Gives ghosts the ability to spook mirrors (#30817)

* adds behavior

* transparency test

* transparency

* mask and logic

* comments

* removed the chance for mirrors to break

* linting

* autodoc

code/game/objects/structures/mirror.dm

@@ -10,7 +10,13 @@
 	var/list/ui_users = list()
 	var/broken_icon_state = "mirror_broke"
 
+	/// what to show when a ghost Boo!'s this mirror
+	var/icon/spooked_icon
+	/// Whether a mirror can be Boo!'d or not. Magic mirrors are animated, so this is used to stop them from looking weird
+	var/can_be_spooked = TRUE
+
 /obj/structure/mirror/organ
+	can_be_spooked = FALSE
 
 /obj/structure/mirror/Initialize(mapload, newdir = SOUTH, building = FALSE)
 	. = ..()
@@ -25,6 +31,7 @@
 			if(WEST)
 				pixel_x = 32
 	GLOB.mirrors += src
+	spooked_icon = update_spooked_icon(icon("icons/mob/human.dmi", "husk_s"), SOUTH, 8, 0)
 
 /obj/structure/mirror/Destroy()
 	QDEL_LIST_ASSOC_VAL(ui_users)
@@ -86,6 +93,32 @@
 		if(BURN)
 			playsound(src, 'sound/effects/hit_on_shattered_glass.ogg', 70, TRUE)
 
+/obj/structure/mirror/get_spooked()
+	if(!can_be_spooked || broken)
+		return
+	flicker_ghost(spooked_icon)
+	return TRUE
+
+/// This proc sets the icon that will show up in the mirror when spooked
+/// * icon_to_show - which icon
+/// * offset_dir - you might want to move the icon so it appears in the mirror
+/// * offset_pixels - how many pixels you need to move the icon
+/// * wrap - if the icon should wrap around
+/obj/structure/mirror/proc/update_spooked_icon(icon/icon_to_show, offset_dir, offset_pixels, wrap)
+	var/icon/our_icon = icon_to_show
+	our_icon.Shift(offset_dir,offset_pixels,wrap)
+	var/icon/alpha_mask = new("icons/obj/watercloset.dmi", "mirror_mask")
+	our_icon.AddAlphaMask(alpha_mask)
+	var/icon/added_icons = new("icons/obj/watercloset.dmi", "mirror")
+	added_icons.Blend(our_icon, ICON_OVERLAY)
+	return added_icons
+
+/// Shows the icon in the mirror with its mask
+/obj/structure/mirror/proc/flicker_ghost(icon/icon_to_show)
+	icon = icon_to_show
+	sleep(rand(5,10))
+	icon = initial(icon)
+	return
 
 /obj/item/mounted/mirror
 	name = "mirror"
@@ -105,6 +138,7 @@
 	var/options = list("Name", "Body", "Voice")
 	var/organ_warn = FALSE
 	var/actually_magical = TRUE
+	can_be_spooked = FALSE
 
 /obj/structure/mirror/magic/Initialize(mapload, newdir, building)
 	. = ..()
@@ -187,4 +221,3 @@
 	options = list("Body")
 	organ_warn = TRUE
 	actually_magical = FALSE
-