BarSignSystem.cs

using Content.Client.BarSign.Ui;
using Content.Shared.BarSign;
using Content.Shared.Power;
using Robust.Client.GameObjects;
using Robust.Shared.Prototypes;

namespace Content.Client.BarSign;

public sealed class BarSignSystem : VisualizerSystem<BarSignComponent>
{
    [Dependency] private readonly IPrototypeManager _prototypeManager = default!;
    [Dependency] private readonly UserInterfaceSystem _ui = default!;

    public override void Initialize()
    {
        base.Initialize();
        SubscribeLocalEvent<BarSignComponent, AfterAutoHandleStateEvent>(OnAfterAutoHandleState);
    }

    private void OnAfterAutoHandleState(EntityUid uid, BarSignComponent component, ref AfterAutoHandleStateEvent args)
    {
        if (_ui.TryGetOpenUi<BarSignBoundUserInterface>(uid, BarSignUiKey.Key, out var bui))
            bui.Update(component.Current);

        UpdateAppearance(uid, component);
    }

    protected override void OnAppearanceChange(EntityUid uid, BarSignComponent component, ref AppearanceChangeEvent args)
    {
        UpdateAppearance(uid, component, args.Component, args.Sprite);
    }

    private void UpdateAppearance(EntityUid id, BarSignComponent sign, AppearanceComponent? appearance = null, SpriteComponent? sprite = null)
    {
        if (!Resolve(id, ref appearance, ref sprite))
            return;

        AppearanceSystem.TryGetData<bool>(id, PowerDeviceVisuals.Powered, out var powered, appearance);

        if (powered
            && sign.Current != null
            && _prototypeManager.Resolve(sign.Current, out var proto))
        {
            SpriteSystem.LayerSetSprite((id, sprite), 0, proto.Icon);
            sprite.LayerSetShader(0, "unshaded");
        }
        else
        {
            SpriteSystem.LayerSetRsiState((id, sprite), 0, "empty");
            sprite.LayerSetShader(0, null, null);
        }
    }
}