[s] Fix observers being able to manipulate their target's screens (#38097)

* Fix observers being able to move the action button toggle button

* Fix observers using the target's ambient occlusion preference

code/_onclick/hud/action_button.dm

@@ -11,7 +11,24 @@
 	var/id
 	var/ordered = TRUE //If the button gets placed into the default bar
 
+/obj/screen/movable/action_button/proc/can_use(mob/user)
+	if (linked_action)
+		return linked_action.owner == user
+	else if (isobserver(user))
+		var/mob/dead/observer/O = user
+		return !O.observetarget
+	else
+		return TRUE
+
+/obj/screen/movable/action_button/MouseDrop()
+	if (!can_use(usr))
+		return
+	return ..()
+
 /obj/screen/movable/action_button/Click(location,control,params)
+	if (!can_use(usr))
+		return
+
 	var/list/modifiers = params2list(params)
 	if(modifiers["shift"])
 		if(locked)
@@ -44,6 +61,9 @@
 	var/show_state = "show"
 
 /obj/screen/movable/action_button/hide_toggle/Click(location,control,params)
+	if (!can_use(usr))
+		return
+
 	var/list/modifiers = params2list(params)
 	if(modifiers["shift"])
 		if(locked)

code/_onclick/hud/ghost.dm

@@ -73,6 +73,12 @@
 	static_inventory += using
 
 /datum/hud/ghost/show_hud(version = 0, mob/viewmob)
+	// don't show this HUD if observing; show the HUD of the observee
+	var/mob/dead/observer/O = mymob
+	if (istype(O) && O.observetarget)
+		plane_masters_update()
+		return FALSE
+
 	. = ..()
 	if(!.)
 		return

code/_onclick/hud/hud.dm

@@ -131,7 +131,7 @@
 		update_sight()
 
 //Version denotes which style should be displayed. blank or 0 means "next version"
-/datum/hud/proc/show_hud(version = 0,mob/viewmob)
+/datum/hud/proc/show_hud(version = 0, mob/viewmob)
 	if(!ismob(mymob))
 		return FALSE
 	var/mob/screenmob = viewmob || mymob
@@ -195,19 +195,30 @@
 			if(infodisplay.len)
 				screenmob.client.screen -= infodisplay
 
-	for(var/thing in plane_masters)
-		var/obj/screen/plane_master/PM = plane_masters[thing]
-		PM.backdrop(screenmob)
-		screenmob.client.screen += PM
-
 	hud_version = display_hud_version
 	persistent_inventory_update(screenmob)
 	screenmob.update_action_buttons(1)
 	reorganize_alerts()
 	screenmob.reload_fullscreen()
 	update_parallax_pref(screenmob)
+
+	// ensure observers get an accurate and up-to-date view
+	if (!viewmob)
+		plane_masters_update()
+		for(var/M in mymob.observers)
+			show_hud(hud_version, M)
+	else if (viewmob.hud_used)
+		viewmob.hud_used.plane_masters_update()
+
 	return TRUE
 
+/datum/hud/proc/plane_masters_update()
+	// Plane masters are always shown to OUR mob, never to observers
+	for(var/thing in plane_masters)
+		var/obj/screen/plane_master/PM = plane_masters[thing]
+		PM.backdrop(mymob)
+		mymob.client.screen += PM
+
 /datum/hud/human/show_hud(version = 0,mob/viewmob)
 	. = ..()
 	if(!.)
@@ -268,8 +279,9 @@
 		i++
 	for(var/obj/screen/human/equip/E in static_inventory)
 		E.screen_loc = ui_equip_position(mymob)
-	if(mymob.hud_used)
-		show_hud(HUD_STYLE_STANDARD,mymob)
+
+	if(ismob(mymob) && mymob.hud_used == src)
+		show_hud(hud_version)
 
 /datum/hud/proc/update_locked_slots()
 	return