Add the "Perceptual" and "Classic" families of gradient spaces with OkLab as the new default (#4415)

* Add an OkLab gradient interpolation space and make it the new default

* Fix the Properties panel fill row resetting the gradient interpolation space to the default

* Add OkLch, Lab, LCh, and HSL gradient interpolation spaces

* Add a hue direction attribute and picker choice for polar gradient interpolation spaces

* Add an HSV gradient interpolation space

* Rename the sRGB Linear and sRGB Gamma gradient spaces to RGB Linear and RGB Gamma

* Divide the gradient interpolation dropdown between absolute and relative color spaces

* Rename the OkLch gradient interpolation space to OkLCh for channel-notation capitalization

* Shorten the color picker popover's hue direction row label to Arc

* Call the Gradient Interpolation node's parameter Space and extend the picker tooltip title to match

* Rename the gradient interpolation attribute and type family to gradient space

* Rename the gradient tool's gradient space transform to gradient to viewport transform

* Add serde aliases and a node replacement covering the gradient space renames

* Give the gradient space choices artist-facing labels and reorder the dropdown sections

* Add a Gradient Hue Direction node and its attribute read node

* Say interpolate instead of blend for gradient stop color traversal in docs and tooltips

* Label the polar perceptual gradient spaces as Perceptual Hue and group the dropdown sections by geometry

* Add a migration alias covering the gradient space attribute reader rename

* Carry the gradient hue direction attribute through boolean operations

* Register GradientHueDirection wire types in the node registry

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

@@ -11,7 +11,7 @@ use math_parser::value::{Number, Value};
 use rand::{Rng, SeedableRng};
 use std::ops::{Add, Mul, Rem, Sub};
 use vector_types::Gradient;
-use vector_types::markers::{GradientForm as GradientFormAttr, GradientInterpolation as GradientInterpolationAttr, GradientSpread as GradientSpreadAttr};
+use vector_types::markers::{GradientForm as GradientFormAttr, GradientHueDirection as GradientHueDirectionAttr, GradientSpace as GradientSpaceAttr, GradientSpread as GradientSpreadAttr};
 
 /// The struct that stores the context for the maths parser.
 /// This is currently just limited to supplying `a` and `b` until we add better node graph support and UI for variadic inputs.
@@ -1214,18 +1214,24 @@ fn gradient_spread(_: impl Ctx, gradient: Gradient, gradient_spread: vector_type
 	(gradient, Attr(gradient_spread))
 }
 
-/// Sets the color space each gradient in the input list blends between its stops with: linear light or gamma-encoded sRGB.
+/// Sets the color space in which each gradient in the input list interpolates between its stops.
 #[node_macro::node(category("Gradient"))]
-fn gradient_interpolation(_: impl Ctx, gradient: Gradient, gradient_interpolation: vector_types::GradientInterpolation) -> (Gradient, Attr<GradientInterpolationAttr>) {
-	(gradient, Attr(gradient_interpolation))
+fn gradient_space(_: impl Ctx, gradient: Gradient, gradient_space: vector_types::GradientSpace) -> (Gradient, Attr<GradientSpaceAttr>) {
+	(gradient, Attr(gradient_space))
+}
+
+/// Sets the hue path each gradient in the input list interpolates along in polar color spaces.
+#[node_macro::node(category("Gradient"))]
+fn gradient_hue_direction(_: impl Ctx, gradient: Gradient, gradient_hue_direction: vector_types::GradientHueDirection) -> (Gradient, Attr<GradientHueDirectionAttr>) {
+	(gradient, Attr(gradient_hue_direction))
 }
 
 /// 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("Gradient"))]
-fn gradient_positions(_: impl Ctx, mut gradient: Gradient, positions: List<f64>) -> Gradient {
-	let positions: Vec<f64> = positions.iter_element_values().copied().collect();
+fn gradient_positions(_: impl Ctx, mut gradient: Gradient, positions: IList<f64>) -> Gradient {
+	let positions: Vec<f64> = positions.iter().collect();
 	gradient.set_positions(&positions);
 	gradient
 }
@@ -1236,13 +1242,13 @@ fn gradient_positions(_: impl Ctx, mut gradient: Gradient, positions: List<f64>)
 ///
 /// 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("Gradient"))]
-fn gradient_midpoints(_: impl Ctx, mut gradient: Gradient, midpoints: List<f64>) -> Gradient {
-	let midpoints: Vec<f64> = midpoints.iter_element_values().copied().collect();
+fn gradient_midpoints(_: impl Ctx, mut gradient: Gradient, midpoints: IList<f64>) -> Gradient {
+	let midpoints: Vec<f64> = midpoints.iter().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 `gradient_spread` attribute: Pad (default), Reflect, Repeat, or Clear. Colors between stops blend in the gradient's `gradient_interpolation` color space.
+/// 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 `gradient_spread` attribute: Pad (default), Reflect, Repeat, or Clear. Colors between stops interpolate in the gradient's `gradient_space` color space.
 #[node_macro::node(category("Color"))]
 fn sample_gradient(
 	ctx: impl Ctx + ExtractIndex + InjectIndex + Copy,
@@ -1256,8 +1262,9 @@ fn sample_gradient(
 	}
 
 	let gradient_spread = gradient.lane(0).attr::<GradientSpreadAttr>();
-	let gradient_interpolation = gradient.lane(0).attr::<GradientInterpolationAttr>();
-	Ok(gradient.element_ref(0).evaluate(position, gradient_spread, gradient_interpolation))
+	let gradient_space = gradient.lane(0).attr::<GradientSpaceAttr>();
+	let gradient_hue_direction = gradient.lane(0).attr::<GradientHueDirectionAttr>();
+	Ok(gradient.element_ref(0).evaluate(position, gradient_spread, gradient_space, gradient_hue_direction))
 }
 
 /// 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.