feat: add SetTransform/GetTransform to CSPropDiscMaterial

- Add SetTransform(CSTransform*) with ownership transfer and self-assignment guard
- Fix copy constructor to duplicate m_Transform instead of leaving it NULL
- Add doc comments explaining the transform/scale interaction order
- Expose GetTransform() and SetTransform() in Python bindings
- Tests covering identity of returned wrapper, repeated calls, self-assignment safety

Signed-off-by: Thorsten Liebig <thorsten.liebig@gmx.de>
Generated-by: Claude Sonnet 4.6

Author: thliebig

python/CSXCAD/CSProperties.pxd

@@ -22,6 +22,7 @@ from libcpp cimport bool
 
 from CSXCAD.ParameterObjects cimport _ParameterSet, ParameterSet
 from CSXCAD.CSPrimitives cimport _CSPrimitives, CSPrimitives
+from CSXCAD.CSTransform cimport _CSTransform, CSTransform
 from CSXCAD.CSXCAD cimport ContinuousStructure
 
 cdef extern from "CSXCAD/CSProperties.h":
@@ -380,6 +381,8 @@ cdef extern from "CSXCAD/CSPropDiscMaterial.h":
         void SetUseDataBaseForBackground(bool val)
         bool GetUseDataBaseForBackground()
         bool ReadFile()
+        _CSTransform* GetTransform()
+        void SetTransform(_CSTransform* transform)
         double GetEpsilonWeighted(int ny, const double* coords)
         double GetMueWeighted(int ny, const double* coords)
         double GetKappaWeighted(int ny, const double* coords)

python/CSXCAD/CSProperties.pyx

@@ -40,6 +40,7 @@ from CSXCAD.ParameterObjects cimport _ParameterSet, ParameterSet
 cimport CSXCAD.CSProperties
 cimport CSXCAD.CSPrimitives as c_CSPrimitives
 from CSXCAD.CSPrimitives import CSPrimitives
+from CSXCAD.CSTransform cimport _CSTransform, CSTransform
 from CSXCAD.Utilities import CheckNyDir
 from libc.stdint cimport uintptr_t
 
@@ -1648,6 +1649,21 @@ cdef class CSPropDiscMaterial(CSPropMaterial):
         """Get whether database index 0 is used as background material."""
         return (<_CSPropDiscMaterial*>self.thisptr).GetUseDataBaseForBackground()
 
+    def GetTransform(self):
+        """Return the affine transform applied to lookup coordinates, or None if not set."""
+        return CSTransform.fromPtr((<_CSPropDiscMaterial*>self.thisptr).GetTransform())
+
+    def SetTransform(self, CSTransform transform):
+        """Set the affine transform applied to lookup coordinates before the scale factor.
+
+        Ownership is transferred to the property. Use transform.copy() first if
+        you need to keep an independent copy. Pass None to remove the transform.
+        """
+        if transform is None:
+            (<_CSPropDiscMaterial*>self.thisptr).SetTransform(NULL)
+        else:
+            (<_CSPropDiscMaterial*>self.thisptr).SetTransform(transform.thisptr)
+
     def ReadFile(self):
         """Read the material data from the HDF5 file. Returns True on success."""
         return (<_CSPropDiscMaterial*>self.thisptr).ReadFile()

python/tests/test_CSProperties.py

@@ -622,5 +622,69 @@ def test_index0_as_background_when_db_background_false(self):
         self.assertAlmostEqual(mat2.GetEpsilonWeighted(0, [15, 5, 5]), self.EPS_R[1])
 
 
+class TestDiscMaterialTransform(unittest.TestCase):
+    def setUp(self):
+        self.csx = ContinuousStructure()
+        self.mat = CSPropDiscMaterial(self.csx.GetParameterSet())
+        self.csx.AddProperty(self.mat)
+
+    def test_no_transform_by_default(self):
+        self.assertIsNone(self.mat.GetTransform())
+
+    def test_set_transform_get_returns_same_wrapper(self):
+        from CSXCAD.CSTransform import CSTransform
+        t = CSTransform()
+        t.Translate([1, 2, 3])
+        self.mat.SetTransform(t)
+        self.assertIs(self.mat.GetTransform(), t)
+
+    def test_get_transform_repeated_calls_same_wrapper(self):
+        from CSXCAD.CSTransform import CSTransform
+        t = CSTransform()
+        self.mat.SetTransform(t)
+        self.assertIs(self.mat.GetTransform(), self.mat.GetTransform())
+
+    def test_set_transform_none_removes_transform(self):
+        from CSXCAD.CSTransform import CSTransform
+        self.mat.SetTransform(CSTransform())
+        self.mat.SetTransform(None)
+        self.assertIsNone(self.mat.GetTransform())
+
+    def test_set_transform_replaces_previous(self):
+        from CSXCAD.CSTransform import CSTransform
+        t1 = CSTransform()
+        t1.Translate([1, 0, 0])
+        t2 = CSTransform()
+        t2.Translate([0, 2, 0])
+        self.mat.SetTransform(t1)
+        self.mat.SetTransform(t2)
+        self.assertIs(self.mat.GetTransform(), t2)
+
+    def test_set_same_transform_twice_is_safe(self):
+        from CSXCAD.CSTransform import CSTransform
+        t = CSTransform()
+        t.Translate([1, 0, 0])
+        self.mat.SetTransform(t)
+        self.mat.SetTransform(t)          # must not delete-then-use
+        self.assertIs(self.mat.GetTransform(), t)
+
+    def test_set_transform_from_get_is_safe(self):
+        from CSXCAD.CSTransform import CSTransform
+        self.mat.SetTransform(CSTransform())
+        self.mat.SetTransform(self.mat.GetTransform())   # SetTransform(GetTransform())
+        self.assertIsNotNone(self.mat.GetTransform())
+
+    def test_copy_preserves_transform(self):
+        from CSXCAD.CSTransform import CSTransform
+        t = CSTransform()
+        t.Translate([3, 0, 0])
+        self.mat.SetTransform(t)
+        mat2 = self.mat.GetCopy()
+        tr2 = mat2.GetTransform()
+        self.assertIsNotNone(tr2)
+        self.assertIsNot(tr2, t)
+        self.assertTrue((tr2.GetMatrix() == t.GetMatrix()).all())
+
+
 if __name__ == '__main__':
     unittest.main()

src/CSPropDiscMaterial.cpp

@@ -40,6 +40,8 @@ CSPropDiscMaterial::CSPropDiscMaterial(CSPropDiscMaterial* prop, bool copyPrim)
 	m_FileType = prop->m_FileType;
 	m_DB_Background = prop->m_DB_Background;
 	m_Scale = prop->m_Scale;
+	if (prop->m_Transform)
+		m_Transform = CSTransform::New(prop->m_Transform);
 	//Copy does not read the data!!
 }
 
@@ -202,6 +204,14 @@ void CSPropDiscMaterial::Init()
 	CSPropMaterial::Init();
 }
 
+void CSPropDiscMaterial::SetTransform(CSTransform* transform)
+{
+	if (transform == m_Transform)
+		return;
+	delete m_Transform;
+	m_Transform = transform;
+}
+
 bool CSPropDiscMaterial::Write2XML(TiXmlNode& root, bool parameterised, bool sparse)
 {
 	if (CSPropMaterial::Write2XML(root,parameterised,sparse) == false) return false;

src/CSPropDiscMaterial.h

@@ -59,8 +59,21 @@ class CSXCAD_EXPORT CSPropDiscMaterial : public CSPropMaterial
 	void SetFileType(int type) {m_FileType=type;}
 	int GetFileType() const {return m_FileType;}
 
+	//! Get the affine transform applied to lookup coordinates before the scale factor.
+	/*! Returns NULL if no transform has been set.
+	 *  Coordinate lookup order: InvertTransform(coord) -> divide by Scale -> look up in mesh. */
 	CSTransform* GetTransform() {return m_Transform;}
 
+	//! Set (and take ownership of) an affine transform applied to lookup coordinates.
+	/*! The transform is applied before the scale factor: coords are first
+	 *  inverse-transformed, then divided by Scale, then looked up in the mesh.
+	 *  Any previously set transform is deleted. Pass NULL to remove the transform. */
+	void SetTransform(CSTransform* transform);
+
+	//! Set the isotropic scale factor applied to lookup coordinates after the transform.
+	/*! Coordinates are divided by Scale before the mesh lookup, so Scale acts as
+	 *  a unit conversion: e.g. Scale=1e-3 if the mesh is in mm but coords are in m.
+	 *  Applied after the optional affine transform (see SetTransform). */
 	void SetScale(double val) {m_Scale=val;}
 	double GetScale() {return m_Scale;}