Thumbnails for the layer node (#1210)

* Thumbnails for the layer node

* Raster node graph frames

* Downscale to a random resolution

* Cleanup and bug fixes

* Generate paths before duplicating outputs

* Fix stable id test

* Code review changes

* Code review pass with minor changes

---------

Co-authored-by: Keavon Chambers <keavon@keavon.com>

node-graph/graph-craft/src/document.rs

@@ -243,6 +243,10 @@ impl DocumentNodeImplementation {
 			_ => None,
 		}
 	}
+
+	pub const fn proto(name: &'static str) -> Self {
+		Self::Unresolved(NodeIdentifier::new(name))
+	}
 }
 
 #[derive(Clone, Copy, Debug, Default, PartialEq, DynAny, specta::Type, Hash)]
@@ -812,6 +816,28 @@ impl NodeNetwork {
 			nodes: nodes.clone(),
 		})
 	}
+
+	/// Create a [`RecursiveNodeIter`] that iterates over all [`DocumentNode`]s, including ones that are deeply nested.
+	pub fn recursive_nodes(&self) -> RecursiveNodeIter {
+		let nodes = self.nodes.iter().map(|(id, node)| (node, self, vec![*id])).collect();
+		RecursiveNodeIter { nodes }
+	}
+}
+
+/// An iterator over all [`DocumentNode`]s, including ones that are deeply nested.
+pub struct RecursiveNodeIter<'a> {
+	nodes: Vec<(&'a DocumentNode, &'a NodeNetwork, Vec<NodeId>)>,
+}
+
+impl<'a> Iterator for RecursiveNodeIter<'a> {
+	type Item = (&'a DocumentNode, &'a NodeNetwork, Vec<NodeId>);
+	fn next(&mut self) -> Option<Self::Item> {
+		let (node, network, path) = self.nodes.pop()?;
+		if let DocumentNodeImplementation::Network(network) = &node.implementation {
+			self.nodes.extend(network.nodes.iter().map(|(id, node)| (node, network, [path.as_slice(), &[*id]].concat())));
+		}
+		Some((node, network, path))
+	}
 }
 
 #[cfg(test)]