Shoulder Sling attachment (#3860)

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## About The Pull Request

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documented or this can delay review and even discourage maintainers from
merging your PR! -->

Adds the shoulder sling attachment to cargo for 500 credits.

The shoulder sling can be attached any long arm gun with a weight class
of bulky or up. The sling allows for the gun to be carried in your suit
storage slot without an armor holster.

Adds support for attachment overlays to render under the attached gun.

Shoulder sling sprites by Moffball.


![image](https://github.com/user-attachments/assets/f6b9910f-b42b-4e38-87fa-a146061c05d5)

## Why It's Good For The Game

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benefit the game. If you can't justify it in words, it might not be
worth adding. -->
This gives players more options for fashion and accessorizing. You're no
longer stuck with wearing a boring armor vest to hold your bulky
weapons, and the other option of carrying your gun everywhere in your
hands makes you look like a maniac. Balance wise this should be fine,
since you can buy armor from the outpost anyways, which provides the
same benefit with it's holster while being objectively better because
well. It's armored.


## Changelog

:cl:
add: Shoulder slings to outpost cargo for 500 credits.
/:cl:

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the changes rather than a summary of the PR's contents. -->

code/__DEFINES/traits.dm

@@ -305,6 +305,7 @@ Remember to update _globalvars/traits.dm if you're adding/removing/renaming trai
 /// A transforming item that is actively extended / transformed
 #define TRAIT_TRANSFORM_ACTIVE "active_transform"
 #define TRAIT_WIELDED "wielded" //The item is currently being wielded
+#define TRAIT_FORCE_SUIT_STORAGE "force_suit_storage" // the item can be worn in suit storage without an outerclothing
 
 //quirk traits
 #define TRAIT_ALCOHOL_TOLERANCE "alcohol_tolerance"

code/datums/components/attachment.dm

@@ -76,9 +76,15 @@
 	parent.attack_self(user)
 	return TRUE
 
-/datum/component/attachment/proc/update_overlays(obj/item/parent, list/overlays, list/offset)
+/datum/component/attachment/proc/update_overlays(obj/item/attachment/parent, list/overlays, list/offset)
 	if(!(attach_features_flags & ATTACH_NO_SPRITE))
-		overlays += mutable_appearance(parent.icon, "[parent.icon_state]-attached")
+		var/overlay_layer = FLOAT_LAYER
+		var/overlay_plane = FLOAT_PLANE
+		if(parent.render_layer)
+			overlay_layer = parent.render_layer
+		if(parent.render_plane)
+			overlay_layer = parent.render_plane
+		overlays += mutable_appearance(parent.icon, "[parent.icon_state]-attached",overlay_layer,overlay_plane)
 
 /datum/component/attachment/proc/try_attach(obj/item/parent, obj/item/holder, mob/user, bypass_checks)
 	SIGNAL_HANDLER

code/game/objects/items/attachments/_attachment.dm

@@ -25,6 +25,9 @@
 	var/pixel_shift_x = 16
 	///Determines the amount of pixels to move the icon state for the overlay. in the y direction
 	var/pixel_shift_y = 16
+	/// Determines what layer the icon state for the overlay renders on.
+	var/render_layer = FLOAT_LAYER //inhands
+	var/render_plane = FLOAT_PLANE //world
 
 	//Toggle modifers are handled seperatly
 	///Modifier applied to the parent

code/game/objects/items/attachments/shoulder_sling.dm

@@ -0,0 +1,31 @@
+/obj/item/attachment/sling
+	name = "shoulder sling"
+	desc = "A leather shoulder sling for longarms to allow for easy carrying on the shoulder without the need for traditional armor holsters."
+	icon_state = "sling"
+
+	attach_features_flags = ATTACH_REMOVABLE_HAND
+	pixel_shift_x = 14
+	pixel_shift_y = 15
+	render_layer = BELOW_OBJ_LAYER
+	render_plane = BELOW_OBJ_LAYER
+	wield_delay = 0.2 SECONDS
+
+	var/check_size = TRUE
+
+/obj/item/attachment/sling/apply_attachment(obj/item/gun/gun, mob/user)
+	. = ..()
+	if(initial(gun.w_class) < WEIGHT_CLASS_BULKY && check_size)
+		to_chat(user,span_warning("The frame of the \the [gun] isn't large enough to support \the [src]!"))
+		return FALSE
+	if(!(gun.slot_flags | ITEM_SLOT_SUITSTORE))
+		gun.slot_flags = gun.slot_flags | ITEM_SLOT_SUITSTORE
+	ADD_TRAIT(gun,TRAIT_FORCE_SUIT_STORAGE,REF(src))
+
+/obj/item/attachment/sling/remove_attachment(obj/item/gun/gun, mob/user)
+	. = ..()
+	gun.slot_flags = initial(gun.slot_flags)
+	REMOVE_TRAIT(gun,TRAIT_FORCE_SUIT_STORAGE, REF(src))
+
+/obj/item/attachment/sling/examine(mob/user)
+	. = ..()
+	. += span_notice("The shoulder sling can only be attached to bulky or heavier guns.")

code/modules/cargo/packs/gun.dm

@@ -684,3 +684,10 @@
 	cost = 250
 	contains = list(/obj/item/attachment/silencer)
 	crate_name = "suppressor crate"
+
+/datum/supply_pack/gun/attachment/sling
+	name = "Shoulder Sling Crate"
+	desc = "Contains a single shoulder sling to be mounted on a firearm for easy carrying without armor holsters. Only compatible with longarms."
+	cost = 250
+	contains = list(/obj/item/attachment/sling)
+	crate_name = "shoulder sling crate"

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

@@ -1238,6 +1238,8 @@ GLOBAL_LIST_EMPTY(roundstart_races)
 				return FALSE
 			if(H.s_store && !swap)
 				return FALSE
+			if(HAS_TRAIT(I, TRAIT_FORCE_SUIT_STORAGE))
+				return TRUE
 			if(!H.wear_suit)
 				if(!disable_warning)
 					to_chat(H, "<span class='warning'>You need a suit before you can attach this [I.name]!</span>")

code/modules/projectiles/guns/ballistic.dm

@@ -23,7 +23,8 @@
 		/obj/item/attachment/silencer,
 		/obj/item/attachment/laser_sight,
 		/obj/item/attachment/rail_light,
-		/obj/item/attachment/bayonet
+		/obj/item/attachment/bayonet,
+		/obj/item/attachment/sling
 	)
 	slot_available = list(
 		ATTACHMENT_SLOT_MUZZLE = 1,

code/modules/projectiles/guns/energy.dm

@@ -36,7 +36,8 @@
 	valid_attachments = list(
 		/obj/item/attachment/laser_sight,
 		/obj/item/attachment/rail_light,
-		/obj/item/attachment/bayonet
+		/obj/item/attachment/bayonet,
+		/obj/item/attachment/sling
 	)
 	slot_available = list(
 		ATTACHMENT_SLOT_RAIL = 1

shiptest.dme

@@ -1254,6 +1254,7 @@
 #include "code\game\objects\items\attachments\laser_sight.dm"
 #include "code\game\objects\items\attachments\m17_barrel.dm"
 #include "code\game\objects\items\attachments\rail_light.dm"
+#include "code\game\objects\items\attachments\shoulder_sling.dm"
 #include "code\game\objects\items\attachments\silencer.dm"
 #include "code\game\objects\items\attachments\stock.dm"
 #include "code\game\objects\items\circuitboards\circuitboard.dm"