Automatic holiday sprites (#22929)

Content.Client/Holiday/HolidaySystem.cs

@@ -0,0 +1,34 @@
+using Content.Shared.Holiday;
+using Content.Shared.Item;
+using Robust.Client.GameObjects;
+using Robust.Client.Graphics;
+using Robust.Client.ResourceManagement;
+using Robust.Shared.Serialization.TypeSerializers.Implementations;
+
+namespace Content.Client.Holiday;
+
+public sealed class HolidaySystem : EntitySystem
+{
+    [Dependency] private readonly IResourceCache _rescache = default!;
+    [Dependency] private readonly SharedAppearanceSystem _appearance = default!;
+
+    /// <inheritdoc/>
+    public override void Initialize()
+    {
+        SubscribeLocalEvent<HolidayRsiSwapComponent, AppearanceChangeEvent>(OnAppearanceChange);
+    }
+
+    private void OnAppearanceChange(Entity<HolidayRsiSwapComponent> ent, ref AppearanceChangeEvent args)
+    {
+        if (!_appearance.TryGetData<string>(ent, HolidayVisuals.Holiday, out var data, args.Component))
+            return;
+
+        var comp = ent.Comp;
+        if (!comp.Sprite.TryGetValue(data, out var rsistring) || args.Sprite == null)
+            return;
+
+        var path = SpriteSpecifierSerializer.TextureRoot / rsistring;
+        if (_rescache.TryGetResource(path, out RSIResource? rsi))
+            args.Sprite.BaseRSI = rsi.RSI;
+    }
+}