Merge remote-tracking branch 'origin/main' into codex/region-measurement-persistence

# Conflicts:
#	src/app/doc_api.rs

src/entities/helix.rs

@@ -53,9 +53,16 @@ fn spline_curve(spline: &Spline) -> Option<NurbsCurve3> {
 fn axis_frame(helix: &Helix) -> Option<(Vec3, Vec3, Vec3)> {
     let base = point(helix.axis_base_point);
     let axis = point(helix.axis_vector).normalize()?;
-    let radial = point(helix.start_point) - base;
-    let start_direction = (radial - axis * radial.dot(axis)).normalize()?;
-    Some((base, axis, start_direction))
+    let tangent = spline_curve(&helix.spline)
+        .map(|curve| Vec3::from(curve.tangent_at(0.0)))
+        .and_then(Vec3::normalize)
+        .or_else(|| perpendicular(axis))?;
+    let (axis, radial, _) = HelixCurve::frame_from_points(base.to_array(),point(helix.axis_vector).to_array(),point(helix.start_point).to_array(),tangent.to_array())?;
+    Some((base,Vec3::from(axis),Vec3::from(radial)))
+}
+
+fn base_radius(helix: &Helix) -> Option<f64> {
+    radius_from_axis(helix, point(helix.start_point))
 }
 
 fn radius_from_axis(helix: &Helix, value: Vec3) -> Option<f64> {
@@ -65,6 +72,7 @@ fn radius_from_axis(helix: &Helix, value: Vec3) -> Option<f64> {
 }
 
 fn top_radius(helix: &Helix) -> f64 {
+    if helix.turns == 0.0 { return helix.radius; }
     spline_curve(&helix.spline)
         .map(|curve| Vec3::from(curve.point_at(1.0)))
         .and_then(|endpoint| radius_from_axis(helix, endpoint))
@@ -77,7 +85,7 @@ fn kernel_curve(helix: &Helix, top_radius: f64) -> Option<HelixCurve> {
         base_center: base.to_array(),
         axis_direction: axis.to_array(),
         start_direction: start_direction.to_array(),
-        base_radius: helix.radius,
+        base_radius: base_radius(helix)?,
         top_radius,
         height: helix.turns * helix.turn_height,
         turns: helix.turns,
@@ -89,6 +97,36 @@ fn kernel_curve(helix: &Helix, top_radius: f64) -> Option<HelixCurve> {
     })
 }
 
+/// Reverse generating parameters together with the exact stored spline.
+pub(crate) fn reversed(helix: &Helix) -> Option<Helix> {
+    let original_curve = spline_curve(&helix.spline)?;
+    let parameters = kernel_curve(helix, top_radius(helix))?.reversed()?;
+    let mut result = helix.clone();
+    result.axis_base_point = vector(Vec3::from(parameters.base_center));
+    result.axis_vector = vector(Vec3::from(parameters.axis_direction));
+    result.start_point = vector(Vec3::from(original_curve.point_at(1.0)));
+    result.radius = parameters.top_radius;
+    // Reverse the evaluated curve itself instead of fitting it again.
+    let reversed_curve = original_curve.reversed()?;
+    result.spline.control_points = reversed_curve
+        .control_points()
+        .iter()
+        .map(|point| Vector3::new(point[0], point[1], point[2]))
+        .collect();
+    result.spline.fit_points.reverse();
+    result.spline.weights = if helix.spline.weights.is_empty() {
+        Vec::new()
+    } else {
+        reversed_curve.weights().to_vec()
+    };
+    result.spline.knots = reversed_curve.knots().to_vec();
+    let begin = helix.spline.begin_tangent;
+    let end = helix.spline.end_tangent;
+    result.spline.begin_tangent = Vector3::new(-end.x, -end.y, -end.z);
+    result.spline.end_tangent = Vector3::new(-begin.x, -begin.y, -begin.z);
+    Some(result)
+}
+
 fn projected_direction(direction: Vec3, axis: Vec3) -> Option<Vec3> {
     (direction - axis * direction.dot(axis)).normalize()
 }
@@ -105,12 +143,18 @@ fn perpendicular(axis: Vec3) -> Option<Vec3> {
 }
 
 fn rebuild(helix: &mut Helix, top_radius: f64) -> bool {
-    let Some(curve) = kernel_curve(helix, top_radius) else {
+    rebuild_with_radial(helix, top_radius, None)
+}
+
+fn rebuild_with_radial(helix: &mut Helix, top_radius: f64, radial: Option<Vec3>) -> bool {
+    let Some(mut curve) = kernel_curve(helix, top_radius) else {
         return false;
     };
+    if let Some(radial) = radial { curve.start_direction = radial.to_array(); }
     let Some(nurbs) = curve.nurbs() else {
         return false;
     };
+    helix.radius = top_radius;
     helix.spline.degree = nurbs.degree() as i32;
     helix.spline.knots = nurbs.knots().to_vec();
     helix.spline.control_points = nurbs
@@ -127,7 +171,7 @@ fn rebuild(helix: &mut Helix, top_radius: f64) -> bool {
     helix.spline.flags.closed = false;
     helix.spline.flags.periodic = false;
     helix.spline.flags.rational = nurbs.is_rational();
-    helix.spline.flags.planar = false;
+    helix.spline.flags.planar = curve.height == 0.0;
     helix.spline.flags.linear = false;
     true
 }
@@ -194,7 +238,7 @@ fn properties(helix: &Helix) -> Vec<PropSection> {
             edit(t!("Height").as_ref(), "height", height),
             edit(t!("Turns").as_ref(), "turns", helix.turns),
             edit(t!("Turn height").as_ref(), "turn_height", helix.turn_height),
-            edit(t!("Base radius").as_ref(), "base_radius", helix.radius),
+            edit(t!("Base radius").as_ref(), "base_radius", base_radius(helix).unwrap_or(0.0)),
             edit(t!("Top radius").as_ref(), "top_radius", top_radius),
             choice(t!("Twist").as_ref(), "twist", &twist, &twist_options),
             ro(t!("Turn slope").as_ref(), "turn_slope", format_angle(turn_slope)),
@@ -249,10 +293,15 @@ fn apply_geom_prop(helix: &mut Helix, field: &str, value: &str) {
             helix.axis_base_point = vector(base);
             helix.start_point = vector(point(helix.start_point) + delta);
         }
-        "height" if number.abs() > EPSILON => {
+        "height" => {
+            if helix.turns == 0.0 && number != 0.0 {
+                return;
+            }
+            if number < 0.0 { helix.axis_vector = vector(-point(helix.axis_vector)); }
+            let number = number.abs();
             if helix.constraint == HelixConstraint::TurnHeight && helix.turn_height.abs() > EPSILON {
                 let turns = number / helix.turn_height;
-                if turns <= EPSILON {
+                if turns < 0.0 {
                     return;
                 }
                 helix.turns = turns;
@@ -260,16 +309,18 @@ fn apply_geom_prop(helix: &mut Helix, field: &str, value: &str) {
                 helix.turn_height = number / helix.turns.max(EPSILON);
             }
         }
-        "turns" if number > EPSILON => {
-            if helix.constraint == HelixConstraint::TurnHeight {
+        "turns" if number >= 0.0 => {
+            if number == 0.0 { helix.turns = 0.0; }
+            else if helix.constraint == HelixConstraint::TurnHeight {
                 helix.turns = number;
             } else {
                 helix.turns = number;
                 helix.turn_height = old_height / number;
             }
         }
-        "turn_height" if number.abs() > EPSILON => {
-            if helix.constraint == HelixConstraint::Turns {
+        "turn_height" if number >= 0.0 => {
+            if number == 0.0 { helix.turn_height = 0.0; }
+            else if helix.constraint == HelixConstraint::Turns {
                 helix.turn_height = number;
             } else {
                 let turns = old_height / number;
@@ -280,12 +331,13 @@ fn apply_geom_prop(helix: &mut Helix, field: &str, value: &str) {
                 helix.turns = turns;
             }
         }
-        "base_radius" if number > EPSILON => {
+        "base_radius" if number >= 0.0 => {
             let Some((base, _, start_direction)) = axis_frame(helix) else {
                 return;
             };
-            helix.radius = number;
             helix.start_point = vector(base + start_direction * number);
+            if !rebuild_with_radial(helix, top, Some(start_direction)) { *helix = original; }
+            return;
         }
         "top_radius" if number >= 0.0 => {
             if !rebuild(helix, number) {
@@ -303,6 +355,7 @@ fn apply_geom_prop(helix: &mut Helix, field: &str, value: &str) {
 fn apply_grip(helix: &mut Helix, grip_id: usize, apply: GripApply) {
     let original = helix.clone();
     let top = top_radius(helix);
+    let Some(base_radius) = base_radius(helix) else { return; };
     let Some((base, axis, start_direction)) = axis_frame(helix) else {
         return;
     };
@@ -334,7 +387,6 @@ fn apply_grip(helix: &mut Helix, grip_id: usize, apply: GripApply) {
             if radius <= EPSILON {
                 return;
             }
-            helix.radius = radius;
             helix.start_point = vector(base + radial);
         }
         (2, GripApply::Absolute(position)) => {
@@ -362,7 +414,7 @@ fn apply_grip(helix: &mut Helix, grip_id: usize, apply: GripApply) {
                 *helix = original;
                 return;
             };
-            helix.start_point = vector(base + start_direction * helix.radius);
+            helix.start_point = vector(base + start_direction * base_radius);
         }
         (3, GripApply::Absolute(position)) => {
             let position = kernel(position);
@@ -455,3 +507,98 @@ impl Transformable for Helix {
         apply_transform(self, transform);
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn zero_base_point_helix() -> Helix {
+        let curve = HelixCurve {
+            base_center: [1.0, 2.0, 3.0],
+            axis_direction: [0.0, 0.0, 1.0],
+            start_direction: [1.0, 0.0, 0.0],
+            base_radius: 0.0,
+            top_radius: 2.0,
+            height: 0.0,
+            turns: 0.0,
+            direction: HelixDirection::CounterClockwise,
+        };
+        let nurbs = curve.nurbs().unwrap();
+        let mut helix = Helix::new();
+        helix.axis_base_point = Vector3::new(1.0, 2.0, 3.0);
+        helix.axis_vector = Vector3::UNIT_Z;
+        helix.start_point = helix.axis_base_point;
+        helix.radius = 2.0;
+        helix.turns = 0.0;
+        helix.turn_height = 0.0;
+        helix.spline.degree = nurbs.degree() as i32;
+        helix.spline.knots = nurbs.knots().to_vec();
+        helix.spline.control_points = nurbs
+            .control_points()
+            .iter()
+            .map(|point| Vector3::new(point[0], point[1], point[2]))
+            .collect();
+        helix
+    }
+
+    #[test]
+    fn zero_base_point_locus_retains_an_editable_frame() {
+        let mut helix = zero_base_point_helix();
+        assert_eq!(base_radius(&helix), Some(0.0));
+        assert_eq!(top_radius(&helix), 2.0);
+
+        let original = helix.clone();
+        apply_geom_prop(&mut helix, "height", "5");
+        assert_eq!(helix, original);
+    }
+
+    #[test]
+    fn reversing_twice_restores_a_conical_helix_and_radius_roles() {
+        let curve = HelixCurve {
+            base_center: [1.0, 2.0, 3.0],
+            axis_direction: [0.0, 1.0, 1.0],
+            start_direction: [1.0, 0.0, 0.0],
+            base_radius: 1.0,
+            top_radius: 2.5,
+            height: 4.0,
+            turns: 1.25,
+            direction: HelixDirection::Clockwise,
+        };
+        let nurbs = curve.nurbs().expect("valid helix");
+        let mut helix = Helix::new();
+        helix.axis_base_point = Vector3::new(1.0, 2.0, 3.0);
+        let axis = Vec3::from(curve.axis_direction).normalize().unwrap();
+        helix.axis_vector = vector(axis);
+        helix.start_point = Vector3::new(2.0, 2.0, 3.0);
+        helix.radius = curve.top_radius;
+        helix.turns = curve.turns;
+        helix.turn_height = curve.height / curve.turns;
+        helix.handedness = false;
+        helix.spline.degree = nurbs.degree() as i32;
+        helix.spline.control_points = nurbs
+            .control_points()
+            .iter()
+            .map(|point| Vector3::new(point[0], point[1], point[2]))
+            .collect();
+        helix.spline.knots = nurbs.knots().to_vec();
+        helix.spline.weights = nurbs.weights().to_vec();
+
+        let once = reversed(&helix).expect("first reversal");
+        assert!((once.radius - curve.base_radius).abs() < 1.0e-12);
+        assert_eq!(once.turns, helix.turns);
+        assert_eq!(once.turn_height, helix.turn_height);
+        assert_eq!(once.handedness, helix.handedness);
+        let original_curve = spline_curve(&helix.spline).unwrap();
+        let once_curve = spline_curve(&once.spline).unwrap();
+        assert!(Vec3::from(once_curve.point_at(0.0))
+            .distance(Vec3::from(original_curve.point_at(1.0))) < 1.0e-9);
+
+        let twice = reversed(&once).expect("second reversal");
+        assert!((twice.radius - helix.radius).abs() < 1.0e-12);
+        let twice_curve = spline_curve(&twice.spline).unwrap();
+        for parameter in [0.0, 0.2, 0.5, 0.8, 1.0] {
+            assert!(Vec3::from(twice_curve.point_at(parameter))
+                .distance(Vec3::from(original_curve.point_at(parameter))) < 1.0e-8);
+        }
+    }
+}