Added world sprite system (#397)

* Added world sprite system

* Added important comment

Content.Client/_CP14/WorldSprite/CP14WorldSpriteSystem.cs

@@ -0,0 +1,65 @@
+using Content.Shared._CP14.WorldSprite;
+using Content.Shared.Throwing;
+using Robust.Client.GameObjects;
+using Robust.Shared.Map.Components;
+
+namespace Content.Client._CP14.WorldSprite;
+
+public sealed class CP14WorldSpriteSystem : EntitySystem
+{
+    [Dependency] private readonly AppearanceSystem _appearance = default!;
+
+    public override void Initialize()
+    {
+        base.Initialize();
+
+#if DEBUG
+        SubscribeLocalEvent<CP14WorldSpriteComponent, ComponentInit>(OnComponentInit);
+#endif
+
+        SubscribeLocalEvent<CP14WorldSpriteComponent, EntParentChangedMessage>(OnParentChanged);
+        SubscribeLocalEvent<CP14WorldSpriteComponent, ThrownEvent>(OnThrown);
+    }
+
+    public override void Update(float frameTime)
+    {
+        base.Update(frameTime);
+
+        var query = EntityQueryEnumerator<CP14WorldSpriteComponent>();
+        while (query.MoveNext(out var uid, out var worldSpriteComponent))
+        {
+            if (worldSpriteComponent.Inited)
+                continue;
+
+            Update(uid);
+        }
+    }
+
+#if DEBUG
+    private void OnComponentInit(Entity<CP14WorldSpriteComponent> entity, ref ComponentInit args)
+    {
+        if (!HasComp<AppearanceComponent>(entity))
+            Log.Error($"Requires an {nameof(AppearanceComponent)} for {entity}");
+    }
+#endif
+
+    private void OnParentChanged(Entity<CP14WorldSpriteComponent> entity, ref EntParentChangedMessage args)
+    {
+        Update(entity);
+    }
+
+    private void OnThrown(Entity<CP14WorldSpriteComponent> entity, ref ThrownEvent args)
+    {
+        // Idk, but throw don't call reparent
+        Update(entity, args.User);
+    }
+
+    private void Update(EntityUid entity, EntityUid? parent = null)
+    {
+        parent ??= Transform(entity).ParentUid;
+
+        var inWorld = HasComp<MapComponent>(parent) || HasComp<MapGridComponent>(parent);
+
+        _appearance.SetData(entity, WorldSpriteVisualLayers.Layer, inWorld);
+    }
+}