[Core] Transform2D add set_scale and fix set_rotation

Note: These are still not exposed to GDScript

core/math/basis.cpp

@@ -258,7 +258,7 @@ Vector3 Basis::get_scale_abs() const {
 }
 
 Vector3 Basis::get_scale_local() const {
-	real_t det_sign = determinant() > 0 ? 1 : -1;
+	real_t det_sign = SGN(determinant());
 	return det_sign * Vector3(elements[0].length(), elements[1].length(), elements[2].length());
 }
 
@@ -284,7 +284,7 @@ Vector3 Basis::get_scale() const {
 	// matrix elements.
 	//
 	// The rotation part of this decomposition is returned by get_rotation* functions.
-	real_t det_sign = determinant() > 0 ? 1 : -1;
+	real_t det_sign = SGN(determinant());
 	return det_sign * Vector3(
 							  Vector3(elements[0][0], elements[1][0], elements[2][0]).length(),
 							  Vector3(elements[0][1], elements[1][1], elements[2][1]).length(),

core/math/transform_2d.cpp

@@ -80,13 +80,14 @@ real_t Transform2D::get_rotation() const {
 }
 
 void Transform2D::set_rotation(real_t p_rot) {
-
+	Size2 scale = get_scale();
 	real_t cr = Math::cos(p_rot);
 	real_t sr = Math::sin(p_rot);
 	elements[0][0] = cr;
 	elements[0][1] = sr;
 	elements[1][0] = -sr;
 	elements[1][1] = cr;
+	set_scale(scale);
 }
 
 Transform2D::Transform2D(real_t p_rot, const Vector2 &p_pos) {
@@ -101,10 +102,17 @@ Transform2D::Transform2D(real_t p_rot, const Vector2 &p_pos) {
 }
 
 Size2 Transform2D::get_scale() const {
-	real_t det_sign = basis_determinant() > 0 ? 1 : -1;
+	real_t det_sign = SGN(basis_determinant());
 	return Size2(elements[0].length(), det_sign * elements[1].length());
 }
 
+void Transform2D::set_scale(Size2 &p_scale) {
+	elements[0].normalize();
+	elements[1].normalize();
+	elements[0] *= p_scale.x;
+	elements[1] *= p_scale.y;
+}
+
 void Transform2D::scale(const Size2 &p_scale) {
 	scale_basis(p_scale);
 	elements[2] *= p_scale;

core/math/transform_2d.h

@@ -81,6 +81,7 @@ struct Transform2D {
 	real_t basis_determinant() const;
 
 	Size2 get_scale() const;
+	void set_scale(Size2 &p_scale);
 
 	_FORCE_INLINE_ const Vector2 &get_origin() const { return elements[2]; }
 	_FORCE_INLINE_ void set_origin(const Vector2 &p_origin) { elements[2] = p_origin; }