Add conditional camera offset based on cursor - Hristov Rework, Part 1 (#31626)

(cherry picked from commit 5c782d30283d5e3661e1ce6ebc6d972f12671c41)

Content.Client/Wieldable/WieldableSystem.cs

@@ -0,0 +1,49 @@
+using System.Numerics;
+using Content.Client.Movement.Components;
+using Content.Client.Movement.Systems;
+using Content.Shared.Camera;
+using Content.Shared.Hands;
+using Content.Shared.Movement.Components;
+using Content.Shared.Wieldable;
+using Content.Shared.Wieldable.Components;
+using Robust.Client.Timing;
+
+namespace Content.Client.Wieldable;
+
+public sealed class WieldableSystem : SharedWieldableSystem
+{
+    [Dependency] private readonly EyeCursorOffsetSystem _eyeOffset = default!;
+    [Dependency] private readonly IClientGameTiming _gameTiming = default!;
+
+    public override void Initialize()
+    {
+        base.Initialize();
+
+        SubscribeLocalEvent<CursorOffsetRequiresWieldComponent, ItemUnwieldedEvent>(OnEyeOffsetUnwielded);
+        SubscribeLocalEvent<CursorOffsetRequiresWieldComponent, HeldRelayedEvent<GetEyeOffsetRelayedEvent>>(OnGetEyeOffset);
+    }
+
+    public void OnEyeOffsetUnwielded(Entity<CursorOffsetRequiresWieldComponent> entity, ref ItemUnwieldedEvent args)
+    {
+        if (!TryComp(entity.Owner, out EyeCursorOffsetComponent? cursorOffsetComp))
+            return;
+
+        if (_gameTiming.IsFirstTimePredicted)
+            cursorOffsetComp.CurrentPosition = Vector2.Zero;
+    }
+
+    public void OnGetEyeOffset(Entity<CursorOffsetRequiresWieldComponent> entity, ref HeldRelayedEvent<GetEyeOffsetRelayedEvent> args)
+    {
+        if (!TryComp(entity.Owner, out WieldableComponent? wieldableComp))
+            return;
+
+        if (!wieldableComp.Wielded)
+            return;
+
+        var offset = _eyeOffset.OffsetAfterMouse(entity.Owner, null);
+        if (offset == null)
+            return;
+
+        args.Args.Offset += offset.Value;
+    }
+}