Steam transport Integration

[saint4626]

Summary

This PR adds a new embedded com.basis.steamtransport package for Steam networking support on top of the new multi-network stack.

The package registers a steam network stack and adds Steam lobby creation/joining, Steam relay transport, invite handling, lobby metadata, and a Steam Lobbies panel in the Basis menu. The existing LiteNetLib/default networking path is left intact.

I kept changes outside the Steam package as small as possible. The only shared Basis changes are:

• an OnUpdate hook in BasisEventDriver so Steam callbacks and transport polling can run through the existing event driver
• small public bridge methods/constructors in BasisNetworkShell so a custom NetManager can raise network events without reflection
• the Unity package lock entry for the embedded Steam package

Required checks

All boxes below must be ticked before this PR can merge. If a check is genuinely N/A, tick it anyway and explain under Notes.

• Tested — I built and ran this locally. The change works in the editor and (where relevant) in a built player.
• Transform access is combined and limited — In hot paths, transform reads/writes go through TransformAccessArray or are otherwise batched. I have not added per-frame transform.position / transform.rotation / transform.localPosition calls inside loops. Whenever I need both position and rotation, I use the combined APIs — SetPositionAndRotation / SetLocalPositionAndRotation for writes, GetPositionAndRotation / GetLocalPositionAndRotation for reads — instead of two separate property accesses; the combined call does one local-to-world matrix traversal instead of two.
• Addressables used for asset/memory loading — Any new asset loads go through Addressables. No new Resources.Load, no direct asset references that pull large content into memory on scene load.
• No new GetComponent / AddComponent where avoidable — Where unavoidable, the result is cached on a field, and any GetComponent<T> is replaced with TryGetComponent<T>(out var x) — bare GetComponent will be denied. TryGetComponent is the modern API (Unity 2019.2+) and skips the Editor-only GC allocation GetComponent causes when a component is missing: Unity wraps the null return in a managed "fake null" object so its overloaded == operator can still detect destroyed C++ objects, and constructing that wrapper allocates; TryGetComponent returns a bool plus out parameter and never builds the wrapper. None of these calls run inside Update, LateUpdate, FixedUpdate, jobs, or other per-frame code paths.
• Per-frame work is scheduled through BasisEventDriver — Any new per-frame work hooks into BasisEventDriver rather than adding standalone Update / LateUpdate / FixedUpdate callbacks on a MonoBehaviour.
• Considered jobification — I asked whether this work can be moved to a Unity Job (Burst-compiled where possible). If it can, it is. If it cannot, the reason is in Notes.
• No needless { get; set; } properties or access lockdowns — Public fields are fine; Basis is meant to be read and modified freely, so don't wall things off private/internal without a real reason. Don't wrap a field in { get; set; } when the accessors do nothing — property accessors have a real performance cost vs direct field access, and the lead maintainer prefers plain fields (or a method / setter-only property when only the setter needs logic) over a noop-getter pair. For .Instance singletons, callers reassigning Type.Instance is allowed; if that would break your code, log a warning or throw — don't block the assignment. Locking down access is not your call.
• Camera access goes through BasisLocalCameraDriver — Code that needs the local camera (transform, projection, rig data, etc.) pulls it from BasisLocalCameraDriver rather than looking one up itself. Don't roll a separate camera discovery path.
• Logging uses BasisDebug — All new logging calls go through BasisDebug.Log / BasisDebug.LogWarning / BasisDebug.LogError (with an appropriate LogTag) instead of UnityEngine.Debug.Log / Debug.LogWarning / Debug.LogError. BasisDebug routes through Basis's tagged, color-coded logger and respects the project-wide LoggingDisabled toggle so logging can be killed at runtime; bare Debug.Log calls bypass that and will be denied.
• No scene-wide discovery for dependencies — New code is architected so it does not need FindObjectOfType / FindObjectsOfType / GameObject.Find / FindGameObjectsWithTag to locate what it depends on. References are wired in — registered through an existing manager/driver, injected at init, or passed in by the caller — rather than discovered by scanning the scene at runtime. If a scene scan is genuinely unavoidable, justify it under Notes.
• No allocations in hot paths — Per-frame code (Update / LateUpdate / FixedUpdate, simulation loops, jobs, anything called once per frame or more) does not allocate. No new on reference types, no LINQ, no string concatenation/interpolation, no boxing, no foreach over interface-typed collections. Allocate once at init and reuse the buffer.
• No debugging in hot paths — No log calls of any kind on per-frame paths, including BasisDebug. Hot-path logging floods the console and incurs cost on every frame regardless of whether the message is filtered out downstream. If a hot-path log is needed while iterating, gate it behind #if UNITY_EDITOR and remove (or leave gated) before merge.
• Hot-path collection access is optimized — Cache .Count (lists) / .Length (arrays) into a local int before the loop instead of re-reading the property each iteration. Prefer T[] (with a separate length int when the array is over-sized) over List<T> where the data is hot — Unity's mono BCL doesn't expose CollectionsMarshal.AsSpan(List<T>), so a list can't be fed into Span<T> / unsafe paths cleanly. Where the perf justifies it, drop into Span<T> / ref locals / Unsafe.As / unsafe pointer code to skip bounds checks and copies, and call out the invariants you're relying on under Notes so reviewers can sanity-check them.

Testing details

Tick the platforms you actually tested on. Leave the rest unticked — these are informational and do not block merge.

• Windows
• Linux
• Android
• iOS
• macOS

Input / control mode coverage:

• Tested in VR (note headset under Notes)
• Tested in desktop / non-VR mode
• Tested with phone controls (mobile touch input)
• N/A — change does not touch player/XR/input code

Where applicable, confirm these flows still work after your changes:

• Hot-switching (desktop ↔ VR mode swap at runtime)
• Avatar swapping
• Server swapping (joining / leaving / changing servers)
• N/A — change does not touch any of the above

Notes

Tested on Windows in the Unity Editor and in a local build.

I tested both desktop/non-VR mode and VR mode.
VR headset: Pico 4.

I also checked the main runtime flows I expected this to affect:

• Steam transport registers as the steam network stack
• avatar swapping works
• porps works spawns
• desktop/VR hot-switching still works

Steam App ID note: BasisSteamSettings currently defaults to Steam AppId 480 for development/testing. For the real Basis Steam build, this should be changed to the actual Basis Steam App ID so lobbies, invites, and relay all run under the shipped app.

Jobification note: I do not think this work is a good fit for Unity Jobs. The new work is mostly Steamworks callbacks, lobby state, transport event bridging, and Basis network lifecycle calls, which need to stay on the managed/main-thread side.

Hot-path note: Steam callbacks and transport polling are routed through BasisEventDriver.OnUpdate. Receive processing is bounded, and transport trace logging is opt-in through BasisSteamSettings.EnableTransportTrace.

[uyjulian]

May I suggest https://github.com/ValveSoftware/GameNetworkingSockets so the networking under this backend can be tested without needing Steamworks API

[saint4626]

May I suggest https://github.com/ValveSoftware/GameNetworkingSockets so the networking under this backend can be tested without needing Steamworks API

I agree this could be useful for transport-level testing without requiring Steamworks initialization/AppId.

For PR I kept the scope focused on the actual Steamworks path because the goal is Steam lobbies, invites, and Steam relay integration. GameNetworkingSockets sounds like a good follow-up as a separate test/non-Steam backend, but I would not want to mix that into this PR and expand the scope.

[dooly123]

finally getting to this:

public static Action OnUpdate; points at a larger issue with the steam intergration package

that its tied down to the main thread and consumes time on main thread

any reason its on main thread?

[dooly123]

I have merged the function additions

[saint4626]

finally getting to this:

public static Action OnUpdate; points at a larger issue with the steam intergration package

that its tied down to the main thread and consumes time on main thread

any reason its on main thread?

I kept it on the main thread because Steamworks callbacks run on the caller thread, and the current callback path touches lifecycle state

i think the architecture could be improved in future

[dooly123]

oki in that case is there a better spot for the event?

[saint4626]

oki in that case is there a better spot for the event?

cleaner path might be to call BasisNetworkStackRegistry.TickActive from the existing network update path and remove the extra OnUpdate hook.
The only part I’m less sure about is SteamClient.RunCallbacks, because that also drives lobby/invite callbacks before there is necessarily an active network connection.