Jetpacks (#9023)

* Movement acceleration

* tweaks

* Weightless refactor coz fuck it

* CCVars

* weightless movement tweaks

* Some cleanup while I'm here

* dorkpacks

* thanks fork

* fixes

* zoomies

* toggles

* hmm

* yamls

* b

* so true

* Effects refactor

* namespace

* review

Content.Shared/Movement/Systems/MovementSpeedModifierSystem.cs

@@ -0,0 +1,79 @@
+using Content.Shared.Inventory;
+using Content.Shared.Movement.Components;
+using Robust.Shared.GameStates;
+using Robust.Shared.Serialization;
+
+namespace Content.Shared.Movement.Systems
+{
+    public sealed class MovementSpeedModifierSystem : EntitySystem
+    {
+        public override void Initialize()
+        {
+            base.Initialize();
+            SubscribeLocalEvent<MovementSpeedModifierComponent, ComponentGetState>(OnGetState);
+            SubscribeLocalEvent<MovementSpeedModifierComponent, ComponentHandleState>(OnHandleState);
+        }
+
+        private void OnGetState(EntityUid uid, MovementSpeedModifierComponent component, ref ComponentGetState args)
+        {
+            args.State = new MovementSpeedModifierComponentState
+            {
+                BaseWalkSpeed = component.BaseWalkSpeed,
+                BaseSprintSpeed = component.BaseSprintSpeed,
+                WalkSpeedModifier = component.WalkSpeedModifier,
+                SprintSpeedModifier = component.SprintSpeedModifier
+            };
+        }
+
+        private void OnHandleState(EntityUid uid, MovementSpeedModifierComponent component, ref ComponentHandleState args)
+        {
+            if (args.Current is not MovementSpeedModifierComponentState state) return;
+            component.BaseWalkSpeed = state.BaseWalkSpeed;
+            component.BaseSprintSpeed = state.BaseSprintSpeed;
+            component.WalkSpeedModifier = state.WalkSpeedModifier;
+            component.SprintSpeedModifier = state.SprintSpeedModifier;
+        }
+
+        public void RefreshMovementSpeedModifiers(EntityUid uid, MovementSpeedModifierComponent? move = null)
+        {
+            if (!Resolve(uid, ref move, false))
+                return;
+
+            var ev = new RefreshMovementSpeedModifiersEvent();
+            RaiseLocalEvent(uid, ev);
+
+            move.WalkSpeedModifier = ev.WalkSpeedModifier;
+            move.SprintSpeedModifier = ev.SprintSpeedModifier;
+
+            Dirty(move);
+        }
+
+        [Serializable, NetSerializable]
+        private sealed class MovementSpeedModifierComponentState : ComponentState
+        {
+            public float BaseWalkSpeed;
+            public float BaseSprintSpeed;
+            public float WalkSpeedModifier;
+            public float SprintSpeedModifier;
+        }
+    }
+
+    /// <summary>
+    ///     Raised on an entity to determine its new movement speed. Any system that wishes to change movement speed
+    ///     should hook into this event and set it then. If you want this event to be raised,
+    ///     call <see cref="MovementSpeedModifierSystem.RefreshMovementSpeedModifiers"/>.
+    /// </summary>
+    public sealed class RefreshMovementSpeedModifiersEvent : EntityEventArgs, IInventoryRelayEvent
+    {
+        public SlotFlags TargetSlots { get; } = ~SlotFlags.POCKET;
+
+        public float WalkSpeedModifier { get; private set; } = 1.0f;
+        public float SprintSpeedModifier { get; private set; } = 1.0f;
+
+        public void ModifySpeed(float walk, float sprint)
+        {
+            WalkSpeedModifier *= walk;
+            SprintSpeedModifier *= sprint;
+        }
+    }
+}