From a0c28aba754e943c80d8df26c0019f4d85b5bbbf Mon Sep 17 00:00:00 2001
From: PaddleStroke <pierrelouis.boyer@gmail.com>
Date: Tue, 14 Oct 2025 11:40:10 +0200
Subject: [PATCH] Assembly: Fix lengths cannot be negative (#24625)

* Assembly: Fix lengths cannot be negative

* Update PropertyUnits.cpp

* Update PropertyUnits.h

* Update JointObject.py
---
 src/App/PropertyContainerPyImp.cpp | 9 +++++++++
 src/App/PropertyUnits.cpp          | 8 +++++++-
 src/App/PropertyUnits.h            | 3 +++
 src/Mod/Assembly/JointObject.py    | 5 +++++
 4 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/src/App/PropertyContainerPyImp.cpp b/src/App/PropertyContainerPyImp.cpp
index cba8d8285e..a630f7fe2b 100644
--- a/src/App/PropertyContainerPyImp.cpp
+++ b/src/App/PropertyContainerPyImp.cpp
@@ -30,6 +30,8 @@
 #include <boost/iostreams/device/array.hpp>
 #include <boost/iostreams/stream.hpp>
 
+#include "PropertyUnits.h"
+
 // inclusion of the generated files (generated out of PropertyContainerPy.xml)
 #include "PropertyContainerPy.h"
 #include "PropertyContainerPy.cpp"
@@ -272,6 +274,12 @@ PyObject* PropertyContainerPy::setPropertyStatus(PyObject* args)
                     continue;
                 }
 
+                auto lengthProp = freecad_cast<App::PropertyLength*>(prop);
+                if (lengthProp && v == "AllowNegativeValues") {
+                    lengthProp->enableNegative(value);
+                    continue;
+                }
+
                 PyErr_Format(PyExc_ValueError, "Unknown property status '%s'", v.c_str());
                 return nullptr;
             }
@@ -721,3 +729,4 @@ PyObject* PropertyContainerPy::renameProperty(PyObject* args) const
     }
     PY_CATCH
 }
+
diff --git a/src/App/PropertyUnits.cpp b/src/App/PropertyUnits.cpp
index ecb0a68397..42d63d3c10 100644
--- a/src/App/PropertyUnits.cpp
+++ b/src/App/PropertyUnits.cpp
@@ -518,7 +518,12 @@ TYPESYSTEM_SOURCE(App::PropertyLength, App::PropertyQuantityConstraint)
 PropertyLength::PropertyLength()
 {
     setUnit(Base::Unit::Length);
-    setConstraints(&LengthStandard);
+    enableNegative(false);
+}
+
+void PropertyLength::enableNegative(bool on)
+{
+    setConstraints(on ? nullptr : &LengthStandard);
 }
 
 //**************************************************************************
@@ -863,3 +868,4 @@ PropertyYoungsModulus::PropertyYoungsModulus()
 {
     setUnit(Base::Unit::YoungsModulus);
 }
+
diff --git a/src/App/PropertyUnits.h b/src/App/PropertyUnits.h
index 2e2cca365c..6e3a44c5d1 100644
--- a/src/App/PropertyUnits.h
+++ b/src/App/PropertyUnits.h
@@ -515,6 +515,8 @@ class AppExport PropertyLength: public PropertyQuantityConstraint
 public:
     PropertyLength();
     ~PropertyLength() override = default;
+
+    void enableNegative(bool on);
 };
 
 /** LuminousIntensity property
@@ -923,3 +925,4 @@ public:
 }  // namespace App
 
 #endif  // APP_PROPERTYUNITS_H
+
diff --git a/src/Mod/Assembly/JointObject.py b/src/Mod/Assembly/JointObject.py
index 7d14f08d2e..d4a1a3964f 100644
--- a/src/Mod/Assembly/JointObject.py
+++ b/src/Mod/Assembly/JointObject.py
@@ -370,6 +370,11 @@ class Joint:
         if not hasattr(joint, "AngleMax"):
             self.addAngleMaxProperty(joint)
 
+        joint.setPropertyStatus("Distance", "AllowNegativeValues")
+        joint.setPropertyStatus("Distance2", "AllowNegativeValues")
+        joint.setPropertyStatus("LengthMin", "AllowNegativeValues")
+        joint.setPropertyStatus("LengthMax", "AllowNegativeValues")
+
     def addAngleProperty(self, joint):
         joint.addProperty(
             "App::PropertyAngle",