Skill: tebjan/vvvv-troubleshooting (version 1.0.1)

--- name: vvvv-troubleshooting description: Diagnoses and fixes common vvvv gamma errors in C# nodes, SDSL shaders, and runtime behavior. Use when encountering errors, exceptions, crashes, red nodes, shader compilation failures, missing nodes in the browser, performance issues, or unexpected behavior. license: CC-BY-SA-4.0 compatibility: Designed for coding AI agents assisting with vvvv gamma development metadata: author: Tebjan Halm version: "1.1" --- # vvvv gamma Troubleshooting ## C# / ProcessNode Issues ### "Node" Suffix in Class Name **Symptom**: Node works but has ugly name in vvvv. **Fix**: Remove "Node" suffix — vvvv convention forbids it. ```csharp // WRONG [ProcessNode] public class SteeringBehaviorNode { } // CORRECT [ProcessNode] public class SteeringBehavior { } ``` ### Out Parameters After Inputs **Symptom**: Pins appear in wrong order or node doesn't compile correctly. **Fix**: `out` parameters must come FIRST in Update signature. ```csharp // WRONG public void Update(float input = 0f, out float result) { ... } // CORRECT public void Update(out float result, float input = 0f) { ... } ``` ### Node Not Appearing in Node Browser **Symptom**: Your C# class exists but doesn't show up in vvvv. **Fix**: Check these in order: 1. `[assembly: ImportAsIs]` attribute exists in your project 2. `[ProcessNode]` attribute on the class 3. Project targets `net8.0` 4. DLL is in the correct `lib/net8.0/` path relative to `.vl` document 5. Project builds without errors ### Allocations Causing Frame Drops **Symptom**: GC spikes, stuttering, frame drops. **Diagnosis**: Allocations in the Update loop. Common culprits: - `new` keyword in Update method - LINQ operators (`.Where()`, `.Select()`, `.ToList()`) - String concatenation (`+` operator on strings) - Boxing value types (passing `int` where `object` expected) **Fix**: Cache everything, pre-allocate buffers, eliminate LINQ from hot paths. ### Missing Change Detection **Symptom**: CPU usage high even when nothing changes. **Fix**: Compare inputs to cached values, only recompute on change. ```csharp if (param != _lastParam) { _cached = Compute(param); _lastParam = param; } result = _cached; // Always output cached ``` ### Downstream Nodes See null/default **Symptom**: Connected nodes get no data, even though the node "works". **Fix**: Always output cached result, even when no computation happens. ```csharp // WRONG — output is only set inside the if block public void Update(out float result, float input = 0f) { if (input != _last) { result = Compute(input); _last = input; } // result is unassigned when input hasn't changed! } // CORRECT — always assign output public void Update(out float result, float input = 0f) { if (input != _last) { _cached = Compute(input); _last = input; } result = _cached; } ``` ## SDSL Shader Issues For SDSL syntax rules, common mistakes, and correct/wrong examples, consult the **vvvv-shaders** skill and its `syntax-rules.md`. Key issues: `static const` scope, missing semicolons, missing `override`, enum binding format. ## Runtime Issues ### Memory Leaks **Symptom**: Memory usage grows over time. **Causes**: - Missing `IDisposable` on nodes with native resources - COM objects (`ComPtr<T>`) not disposed - Event handler subscriptions not unsubscribed ### Thread Safety **Symptom**: Intermittent crashes, data corruption. **Fix**: `Update()` runs on the main thread. Capture `SynchronizationContext` in the constructor, then marshal background results back: ```csharp private SynchronizationContext _vlSyncContext; public MyNode() { _vlSyncContext = SynchronizationContext.Current!; } // From background thread: _vlSyncContext.Post(_ => { /* runs on VL thread */ }, null); ``` ### Circular Dependencies **Symptom**: vvvv warns about circular dependency, patch won't compile. **Fix**: Insert a `FrameDelay` node to break the cycle. ## Build Issues ### Target Framework Mismatch **Symptom**: DLL loads but types aren't found. **Fix**: Ensure `.csproj` targets `net8.0` (matching vvvv gamma's runtime). ### Assembly Version Conflicts **Symptom**: `FileLoadException` or `TypeLoadException` at runtime. **Fix**: Align package versions with vvvv's bundled versions. Check vvvv's `lib/` folder for reference. For detailed error-to-solution mapping, see [error-catalog.md](error-catalog.md).


Security scan verdicts — ClawScan: clean | static analysis: clean | VirusTotal: clean | SkillSpector: clean (LOW)