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/nodes/brush/src/lib.rs

@@ -5,7 +5,7 @@ pub mod brush_stroke;
 pub mod migrations {
 	use crate::brush_stroke::BrushStroke;
 
-	// TODO: Eventually remove this migration document upgrade code
+	// TODO: Eventually remove this document upgrade code
 	pub fn migrate_to_brush_strokes<'de, D: serde::Deserializer<'de>>(deserializer: D) -> Result<Vec<BrushStroke>, D::Error> {
 		use serde::Deserialize;
 

node-graph/nodes/graphic/src/graphic.rs

@@ -15,7 +15,7 @@ use raster_types::{CPU, GPU, Raster};
 use std::cmp::Ordering;
 
 use vector_types::gradient::{GradientSpreadMethod, GradientType as GradientTypeValue};
-use vector_types::{Gradient, GradientStop, ReferencePoint};
+use vector_types::{Gradient, ReferencePoint};
 
 /// Resolves a signed index over `total` lanes: negatives count from the end,
 /// out of range resolves to nothing.
@@ -999,16 +999,7 @@ pub fn flatten_gradient<T: IntoGraphicList>(_: impl Ctx, #[implementations(List<
 /// Constructs a gradient from a `Color[]`, where the colors are evenly distributed as gradient stops across the range from 0 to 1.
 #[node_macro::node(category("Color"), name("Colors to Gradient"))]
 fn colors_to_gradient<T: IntoGraphicList>(_: impl Ctx, #[implementations(List<Graphic>, List<Color>)] colors: T) -> Gradient {
-	let colors = colors.into_flattened_list::<Color>();
-	let stop = |position: f64, color: Color| GradientStop { position, midpoint: 0.5, color };
-	match colors.len() {
-		0 => Gradient::new(vec![stop(0., Color::BLACK), stop(1., Color::BLACK)]),
-		1 => Gradient::new(vec![
-			stop(0., colors.element(0).copied().unwrap_or(Color::BLACK)),
-			stop(1., colors.element(0).copied().unwrap_or(Color::BLACK)),
-		]),
-		total => Gradient::new(colors.into_iter().enumerate().map(|(index, row)| stop(index as f64 / (total - 1) as f64, row.into_element()))),
-	}
+	Gradient::from(colors.into_flattened_list::<Color>())
 }
 
 #[cfg(test)]

node-graph/nodes/math/src/lib.rs

@@ -1199,7 +1199,7 @@ fn hex_to_color(ctx: impl Ctx + ExtractIndex + InjectIndex + Copy, hex_code: Str
 
 /// Constructs a gradient value which may be set to any sequence of color stops to represent the transition between colors.
 #[node_macro::node(category("Value"))]
-fn gradient_value(_: impl Ctx, _primary: (), gradient: Gradient) -> Gradient {
+fn gradient_value(_: impl Ctx, _primary: (), #[default(Color::BLACK, Color::WHITE)] gradient: Gradient) -> Gradient {
 	gradient
 }
 
@@ -1215,16 +1215,43 @@ fn spread_method(_: impl Ctx, gradient: Gradient, spread_method: vector_types::G
 	(gradient, Attr(spread_method))
 }
 
-/// Gets the color at the specified position along the gradient, given a position from 0 (left) to 1 (right).
+/// Sets the position of each of a gradient's stops, a factor from 0 to 1 along the gradient.
+///
+/// A list shorter than the stop count repeats its last value, a longer list is truncated, and an empty list sets each stop to its default evenly spaced position.
 #[node_macro::node(category("Color"))]
-fn sample_gradient(ctx: impl Ctx + ExtractIndex + InjectIndex + Copy, _primary: (), gradient: IList<Gradient>, position: Fraction) -> Result<IList<Color>, Interrupt> {
+fn gradient_positions(_: impl Ctx, mut gradient: Gradient, positions: List<f64>) -> Gradient {
+	let positions: Vec<f64> = positions.iter_element_values().copied().collect();
+	gradient.set_positions(&positions);
+	gradient
+}
+
+/// Sets the interpolation midpoint for each interval between gradient stops, a factor from 0 to 1 where the 0.5 default means linear interpolation and another value skews the transition speed toward one stop or the other.
+///
+/// The final stop belongs to no interval so its midpoint is ignored.
+///
+/// A list shorter than the stop count repeats its last value, a longer list is truncated, and an empty list sets each midpoint to its default of 0.5.
+#[node_macro::node(category("Color"))]
+fn gradient_midpoints(_: impl Ctx, mut gradient: Gradient, midpoints: List<f64>) -> Gradient {
+	let midpoints: Vec<f64> = midpoints.iter_element_values().copied().collect();
+	gradient.set_midpoints(&midpoints);
+	gradient
+}
+
+/// Evaluates the color at the specified position along the gradient, given a position from 0 (left) to 1 (right). Positions beyond that range follow the gradient's `spread_method` attribute: Pad (default), Reflect, or Repeat.
+#[node_macro::node(category("Color"))]
+fn sample_gradient(
+	ctx: impl Ctx + ExtractIndex + InjectIndex + Copy,
+	_primary: (),
+	#[default(Color::BLACK, Color::WHITE)] gradient: IList<Gradient>,
+	position: Fraction,
+) -> Result<IList<Color>, Interrupt> {
 	// An unwired gradient serves an empty level: no color
 	if gradient.is_empty() || ctx.index() != 0 {
 		return Err(GraphError::past_end().into());
 	}
 
-	let position = position.clamp(0., 1.);
-	Ok(gradient.element_ref(0).evaluate(position))
+	let spread_method = gradient.lane(0).attr::<SpreadMethodAttr>();
+	Ok(gradient.element_ref(0).evaluate(position, spread_method))
 }
 
 /// Constructs a footprint value which may be set to any transformation of a unit square describing a render area, and a render resolution at least 1x1 integer pixels.

node-graph/nodes/raster/src/adjust.rs

@@ -24,9 +24,7 @@ mod adjust_std {
 	}
 	impl Adjust<Color> for Gradient {
 		fn adjust(&mut self, map_fn: impl Fn(&Color) -> Color) {
-			for color in self.color.iter_mut() {
-				*color = map_fn(color);
-			}
+			*self = self.map_colors(map_fn);
 		}
 	}
 }

node-graph/nodes/raster/src/blending_nodes.rs

@@ -38,16 +38,19 @@ mod blend_std {
 
 	impl Blend<Color> for Gradient {
 		fn blend(&self, under: &Self, blend_fn: impl Fn(Color, Color) -> Color) -> Self {
-			let mut combined_stops = self.position.iter().chain(under.position.iter()).copied().collect::<Vec<_>>();
-			combined_stops.dedup_by(|a, b| (*a - *b).abs() < 1e-6);
+			let mut combined_stops = self.positions().into_iter().chain(under.positions()).collect::<Vec<_>>();
 			combined_stops.sort_by(|a, b| a.partial_cmp(b).unwrap_or(Ordering::Equal));
+			combined_stops.dedup_by(|a, b| (*a - *b).abs() < 1e-6);
 			let stops = combined_stops.into_iter().map(|position| {
-				let over_color = self.evaluate(position);
-				let under_color = under.evaluate(position);
+				let over_color = self.evaluate(position, Default::default());
+				let under_color = under.evaluate(position, Default::default());
 				let color = blend_fn(over_color, under_color);
 				GradientStop { position, midpoint: 0.5, color }
 			});
-			Gradient::new(stops)
+
+			let mut gradient = Gradient::new(stops);
+			gradient.elide_default_attributes();
+			gradient
 		}
 	}
 }

node-graph/nodes/raster/src/gradient_map.rs

@@ -17,18 +17,19 @@ fn gradient_map<T: Adjust<Color> + Clone + Send + Sync + core_types::CacheHash +
 		Gradient,
 	)]
 	mut image: T,
-	gradient: IList<Gradient>,
+	#[default(Color::BLACK, Color::WHITE)] gradient: IList<Gradient>,
 	reverse: bool,
 ) -> T {
 	if gradient.is_empty() {
 		return image;
 	}
+	let spread_method = gradient.lane(0).attr::<vector_types::markers::SpreadMethod>();
 	let gradient = gradient.element_ref(0);
 
 	image.adjust(|color| {
 		let intensity = color.luminance_rec_709();
 		let intensity = if reverse { 1. - intensity } else { intensity };
-		gradient.evaluate(intensity as f64)
+		gradient.evaluate(intensity as f64, spread_method)
 	});
 
 	image

node-graph/nodes/text/src/font.rs

@@ -64,7 +64,7 @@ impl Default for Font {
 	}
 }
 
-// TODO: Eventually remove this migration document upgrade code
+// TODO: Eventually remove this document upgrade code
 fn migrate_font_style<'de, D: serde::Deserializer<'de>>(deserializer: D) -> Result<String, D::Error> {
 	use serde::Deserialize;
 	String::deserialize(deserializer).map(|name| if name == "Normal (400)" { "Regular (400)".to_string() } else { name })

node-graph/nodes/vector/src/vector_nodes.rs

@@ -72,7 +72,7 @@ fn assign_color_at(gradient: &Gradient, position: usize, length: usize, randomiz
 			_ => position as f64 % repeat_every as f64 / (repeat_every - 1) as f64,
 		},
 	};
-	gradient.evaluate(factor)
+	gradient.evaluate(factor, Default::default())
 }
 
 /// Uniquely sets the fill and/or stroke style of every vector element to individual colors sampled along a chosen gradient.
@@ -88,6 +88,7 @@ fn assign_colors<'e>(
 	/// Whether to style the stroke.
 	stroke: bool,
 	/// The range of colors to select from.
+	#[default(Color::BLACK, Color::WHITE)]
 	#[widget(ParsedWidgetOverride::Custom = "assign_colors_gradient")]
 	gradient: IList<Gradient>,
 	/// Whether to reverse the gradient.
@@ -337,7 +338,7 @@ fn fill<'e>(
 	#[default(Color::BLACK)]
 	fill: IList<Graphic<'static>>,
 	_backup_color: IList<Color>,
-	_backup_gradient: IList<Gradient>,
+	#[default(Color::BLACK, Color::WHITE)] _backup_gradient: IList<Gradient>,
 	_gradient_type: GradientType,
 	_spread_method: GradientSpreadMethod,
 	_has_transform: bool,
@@ -358,7 +359,7 @@ fn fill_graphic_leveled<'e>(
 	(element, _content_fill): (Graphic<'static>, Attr<Fill>),
 	#[default(Color::BLACK)] fill: IList<Graphic<'static>>,
 	_backup_color: IList<Color>,
-	_backup_gradient: IList<Gradient>,
+	#[default(Color::BLACK, Color::WHITE)] _backup_gradient: IList<Gradient>,
 	_gradient_type: GradientType,
 	_spread_method: GradientSpreadMethod,
 	_has_transform: bool,
@@ -2924,14 +2925,12 @@ fn morph_core(flattened: List<Vector>, snapshot: List<Graphic<'static>>, progres
 		match (a.element(0), b.element(0)) {
 			(Some(Graphic::Color(color_a)), Some(Graphic::Color(color_b))) => Some(List::new_from_element(Graphic::from(color_a.lerp(color_b, time as f32)))),
 			(Some(Graphic::Color(color_a)), Some(Graphic::Gradient(stops_b))) => {
-				let mut solid_to_gradient = stops_b.clone();
-				solid_to_gradient.color.iter_mut().for_each(|color| *color = *color_a);
+				let solid_to_gradient = stops_b.map_colors(|_| *color_a);
 				let stops = solid_to_gradient.lerp(stops_b, time);
 				Some(gradient_paint(b, stops, None))
 			}
 			(Some(Graphic::Gradient(stops_a)), Some(Graphic::Color(color_b))) => {
-				let mut gradient_to_solid = stops_a.clone();
-				gradient_to_solid.color.iter_mut().for_each(|color| *color = *color_b);
+				let gradient_to_solid = stops_a.map_colors(|_| *color_b);
 				let stops = stops_a.lerp(&gradient_to_solid, time);
 				Some(gradient_paint(a, stops, None))
 			}