOB_HUD_EXECUTE = new /datum/mob_hud/execute_hud(),
 	))
 
 /datum/mob_hud
@@ -167,6 +168,9 @@ GLOBAL_LIST_INIT_TYPED(huds, /datum/mob_hud, list(
 /datum/mob_hud/xeno_hostile
 	hud_icons = list(XENO_HOSTILE_ACID, XENO_HOSTILE_SLOW, XENO_HOSTILE_TAG, XENO_HOSTILE_FREEZE)
 
+/datum/mob_hud/execute_hud
+	hud_icons = list(XENO_EXECUTE)
+
 /datum/mob_hud/hunter_clan
 	hud_icons = list(HUNTER_CLAN)
 
@@ -259,6 +263,11 @@ GLOBAL_LIST_INIT_TYPED(huds, /datum/mob_hud, list(
 		var/datum/mob_hud/hostile_hud = GLOB.huds[MOB_HUD_XENO_HOSTILE]
 		hostile_hud.remove_hud_from(src, src)
 
+	if (execute_hud)
+		execute_hud = FALSE
+		var/datum/mob_hud/execute = GLOB.huds[MOB_HUD_EXECUTE]
+		execute.remove_hud_from(src, src)
+
 
 
 /mob/proc/refresh_huds(mob/source_mob)
@@ -772,6 +781,16 @@ GLOBAL_DATUM(hud_icon_hudfocus, /image)
 	var/image/holder = hud_list[HOLOCARD_HUD]
 	holder.icon_state = holo_card_color ? "holo_card_[holo_card_color]" : "hudblank"
 
+// Vampire Execute HUD
+/mob/living/carbon/human/proc/update_execute_hud()
+	var/image/execute_holder = hud_list[XENO_EXECUTE]
+
+	execute_holder.icon_state = "hudblank"
+	execute_holder.overlays.Cut()
+
+	if(stat == UNCONSCIOUS || (stat != DEAD && HAS_TRAIT(src, TRAIT_KNOCKEDOUT)))
+		execute_holder.overlays += image('icons/mob/hud/hud.dmi', src, "prae_tag")
+
 // Xeno "hostile" HUD
 /mob/living/carbon/human/proc/update_xeno_hostile_hud()
 	var/image/acid_holder = hud_list[XENO_HOSTILE_ACID]

code/modules/mob/living/carbon/human/death.dm

@@ -131,3 +131,5 @@
 	else if(death_data?.cause_name == "existing")
 		// Corpses spawn as gibbed true to avoid sfx, even though they aren't actually gibbed...
 		AddComponent(/datum/component/weed_food)
+
+	update_execute_hud()

code/modules/mob/living/carbon/human/human.dm

@@ -1704,3 +1704,18 @@
 			item.showoff(src)
 			return TRUE
 	return ..()
+
+/mob/living/carbon/human/on_knockedout_trait_gain(datum/source)
+	. = ..()
+
+	update_execute_hud()
+
+	return .
+
+/mob/living/carbon/human/on_knockedout_trait_loss(datum/source)
+	. = ..()
+
+	update_execute_hud()
+
+	return .
+

code/modules/mob/living/carbon/human/human_defines.dm

@@ -137,7 +137,7 @@
 	var/last_chew = 0
 
 	//taken from human.dm
-	hud_possible = list(HEALTH_HUD, STATUS_HUD, STATUS_HUD_OOC, STATUS_HUD_XENO_INFECTION, STATUS_HUD_XENO_CULTIST, ID_HUD, WANTED_HUD, ORDER_HUD, XENO_HOSTILE_ACID, XENO_HOSTILE_SLOW, XENO_HOSTILE_TAG, XENO_HOSTILE_FREEZE, HUNTER_CLAN, HUNTER_HUD, FACTION_HUD, HOLOCARD_HUD)
+	hud_possible = list(HEALTH_HUD, STATUS_HUD, STATUS_HUD_OOC, STATUS_HUD_XENO_INFECTION, STATUS_HUD_XENO_CULTIST, ID_HUD, WANTED_HUD, ORDER_HUD, XENO_HOSTILE_ACID, XENO_HOSTILE_SLOW, XENO_HOSTILE_TAG, XENO_HOSTILE_FREEZE, XENO_EXECUTE, HUNTER_CLAN, HUNTER_HUD, FACTION_HUD, HOLOCARD_HUD)
 	var/embedded_flag //To check if we've need to roll for damage on movement while an item is imbedded in us.
 	var/allow_gun_usage = TRUE
 	var/melee_allowed = TRUE

code/modules/mob/living/carbon/xenomorph/Xenomorph.dm

@@ -218,6 +218,7 @@
 	//////////////////////////////////////////////////////////////////
 	var/xeno_mobhud = FALSE //whether the xeno mobhud is activated or not.
 	var/xeno_hostile_hud = FALSE // 'Hostile' HUD - the verb Xenos use to see tags, etc on humans
+	var/execute_hud = FALSE // Crit HUD, only visible to vampire lurkers
 	var/list/plasma_types = list() //The types of plasma the caste contains
 	var/list/xeno_shields = list() // List of /datum/xeno_shield that holds all active shields on the Xeno.
 	var/acid_splash_cooldown = 5 SECONDS //Time it takes between acid splash retaliate procs

code/modules/mob/living/carbon/xenomorph/strains/castes/lurker/vampire.dm

@@ -25,4 +25,8 @@
 	lurker.damage_modifier -= XENO_DAMAGE_MOD_VERY_SMALL
 	lurker.attack_speed_modifier -= 2
 
+	var/datum/mob_hud/execute_hud = GLOB.huds[MOB_HUD_EXECUTE]
+	execute_hud.add_hud_to(lurker, lurker)
+	lurker.execute_hud = TRUE
+
 	lurker.recalculate_everything()