Some grab fixes.. (#17895)

* Some grab fixes..

* A tradeoff in jank

* Address review comments

* .. and a small comment

code/modules/mob/living/living.dm

@@ -540,25 +540,12 @@
 	if(restrained())
 		stop_pulling()
 
-	var/turf/T = loc
+	var/turf/old_loc = loc
 	. = ..()
 	if(.)
 		step_count++
-
-		if(pulling && pulling == pullee) // we were pulling a thing and didn't lose it during our move.
-			if(pulling.anchored)
-				stop_pulling()
-				return
-
-			var/pull_dir = get_dir(src, pulling)
-			if(get_dist(src, pulling) > 1 || (moving_diagonally != SECOND_DIAG_STEP && ((pull_dir - 1) & pull_dir))) // puller and pullee more than one tile away or in diagonal position
-				if(isliving(pulling))
-					var/mob/living/M = pulling
-					if(M.lying && !M.buckled && (prob(M.getBruteLoss() * 200 / M.maxHealth)))
-						M.makeTrail(T)
-				pulling.Move(T, get_dir(pulling, T), movetime) // the pullee tries to reach our previous position
-				if(pulling && get_dist(src, pulling) > 1) // the pullee couldn't keep up
-					stop_pulling()
+		pull_pulled(old_loc, pullee, movetime)
+		pull_grabbed(old_loc, direct, movetime)
 
 	if(pulledby && moving_diagonally != FIRST_DIAG_STEP && get_dist(src, pulledby) > 1) //seperated from our puller and not in the middle of a diagonal move
 		pulledby.stop_pulling()
@@ -566,6 +553,67 @@
 	if(s_active && !(s_active in contents) && get_turf(s_active) != get_turf(src))	//check !( s_active in contents ) first so we hopefully don't have to call get_turf() so much.
 		s_active.close(src)
 
+/mob/living/proc/pull_pulled(turf/dest, atom/movable/pullee, movetime)
+	if(pulling && pulling == pullee) // we were pulling a thing and didn't lose it during our move.
+		if(pulling.anchored)
+			stop_pulling()
+			return
+
+		var/pull_dir = get_dir(src, pulling)
+		if(get_dist(src, pulling) > 1 || (moving_diagonally != SECOND_DIAG_STEP && ((pull_dir - 1) & pull_dir))) // puller and pullee more than one tile away or in diagonal position
+			if(isliving(pulling))
+				var/mob/living/M = pulling
+				if(M.lying && !M.buckled && (prob(M.getBruteLoss() * 200 / M.maxHealth)))
+					M.makeTrail(dest)
+			pulling.Move(dest, get_dir(pulling, dest), movetime) // the pullee tries to reach our previous position
+			if(pulling && get_dist(src, pulling) > 1) // the pullee couldn't keep up
+				stop_pulling()
+
+/mob/living/proc/pull_grabbed(turf/old_turf, direct, movetime)
+	if(!Adjacent(old_turf))
+		return
+	// yes, this is four distinct `for` loops. No, they can't be merged.
+	var/list/grabbing = list()
+	for(var/mob/M in ret_grab())
+		if(src != M)
+			grabbing |= M
+	for(var/mob/M in grabbing)
+		M.currently_grab_pulled = TRUE
+		M.animate_movement = SYNC_STEPS
+	for(var/i in 1 to length(grabbing))
+		var/mob/M = grabbing[i]
+		if(QDELETED(M))  // old code warned me that M could go missing during a move, so I'm cargo-culting it here
+			continue
+		// compile a list of turfs we can maybe move them towards
+		// importantly, this should happen before actually trying to move them to either of those
+		// otherwise they can be moved twice (since `Move` returns TRUE only if it managed to
+		// *fully* move where you wanted it to; it can still move partially and return FALSE)
+		var/possible_dest = list()
+		for(var/turf/dest in orange(src, 1))
+			if(dest.Adjacent(M))
+				possible_dest |= dest
+		if(i == 1) // at least one of them should try to trail behind us, for aesthetics purposes
+			if(M.Move(old_turf, get_dir(M, old_turf), movetime))
+				continue
+		// By this time the `old_turf` is definitely occupied by something immovable.
+		// So try to move them into some other adjacent turf, in a believable way
+		if(Adjacent(M))
+			continue // they are already adjacent
+		for(var/turf/dest in possible_dest)
+			if(M.Move(dest, get_dir(M, dest), movetime))
+				break
+	for(var/mob/M in grabbing)
+		M.currently_grab_pulled = null
+		M.animate_movement = SLIDE_STEPS
+
+	for(var/obj/item/grab/G in src)
+		if(G.state == GRAB_NECK)
+			setDir(angle2dir((dir2angle(direct) + 202.5) % 365))
+		G.adjust_position()
+	for(var/obj/item/grab/G in grabbed_by)
+		G.adjust_position()
+
+
 /mob/living/proc/makeTrail(turf/T)
 	if(!has_gravity(src))
 		return

code/modules/mob/mob_defines.dm

@@ -40,7 +40,7 @@
 
 	var/last_log = 0
 	var/obj/machinery/machine = null
-	var/other_mobs = null
+	var/currently_grab_pulled = null  /// only set while the move is ongoing, to prevent shuffling between pullees
 	var/memory = ""
 	var/next_move = null
 	var/notransform = null	//Carbon

code/modules/mob/mob_movement.dm

@@ -11,8 +11,8 @@
 		return TRUE
 	if(ismob(mover))
 		var/mob/moving_mob = mover
-		if((other_mobs && moving_mob.other_mobs))
-			return TRUE
+		if((currently_grab_pulled && moving_mob.currently_grab_pulled))
+			return FALSE
 		if(mover in buckled_mobs)
 			return TRUE
 	return (!mover.density || !density || lying)
@@ -131,50 +131,23 @@
 
 	delay = TICKS2DS(-round(-(DS2TICKS(delay)))) //Rounded to the next tick in equivalent ds
 
+
 	if(locate(/obj/item/grab, mob))
 		delay += 7
-		var/list/L = mob.ret_grab()
-		if(istype(L, /list))
-			if(L.len == 2)
-				L -= mob
-				var/mob/M = L[1]
-				if(M)
-					if((get_dist(mob, M) <= 1 || M.loc == mob.loc))
-						var/turf/prev_loc = mob.loc
-						. = mob.SelfMove(n, direct, delay)
-						if(M && isturf(M.loc)) // Mob may get deleted during parent call
-							var/diag = get_dir(mob, M)
-							if((diag - 1) & diag)
-							else
-								diag = null
-							if((get_dist(mob, M) > 1 || diag))
-								M.Move(prev_loc, get_dir(M.loc, prev_loc), delay)
-			else
-				for(var/mob/M in L)
-					M.other_mobs = 1
-					if(mob != M)
-						M.animate_movement = 3
-				for(var/mob/M in L)
-					spawn(0)
-						M.Move(get_step(M,direct), direct, delay)
-					spawn(1)
-						M.other_mobs = null
-						M.animate_movement = 2
 
-	else
-		var/mob/living/L = mob
-		if(L)
-			var/newdir = NONE
-			var/confusion = L.get_confusion()
-			if(confusion > CONFUSION_MAX)
-				newdir = pick(GLOB.alldirs)
-			else if(prob(confusion * CONFUSION_HEAVY_COEFFICIENT))
-				newdir = angle2dir(dir2angle(direct) + pick(90, -90))
-			else if(prob(confusion * CONFUSION_LIGHT_COEFFICIENT))
-				newdir = angle2dir(dir2angle(direct) + pick(45, -45))
-			if(newdir)
-				direct = newdir
-				n = get_step(mob, direct)
+	var/mob/living/living_mob = mob
+	if(istype(living_mob))
+		var/newdir = NONE
+		var/confusion = living_mob.get_confusion()
+		if(confusion > CONFUSION_MAX)
+			newdir = pick(GLOB.alldirs)
+		else if(prob(confusion * CONFUSION_HEAVY_COEFFICIENT))
+			newdir = angle2dir(dir2angle(direct) + pick(90, -90))
+		else if(prob(confusion * CONFUSION_LIGHT_COEFFICIENT))
+			newdir = angle2dir(dir2angle(direct) + pick(45, -45))
+		if(newdir)
+			direct = newdir
+			n = get_step(mob, direct)
 
 	var/prev_pulling_loc = null
 	if(mob.pulling)
@@ -198,13 +171,6 @@
 	else
 		mob.setDir(direct)
 
-	for(var/obj/item/grab/G in mob)
-		if(G.state == GRAB_NECK)
-			mob.setDir(angle2dir((dir2angle(direct) + 202.5) % 365))
-		G.adjust_position()
-	for(var/obj/item/grab/G in mob.grabbed_by)
-		G.adjust_position()
-
 	moving = 0
 	if(mob && .)
 		if(mob.throwing)