Do not discard minimum-length paths in `FlexPath::remove_overlapping_…

…points()` (#278)

* Test minimum-length paths

* Only discard point if length is strictly less than tolerance

src/flexpath.cpp

@@ -226,7 +226,7 @@ void FlexPath::remove_overlapping_points() {
     const double tol_sq = spine.tolerance * spine.tolerance;
     Array<Vec2>* array = &spine.point_array;
     for (uint64_t i = 1; i < array->count;) {
-        if (((*array)[i] - (*array)[i - 1]).length_sq() <= tol_sq) {
+        if (((*array)[i] - (*array)[i - 1]).length_sq() < tol_sq) {
             array->remove(i);
             FlexPathElement* el = elements;
             for (uint64_t ne = 0; ne < num_elements; ne++, el++)

tests/flexpath_test.py

@@ -166,3 +166,12 @@ def test_raith_data():
     assert path.raith_data.periods == 5
     assert path.raith_data.grating_type == 6
     assert path.raith_data.dots_per_cycle == 7
+
+
+def test_min_length():
+    lib = gdstk.Library("test")
+    tol = lib.precision / lib.unit
+
+    path = gdstk.FlexPath(((0, 0), (tol, 0)), width=0.01, tolerance=tol)
+    assert path.to_polygons()
+

tests/library_test.py

@@ -5,11 +5,14 @@
 # Boost Software License - Version 1.0.  See the accompanying
 # LICENSE file or <http://www.boost.org/LICENSE_1_0.txt>
 
-from datetime import datetime
 import hashlib
 import pathlib
-import pytest
+from datetime import datetime
+from typing import Callable, Union
+
 import numpy
+import pytest
+
 import gdstk
 
 
@@ -532,3 +535,29 @@ def test_roundtrip_path_ends(tmpdir: pathlib.Path):
         assert (
             path.ends == gds_path.ends and path.ends == oas_path.ends
         ), f"expected: {path.ends}, gds: {gds_path.ends}, oas: {oas_path.ends}"
+
+
+@pytest.mark.parametrize(
+    "write_f, read_f",
+    (
+        (gdstk.Library.write_oas, gdstk.read_oas),
+        (gdstk.Library.write_gds, gdstk.read_gds),
+    ),
+)
+def test_write_min_length_path(
+    write_f: Callable[[gdstk.Library, Union[str, pathlib.Path]], None],
+    read_f: Callable[Union[str, pathlib.Path], gdstk.Library],
+    tmp_path: pathlib.Path
+):
+    source = gdstk.read_oas(pathlib.Path(__file__).parent / "min_length_path.oas")
+    assert source.cells[0].paths
+
+    rw_path = tmp_path / "out"
+    write_f(source, rw_path)
+    rw = read_f(rw_path)
+    assert rw.cells[0].paths
+
+    assert numpy.array_equal(
+        source.cells[0].paths[0].spine(),
+        rw.cells[0].paths[0].spine(),
+    )