From 6f233441b3bfff9fe82b795493bbe1db58f429ee Mon Sep 17 00:00:00 2001
From: Jonathan Haas <haasjona@gmail.com>
Date: Thu, 24 Apr 2025 18:00:13 +0200
Subject: [PATCH] Fix a special case in the reduce function when pass1 created
 very short segments

Fixes #286

Also add testcase.
---
 packages/core/src/bezier.mjs      | 10 +++++++++-
 packages/core/tests/path.test.mjs | 13 +++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/packages/core/src/bezier.mjs b/packages/core/src/bezier.mjs
index c9e3dd0d1d3..d8c8b1e0bc2 100644
--- a/packages/core/src/bezier.mjs
+++ b/packages/core/src/bezier.mjs
@@ -38,7 +38,15 @@ class Bezier extends UpstreamBezier {
       const splitTs = []
       let t1 = 0
 
-      if (bezier._t2 - bezier._t1 < EPSILON || bezier.simple()) {
+      // This is a inverted to return [] on NaN _tX values
+      // since NaN compared with something is always false
+      if (!(bezier._t2 - bezier._t1 >= EPSILON)) {
+        // very short, ignore
+        return []
+      }
+
+      if (bezier.simple()) {
+        // already simple
         return [bezier]
       }
 
diff --git a/packages/core/tests/path.test.mjs b/packages/core/tests/path.test.mjs
index d3bd9467b92..2356d3fc0bc 100644
--- a/packages/core/tests/path.test.mjs
+++ b/packages/core/tests/path.test.mjs
@@ -157,6 +157,19 @@ describe('Path', () => {
       expect(round(bbox.bottomRight.y)).to.equal(38.26)
     })
 
+    it('Should offset a problematic curve', () => {
+      // https://codeberg.org/freesewing/freesewing/issues/286
+      const curve = new Path()
+        .move(new Point(233.58820676923352, 437.7581608165166))
+        .curve(
+          new Point(231.23631634571132, 415.3814181707305),
+          new Point(221.70910430613077, 371.13489592600627),
+          new Point(219.35721388260856, 348.75815328022014)
+        )
+      const offset = curve.offset(10)
+      expect(offset.length()).to.be.greaterThan(0)
+    })
+
     it('Should offset a curve where cp1 = start', () => {
       const curve = new Path().move(new Point(0, 0))._curve(new Point(123, 34), new Point(23, 4))
       const offset = curve.offset(10)