Xeno Backpacks (#1274)

<!-- Write **BELOW** The Headers and **ABOVE** The comments else it may
not be viewable. -->

## About The Pull Request
This pull request adds support for marines to strap a backpack onto
allied xenos. The xeno cannot view the contents of the bag nor interact
with it any way other than through a new shake verb. Marines also have
access to the new shake verb for any emptyable storage item. Shaking a
storage item that is either in your hands or back slot has a high chance
to drop out a single item. Xenos that shake an empty backpack also have
a low chance to drop the backpack on the ground.

Strapping on, unstrapping, and accessing any allied xeno backpack does
take some time to complete.

The item class size of gardener and healer fruit has been lowered to
medium, but they occupy more space in a bag than a regular medium item
(so only five can fit in a typical bag). The intention of this change is
to allow a bag loaded with either fruit (for xenos) or medical supplies
(for marines) that a xeno can go out and distribute, but its primarily
on a marine to facilitate this.

Sprites were created by Jean 'Docteur' Corbeau aka SubjectD9341.


![Preview](https://user-images.githubusercontent.com/76988376/196059419-9833c1a5-5d6e-4354-b9c6-1f8c0ff3bd5a.png)
**NOTE:** _**Some sprites in above are no longer accurate. See updated
images below...**_


![Defender](https://user-images.githubusercontent.com/76988376/207441985-a89accaf-482c-4d94-8fad-cd04737adef7.png)

![SentDroneSpitter](https://user-images.githubusercontent.com/76988376/207442096-b67daf74-8618-4c9f-83b4-d3b3cd067aa0.png)

![RunnerPraeWarrior](https://user-images.githubusercontent.com/76988376/207442390-a32fac4e-2e26-4337-86f0-5c7cc4b8b344.png)

Sprite progress (though ultimately up to them how far they want to go):
- [X] Medic bag on Drone
- [X] Regular bag on Drone
- [X] Medic bag on Defender
- [X] Regular bag on Defender
- [X] Medic bag on Sentinel
- [X] Regular bag on Sentinel
- [X] Medic bag on Runner
- [X] Regular bag on Runner
- [X] Medic bag on Warrior
- [X] Regular bag on Warrior
- [X] Medic bag on Spitter
- [X] Regular bag on Spitter
- [X] Medic bag on Praetorian
- [X] Regular bag on Praetorian

Any unlisted castes aren't planned at this time.

<!-- Describe The Pull Request. Please be sure every change is
documented or this can delay review and even discourage maintainers from
merging your PR! -->

## Why It's Good For The Game

<!-- Please add a short description of why you think these changes would
benefit the game. If you can't justify it in words, it might not be
worth adding, and may discourage maintainers from reviewing or merging
your PR. This section is not strictly required for (non-controversial)
fix PRs or backend PRs. -->
Opens up more interactions between marines and xenos, namely for
friendly "greenos". Encourages more cooperation between a friendly xeno
faction because equipping and loading of these backpacks can only be
performed by a marine; a xeno can only shake items out or shake the bag
off. Allowing fruit to be placed in bags is primarily to allow a medic
roony to either provide healing to xenos by shaking out some fruit, or
to marines by shaking out some medical supplies.
## Changelog

<!-- You can use multiple of the same prefix (they're only used for the
icon ingame) and delete the unneeded ones. Despite some of the tags,
changelogs should generally represent how a player might be affected by
the changes rather than a summary of the PR's contents. -->

<!-- If your PR modifies aspects of the game that can be concretely
observed by players or admins you should add a changelog. If your change
does NOT meet this description, remove this section. Be sure to properly
mark your PRs to prevent unnecessary GBP loss. Please note that
maintainers freely reserve the right to remove and add tags should they
deem it appropriate. You can attempt to finagle the system all you want,
but it's best to shoot for clear communication right off the bat. -->

:cl: Drathek, SubjectD9341
add: Standard issue marine backpacks can now be equipped to most allied
xenos (Runners/Praetorians/Drones/Defenders/Warriors/Sentinels/Spitters)
and accessed. Use a pack in help intent on a xeno to strap it to her
after a duration. Access it with an empty hand in help intent after a
duration. Drag a xeno with a pack to you when you have an empty hand to
unstrap it from her after a duration.
add: Added the Shake verb to storage items. Humans and xenos can now
shake emptyable inventories which has a 75% chance to drop an item if
there are any. Xenos also have a 25% chance to cause the pack fall off
them when empty.
balance: Resin fruit is now class size medium but size cost large so
five can fit in a backpack.
soundadd: Emptying a storage item now uses the existing rustle sound (or
whatever use_sound its configured to use).
soundadd: Unequipping a backpack now uses the existing rustle sound (or
whatever use_sound its configured to use).
imageadd: Added sprites for regular and medical packs on
Runners/Praetorians/Drones/Defenders/Warriors/Sentinels/Spitters.
code: Any storage item that is STORAGE_ALLOW_EMPTY now either
adds/removes empty_verb and toggle_click_empty depending on if the user
is a xeno.
code: Refactored /atom/movable/vis_obj/xeno_wounds so it can be more
generic as just vis_obj (now it will be used by both wounds and packs
and packs don't need to be xeno_wounds) and use VIS_INHERIT_DIR instead
of a signal.
fix: Xeno wounds no longer inherit hive color.
/:cl:

<!-- Both :cl:'s are required for the changelog to work! You can put
your name to the right of the first :cl: if you want to overwrite your
GitHub username as author ingame. -->

code/__DEFINES/mobs.dm

@@ -392,6 +392,16 @@ var/list/default_onmob_icons = list(
 		WEAR_ACCESSORIES = 'icons/mob/humans/onmob/ties.dmi'
 		)
 
+var/list/default_xeno_onmob_icons = list(
+		/mob/living/carbon/Xenomorph/Runner = 'icons/mob/xenos/onmob/runner.dmi',
+		/mob/living/carbon/Xenomorph/Praetorian = 'icons/mob/xenos/onmob/praetorian.dmi',
+		/mob/living/carbon/Xenomorph/Drone = 'icons/mob/xenos/onmob/drone.dmi',
+		/mob/living/carbon/Xenomorph/Warrior = 'icons/mob/xenos/onmob/warrior.dmi',
+		/mob/living/carbon/Xenomorph/Defender = 'icons/mob/xenos/onmob/defender.dmi',
+		/mob/living/carbon/Xenomorph/Sentinel = 'icons/mob/xenos/onmob/sentinel.dmi',
+		/mob/living/carbon/Xenomorph/Spitter = 'icons/mob/xenos/onmob/spitter.dmi'
+		)
+
 // species names
 #define SPECIES_HUMAN "Human"
 #define SPECIES_YAUTJA "Yautja"

code/_onclick/adjacent.dm

@@ -100,7 +100,10 @@ Quick adjacency (to turf):
 		if(recurse > 0)
 			return loc.Adjacent(neighbor, recurse - 1)
 		return FALSE
+	else if(isXeno(loc)) //Xenos don't count as storage depth.
+		return loc.Adjacent(neighbor, recurse)
 	return ..()
+
 /*
 	Special case: This allows you to reach a door when it is visally on top of,
 	but technically behind, a fire door

code/_onclick/human.dm

@@ -92,6 +92,36 @@
 	if(user != src)
 		return . = ..()
 
+	if(isXeno(dropping))
+		var/mob/living/carbon/Xenomorph/xeno = dropping
+		if(xeno.back)
+			var/obj/item/back_item = xeno.back
+			if(xeno.stat != DEAD) // If the Xeno is alive, fight back
+				var/mob/living/carbon/carbon_user = user
+				if(!carbon_user || !carbon_user.ally_of_hivenumber(xeno.hivenumber))
+					user.KnockDown(rand(xeno.caste.tacklestrength_min, xeno.caste.tacklestrength_max))
+					playsound(user.loc, 'sound/weapons/pierce.ogg', 25, TRUE)
+					user.visible_message(SPAN_WARNING("\The [user] tried to unstrap \the [back_item] from [xeno] but instead gets a tail swipe to the head!"))
+					return
+			if(user.get_active_hand())
+				to_chat(user, SPAN_WARNING("You can't unstrap \the [back_item] from [xeno] with your hands full."))
+				return
+			user.visible_message(SPAN_NOTICE("\The [user] starts unstrapping \the [back_item] from [xeno]"), \
+			SPAN_NOTICE("You start unstrapping \the [back_item] from [xeno]."), null, 5, CHAT_TYPE_FLUFF_ACTION)
+			if(!do_after(user, HUMAN_STRIP_DELAY * user.get_skill_duration_multiplier(), INTERRUPT_ALL, BUSY_ICON_GENERIC, xeno, INTERRUPT_MOVED, BUSY_ICON_GENERIC))
+				to_chat(user, SPAN_WARNING("You were interrupted!"))
+				return
+
+			if(user.get_active_hand())
+				return
+			if(!user.Adjacent(xeno))
+				return
+			xeno.drop_inv_item_on_ground(back_item)
+			if(!back_item || QDELETED(back_item)) //Might be self-deleted?
+				return
+			user.put_in_active_hand(back_item)
+			return
+
 	if(pulling != dropping || grab_level != GRAB_AGGRESSIVE || !ishuman(dropping) || !(a_intent & INTENT_GRAB))
 		return . = ..()
 

code/game/objects/items.dm

@@ -97,7 +97,7 @@
 
 	var/mob/living/carbon/human/locked_to_mob = null	// If the item uses flag MOB_LOCK_ON_PICKUP, this is the mob owner reference.
 
-	var/list/equip_sounds//Sounds played when this item is equipped
+	var/list/equip_sounds //Sounds played when this item is equipped
 	var/list/unequip_sounds //Same but when unequipped
 
 	 ///Vision impairing effect if worn on head/mask/glasses.

code/game/objects/items/storage/backpack.dm

@@ -16,6 +16,8 @@
 	var/obj/item/card/id/locking_id = null
 	var/is_id_lockable = FALSE
 	var/lock_overridable = TRUE
+	var/xeno_icon_state = null //the icon_state for xeno's wearing this (using the dmi defined in default_xeno_onmob_icons list)
+	var/list/xeno_types = null //what xeno types can equip this backpack
 
 /obj/item/storage/backpack/attackby(obj/item/W, mob/user)
 	if(istype(W, /obj/item/card/id/) && is_id_lockable && ishuman(user))
@@ -27,6 +29,51 @@
 	if (..() && use_sound)
 		playsound(loc, use_sound, 15, TRUE, 6)
 
+/obj/item/storage/backpack/attack(mob/living/target_mob, mob/living/user)
+	if(!xeno_icon_state)
+		return ..()
+	if(target_mob.back)
+		return ..()
+	if(user.a_intent != INTENT_HELP)
+		return ..()
+	if(!xeno_types || !(target_mob.type in xeno_types))
+		return ..()
+	if(!isXeno(target_mob))
+		return ..()
+	if(HAS_TRAIT(target_mob, TRAIT_XENONID))
+		return ..() // We don't have backpack sprites for xenoids (yet?)
+	var/mob/living/carbon/Xenomorph/xeno = target_mob
+	if(target_mob.stat != DEAD) // If the Xeno is alive, fight back
+		var/mob/living/carbon/carbon_user = user
+		if(!carbon_user || !carbon_user.ally_of_hivenumber(xeno.hivenumber))
+			user.KnockDown(rand(xeno.caste.tacklestrength_min, xeno.caste.tacklestrength_max))
+			playsound(user.loc, 'sound/weapons/pierce.ogg', 25, TRUE)
+			user.visible_message(SPAN_WARNING("\The [user] tried to strap \the [src] onto [target_mob] but instead gets a tail swipe to the head!"))
+			return FALSE
+
+	user.visible_message(SPAN_NOTICE("\The [user] starts strapping \the [src] onto [target_mob]."), \
+	SPAN_NOTICE("You start strapping \the [src] onto [target_mob]."), null, 5, CHAT_TYPE_FLUFF_ACTION)
+	if(!do_after(user, HUMAN_STRIP_DELAY * user.get_skill_duration_multiplier(), INTERRUPT_ALL, BUSY_ICON_GENERIC, target_mob, INTERRUPT_MOVED, BUSY_ICON_GENERIC))
+		to_chat(user, SPAN_WARNING("You were interrupted!"))
+		return FALSE
+
+	// Ensure conditions still valid
+	if(src != user.get_active_hand())
+		return FALSE
+	if(!user.Adjacent(target_mob))
+		return FALSE
+	user.drop_inv_item_on_ground(src)
+	if(!src || QDELETED(src)) //Might be self-deleted?
+		return FALSE
+
+	// Create their vis object if needed
+	if(!xeno.backpack_icon_carrier)
+		xeno.backpack_icon_carrier = new(null, xeno)
+		xeno.vis_contents += xeno.backpack_icon_carrier
+
+	target_mob.put_in_back(src)
+	return FALSE
+
 /obj/item/storage/backpack/proc/toggle_lock(obj/item/card/id/card, mob/living/carbon/human/H)
 	if(QDELETED(locking_id))
 		to_chat(H, SPAN_NOTICE("You lock \the [src]!"))
@@ -48,6 +95,12 @@
 			storage_close(user)
 	..()
 
+/obj/item/storage/unequipped(mob/user, slot, silent)
+	if(slot == WEAR_BACK)
+		if(use_sound && !silent)
+			playsound(loc, use_sound, 15, TRUE, 6)
+	..()
+
 /obj/item/storage/backpack/dropped(mob/user)
 	mouse_opacity = initial(mouse_opacity)
 	..()
@@ -312,18 +365,24 @@ obj/item/storage/backpack/proc/compare_id(var/mob/living/carbon/human/H)
 	icon_state = "marinepack"
 	item_state = "marinepack"
 	has_gamemode_skin = TRUE //replace this with the atom_flag NO_SNOW_TYPE at some point, just rename it to like, NO_MAP_VARIANT_SKIN
+	xeno_icon_state = "marinepack"
+	xeno_types = list(/mob/living/carbon/Xenomorph/Runner, /mob/living/carbon/Xenomorph/Praetorian, /mob/living/carbon/Xenomorph/Drone, /mob/living/carbon/Xenomorph/Warrior, /mob/living/carbon/Xenomorph/Defender, /mob/living/carbon/Xenomorph/Sentinel, /mob/living/carbon/Xenomorph/Spitter)
 
 /obj/item/storage/backpack/marine/medic
 	name = "\improper USCM corpsman backpack"
 	desc = "A standard-issue backpack worn by USCM medics."
 	icon_state = "marinepack_medic"
 	item_state = "marinepack_medic"
+	xeno_icon_state = "medicpack"
+	xeno_types = list(/mob/living/carbon/Xenomorph/Runner, /mob/living/carbon/Xenomorph/Praetorian, /mob/living/carbon/Xenomorph/Drone, /mob/living/carbon/Xenomorph/Warrior, /mob/living/carbon/Xenomorph/Defender, /mob/living/carbon/Xenomorph/Sentinel, /mob/living/carbon/Xenomorph/Spitter)
 
 /obj/item/storage/backpack/marine/tech
 	name = "\improper USCM technician backpack"
 	desc = "A standard-issue backpack worn by USCM technicians."
 	icon_state = "marinepack_techi"
 	item_state = "marinepack_techi"
+	xeno_icon_state = "marinepack"
+	xeno_types = list(/mob/living/carbon/Xenomorph/Runner, /mob/living/carbon/Xenomorph/Praetorian, /mob/living/carbon/Xenomorph/Drone, /mob/living/carbon/Xenomorph/Warrior, /mob/living/carbon/Xenomorph/Defender, /mob/living/carbon/Xenomorph/Sentinel, /mob/living/carbon/Xenomorph/Spitter)
 
 /obj/item/storage/backpack/marine/satchel/intel
 	name = "\improper USCM lightweight expedition pack"
@@ -338,6 +397,7 @@ obj/item/storage/backpack/proc/compare_id(var/mob/living/carbon/human/H)
 	worn_accessible = TRUE
 	storage_slots = null
 	max_storage_space = 15
+	xeno_types = null
 
 /obj/item/storage/backpack/marine/satchel/big //wacky squad marine loadout item, its the IO backpack.
 	name = "\improper USCM logistics IMP backpack"
@@ -347,7 +407,6 @@ obj/item/storage/backpack/proc/compare_id(var/mob/living/carbon/human/H)
 	storage_slots = null
 	max_storage_space = 21 //backpack size
 
-
 /obj/item/storage/backpack/marine/satchel/medic
 	name = "\improper USCM corpsman satchel"
 	desc = "A heavy-duty satchel used by USCM medics. It sacrifices capacity for usability. A small patch is sewn to the top flap."
@@ -497,20 +556,23 @@ GLOBAL_LIST_EMPTY_TYPED(radio_packs, /obj/item/storage/backpack/marine/satchel/r
 	desc = "A specially-designed smock with pockets for all your sniper needs."
 	icon_state = "smock"
 	worn_accessible = TRUE
+	xeno_types = null
 
 /obj/item/storage/backpack/marine/marsoc
 	name = "\improper USCM SOF IMP tactical rucksack"
 	icon_state = "tacrucksack"
 	desc = "With a backpack like this, you'll forget you're on a hell march designed to kill you."
 	worn_accessible = TRUE
 	has_gamemode_skin = FALSE
+	xeno_types = null
 
 /obj/item/storage/backpack/marine/rocketpack
 	name = "\improper USCM IMP M22 rocket bags"
 	desc = "A specially-designed backpack that fits to the IMP mounting frame on standard USCM pattern M3 armors. It's made of two waterproofed reinforced tubes and one smaller satchel slung at the bottom. The two silos are for rockets, but no one is stopping you from cramming other things in there."
 	icon_state = "rocketpack"
 	worn_accessible = TRUE
 	has_gamemode_skin = FALSE //monkeysfist101 never sprited a snowtype but included duplicate icons. Why?? Recolor and touch up sprite at a later date.
+	xeno_types = null
 
 /obj/item/storage/backpack/marine/grenadepack
 	name = "\improper USCM IMP M63A1 grenade satchel"
@@ -523,6 +585,7 @@ GLOBAL_LIST_EMPTY_TYPED(radio_packs, /obj/item/storage/backpack/marine/satchel/r
 	can_hold = list(/obj/item/explosive/grenade)
 	is_id_lockable = TRUE
 	has_gamemode_skin = FALSE
+	xeno_types = null
 
 /obj/item/storage/backpack/marine/grenadepack/attackby(obj/item/W, mob/user)
 	if(istype(W, /obj/item/storage/box/nade_box) || istype(W, /obj/item/storage/backpack/marine/grenadepack) || istype(W, /obj/item/storage/belt/grenade))
@@ -537,6 +600,7 @@ GLOBAL_LIST_EMPTY_TYPED(radio_packs, /obj/item/storage/backpack/marine/satchel/r
 	max_w_class = SIZE_HUGE
 	storage_slots = 8
 	can_hold = list(/obj/item/mortar_shell)
+	xeno_types = null
 
 /// G-8-a general pouch belt
 /obj/item/storage/backpack/general_belt
@@ -715,7 +779,7 @@ GLOBAL_LIST_EMPTY_TYPED(radio_packs, /obj/item/storage/backpack/marine/satchel/r
 	max_storage_space = 18
 	storage_slots = null
 	has_gamemode_skin = TRUE
-
+	xeno_types = null
 
 /obj/item/storage/backpack/marine/engineerpack/Initialize()
 	. = ..()

code/game/objects/items/storage/smartpack.dm

@@ -12,6 +12,7 @@
 	max_storage_space = 14
 	worn_accessible = TRUE
 	actions_types = list(/datum/action/item_action/toggle)
+	xeno_types = null
 
 	var/show_exoskeleton = FALSE
 

code/game/objects/items/storage/storage.dm

@@ -523,6 +523,16 @@ W is always an item. stop_warning prevents messaging. user may be null.**/
 
 	return attempt_item_insertion(W, FALSE, user)
 
+/obj/item/storage/equipped(mob/user, slot, silent)
+	if ((storage_flags & STORAGE_ALLOW_EMPTY))
+		if(!isXeno(user))
+			verbs |= /obj/item/storage/verb/empty_verb
+			verbs |= /obj/item/storage/verb/toggle_click_empty
+		else
+			verbs -= /obj/item/storage/verb/empty_verb
+			verbs -= /obj/item/storage/verb/toggle_click_empty
+	..()
+
 /obj/item/storage/proc/attempt_item_insertion(obj/item/W as obj, prevent_warning = FALSE, mob/user as mob)
 	if(!can_be_inserted(W))
 		return
@@ -608,6 +618,61 @@ W is always an item. stop_warning prevents messaging. user may be null.**/
 		remove_from_storage(I, T)
 	user.visible_message(SPAN_NOTICE("[user] empties \the [src]."),
 		SPAN_NOTICE("You empty \the [src]."))
+	if (use_sound)
+		playsound(loc, use_sound, 25, TRUE, 3)
+
+/obj/item/storage/verb/shake_verb()
+	set name = "Shake"
+	set category = "Object"
+	set src in usr
+	var/mob/user_mob = usr
+	shake(user_mob, get_turf(user_mob))
+
+/obj/item/storage/proc/shake(var/mob/user, var/turf/tile)
+	if(!(storage_flags & STORAGE_ALLOW_EMPTY))
+		return
+
+	if(user.l_hand != src && user.r_hand != src && user.back != src)
+		return
+
+	if(user.is_mob_incapacitated())
+		return
+
+	if (!isturf(tile) || get_dist(src, tile) > 1)
+		tile = get_turf(src)
+
+	if (use_sound)
+		playsound(loc, use_sound, 25, TRUE, 3)
+
+	if(!length(contents))
+		if(prob(25) && isXeno(user))
+			user.drop_inv_item_to_loc(src, tile)
+			user.visible_message(SPAN_NOTICE("[user] shakes \the [src] off."),
+				SPAN_NOTICE("You shake \the [src] off."))
+		else
+			user.visible_message(SPAN_NOTICE("[user] shakes \the [src] but nothing falls out."),
+				SPAN_NOTICE("You shake \the [src] but nothing falls out. It feels empty."))
+		return
+
+	if(!allowed(user))
+		user.visible_message(SPAN_NOTICE("[user] shakes \the [src] but nothing falls out."),
+			SPAN_NOTICE("You shake \the [src] but nothing falls out. Access denied."))
+		return
+
+	if(!prob(75))
+		user.visible_message(SPAN_NOTICE("[user] shakes \the [src] but nothing falls out."),
+			SPAN_NOTICE("You shake \the [src] but nothing falls out."))
+		return
+
+	storage_close(user)
+	var/obj/item/item_obj
+	if(storage_flags & STORAGE_USING_FIFO_DRAWING)
+		item_obj = contents[1]
+	else
+		item_obj = contents[contents.len]
+	remove_from_storage(item_obj, tile)
+	user.visible_message(SPAN_NOTICE("[user] shakes \the [src] and \a [item_obj] falls out."),
+		SPAN_NOTICE("You shake \the [src] and \a [item_obj] falls out."))
 
 /obj/item/storage/proc/dump_ammo_to(obj/item/ammo_magazine/ammo_dumping, mob/user, var/amount_to_dump = 5) //amount_to_dump should never actually need to be used as default value
 	if(user.action_busy)
@@ -674,6 +739,7 @@ W is always an item. stop_warning prevents messaging. user may be null.**/
 	if (!(storage_flags & STORAGE_ALLOW_EMPTY))
 		verbs -= /obj/item/storage/verb/empty_verb
 		verbs -= /obj/item/storage/verb/toggle_click_empty
+		verbs -= /obj/item/storage/verb/shake_verb
 
 	boxes = new
 	boxes.name = "storage"

code/modules/cm_aliens/structures/fruit.dm

@@ -323,7 +323,8 @@
 	desc = "A strange fruit that you could eat.. if you REALLY wanted to. Its roots seem to twitch every so often."
 	icon = 'icons/mob/xenos/fruits.dmi'
 	icon_state = "fruit_lesser_item"
-	w_class = SIZE_LARGE
+	w_class = SIZE_MEDIUM
+	storage_cost = SIZE_LARGE
 	bitesize = 2
 	var/mob/living/carbon/Xenomorph/bound_xeno //Drone linked to this fruit
 	var/fruit_type = /obj/effect/alien/resin/fruit

code/modules/cm_marines/Donor_Items.dm

@@ -1309,6 +1309,8 @@
 	desc = "Black gloves, favored by Special Operations teams.  DONOR ITEM"
 	name = "Black Ops Black Gloves"
 
+/obj/item/storage/backpack/marine/fluff
+	xeno_types = null
 
 /obj/item/storage/backpack/marine/fluff/Sado
 	name = "Tanya's Backpack"

code/modules/mob/inventory.dm

@@ -60,7 +60,7 @@
 	if(hand)	return put_in_r_hand(W)
 	else		return put_in_l_hand(W)
 
-//Puts the item our active hand if possible. Failing that it tries our inactive hand. Returns 1 on success.
+//Puts the item into our active hand if possible. Failing that it tries our inactive hand. Returns 1 on success.
 //If both fail it drops it on the floor and returns 0.
 //This is probably the main one you need to know :)
 /mob/proc/put_in_hands(var/obj/item/W)
@@ -76,7 +76,24 @@
 		W.dropped(src)
 		return FALSE
 
-
+//Puts the item into our back if possible. Returns 1 on success.
+/mob/proc/put_in_back(var/obj/item/item)
+	if(!item)
+		return FALSE
+	if(!istype(item))
+		return FALSE
+	if(back)
+		return FALSE
+	if(item.loc == src && !(item.flags_item & DELONDROP))
+		item.dropped(src)
+	item.pickup(src)
+	item.forceMove(src)
+	back = item
+	item.layer = ABOVE_HUD_LAYER
+	item.plane = ABOVE_HUD_PLANE
+	item.equipped(src, WEAR_BACK)
+	update_inv_back()
+	return TRUE
 
 /mob/proc/drop_item_v()		//this is dumb.
 	if(stat == CONSCIOUS && isturf(loc))
@@ -366,3 +383,5 @@
 		return WEAR_L_HAND
 	if(I == r_hand)
 		return WEAR_R_HAND
+	if(I == back)
+		return WEAR_BACK