Fix #5670. No double endpoints in Path.to_polygon

matplotlib · tacaswell · Dec 15, 2015 · Dec 14, 2015 · Dec 14, 2015 · Dec 14, 2015
commit 36ce4a7f3afd775dfb8b91fe4997a2ee0ab929fc
diff --git a/lib/matplotlib/tests/test_path.py b/lib/matplotlib/tests/test_path.py
@@ -10,6 +10,7 @@
 from nose.tools import assert_raises, assert_equal
 from matplotlib.testing.decorators import image_comparison
 import matplotlib.pyplot as plt
+from matplotlib import transforms


 def test_readonly_path():
@@ -113,6 +114,42 @@ def test_marker_paths_pdf():
    plt.ylim(-1, 7)


+def test_path_no_doubled_point_in_to_polygon():
+    hand = np.array(
+        [[ 1.64516129,  1.16145833 ],
+         [ 1.64516129,  1.59375    ],
+         [ 1.35080645,  1.921875   ],
+         [ 1.375     ,  2.18229167 ],
+         [ 1.68548387,  1.9375     ],
+         [ 1.60887097,  2.55208333 ],
+         [ 1.68548387,  2.69791667 ],
+         [ 1.76209677,  2.56770833 ],
+         [ 1.83064516,  1.97395833 ],
+         [ 1.89516129,  2.75       ],
+         [ 1.9516129 ,  2.84895833 ],
+         [ 2.01209677,  2.76041667 ],
+         [ 1.99193548,  1.99479167 ],
+         [ 2.11290323,  2.63020833 ],
+         [ 2.2016129 ,  2.734375   ],
+         [ 2.25403226,  2.60416667 ],
+         [ 2.14919355,  1.953125   ],
+         [ 2.30645161,  2.36979167 ],
+         [ 2.39112903,  2.36979167 ],
+         [ 2.41532258,  2.1875     ],
+         [ 2.1733871 ,  1.703125   ],
+         [ 2.07782258,  1.16666667 ]])
+
+    (r0, c0, r1, c1) = (1.0, 1.5, 2.1, 2.5)
+
+    poly = Path(np.vstack((hand[:, 1], hand[:, 0])).T, closed=True)
+    clip_rect = transforms.Bbox([[r0, c0], [r1, c1]])
+    poly_clipped = poly.clip_to_bbox(clip_rect).to_polygons()[0]
+
+    assert np.all(poly_clipped[-2] != poly_clipped[-1])
+    assert np.all(poly_clipped[-1] == poly_clipped[0])
+
+
+
 if __name__ == '__main__':
    import nose
    nose.runmodule(argv=['-s', '--with-doctest'], exit=False)
diff --git a/src/_path.h b/src/_path.h
@@ -27,6 +27,16 @@ struct XY
    XY(double x_, double y_) : x(x_), y(y_)
    {
    }
+
+    bool operator==(const XY& o)
+    {
+        return (x == o.x && y == o.y);
+    }
+
+    bool operator!=(const XY& o)
+    {
+        return (x != o.x || y != o.y);
+    }
 };

 //
@@ -838,6 +848,25 @@ bool path_intersects_path(PathIterator1 &p1, PathIterator2 &p2)
    return false;
 }

+void _finalize_polygon(std::vector<Polygon> &result)
+{
+    Polygon &polygon = result.back();
+
+    if (result.size() == 0) {
+        return;
+    }
+
+    /* Clean up the last polygon in the result.  If less than a
+       triangle, remove it. */
+    if (polygon.size() < 3) {
+        result.pop_back();
+    } else {
+        if (polygon.front() != polygon.back()) {
+            polygon.push_back(polygon.front());
+        }
+    }
+}
+
 template <class PathIterator>
 void convert_path_to_polygons(PathIterator &path,
                              agg::trans_affine &trans,
@@ -867,24 +896,20 @@ void convert_path_to_polygons(PathIterator &path,

    while ((code = curve.vertex(&x, &y)) != agg::path_cmd_stop) {
        if ((code & agg::path_cmd_end_poly) == agg::path_cmd_end_poly) {
-            if (polygon->size() >= 1) {
-                polygon->push_back((*polygon)[0]);
-                result.push_back(Polygon());
-                polygon = &result.back();
-            }
+            _finalize_polygon(result);
+            result.push_back(Polygon());
+            polygon = &result.back();
        } else {
-            if (code == agg::path_cmd_move_to && polygon->size() >= 1) {
-                polygon->push_back((*polygon)[0]);
+            if (code == agg::path_cmd_move_to) {
+                _finalize_polygon(result);
                result.push_back(Polygon());
                polygon = &result.back();
            }
            polygon->push_back(XY(x, y));
        }
    }

-    if (polygon->size() == 0) {
-        result.pop_back();
-    }
+    _finalize_polygon(result);
 }

 template <class VertexSource>

diff --git a/src/_path_wrapper.cpp b/src/_path_wrapper.cpp
@@ -8,16 +8,29 @@
 PyObject *convert_polygon_vector(std::vector<Polygon> &polygons)
 {
    PyObject *pyresult = PyList_New(polygons.size());
+    bool fix_endpoints;

    for (size_t i = 0; i < polygons.size(); ++i) {
        Polygon poly = polygons[i];
-        npy_intp dims[] = {(npy_intp)poly.size() + 1, 2 };
-        numpy::array_view<double, 2> subresult(dims);
+        npy_intp dims[2];
+        dims[1] = 2;
+
+        if (poly.front() != poly.back()) {
+            /* Make last point same as first, if not already */
+            dims[0] = (npy_intp)poly.size() + 1;
+            fix_endpoints = true;
+        } else {
+            dims[0] = (npy_intp)poly.size();
+            fix_endpoints = false;
+        }

-        /* Make last point same as first. */
+        numpy::array_view<double, 2> subresult(dims);
        memcpy(subresult.data(), &poly[0], sizeof(double) * poly.size() * 2);
-        subresult(poly.size(), 0) = poly[0].x;
-        subresult(poly.size(), 1) = poly[0].y;
+
+        if (fix_endpoints) {
+            subresult(poly.size(), 0) = poly.front().x;
+            subresult(poly.size(), 1) = poly.front().y;
+        }

        if (PyList_SetItem(pyresult, i, subresult.pyobj())) {
            Py_DECREF(pyresult);