Fixes #8508

Checks for blood splatter in the target location properly and avoids creating too many blood atoms.

code/__HELPERS/unsorted.dm

@@ -1923,3 +1923,10 @@ var/mob/dview/dview_mob = new
 			shift = list("x" = -amount_x, "y" = -amount_y)
 
 	return shift
+
+//Return a list of atoms in a location of a given type. Can be refined to look for pixel-shift.
+/proc/get_atoms_of_type_here(var/atom/here, var/type, var/p_x = 0, var/p_y = 0)
+	. = list()
+	for(var/atom/thing in here)
+		if(istype(thing, type) && (p_x && thing.pixel_x == p_x) && (p_y && thing.pixel_y == p_y))
+			. += thing

code/game/objects/effects/decals/Cleanable/aliens.dm

@@ -6,6 +6,11 @@
 	bloodiness = MAX_SHOE_BLOODINESS
 	blood_state = BLOOD_STATE_XENO
 
+
+/obj/effect/decal/cleanable/blood/xeno/splatter
+	random_icon_states = list("mgibbl1", "mgibbl2", "mgibbl3", "mgibbl4", "mgibbl5")
+	amount = 2
+
 /obj/effect/decal/cleanable/blood/gibs/xeno
 	name = "xeno gibs"
 	desc = "Gnarly..."

code/game/objects/effects/decals/Cleanable/robots.dm

@@ -58,4 +58,4 @@
 
 /obj/effect/decal/cleanable/blood/oil/streak
 	random_icon_states = list("mgibbl1", "mgibbl2", "mgibbl3", "mgibbl4", "mgibbl5")
-	amount = 2
+	amount = 2

code/modules/surgery/organs/blood.dm

@@ -260,11 +260,14 @@
 			return
 
 	// Find a blood decal or create a new one.
-	var/obj/effect/decal/cleanable/blood/B
-	if(!(locate(B) in T) || pixel_x || pixel_y)
-		B = new /obj/effect/decal/cleanable/blood/splatter(T)
-	else
-		B = locate() in T
+	var/obj/effect/decal/cleanable/blood/splatter/B = locate() in T
+	var/list/bloods = get_atoms_of_type_here(T, B, 0, 0) //Get all the non-projectile-splattered blood on this turf.
+	if(shift_x || shift_y)
+		bloods = get_atoms_of_type_here(T, B, shift_x, shift_y) //Get all the projectile-splattered blood at these pixels on this turf.
+		B = locate() in bloods
+	if(!B)
+		B = new(T)
+
 	B.transfer_mob_blood_dna(src) //give blood info to the blood decal.
 	if(temp_blood_DNA)
 		B.blood_DNA |= temp_blood_DNA
@@ -282,11 +285,15 @@
 /mob/living/carbon/alien/add_splatter_floor(turf/T, small_drip, shift_x, shift_y)
 	if(!T)
 		T = get_turf(src)
-	var/obj/effect/decal/cleanable/blood/xeno/B
-	if(!(locate(B) in T) || pixel_x || pixel_y)
+
+	var/obj/effect/decal/cleanable/blood/xeno/splatter/B = locate() in T
+	var/list/bloods = get_atoms_of_type_here(T, B, 0, 0) //The more the better.
+	if(shift_x || shift_y)
+		bloods = get_atoms_of_type_here(T, B, shift_x, shift_y)
+		B = locate() in bloods
+	if(!B)
 		B = new(T)
-	else
-		B = locate() in T
+
 	B.blood_DNA["UNKNOWN DNA"] = "X*"
 	B.pixel_x = (shift_x)
 	B.pixel_y = (shift_y)
@@ -297,13 +304,17 @@
 /mob/living/silicon/robot/add_splatter_floor(turf/T, small_drip, shift_x, shift_y)
 	if(!T)
 		T = get_turf(src)
-	var/obj/effect/decal/cleanable/blood/oil/B
-	if(!(locate(B) in T) || pixel_x || pixel_y)
-		B = new(T)
-	else
-		B = locate() in T
-	B.pixel_x = (shift_x)
-	B.pixel_y = (shift_y)
+
+	var/obj/effect/decal/cleanable/blood/oil/streak/O = locate() in T
+	var/list/oils = get_atoms_of_type_here(T, O, 0, 0) //Don't let OSHA catch wind of this.
 	if(shift_x || shift_y)
-		B.off_floor = TRUE
-		B.layer = BELOW_MOB_LAYER
+		oils = get_atoms_of_type_here(T, O, shift_x, shift_y)
+		O = locate() in oils
+	if(!O)
+		O = new(T)
+
+	O.pixel_x = (shift_x)
+	O.pixel_y = (shift_y)
+	if(shift_x || shift_y)
+		O.off_floor = TRUE
+		O.layer = BELOW_MOB_LAYER