From bc86eb1780a8793e5c511073eb20d5f6e7fd2e0b Mon Sep 17 00:00:00 2001
From: Tiago Chaves <laurelkeys>
Date: Thu, 20 Feb 2020 13:57:32 +1100
Subject: mathutils: support Vector.rotate for 2D vectors

---
 source/blender/python/mathutils/mathutils_Matrix.c | 17 +++++++++
 source/blender/python/mathutils/mathutils_Matrix.h |  1 +
 source/blender/python/mathutils/mathutils_Vector.c | 43 ++++++++++++++--------
 3 files changed, 45 insertions(+), 16 deletions(-)

diff --git a/source/blender/python/mathutils/mathutils_Matrix.c b/source/blender/python/mathutils/mathutils_Matrix.c
index 32921ae0ca9..b31e069651b 100644
--- a/source/blender/python/mathutils/mathutils_Matrix.c
+++ b/source/blender/python/mathutils/mathutils_Matrix.c
@@ -3306,6 +3306,23 @@ int Matrix_ParseAny(PyObject *o, void *p)
   return 1;
 }
 
+int Matrix_Parse2x2(PyObject *o, void *p)
+{
+  MatrixObject **pymat_p = p;
+  MatrixObject *pymat = (MatrixObject *)o;
+
+  if (!Matrix_ParseCheck(pymat)) {
+    return 0;
+  }
+  if ((pymat->num_col != 2) || (pymat->num_row != 2)) {
+    PyErr_SetString(PyExc_ValueError, "matrix must be 2x2");
+    return 0;
+  }
+
+  *pymat_p = pymat;
+  return 1;
+}
+
 int Matrix_Parse3x3(PyObject *o, void *p)
 {
   MatrixObject **pymat_p = p;
diff --git a/source/blender/python/mathutils/mathutils_Matrix.h b/source/blender/python/mathutils/mathutils_Matrix.h
index 3b42e22a787..6f2b5d4ac6d 100644
--- a/source/blender/python/mathutils/mathutils_Matrix.h
+++ b/source/blender/python/mathutils/mathutils_Matrix.h
@@ -76,6 +76,7 @@ PyObject *Matrix_CreatePyObject_cb(PyObject *user,
 
 /* PyArg_ParseTuple's "O&" formatting helpers. */
 int Matrix_ParseAny(PyObject *o, void *p);
+int Matrix_Parse2x2(PyObject *o, void *p);
 int Matrix_Parse3x3(PyObject *o, void *p);
 int Matrix_Parse4x4(PyObject *o, void *p);
 
diff --git a/source/blender/python/mathutils/mathutils_Vector.c b/source/blender/python/mathutils/mathutils_Vector.c
index 387e560d946..82c4e70b657 100644
--- a/source/blender/python/mathutils/mathutils_Vector.c
+++ b/source/blender/python/mathutils/mathutils_Vector.c
@@ -1273,31 +1273,42 @@ static PyObject *Vector_slerp(VectorObject *self, PyObject *args)
   return Vector_CreatePyObject(ret_vec, size, Py_TYPE(self));
 }
 
-PyDoc_STRVAR(Vector_rotate_doc,
-             ".. function:: rotate(other)\n"
-             "\n"
-             "   Rotate the vector by a rotation value.\n"
-             "\n"
-             "   :arg other: rotation component of mathutils value\n"
-             "   :type other: :class:`Euler`, :class:`Quaternion` or :class:`Matrix`\n");
+PyDoc_STRVAR(
+    Vector_rotate_doc,
+    ".. function:: rotate(other)\n"
+    "\n"
+    "   Rotate the vector by a rotation value.\n"
+    "\n"
+    "   .. note:: 2D vectors are a special case that can only be rotated by a 2x2 matrix.\n"
+    "\n"
+    "   :arg other: rotation component of mathutils value\n"
+    "   :type other: :class:`Euler`, :class:`Quaternion` or :class:`Matrix`\n");
 static PyObject *Vector_rotate(VectorObject *self, PyObject *value)
 {
-  float other_rmat[3][3];
-
   if (BaseMath_ReadCallback_ForWrite(self) == -1) {
     return NULL;
   }
 
-  if (mathutils_any_to_rotmat(other_rmat, value, "Vector.rotate(value)") == -1) {
-    return NULL;
+  if (self->size == 2) {
+    /* Special case for 2D Vector with 2x2 matrix, so we avoid resizing it to a 3x3. */
+    float other_rmat[2][2];
+    MatrixObject *pymat;
+    if (!Matrix_Parse2x2(value, &pymat)) {
+      return NULL;
+    }
+    normalize_m2_m2(other_rmat, (const float(*)[2])pymat->matrix);
+    /* Equivalent to a rotation along the Z axis. */
+    mul_m2_v2(other_rmat, self->vec);
   }
+  else {
+    float other_rmat[3][3];
 
-  if (self->size < 3 || self->size > 4) {
-    PyErr_SetString(PyExc_ValueError, "Vector must be 3D or 4D");
-    return NULL;
-  }
+    if (mathutils_any_to_rotmat(other_rmat, value, "Vector.rotate(value)") == -1) {
+      return NULL;
+    }
 
-  mul_m3_v3(other_rmat, self->vec);
+    mul_m3_v3(other_rmat, self->vec);
+  }
 
   (void)BaseMath_WriteCallback(self);
   Py_RETURN_NONE;
-- 
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