Writing Custom Nodes for vvvv gamma

What [ProcessNode] actually does (and what it does NOT do)

Important reality check. vvvv imports every public class, struct, enum, method, and property from the assembly's configured namespaces — [ProcessNode] does NOT control whether a class becomes a node. A plain public class Foo { public int Bar(int x) => x; } will appear in the node browser exactly the same way as one decorated with [ProcessNode]. The attribute affects how the runtime treats the class, not whether it gets imported.

What [ProcessNode] DOES:

• Tells vvvv "this is a stateful node — keep ONE instance alive per node in the patch and call its Update() method each frame".
• Lets you set Name = "..." (rename for the node browser), Category = "..." (override the assembly's category), and HasStateOutput = true (expose the instance as an output pin).
• Engages live reload, IDisposable cleanup, and the NodeContext constructor injection.

What [ProcessNode] does NOT do:

• It does NOT make a class visible to vvvv. Visibility comes from the C# public access modifier plus an [assembly: ImportAsIs/ImportNamespace/ImportType] attribute. See vvvv-node-libraries for the import rules.
• It does NOT hide internal helpers. If a helper is public and its namespace is imported, it's a node. To hide one: make it internal (removes it from VL entirely), or keep it public and tag it [Smell(SymbolSmell.Internal)] / [Smell(SymbolSmell.Hidden)] (stays usable as a pin type, just isn't browsable). See advanced.md → Smell Attribute.
• It does NOT change pin generation. Pin generation is driven by the Update() method signature for [ProcessNode] classes, and by public method/property signatures for non-[ProcessNode] classes.

When to use [ProcessNode]: the class needs frame-by-frame updates, persistent state between frames, or IDisposable cleanup. When to skip [ProcessNode]: stateless utility classes, value types, static helper methods — leaving the attribute off avoids the per-frame Update() ceremony, and the public methods become operation nodes automatically.