Swarm Component + Pixel shift attack animation (#17179)

* Swarm!!

* carp dmi

* swarm

* Proper swarming

* Swarmers

* Update

---------

Co-authored-by: Selis <12716288+ItsSelis@users.noreply.github.com>

code/datums/components/connect_loc_behalf.dm

@@ -0,0 +1,66 @@
+/// This component behaves similar to connect_loc, hooking into a signal on a tracked object's turf
+/// It has the ability to react to that signal on behalf of a separate listener however
+/// This has great use, primarily for components, but it carries with it some overhead
+/// So we do it separately as it needs to hold state which is very likely to lead to bugs if it remains as an element.
+/datum/component/connect_loc_behalf
+	dupe_mode = COMPONENT_DUPE_UNIQUE
+
+	/// An assoc list of signal -> procpath to register to the loc this object is on.
+	var/list/connections
+	var/atom/movable/tracked
+	var/atom/tracked_loc
+
+/datum/component/connect_loc_behalf/Initialize(atom/movable/tracked, list/connections)
+	. = ..()
+	if(!istype(tracked))
+		return COMPONENT_INCOMPATIBLE
+	src.connections = connections
+	src.tracked = tracked
+
+/datum/component/connect_loc_behalf/RegisterWithParent()
+	RegisterSignal(tracked, COMSIG_MOVABLE_MOVED, PROC_REF(on_moved))
+	RegisterSignal(tracked, COMSIG_PARENT_QDELETING, PROC_REF(handle_tracked_qdel))
+	update_signals()
+
+/datum/component/connect_loc_behalf/UnregisterFromParent()
+	unregister_signals()
+	UnregisterSignal(tracked, list(
+		COMSIG_MOVABLE_MOVED,
+		COMSIG_PARENT_QDELETING,
+	))
+
+	tracked = null
+
+/datum/component/connect_loc_behalf/proc/handle_tracked_qdel()
+	SIGNAL_HANDLER // COMSIG_PARENT_QDELETING
+	qdel(src)
+
+/datum/component/connect_loc_behalf/proc/update_signals()
+	unregister_signals()
+	//You may ask yourself, isn't this just silencing an error?
+	//The answer is yes, but there's no good cheap way to fix it
+	//What happens is the tracked object or hell the listener gets say, deleted, which makes targets[old_loc] return a null
+	//The null results in a bad index, because of course it does
+	//It's not a solvable problem though, since both actions, the destroy and the move, are sourced from the same signal send
+	//And sending a signal should be agnostic of the order of listeners
+	//So we need to either pick the order agnositic, or destroy safe
+	//And I picked destroy safe. Let's hope this is the right path!
+	if(isnull(tracked.loc))
+		return
+
+	tracked_loc = tracked.loc
+
+	for(var/signal in connections)
+		parent.RegisterSignal(tracked_loc, signal, connections[signal])
+
+/datum/component/connect_loc_behalf/proc/unregister_signals()
+	if(isnull(tracked_loc))
+		return
+
+	parent.UnregisterSignal(tracked_loc, connections)
+
+	tracked_loc = null
+
+/datum/component/connect_loc_behalf/proc/on_moved(sigtype, atom/movable/tracked, atom/old_loc)
+	SIGNAL_HANDLER // COMSIG_MOVABLE_MOVED
+	update_signals()

code/datums/components/swarm.dm

@@ -0,0 +1,59 @@
+/datum/component/swarming
+	var/offset_x = 0
+	var/offset_y = 0
+	var/is_swarming = FALSE
+	var/list/swarm_members = list()
+	var/static/list/swarming_loc_connections = list(
+		COMSIG_ATOM_EXITED = PROC_REF(leave_swarm),
+		COMSIG_ATOM_ENTERED = PROC_REF(join_swarm)
+	)
+
+
+/datum/component/swarming/Initialize(max_x = 24, max_y = 24)
+	if(!ismovable(parent))
+		return COMPONENT_INCOMPATIBLE
+	offset_x = rand(-max_x, max_x)
+	offset_y = rand(-max_y, max_y)
+
+	AddComponent(/datum/component/connect_loc_behalf, parent, swarming_loc_connections)
+
+/datum/component/swarming/Destroy()
+	for(var/other in swarm_members)
+		var/datum/component/swarming/other_swarm = other
+		other_swarm.swarm_members -= src
+		if(!length(other_swarm.swarm_members))
+			other_swarm.unswarm()
+	swarm_members = null
+	return ..()
+
+/datum/component/swarming/proc/join_swarm(datum/source, atom/movable/arrived, atom/old_loc, list/atom/old_locs)
+	var/datum/component/swarming/other_swarm = arrived.GetComponent(/datum/component/swarming)
+	if(!other_swarm)
+		return
+	swarm()
+	swarm_members |= other_swarm
+	other_swarm.swarm()
+	other_swarm.swarm_members |= src
+
+/datum/component/swarming/proc/leave_swarm(datum/source, atom/movable/gone, direction)
+	var/datum/component/swarming/other_swarm = gone.GetComponent(/datum/component/swarming)
+	if(!other_swarm || !(other_swarm in swarm_members))
+		return
+	swarm_members -= other_swarm
+	if(!length(swarm_members))
+		unswarm()
+	other_swarm.swarm_members -= src
+	if(!length(other_swarm.swarm_members))
+		other_swarm.unswarm()
+
+/datum/component/swarming/proc/swarm()
+	var/atom/movable/owner = parent
+	if(!is_swarming)
+		is_swarming = TRUE
+		animate(owner, pixel_x = owner.pixel_x + offset_x, pixel_y = owner.pixel_y + offset_y, time = 2)
+
+/datum/component/swarming/proc/unswarm()
+	var/atom/movable/owner = parent
+	if(is_swarming)
+		animate(owner, pixel_x = owner.pixel_x - offset_x, pixel_y = owner.pixel_y - offset_y, time = 2)
+		is_swarming = FALSE