created Polygon.area attribute

Author: Emc2356

docs/geometry.rst

@@ -150,6 +150,8 @@ other objects.
 
     perimeter: The perimeter of the polygon.
 
+    area: The area of the polygon.
+
 **Here is the full list of methods:**
 ::
     move: Moves the polygon by the given amount.

geometry.pyi

@@ -191,6 +191,7 @@ class Polygon:
     c_x: float
     c_y: float
     center: Tuple[float, float]
+    area: float
     __safe_for_unpickling__: Literal[True]
     __hash__: None  # type: ignore
 

src_c/polygon.c

@@ -1407,6 +1407,23 @@ pg_polygon_get_perimeter(pgPolygonObject *self, void *closure)
     return PyFloat_FromDouble(perimeter);
 }
 
+static PyObject *
+pg_polygon_get_area(pgPolygonObject *self, void *closure)
+{
+    double area = 0;
+    double *vertices = self->polygon.vertices;
+    int vert_num = self->polygon.verts_num;
+    Py_ssize_t i;
+    for (i = 0; i < vert_num; i++) {
+        area +=
+            vertices[(i * 2)] * vertices[(((i + 1) * 2) + 1) % (vert_num * 2)];
+        area -=
+            vertices[((i + 1) * 2) % (vert_num * 2)] * vertices[(i * 2) + 1];
+    }
+
+    return PyFloat_FromDouble(ABS(area / 2));
+}
+
 static int
 pg_polygon_set_center(pgPolygonObject *self, PyObject *value, void *closure)
 {
@@ -1434,6 +1451,7 @@ static PyGetSetDef pg_polygon_getsets[] = {
      (setter)pg_polygon_set_vertices, "Vertices of the polygon", NULL},
     {"perimeter", (getter)pg_polygon_get_perimeter, NULL,
      "Perimeter of the polygon", NULL},
+    {"area", (getter)pg_polygon_get_area, NULL, "area of the polygon", NULL},
     {"__safe_for_unpickling__", (getter)pg_polygon_getsafepickle, NULL, NULL,
      NULL},
     {NULL, 0, NULL, NULL, NULL} /* Sentinel */

test/test_geometry.py

@@ -153,6 +153,15 @@ class TestCircle(Circle):
         self.assertEqual(radius, c.r)
         # =================================================
 
+    def test_area(self):
+        poly = Polygon((-3, -2), (-1, 4), (6, 1), (3, 10), (-4, 9))
+
+        self.assertEqual(60, poly.area)
+
+        poly = Polygon((0, 0), (0, 4), (4, 4), (4, 0))
+
+        self.assertEqual(16, poly.area)
+
     def test_is_polygon(self):
         """Test is_polygon function"""