Polygon as_segments()

docs/polygon.rst

@@ -149,6 +149,15 @@ Polygon Methods
 
       .. ## Polygon.collidepoint ##
 
+    .. method:: as_segments
+
+        | :sl:`returns the line segments of the polygon`
+        | :sg:`as_segments() -> list[Line]`
+
+        Returns a list of the line segments of the polygon given as self.
+
+      .. ## Polygon.as_segments ##
+
     .. method:: copy
 
         | :sl:`returns a copy of the polygon`

geometry.pyi

@@ -208,6 +208,8 @@ class Polygon:
     @overload
     def move(self, move_by: Coordinate) -> Polygon: ...
     @overload
+    def as_segments(self) -> List[Line]: ...
+    @overload
     def move_ip(self, x: float, y: float) -> None: ...
     @overload
     def move_ip(self, move_by: Coordinate) -> None: ...

src_c/geometry.c

@@ -400,3 +400,4 @@ MODINIT_DEFINE(geometry)
     }
     return module;
 }
+

src_c/polygon.c

@@ -773,6 +773,33 @@ pg_polygon_move(pgPolygonObject *self, PyObject *const *args, Py_ssize_t nargs)
     return (PyObject *)ret;
 }
 
+static PyObject *
+pg_polygon_as_segments(pgPolygonObject *self, PyObject *_null) {
+    double *vertices = self->polygon.vertices;
+    Py_ssize_t verts_num = self->polygon.verts_num;
+    Py_ssize_t verts_num_double = verts_num * 2;
+
+    PyObject *list = PyList_New(verts_num);
+    if (!list) {
+        return NULL;
+    }
+
+    for (Py_ssize_t i = 0; i < verts_num; i++) {
+        Py_ssize_t i2 = i * 2;
+        PyObject *line = pgLine_New4(vertices[i2], vertices[i2 + 1],
+                                        vertices[(i2 + 2) % verts_num_double],
+                                        vertices[(i2 + 3) % verts_num_double]);
+        if (!line) {
+            Py_DECREF(list);
+            return NULL;
+        }
+
+        PyList_SET_ITEM(list, i, line);
+    }
+
+    return list;
+}
+
 static PyObject *
 pg_polygon_move_ip(pgPolygonObject *self, PyObject *const *args,
                    Py_ssize_t nargs)
@@ -987,6 +1014,7 @@ pg_polygon_is_convex(pgPolygonObject *self, PyObject *_null)
 }
 
 static struct PyMethodDef pg_polygon_methods[] = {
+    {"as_segments", (PyCFunction)pg_polygon_as_segments, METH_NOARGS, NULL},
     {"move", (PyCFunction)pg_polygon_move, METH_FASTCALL, NULL},
     {"move_ip", (PyCFunction)pg_polygon_move_ip, METH_FASTCALL, NULL},
     {"rotate", (PyCFunction)pg_polygon_rotate, METH_O, NULL},
@@ -1243,4 +1271,4 @@ static PyTypeObject pgPolygon_Type = {
     .tp_getset = pg_polygon_getsets,
     .tp_init = (initproc)pg_polygon_init,
     .tp_new = pg_polygon_new,
-};
+};

test/test_polygon.py

@@ -4,7 +4,7 @@
 from pygame import Vector2, Vector3, Rect
 
 import geometry
-from geometry import Polygon
+from geometry import Polygon, Line
 
 import math
 
@@ -582,6 +582,33 @@ def test__repr__(self):
         self.assertEqual(repr(polygon), p_repr)
         self.assertEqual(polygon.__repr__(), p_repr)
 
+    def test_as_segments(self):
+        """Checks whether polygon segments are correct"""
+        poly = Polygon([(0, 0), (1, 0), (1, 1), (0, 1)])
+        self.assertEqual(
+            poly.as_segments(),
+            [
+                Line((0, 0), (1, 0)),
+                Line((1, 0), (1, 1)),
+                Line((1, 1), (0, 1)),
+                Line((0, 1), (0, 0)),
+            ],
+        )
+        poly = Polygon([(123.23, 35.6), (56.4, 87.45), (43.1, 12.3)])
+        self.assertEqual(
+            poly.as_segments(),
+            [
+                Line((123.23, 35.6), (56.4, 87.45)),
+                Line((56.4, 87.45), (43.1, 12.3)),
+                Line((43.1, 12.3), (123.23, 35.6)),
+            ],
+        )
+        poly = Polygon([[1, 2], [3, 4], [5, 6]])
+        self.assertEqual(
+            poly.as_segments(),
+            [Line((1, 2), (3, 4)), Line((3, 4), (5, 6)), Line((5, 6), (1, 2))],
+        )
+
     def test_move_xy(self):
         """Checks whether polygon move function works correctly with an x-y pair."""
         poly = Polygon(_some_vertices.copy())