RobustToolbox/Robust.Shared/GameObjects/Systems/OccluderSystem.cs

using Robust.Shared.ComponentTrees;
using Robust.Shared.GameStates;
using Robust.Shared.Maths;
using Robust.Shared.Physics;
using Robust.Shared.Utility;

namespace Robust.Shared.GameObjects;
public abstract class OccluderSystem : ComponentTreeSystem<OccluderTreeComponent, OccluderComponent>
{
    public override void Initialize()
    {
        base.Initialize();
        SubscribeLocalEvent<OccluderComponent, ComponentGetState>(OnGetState);
        SubscribeLocalEvent<OccluderComponent, ComponentHandleState>(OnHandleState);
    }

    private void OnGetState(EntityUid uid, OccluderComponent comp, ref ComponentGetState args)
    {
        args.State = new OccluderComponent.OccluderComponentState(comp.Enabled, comp.BoundingBox);
    }
    private void OnHandleState(EntityUid uid, OccluderComponent comp, ref ComponentHandleState args)
    {
        if (args.Current is not OccluderComponent.OccluderComponentState state)
            return;

        SetEnabled(uid, state.Enabled, comp);
        SetBoundingBox(uid, state.BoundingBox, comp);
    }

    #region Component Tree Overrides
    protected override bool DoFrameUpdate => true;
    protected override bool DoTickUpdate => true;

    // this system relies on the assumption that all occluders are parented directly to a grid or map.
    // if this ever changes, this will make server move events very expensive.
    protected override bool Recursive => false;

    protected override Box2 ExtractAabb(in ComponentTreeEntry<OccluderComponent> entry)
    {
        DebugTools.Assert(entry.Transform.ParentUid == entry.Component.TreeUid);
        return entry.Component.BoundingBox.Translated(entry.Transform.LocalPosition);
    }

    protected override Box2 ExtractAabb(in ComponentTreeEntry<OccluderComponent> entry, Vector2 pos, Angle rot)
        => ExtractAabb(in entry);
    #endregion

    #region Setters
    public void SetBoundingBox(EntityUid uid, Box2 box, OccluderComponent? comp = null)
    {
        if (!Resolve(uid, ref comp))
            return;

        comp.BoundingBox = box;
        Dirty(comp);

        if (comp.TreeUid != null)
            QueueTreeUpdate(uid, comp);
    }

    public virtual void SetEnabled(EntityUid uid, bool enabled, OccluderComponent? comp = null)
    {
        if (!Resolve(uid, ref comp, false) || enabled == comp.Enabled)
            return;

        comp.Enabled = enabled;
        Dirty(comp);
        QueueTreeUpdate(uid, comp);
    }
    #endregion
}