Merge pull request gumyr#491 from jdegenstein/try_offset

Fix offset of faces with holes

src/build123d/operations_generic.py

@@ -593,11 +593,14 @@ def offset(
             outer_wire = outer_wire.fix_degenerate_edges(min_edge_length)
         inner_wires = []
         for inner_wire in face.inner_wires():
-            offset_wire = inner_wire.offset_2d(-amount, kind=kind)
-            if min_edge_length is not None:
-                inner_wires.append(offset_wire.fix_degenerate_edges(min_edge_length))
-            else:
-                inner_wires.append(offset_wire)
+            try:
+                offset_wire = inner_wire.offset_2d(-amount, kind=kind)
+                if min_edge_length is not None:
+                    inner_wires.append(offset_wire.fix_degenerate_edges(min_edge_length))
+                else:
+                    inner_wires.append(offset_wire)
+            except:
+                pass
         new_faces.append(Face.make_from_wires(outer_wire, inner_wires))
     if edges:
         if len(edges) == 1 and edges[0].geom_type() == "LINE":

tests/test_build_generic.py

@@ -591,6 +591,27 @@ def test_offset_algebra_wire(self):
         o_line = offset(line, amount=3.177)
         self.assertEqual(len(o_line.edges()), 19)
 
+    def test_offset_face_with_inner_wire(self):
+        # offset amount causes the inner wire to have zero length
+        b = Rectangle(1, 1)
+        b -= RegularPolygon(.25, 3)
+        b = offset(b, amount=0.125)
+        self.assertAlmostEqual(b.area, 1 ** 2 + 2 * 0.125 * 2 + pi * 0.125 ** 2, 5)
+        self.assertEqual(len(b.face().inner_wires()), 0)
+
+    def test_offset_face_with_min_length(self):
+        c = Circle(.5)
+        c = offset(c, amount=0.125, min_edge_length=0.1)
+        self.assertAlmostEqual(c.area, pi * (0.5 + 0.125) ** 2, 5)
+
+    def test_offset_face_with_min_length_and_inner(self):
+        # offset amount causes the inner wire to have zero length
+        c = Circle(.5)
+        c -= RegularPolygon(.25, 3)
+        c = offset(c, amount=0.125, min_edge_length=0.1)
+        self.assertAlmostEqual(c.area, pi * (0.5 + 0.125) ** 2, 5)
+        self.assertEqual(len(c.face().inner_wires()), 0)
+
     def test_offset_bad_type(self):
         with self.assertRaises(TypeError):
             offset(Vertex(), amount=1)