From f94ddb293fba89595adaaea521266a838e99419a Mon Sep 17 00:00:00 2001
From: maj00r <maj00r@host>
Date: Sat, 24 Oct 2026 22:40:28 +0200
Subject: [PATCH] fix(editor): a compound curve of more than three radii, made
 of bends clicked close along a curve or traced, has the transition curves of
 the norms between its arcs too: its radii found with the arcs meeting
 directly, then fitted again with the transitions between them; in abc the
 curve keeps within 0.12 m of the points clicked with them

---
 editor/editorAlignment.cpp    | 6 ++++--
 tests/unit/test_alignment.cpp | 7 +++++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/editor/editorAlignment.cpp b/editor/editorAlignment.cpp
index 6bdeed29..da94be7c 100644
--- a/editor/editorAlignment.cpp
+++ b/editor/editorAlignment.cpp
@@ -3181,9 +3181,11 @@ std::optional<trace_stretch> fit_arcs(design const &Single, std::vector<glm::dve
 			else
 				curve.arcs.push_back({radius, 0.0, share});
 		}
-		// arcs meeting with no transitions between them: the points of a curve clicked by hand ask for the radius to change
-		// quicker than the transitions of the norms let it
+		// the radii found with the arcs meeting directly, which follows the points easily, then with the transitions of the norms
+		// between the arcs, fitted again from there
 		fit_compound(shaped, 0, Points, false);
+		recommend_between(shaped.vertices.front(), Single.speed, Single.norms);
+		fit_compound(shaped, 0, Points, true);
 		// none of an arc too short to be one: a kink the points made
 		auto const fitted{compute(shaped)};
 		auto const kinked{std::any_of(fitted.elements.begin(), fitted.elements.end(), [](element const &Element) {
diff --git a/tests/unit/test_alignment.cpp b/tests/unit/test_alignment.cpp
index 4651eb55..e058f532 100644
--- a/tests/unit/test_alignment.cpp
+++ b/tests/unit/test_alignment.cpp
@@ -286,5 +286,12 @@ TEST_CASE("alignment: bends clicked close along a curve make one compound curve,
 	// the straight before the curve and the one after it
 	CHECK(straights <= 2);
 	CHECK(line.curves.size() <= 2);
+	// the arcs of a compound curve meet through transition curves, the curvature not jumping from one radius to another
+	for (std::size_t i = 0; i + 1 < line.elements.size(); ++i) {
+		auto const &a{line.elements[i]};
+		auto const &b{line.elements[i + 1]};
+		if (a.kind == alignment::element_kind::spiral && b.kind == alignment::element_kind::spiral && a.vertex == b.vertex)
+			CHECK(a.curvature_end == doctest::Approx(b.curvature_start).epsilon(1e-6));
+	}
 	CHECK(design.vertices.size() < 12);
 }