Unity-Technologies/UnityCsReference · error · InvalidOperationException

{RegisterRenderPickingCallback} cannot be called during pick

Error message

{RegisterRenderPickingCallback} cannot be called during picking rendering

What it means

RegisterRenderPickingCallback throws InvalidOperationException when called while a picking render pass is in progress (s_InPickingRendering is true). This guard prevents the static callback list from being modified mid-iteration, which would cause collection corruption or skipped callbacks.

Source

Thrown at Editor/Mono/Handles/HandleUtility.cs:2237

        {
            Internal_Repaint();
        }

        public delegate UnityObject ResolvePickingCallback(int localPickingIndex);
        public delegate UnityObject ResolvePickingWithWorldPositionCallback(int localPickingIndex, Vector3 worldPos, float depth);
        public delegate RenderPickingResult RenderPickingCallback(in RenderPickingArgs args);

        [AutoStaticsCleanupOnCodeReload]
        private static readonly List<RenderPickingCallback> s_RenderPickingCallbacks = new();
        [AutoStaticsCleanupOnCodeReload]
        private static readonly List<(int PickingIndexBegin, int PickingIndexEnd, ResolvePickingCallback Resolver, ResolvePickingWithWorldPositionCallback ResolverWithWorldPos)> s_RenderPickingResults = new();

        public static bool RegisterRenderPickingCallback(RenderPickingCallback renderPickingCallback)
        {
            if (renderPickingCallback == null)
                throw new ArgumentNullException(nameof(renderPickingCallback));
            if (s_InPickingRendering)
                throw new InvalidOperationException($"{nameof(RegisterRenderPickingCallback)} cannot be called during picking rendering");

            foreach (var registered in s_RenderPickingCallbacks)
            {
                if (registered == renderPickingCallback)
                    return false;
            }

            s_RenderPickingCallbacks.Add(renderPickingCallback);
            return true;
        }

        public static bool UnregisterRenderPickingCallback(RenderPickingCallback renderPickingCallback)
        {
            if (renderPickingCallback == null)
                throw new ArgumentNullException(nameof(renderPickingCallback));
            if (s_InPickingRendering)
                throw new InvalidOperationException($"{nameof(UnregisterRenderPickingCallback)} cannot be called during picking rendering");

View on GitHub (pinned to 225b0fbdb5)

Solutions

Move callback registration to OnEnable, OnSceneGui (before repaint), or another non-rendering lifecycle hook.
If dynamic registration is needed during rendering, defer it with EditorApplication.delayCall until the render pass completes.

Example fix

// before
RenderPickingResult OnRenderPicking(in RenderPickingArgs args)
{
    HandleUtility.RegisterRenderPickingCallback(ExtraPicking);
    ...
}
// after
RenderPickingResult OnRenderPicking(in RenderPickingArgs args)
{
    EditorApplication.delayCall += () => HandleUtility.RegisterRenderPickingCallback(ExtraPicking);
    ...
}

Defensive patterns

Strategy: validation

Validate before calling

// s_InPickingRendering is private and cannot be checked directly.
// Instead, ensure registration happens only outside render passes:
void OnEnable() {
    HandleUtility.RegisterRenderPickingCallback(OnRenderPicking);
}

Try / catch

try { HandleUtility.RegisterRenderPickingCallback(cb); }
catch (InvalidOperationException) {
    EditorApplication.delayCall += () => HandleUtility.RegisterRenderPickingCallback(cb);
}

Prevention

Register callbacks in OnEnable, never inside a render-picking callback body.
If deferred registration is unavoidable, use EditorApplication.delayCall to push it outside the render pass.

When it happens

Trigger: Calling RegisterRenderPickingCallback from inside another RenderPickingCallback, or from any code path that executes during the picking render loop.

Common situations: An editor tool that dynamically registers sub-callbacks from within its own picking callback, creating a re-entrant registration; or SceneGUI code that registers during repaint.

Related errors

AI-assisted analysis of Unity-Technologies/UnityCsReference@225b0fbdb5 (2026-08-13). Data as JSON: /api/errors/72e92be5b915f79c. Report an issue: GitHub.