Rework Gradient into a newtype of List<Color> with optional position and midpoint attributes (#4397)

* Rework Gradient into a newtype of List<Color> with optional position and midpoint attributes

* Fix Vello stopless-gradient fallback coverage, empty legacy gradient tables, the node docs gradient swatch, NaN position elision, and wired setter input overwrites

node-graph/node-macro/src/codegen.rs

@@ -8,7 +8,7 @@ use std::sync::atomic::AtomicU64;
 use syn::punctuated::Punctuated;
 use syn::visit::Visit;
 use syn::visit_mut::VisitMut;
-use syn::{GenericArgument, GenericParam, Ident, Lifetime, PatIdent, PathArguments, Type, TypeParam, TypeParamBound};
+use syn::{Expr, ExprPath, GenericArgument, GenericParam, Ident, Lifetime, PatIdent, PathArguments, Token, Type, TypeParam, TypeParamBound};
 
 pub(crate) mod classify;
 mod entries;
@@ -348,6 +348,20 @@ pub(crate) fn generate_node_code(crate_ident: &CrateIdent, parsed: &ParsedNodeFn
 		})
 		.collect();
 
+	let default_colors: Vec<_> = regular_fields
+		.iter()
+		.map(|field| match field.ty.regular() {
+			Some(RegularParsedField {
+				value_source: ParsedValueSource::Default(data),
+				..
+			}) => match color_constant_paths(data) {
+				Some(paths) => quote!(Some(&[#(#paths),*])),
+				None => quote!(None),
+			},
+			_ => quote!(None),
+		})
+		.collect();
+
 	let default_types: Vec<_> = regular_fields
 		.iter()
 		.map(|field| match &field.ty {
@@ -682,6 +696,7 @@ pub(crate) fn generate_node_code(crate_ident: &CrateIdent, parsed: &ParsedNodeFn
 								hidden: #input_hidden,
 								exposed: #exposed,
 								value_source: #value_sources,
+								default_colors: #default_colors,
 								default_type: #default_types,
 								number_soft_min: #number_soft_min_values,
 								number_soft_max: #number_soft_max_values,
@@ -2959,3 +2974,22 @@ pub(crate) fn generate_node_impl(crate_ident: &CrateIdent, parsed: &ParsedNodeFn
 		..Default::default()
 	})
 }
+
+fn color_constant_paths(tokens: &TokenStream2) -> Option<Vec<ExprPath>> {
+	use syn::parse::Parser;
+
+	let expressions = Punctuated::<Expr, Token![,]>::parse_terminated.parse2(tokens.clone()).ok()?;
+	if expressions.is_empty() {
+		return None;
+	}
+
+	expressions
+		.into_iter()
+		.map(|expression| {
+			let Expr::Path(path) = expression else { return None };
+			let segments = &path.path.segments;
+			let is_color_constant = path.qself.is_none() && segments.len() == 2 && segments[0].ident == "Color" && segments.iter().all(|segment| segment.arguments.is_none());
+			is_color_constant.then_some(path)
+		})
+		.collect()
+}

node-graph/node-macro/src/parsing.rs

@@ -267,6 +267,16 @@ pub enum ParsedFieldType {
 	Node(NodeParsedField),
 }
 
+impl ParsedFieldType {
+	/// The shared value-field data, present for every value field but not a lazy `Node`.
+	pub fn regular(&self) -> Option<&RegularParsedField> {
+		match self {
+			ParsedFieldType::Regular(field) => Some(field),
+			ParsedFieldType::Node(_) => None,
+		}
+	}
+}
+
 /// A single numeric endpoint within a `#[soft(..)]` or `#[hard(..)]` bounds range.
 /// Accepts both integer literals (e.g. `1`, `-1`) and float literals (e.g. `1.`, `-500.`).
 #[derive(Clone, Debug)]