Allow content to override ProcessStream and GetOcclusion in AudioSystem (#6268)

* Add optional override methods for ProcessStream and GetOcclusion

* Mark override events as static

* Change audio actions to non-static

Robust.Client/Audio/AudioSystem.cs

@@ -2,6 +2,7 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Numerics;
+using JetBrains.Annotations;
 using OpenTK.Audio.OpenAL;
 using Robust.Client.GameObjects;
 using Robust.Client.Graphics;
@@ -45,6 +46,26 @@ public sealed partial class AudioSystem : SharedAudioSystem
     [Dependency] private readonly SharedTransformSystem _xformSys = default!;
     [Dependency] private readonly SharedPhysicsSystem _physics = default!;
 
+    /// <summary>
+    /// An optional method that, if provided, will override the behavior of <see cref="ProcessStream"/>.
+    /// Contains the same parameters in the same order as the method it overrides.
+    /// </summary>
+    /// <remarks>
+    /// This event only supports a single invocation target.
+    /// </remarks>
+    [PublicAPI]
+    public event Action<EntityUid, AudioComponent, TransformComponent, MapCoordinates>? ProcessStreamOverride;
+
+    /// <summary>
+    /// An optional method that, if provided, will override the behavior of <see cref="GetOcclusion"/>.
+    /// Contains the same parameters in the same order as the method it overrides.
+    /// </summary>
+    /// <remarks>
+    /// This event only supports a single invocation target.
+    /// </remarks>
+    [PublicAPI]
+    public event Func<MapCoordinates, Vector2, float, EntityUid?, float>? GetOcclusionOverride;
+
     /// <summary>
     /// Per-tick cache of relevant streams.
     /// </summary>
@@ -341,6 +362,15 @@ public sealed partial class AudioSystem : SharedAudioSystem
 
     private void ProcessStream(EntityUid entity, AudioComponent component, TransformComponent xform, MapCoordinates listener)
     {
+        // If content wants to process the stream in their own special way, we simply let them handle that.
+        if (ProcessStreamOverride is not null)
+        {
+            // Assert that we are not processing audio multiple times.
+            DebugTools.Assert(ProcessStreamOverride.HasSingleTarget, $"Event {nameof(ProcessStreamOverride)} has multiple invocation targets. This is not permitted.");
+            ProcessStreamOverride.Invoke(entity, component, xform, listener);
+            return; // Exit and do not perform remaining function behavior
+        }
+
         // TODO:
         // I Originally tried to be fancier here but it caused audio issues so just trying
         // to replicate the old behaviour for now.
@@ -434,6 +464,14 @@ public sealed partial class AudioSystem : SharedAudioSystem
     /// </summary>
     public float GetOcclusion(MapCoordinates listener, Vector2 delta, float distance, EntityUid? ignoredEnt = null)
     {
+        // If content has defined a custom occlusion method, use that instead.
+        if (GetOcclusionOverride is not null)
+        {
+            // There can only be one occlusion override defined.
+            DebugTools.Assert(GetOcclusionOverride.HasSingleTarget, $"Event {nameof(GetOcclusionOverride)} has multiple invocation targets. This is not permitted.");
+            return GetOcclusionOverride.Invoke(listener, delta, distance, ignoredEnt);
+        }
+
         float occlusion = 0;
 
         if (distance > 0.1)