Adds true observing -- letting you see what your target sees (#24855)

* bring it back now y'all

* adds a bunch of other changes

* pretty much works at this point

* grep

* Fixes some bugs, still chasing some down

* Add observers to recursive mob check, ensuring they can see messages from their orbitted atom

* tidy some things up

* resolve

* remove unnecessary checks

* Address todos, minor cleanups

* oh dear

* initial testing

* Fix some vulnerabilities (oops)

* Fix some other bugs from testing

* ci fixes

* Add some contingencies against clicking things you shouldn't

* fix some noted bugs

* Add observe to admin jump, improve messaging

* add a few more fixes that should mostly address some runtimes

* oh this wasn't really great

* one last thing

* Fix suit inventory problem

* Remove merge artifact

* Add some missing parens

* Prevents you from observing other ghosts, and should fix the getting stuck outside of your body issue.

* we love testing

* adds to player panel

* Fix more bugs with observers getting stuck outside of their body

* cleans up player panel, verb offerings

* shit

* Update code/_onclick/hud/alert.dm

welp

Co-authored-by: GDN <96800819+GDNgit@users.noreply.github.com>
Signed-off-by: Luc <89928798+lewcc@users.noreply.github.com>

* Fixes some targeting issues

* Fixes targeting on aobserve

* Fix some weird storage bugs

* clean up some doulbed up follow links

* Update code/modules/admin/player_panel.dm

Signed-off-by: Luc <89928798+lewcc@users.noreply.github.com>

* Adds some checks for ghost observe

* Remove mentor debug log

* ahhhhhhhhh that'll do it

* Cleans up some additional checks that were not quite what they should have been

* better logging, too

* mochi review

* one more thing

* Gets robot huds mostly working

* hopefully fix folks not getting observe

* Fix order of operations causing a runtime on qdeleting

* Remove some unnecessary stack traces

* Apply suggestions from code review

Co-authored-by: 1080pCat <96908085+1080pCat@users.noreply.github.com>
Signed-off-by: Luc <89928798+lewcc@users.noreply.github.com>

* Fix bug with items in your inventory disappearing on changing HUD modes

* Fix some bugs with the observe verbs

* possibly fix nullspace issues

* funny review

* missed one

---------

Signed-off-by: Luc <89928798+lewcc@users.noreply.github.com>
Co-authored-by: github-actions <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: GDN <96800819+GDNgit@users.noreply.github.com>
Co-authored-by: S34N <12197162+S34NW@users.noreply.github.com>
Co-authored-by: 1080pCat <96908085+1080pCat@users.noreply.github.com>

code/modules/mob/dead/observer/observer_base.dm

@@ -20,6 +20,8 @@ GLOBAL_DATUM_INIT(ghost_crew_monitor, /datum/ui_module/crew_monitor/ghost, new)
 	move_resist = INFINITY	//  don't get pushed around
 	invisibility = INVISIBILITY_OBSERVER
 	blocks_emissive = FALSE // Ghosts are transparent, duh
+	hud_type = /datum/hud/ghost
+	speaks_ooc = TRUE
 	var/can_reenter_corpse
 	var/bootime = FALSE
 	var/started_as_observer //This variable is set to 1 when you enter the game as an observer.
@@ -41,8 +43,8 @@ GLOBAL_DATUM_INIT(ghost_crew_monitor, /datum/ui_module/crew_monitor/ghost, new)
 	var/datum/orbit_menu/orbit_menu
 	/// The "color" their runechat would have had
 	var/alive_runechat_color = "#FFFFFF"
-	hud_type = /datum/hud/ghost
-	speaks_ooc = TRUE
+	/// UID of the mob which we are currently observing
+	var/mob_observed
 
 /mob/dead/observer/New(mob/body=null, flags=1)
 	set_invisibility(GLOB.observer_default_invisibility)
@@ -120,6 +122,8 @@ GLOBAL_DATUM_INIT(ghost_crew_monitor, /datum/ui_module/crew_monitor/ghost, new)
 	if(seerads)
 		STOP_PROCESSING(SSobj, src)
 	remove_observer_verbs()
+	if(mob_observed)
+		cleanup_observe()
 	return ..()
 
 /mob/dead/observer/examine(mob/user)
@@ -184,25 +188,37 @@ Works together with spawning an observer, noted above.
 	return 1
 
 /mob/proc/ghostize(flags = GHOST_CAN_REENTER, user_color, ghost_name)
-	if(key)
-		if(player_logged) //if they have disconnected we want to remove their SSD overlay
-			overlays -= image('icons/effects/effects.dmi', icon_state = "zzz_glow")
-		if(GLOB.non_respawnable_keys[ckey])
-			flags &= ~GHOST_CAN_REENTER
-		var/mob/dead/observer/ghost = new(src, flags)	//Transfer safety to observer spawning proc.
-		ghost.timeofdeath = src.timeofdeath //BS12 EDIT
-		if(ghost.can_reenter_corpse)
-			ADD_TRAIT(ghost, TRAIT_RESPAWNABLE, GHOSTED)
-		else
-			GLOB.non_respawnable_keys[ckey] = 1
-		if(user_color)
-			add_atom_colour(user_color, ADMIN_COLOUR_PRIORITY)
-			ghost.color = user_color
-		if(ghost_name)
-			ghost.name = ghost_name
-		ghost.key = key
-		ghost.client?.init_verbs()
-		return ghost
+	if(!key)
+		return
+	if(player_logged) // if they have disconnected we want to remove their SSD overlay
+		overlays -= image('icons/effects/effects.dmi', icon_state = "zzz_glow")
+	if(GLOB.non_respawnable_keys[ckey])
+		flags &= ~GHOST_CAN_REENTER
+	var/mob/dead/observer/ghost = new(src, flags) // Transfer safety to observer spawning proc.
+	ghost.timeofdeath = src.timeofdeath // BS12 EDIT
+	if(ghost.can_reenter_corpse)
+		ADD_TRAIT(ghost, TRAIT_RESPAWNABLE, GHOSTED)
+	else
+		GLOB.non_respawnable_keys[ckey] = 1
+
+	// mods, mentors, and the like will have admin observe anyway, so this is moot
+	if(((key in GLOB.antag_hud_users) || (key in GLOB.roundstart_observer_keys)) && !check_rights(R_MOD | R_ADMIN | R_MENTOR, FALSE, src))
+		ghost.verbs |= /mob/dead/observer/proc/do_observe
+		ghost.verbs |= /mob/dead/observer/proc/observe
+	if(user_color)
+		add_atom_colour(user_color, ADMIN_COLOUR_PRIORITY)
+		ghost.color = user_color
+	if(ghost_name)
+		ghost.name = ghost_name
+	ghost.key = key
+
+	ghost.client?.init_verbs()
+
+	for(var/mob/dead/observer/obs in observers)
+		obs.cleanup_observe()
+
+
+	return ghost
 
 /*
 This is the proc mobs get to turn into a ghost. Forked from ghostize due to compatibility issues.
@@ -492,52 +508,67 @@ This is the proc mobs get to turn into a ghost. Forked from ghostize due to comp
 	GLOB.ghost_crew_monitor.ui_interact(src)
 
 /mob/dead/observer/proc/add_observer_verbs()
-	verbs.Add(/mob/dead/observer/proc/ManualFollow)
+	verbs.Add(
+		/mob/dead/observer/proc/ManualFollow,
+	)
 
 /mob/dead/observer/proc/remove_observer_verbs()
-	verbs.Remove(/mob/dead/observer/proc/ManualFollow)
+	verbs.Remove(
+		/mob/dead/observer/proc/ManualFollow,
+		// these might not necessarily be here, but we want to make sure they're gonezo anyway
+		/mob/dead/observer/proc/observe,
+		/mob/dead/observer/proc/do_observe
+	)
 
-// This is the ghost's follow verb with an argument
+// This is the ghost's follow verb with an argument.
+// We need to do the usr check on this verb itself, but the logic follows.
 /mob/dead/observer/proc/ManualFollow(atom/movable/target)
 	set name = "\[Observer\] Orbit"
 	set desc = "Orbits the specified movable atom."
 	set category = null
 
-	if(!target || !isobserver(usr))
+	// this usr check is apparently necessary for security
+	if(!isobserver(usr))
 		return
 
+	return do_manual_follow(target)
+
+// We need to check usr when calling the verb, but we still want this logic to be accessible elsewhere
+/mob/dead/observer/proc/do_manual_follow(atom/movable/target)
 	if(!get_turf(target))
 		return
 
-	if(target != src)
-		if(src in target.get_orbiters())
-			return
+	if(!target || target == src)
+		return
 
-		var/icon/I = icon(target.icon,target.icon_state,target.dir)
+	if(src in target.get_orbiters())
+		return
 
-		var/orbitsize = (I.Width()+I.Height())*0.5
+	var/icon/I = icon(target.icon, target.icon_state, target.dir)
 
-		if(orbitsize == 0)
-			orbitsize = 40
+	var/orbitsize = (I.Width() + I.Height())*0.5
 
-		orbitsize -= (orbitsize/world.icon_size)*(world.icon_size*0.25)
+	if(orbitsize == 0)
+		orbitsize = 40
 
-		var/rot_seg
+	orbitsize -= (orbitsize/world.icon_size)*(world.icon_size*0.25)
 
-		switch(ghost_orbit)
-			if(GHOST_ORBIT_TRIANGLE)
-				rot_seg = 3
-			if(GHOST_ORBIT_SQUARE)
-				rot_seg = 4
-			if(GHOST_ORBIT_PENTAGON)
-				rot_seg = 5
-			if(GHOST_ORBIT_HEXAGON)
-				rot_seg = 6
-			else //Circular
-				rot_seg = 36 //360/10 bby, smooth enough aproximation of a circle
+	var/rot_seg
 
-		to_chat(src, "<span class='notice'>Now following [target].</span>")
-		orbit(target,orbitsize, FALSE, 20, rot_seg)
+	switch(ghost_orbit)
+		if(GHOST_ORBIT_TRIANGLE)
+			rot_seg = 3
+		if(GHOST_ORBIT_SQUARE)
+			rot_seg = 4
+		if(GHOST_ORBIT_PENTAGON)
+			rot_seg = 5
+		if(GHOST_ORBIT_HEXAGON)
+			rot_seg = 6
+		else // Circular
+			rot_seg = 36 // 360/10 bby, smooth enough aproximation of a circle
+
+	to_chat(src, "<span class='notice'>Now following [target].</span>")
+	orbit(target, orbitsize, FALSE, 20, rot_seg)
 
 /mob/dead/observer/orbit(atom/A, radius = 10, clockwise = FALSE, rotation_speed = 20, rotation_segments = 36, pre_rotation = TRUE, lock_in_orbit = FALSE, force_move = FALSE, orbit_layer = GHOST_LAYER)
 	setDir(2)//reset dir so the right directional sprites show up
@@ -825,6 +856,102 @@ This is the proc mobs get to turn into a ghost. Forked from ghostize due to comp
 /mob/dead/observer/get_runechat_color()
 	return alive_runechat_color
 
+/mob/dead/observer/proc/observe()
+	set name = "Observe"
+	set desc = "Observe a mob."
+	set category = "Ghost"
+
+	var/list/possible_targets = list()
+	for(var/mob/living/L in GLOB.player_list)
+		if(!L.mind)
+			continue
+		possible_targets.Add(L)
+
+	if(!length(possible_targets))
+		to_chat(src, "<span class='warning'>There's nobody for you to observe!</span>")
+		return
+
+	var/mob/target = tgui_input_list(usr, "Please, select a player!", "Observe", possible_targets)
+	if(!istype(target) || QDELETED(target))
+		return
+	do_observe(target)
+
+/mob/dead/observer/proc/do_observe(mob/mob_eye)
+	set name = "\[Observer\] Observe"
+	set desc = "Observe the target mob."
+	set category = null
+
+	if(isnewplayer(mob_eye))
+		to_chat(src, "<span class='warning'>You can't observe someone in the lobby.</span>")
+		return
+
+	if(isobserver(mob_eye))
+		to_chat(src, "<span class='warning'>You can't observe a ghost.</span>")
+		return
+
+	if(!mob_eye.mind)
+		to_chat(src, "<span class='notice'>You can only observe mobs that have been or are being inhabited by a player!</span>")
+		return
+
+	if(mob_eye == src)
+		to_chat(src, "<span class='warning'>You can't observe yourself!</span>")
+		return
+
+	if(mob_observed)
+		// clean up first
+		stop_orbit()
+		cleanup_observe()
+
+	// Istype so we filter out points of interest that are not mobs
+	if(client && ismob(mob_eye))
+		// follow the mob so they're technically right there for visible messages n stuff
+		// call the sub-proc since the base one checks for usr
+		do_manual_follow(mob_eye)
+		client.set_eye(mob_eye)
+		add_attack_logs(src, mob_eye, "observed", ATKLOG_ALMOSTALL)
+		client.perspective = EYE_PERSPECTIVE
+		if(mob_eye.hud_used)
+			client.clear_screen()
+			LAZYOR(mob_eye.observers, src)
+			mob_eye.hud_used?.show_hud(mob_eye.hud_used.hud_version, src)
+			mob_observed = mob_eye.UID()
+
+
+		// mentor observing grants you this trait, and provides its own signal handler for this
+		if(!HAS_MIND_TRAIT(src, TRAIT_MENTOR_OBSERVING))
+			RegisterSignal(src, COMSIG_ATOM_ORBITER_STOP, PROC_REF(on_observer_orbit_end), override = TRUE)
+		else
+			if(!check_rights(R_MENTOR, FALSE, src))
+				log_debug("[key_name(src)] has the the mobserve trait while observing, but isn't a mentor. This is likely an error, and may result in them getting stuck")
+
+/// Clean up observing
+/mob/dead/observer/proc/cleanup_observe()
+	if(isnull(mob_observed))
+		return
+
+	var/mob/target = locateUID(mob_observed)
+	add_attack_logs(src, target, "un-observed", ATKLOG_ALL)
+	mob_observed = null
+	reset_perspective(null)
+	client?.perspective = initial(client.perspective)
+	set_sight(initial(sight))
+	UnregisterSignal(src, COMSIG_ATOM_ORBITER_STOP)
+
+	if(s_active)
+		var/obj/item/storage/bag = s_active
+		s_active = null
+		bag.update_viewers(src)
+
+	if(!QDELETED(target) && istype(target))
+		hide_other_mob_action_buttons(target)
+		target.observers -= src
+
+/mob/dead/observer/proc/on_observer_orbit_end(mob/follower, atom)
+	SIGNAL_HANDLER	// COMSIG_ATOM_ORBITER_STOP
+	if(HAS_MIND_TRAIT(src, TRAIT_MENTOR_OBSERVING))
+		log_debug("[key_name(src)] ended up in regular cleanup_observe rather than the mentor cleanup observe despite having TRAIT_MENTOR_OBSERVING. This is likely a bug and may result in them being stuck outside of their bodies.")
+	cleanup_observe()
+
 /mob/dead/observer/proc/update_dead_radio()
 	if(get_preference(PREFTOGGLE_CHAT_GHOSTRADIO))
 		GLOB.deadchat_radio.listeners |= src

code/modules/mob/dead/observer/observer_logout.dm

@@ -1,6 +1,9 @@
 /mob/dead/observer/Logout()
 	if(client)
 		client.images -= GLOB.ghost_images
+	if(mob_observed && ismob(locateUID(mob_observed)))
+		cleanup_observe()
+
 	..()
 	spawn(0)
 		if(src && !key)	//we've transferred to another mob. This ghost should be deleted.

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

@@ -49,6 +49,8 @@
 			r_hand.screen_loc = ui_rhand
 			client.screen += r_hand
 
+		update_observer_view(r_hand)
+
 /mob/living/carbon/update_inv_l_hand(ignore_cuffs)
 	if(handcuffed && !ignore_cuffs)
 		drop_l_hand()
@@ -57,6 +59,7 @@
 		if(client && hud_used && hud_used.hud_version != HUD_STYLE_NOHUD)
 			l_hand.screen_loc = ui_lhand
 			client.screen += l_hand
+		update_observer_view(l_hand)
 
 /mob/living/carbon/update_inv_wear_mask()
 	if(istype(wear_mask, /obj/item/clothing/mask))
@@ -86,3 +89,17 @@
 /mob/living/carbon/proc/update_hud_back(obj/item/I)
 	return
 
+/mob/living/carbon/proc/update_observer_view(obj/item/worn_item, inventory)
+	if(!length(observers))
+		return
+	for(var/mob/dead/observe as anything in observers)
+		if(observe.client && observe.client.eye == src)
+			if(observe.hud_used)
+				if(inventory && !observe.hud_used.inventory_shown)
+					continue
+				observe.client.screen += worn_item
+		else
+			observers -= observe
+			if(!length(observers))
+				observers.Cut()
+				break

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

@@ -186,6 +186,13 @@
 		update_inv_r_hand()
 
 	I.screen_loc = null
+	if(client)
+		client.screen -= I
+	if(length(observers))
+		for(var/mob/dead/observe as anything in observers)
+			if(observe.client)
+				observe.client.screen -= I
+
 	I.forceMove(src)
 	I.equipped(src, slot, initial)
 	I.layer = ABOVE_HUD_LAYER
@@ -271,8 +278,8 @@
 				var/obj/item/clothing/head/hat = I
 				if(hat.vision_flags || hat.see_in_dark || !isnull(hat.lighting_alpha))
 					update_sight()
+			// this calls update_inv_head() on its own
 			head_update(I)
-			update_inv_head()
 		if(SLOT_HUD_SHOES)
 			shoes = I
 			update_inv_shoes()

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

@@ -567,10 +567,7 @@ GLOBAL_LIST_EMPTY(damage_icon_parts)
 			inv.update_icon()
 
 	if(w_uniform && istype(w_uniform, /obj/item/clothing/under))
-		if(client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD)
-			if(hud_used.inventory_shown)			//if the inventory is open ...
-				w_uniform.screen_loc = ui_iclothing //...draw the item in the inventory screen
-			client.screen += w_uniform				//Either way, add the item to the HUD
+		update_hud_uniform(w_uniform)
 
 		var/t_color = w_uniform.item_color
 		if(!t_color)
@@ -644,9 +641,7 @@ GLOBAL_LIST_EMPTY(damage_icon_parts)
 			inv.update_icon()
 
 	if(wear_id)
-		if(client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD)
-			wear_id.screen_loc = ui_id
-			client.screen += wear_id
+		update_hud_id(wear_id)
 
 		if(w_uniform && w_uniform:displays_id)
 			overlays_standing[ID_LAYER]	= mutable_appearance('icons/mob/mob.dmi', "id", layer = -ID_LAYER)
@@ -660,10 +655,7 @@ GLOBAL_LIST_EMPTY(damage_icon_parts)
 			inv.update_icon()
 
 	if(gloves)
-		if(client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD)
-			if(hud_used.inventory_shown)			//if the inventory is open ...
-				gloves.screen_loc = ui_gloves		//...draw the item in the inventory screen
-			client.screen += gloves					//Either way, add the item to the HUD
+		update_hud_gloves(gloves)
 
 		var/t_state = gloves.item_state
 		if(!t_state)	t_state = gloves.icon_state
@@ -702,10 +694,7 @@ GLOBAL_LIST_EMPTY(damage_icon_parts)
 	if(glasses)
 		var/mutable_appearance/new_glasses
 		var/obj/item/organ/external/head/head_organ = get_organ("head")
-		if(client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD)
-			if(hud_used.inventory_shown)			//if the inventory is open ...
-				glasses.screen_loc = ui_glasses		//...draw the item in the inventory screen
-			client.screen += glasses				//Either way, add the item to the HUD
+		update_hud_glasses(glasses)
 
 		if(glasses.icon_override)
 			new_glasses = mutable_appearance(glasses.icon_override, "[glasses.icon_state]", layer = -GLASSES_LAYER)
@@ -744,10 +733,7 @@ GLOBAL_LIST_EMPTY(damage_icon_parts)
 
 	if(l_ear || r_ear)
 		if(l_ear)
-			if(client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD)
-				if(hud_used.inventory_shown)			//if the inventory is open ...
-					l_ear.screen_loc = ui_l_ear			//...draw the item in the inventory screen
-				client.screen += l_ear					//Either way, add the item to the HUD
+			update_hud_l_ear(l_ear)
 
 			var/t_type = l_ear.item_state
 			if(!t_type)
@@ -761,10 +747,7 @@ GLOBAL_LIST_EMPTY(damage_icon_parts)
 				overlays_standing[EARS_LAYER] = mutable_appearance('icons/mob/clothing/ears.dmi', "[t_type]", layer = -EARS_LAYER)
 
 		if(r_ear)
-			if(client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD)
-				if(hud_used.inventory_shown)			//if the inventory is open ...
-					r_ear.screen_loc = ui_r_ear			//...draw the item in the inventory screen
-				client.screen += r_ear					//Either way, add the item to the HUD
+			update_hud_r_ear(r_ear)
 
 			var/t_type = r_ear.item_state
 			if(!t_type)
@@ -786,10 +769,7 @@ GLOBAL_LIST_EMPTY(damage_icon_parts)
 			inv.update_icon()
 
 	if(shoes)
-		if(client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD)
-			if(hud_used.inventory_shown)			//if the inventory is open ...
-				shoes.screen_loc = ui_shoes			//...draw the item in the inventory screen
-			client.screen += shoes					//Either way, add the item to the HUD
+		update_hud_shoes(shoes)
 
 		if(!wear_suit || !(wear_suit.flags_inv & HIDESHOES))
 			var/mutable_appearance/standing
@@ -822,9 +802,7 @@ GLOBAL_LIST_EMPTY(damage_icon_parts)
 			inv.update_icon()
 
 	if(s_store)
-		if(client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD)
-			s_store.screen_loc = ui_sstore1
-			client.screen += s_store
+		update_hud_s_store(s_store)
 
 		var/t_state = s_store.item_state
 		if(!t_state)
@@ -844,6 +822,7 @@ GLOBAL_LIST_EMPTY(damage_icon_parts)
 			inv.update_icon()
 
 	if(head)
+		update_hud_head(head)
 		var/mutable_appearance/standing
 		if(head.sprite_sheets && head.sprite_sheets[dna.species.sprite_sheet_name])
 			standing = mutable_appearance(head.sprite_sheets[dna.species.sprite_sheet_name], "[head.icon_state]", layer = -HEAD_LAYER)
@@ -877,6 +856,7 @@ GLOBAL_LIST_EMPTY(damage_icon_parts)
 			belt.screen_loc = ui_belt
 
 	if(belt)
+		update_observer_view(belt)
 		var/t_state = belt.item_state
 		if(!t_state)
 			t_state = belt.icon_state
@@ -899,10 +879,7 @@ GLOBAL_LIST_EMPTY(damage_icon_parts)
 			inv.update_icon()
 
 	if(wear_suit && istype(wear_suit, /obj/item/clothing/suit))
-		if(client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD)
-			if(hud_used.inventory_shown)					//if the inventory is open ...
-				wear_suit.screen_loc = ui_oclothing	//TODO	//...draw the item in the inventory screen
-			client.screen += wear_suit						//Either way, add the item to the HUD
+		update_hud_wear_suit(wear_suit)
 
 		var/mutable_appearance/standing
 		if(wear_suit.sprite_sheets && wear_suit.sprite_sheets[dna.species.sprite_sheet_name])
@@ -950,12 +927,17 @@ GLOBAL_LIST_EMPTY(damage_icon_parts)
 
 		if(hud_used.hud_version == HUD_STYLE_STANDARD)
 			if(l_store)
-				client.screen += l_store
 				l_store.screen_loc = ui_storage1
+				if(hud_used.hud_shown)
+					client.screen += l_store
+				update_observer_view(l_store)
 
 			if(r_store)
-				client.screen += r_store
 				r_store.screen_loc = ui_storage2
+				if(hud_used.hud_shown)
+					client.screen += r_store
+					r_store.screen_loc = ui_storage2
+				update_observer_view(r_store)
 
 /mob/living/carbon/human/update_inv_wear_pda()
 	if(client && hud_used)
@@ -964,8 +946,7 @@ GLOBAL_LIST_EMPTY(damage_icon_parts)
 			inv.update_icon()
 
 		if(wear_pda)
-			client.screen += wear_pda
-			wear_pda.screen_loc = ui_pda
+			update_hud_wear_pda(wear_pda)
 
 /mob/living/carbon/human/update_inv_wear_mask()
 	..()
@@ -975,6 +956,7 @@ GLOBAL_LIST_EMPTY(damage_icon_parts)
 		if(inv)
 			inv.update_icon()
 	if(wear_mask && (istype(wear_mask, /obj/item/clothing/mask) || istype(wear_mask, /obj/item/clothing/accessory)))
+		update_hud_wear_mask(wear_mask)
 		if(!(SLOT_HUD_WEAR_MASK in check_obscured_slots()))
 			var/obj/item/organ/external/head/head_organ = get_organ("head")
 			if(!istype(head_organ))
@@ -1009,6 +991,7 @@ GLOBAL_LIST_EMPTY(damage_icon_parts)
 	..()
 	remove_overlay(BACK_LAYER)
 	if(back)
+		update_hud_back(back)
 		//determine the icon to use
 		var/t_state = back.item_state
 		if(!t_state)
@@ -1045,6 +1028,7 @@ GLOBAL_LIST_EMPTY(damage_icon_parts)
 	..()
 	remove_overlay(R_HAND_LAYER)
 	if(r_hand)
+		show_hand_to_observers(r_hand, left = FALSE)
 		var/t_state = r_hand.item_state
 		if(!t_state)
 			t_state = r_hand.icon_state
@@ -1064,6 +1048,7 @@ GLOBAL_LIST_EMPTY(damage_icon_parts)
 	..()
 	remove_overlay(L_HAND_LAYER)
 	if(l_hand)
+		show_hand_to_observers(l_hand, left = TRUE)
 		var/t_state = l_hand.item_state
 		if(!t_state)
 			t_state = l_hand.icon_state
@@ -1080,25 +1065,105 @@ GLOBAL_LIST_EMPTY(damage_icon_parts)
 
 //human HUD updates for items in our inventory
 
-//update whether our head item appears on our hud.
-/mob/living/carbon/human/update_hud_head(obj/item/I)
-	if(client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD)
-		if(hud_used.inventory_shown)
-			I.screen_loc = ui_head
-		client.screen += I
+/mob/living/carbon/human/proc/show_hand_to_observers(obj/item/worn_item, left = TRUE)
+	if(client && hud_used && hud_used.hud_version != HUD_STYLE_NOHUD)
+		worn_item.screen_loc = ui_hand_position(left ? 1 : 2)
+		client.screen += worn_item
+		if(length(observers))
+			for(var/mob/dead/observe in observers)
+				if(observe.client && observe.client.eye == src)
+					observe.client.screen += worn_item
+				else
+					observers -= observe
+					if(!length(observers))
+						observers = null
+						break
 
-//update whether our mask item appears on our hud.
-/mob/living/carbon/human/update_hud_wear_mask(obj/item/I)
-	if(client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD)
-		if(hud_used.inventory_shown)
-			I.screen_loc = ui_mask
-		client.screen += I
 
-//update whether our back item appears on our hud.
-/mob/living/carbon/human/update_hud_back(obj/item/I)
-	if(client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD)
-		I.screen_loc = ui_back
-		client.screen += I
+/mob/living/carbon/human/update_hud_wear_mask(obj/item/worn_item)
+	worn_item.screen_loc = ui_mask
+	if((client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD) && (hud_used.inventory_shown && hud_used.hud_shown))
+		client.screen += worn_item
+	update_observer_view(worn_item, TRUE)
+
+
+/mob/living/carbon/human/proc/update_hud_uniform(obj/item/worn_item)
+	worn_item.screen_loc = ui_iclothing
+	if((client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD) && (hud_used.inventory_shown && hud_used.hud_shown))
+		client.screen += worn_item
+	update_observer_view(worn_item, TRUE)
+
+/mob/living/carbon/human/proc/update_hud_id(obj/item/worn_item)
+	worn_item.screen_loc = ui_id
+	if(client && hud_used?.hud_shown && hud_used.hud_version == HUD_STYLE_STANDARD)
+		client.screen += worn_item
+	update_observer_view(worn_item)
+
+/mob/living/carbon/human/proc/update_hud_wear_pda(obj/item/worn_item)
+	worn_item.screen_loc = ui_pda
+	if(client && hud_used?.hud_shown && hud_used.hud_version == HUD_STYLE_STANDARD)
+		client.screen += worn_item
+	update_observer_view(worn_item)
+
+/mob/living/carbon/human/proc/update_hud_gloves(obj/item/worn_item)
+	worn_item.screen_loc = ui_gloves
+	if((client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD) && (hud_used.inventory_shown && hud_used.hud_shown))
+		client.screen += worn_item
+	update_observer_view(worn_item, TRUE)
+
+/mob/living/carbon/human/proc/update_hud_glasses(obj/item/worn_item)
+	worn_item.screen_loc = ui_glasses
+	if((client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD) && (hud_used.inventory_shown && hud_used.hud_shown))
+		client.screen += worn_item
+	update_observer_view(worn_item, TRUE)
+
+/mob/living/carbon/human/proc/update_hud_l_ear(obj/item/worn_item)
+	worn_item.screen_loc = ui_l_ear
+	if((client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD) && (hud_used.inventory_shown && hud_used.hud_shown))
+		client.screen += worn_item
+	update_observer_view(worn_item, TRUE)
+
+/mob/living/carbon/human/proc/update_hud_r_ear(obj/item/worn_item)
+	worn_item.screen_loc = ui_r_ear
+	if((client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD) && (hud_used.inventory_shown && hud_used.hud_shown))
+		client.screen += worn_item
+	update_observer_view(worn_item, TRUE)
+
+/mob/living/carbon/human/proc/update_hud_shoes(obj/item/worn_item)
+	worn_item.screen_loc = ui_shoes
+	if((client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD) && (hud_used.inventory_shown && hud_used.hud_shown))
+		client.screen += worn_item
+	update_observer_view(worn_item, TRUE)
+
+/mob/living/carbon/human/proc/update_hud_s_store(obj/item/worn_item)
+	worn_item.screen_loc = ui_sstore1
+	if(client && hud_used?.hud_shown && hud_used.hud_version == HUD_STYLE_STANDARD)
+		client.screen += worn_item
+	update_observer_view(worn_item, TRUE)
+
+/mob/living/carbon/human/proc/update_hud_wear_suit(obj/item/worn_item)
+	worn_item.screen_loc = ui_oclothing
+	if((client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD) && (hud_used.inventory_shown && hud_used.hud_shown))
+		client.screen += worn_item
+	update_observer_view(worn_item, TRUE)
+
+/mob/living/carbon/human/proc/update_hud_belt(obj/item/worn_item)
+	belt.screen_loc = ui_belt
+	if(client && hud_used?.hud_shown && hud_used.hud_version == HUD_STYLE_STANDARD)
+		client.screen += worn_item
+	update_observer_view(worn_item, TRUE)
+
+/mob/living/carbon/human/update_hud_head(obj/item/worn_item)
+	worn_item.screen_loc = ui_head
+	if((client && hud_used && hud_used.hud_version == HUD_STYLE_STANDARD) && (hud_used.inventory_shown && hud_used.hud_shown))
+		client.screen += worn_item
+	update_observer_view(worn_item, TRUE)
+
+/mob/living/carbon/human/update_hud_back(obj/item/worn_item)
+	worn_item.screen_loc = ui_back
+	if(client && hud_used?.hud_shown && hud_used.hud_version == HUD_STYLE_STANDARD)
+		client.screen += worn_item
+	update_observer_view(worn_item, TRUE)
 
 /mob/living/carbon/human/proc/update_wing_layer()
 	remove_overlay(WING_UNDERLIMBS_LAYER)

code/modules/mob/living/death.dm

@@ -64,7 +64,7 @@
 	if(mind && suiciding)
 		mind.suicided = TRUE
 	reset_perspective(null)
-	hud_used?.reload_fullscreen()
+	reload_fullscreen()
 	update_sight()
 	update_action_buttons_icon()
 	ADD_TRAIT(src, TRAIT_FLOORED, STAT_TRAIT)

code/modules/mob/living/silicon/robot/robot_inventory.dm

@@ -15,6 +15,7 @@
 
 	O.mouse_opacity = MOUSE_OPACITY_OPAQUE
 
+	observer_screen_update(O, add = FALSE)
 	if(client)
 		client.screen -= O
 	contents -= O
@@ -78,6 +79,7 @@
 		set_actions(O)
 	else
 		to_chat(src, "You need to disable a module first!")
+	observer_screen_update(O, add = TRUE)
 	check_module_damage(FALSE)
 	update_icons()
 
@@ -250,3 +252,25 @@
 		hands.icon_state = "nomod"
 	else
 		hands.icon_state = lowertext(module.module_type)
+
+
+/**
+ * Updates the observers's screens with cyborg itemss.
+ * Arguments
+ * * item_module - the item being added or removed from the screen
+ * * add - whether or not the item is being added, or removed.
+ */
+/mob/living/silicon/robot/proc/observer_screen_update(obj/item/item_module, add = TRUE)
+	if(!length(observers))
+		return
+	for(var/mob/dead/observe in observers)
+		if(observe.client && observe.client.eye == src)
+			if(add)
+				observe.client.screen += item_module
+			else
+				observe.client.screen -= item_module
+		else
+			observers -= observe
+			if(!length(observers))
+				observers = null
+				break

code/modules/mob/living/silicon/robot/robot_mob.dm

@@ -27,10 +27,6 @@ GLOBAL_LIST_INIT(robot_verbs_default, list(
 	var/atom/movable/screen/lamp_button = null
 	var/atom/movable/screen/thruster_button = null
 
-	/// Used to determine whether the robot has the module menu shown or not.
-	var/shown_robot_modules = FALSE
-	var/atom/movable/screen/robot_modules_background
-
 	// 3 Modules can be activated at any one time.
 	var/obj/item/robot_module/module = null
 	var/module_active = null
@@ -172,11 +168,6 @@ GLOBAL_LIST_INIT(robot_verbs_default, list(
 
 	wires = new(src)
 
-	robot_modules_background = new()
-	robot_modules_background.icon_state = "block"
-	robot_modules_background.layer = HUD_LAYER	//Objects that appear on screen are on layer 20, UI should be just below it.
-	robot_modules_background.plane = HUD_PLANE
-
 	ident = rand(1, 999)
 	rename_character(null, get_default_name())
 	update_icons()
@@ -664,9 +655,6 @@ GLOBAL_LIST_INIT(robot_verbs_default, list(
 
 /mob/living/silicon/robot/proc/reset_module()
 	notify_ai(2)
-
-	shown_robot_modules = 0
-	client?.screen -= robot_modules_background
 	client?.screen -= hud_used.module_store_icon
 	uneq_all()
 	SStgui.close_user_uis(src)
@@ -699,6 +687,8 @@ GLOBAL_LIST_INIT(robot_verbs_default, list(
 
 	status_flags |= CANPUSH
 
+	hud_used.update_robot_modules_display()
+
 //for borg hotkeys, here module refers to borg inv slot, not core module
 /mob/living/silicon/robot/verb/cmd_toggle_module(module as num)
 	set name = "Toggle Module"

code/modules/mob/living/stat_states.dm

@@ -75,7 +75,7 @@
 		update_blind_effects()
 		update_sight()
 		updatehealth("update revive")
-		hud_used?.reload_fullscreen()
+		reload_fullscreen()
 
 	SEND_SIGNAL(src, COMSIG_LIVING_REVIVE, updating)
 

code/modules/mob/mob.dm

@@ -27,6 +27,10 @@
 		viewing_alternate_appearances = null
 	LAssailant = null
 	runechat_msg_location = null
+	if(length(observers))
+		for(var/mob/dead/observe as anything in observers)
+			observe.reset_perspective(null)
+
 	return ..()
 
 /mob/Initialize(mapload)
@@ -600,7 +604,7 @@ GLOBAL_LIST_INIT(slot_equipment_priority, list( \
 	if(.)
 		// Allows sharing HUDs with ghosts
 		if(hud_used)
-			client.screen = list()
+			client.clear_screen()
 			hud_used.show_hud(hud_used.hud_version)
 
 //mob verbs are faster than object verbs. See http://www.byond.com/forum/?post=1326139&page=2#comment8198716 for why this isn't atom/verb/examine()

code/modules/mob/mob_vars.dm

@@ -207,7 +207,7 @@
 	var/datum/input_focus = null
 	/// Is our mob currently suiciding? Used for suicide code along with many different revival checks
 	var/suiciding = FALSE
-	/// Used for some screen objects, such as
+	/// Used for some screen objects
 	var/list/screens = list()
 	/// lazy list. contains /atom/movable/screen/alert only,  On /mob so clientless mobs will throw alerts properly
 	var/list/alerts
@@ -246,7 +246,8 @@
 	var/next_click_modifier = 1
 	/// Tracks the open UIs that a mob has, used in TGUI for various things, such as updating UIs
 	var/list/open_uis = list()
-
+	/// List of observers currently observing us.
+	var/list/mob/dead/observer/observers = list()
 	/// Does this mob speak OOC?
 	/// Controls whether they can say some symbols.
 	var/speaks_ooc = FALSE

code/modules/mob/new_player/new_player.dm

@@ -182,7 +182,10 @@
 				var/period_human_readable = "within [GLOB.configuration.general.roundstart_observer_period] minute\s"
 				if(GLOB.configuration.general.roundstart_observer_period == 0)
 					period_human_readable = "before the round started"
-				to_chat(src, "<span class='notice'>As you observed [period_human_readable], you can freely toggle antag-hud without losing respawnability.</span>")
+				to_chat(src, "<span class='notice'>As you observed [period_human_readable], you can freely toggle antag-hud without losing respawnability, and can freely observe what other players see.</span>")
+				if(!check_rights(R_MOD | R_ADMIN | R_MENTOR, FALSE, src))
+					// admins always get aobserve
+					add_verb(observer, list(/mob/dead/observer/proc/do_observe, /mob/dead/observer/proc/observe))
 			observer.started_as_observer = 1
 			close_spawn_windows()
 			var/obj/spawn_point