1 /*
2  * Copyright 2014 Google Inc.
3  *
4  * Use of this source code is governed by a BSD-style license that can be
5  * found in the LICENSE file.
6  */
7 
8 #include "SkMatrix.h"
9 #include "SkMatrix22.h"
10 #include "SkPoint.h"
11 #include "SkScalar.h"
12 
13 void SkComputeGivensRotation(const SkVector& h, SkMatrix* G) {
14     const SkScalar& a = h.fX;
15     const SkScalar& b = h.fY;
16     SkScalar c, s;
17     if (0 == b) {
18         c = SkScalarCopySign(SK_Scalar1, a);
19         s = 0;
20         //r = SkScalarAbs(a);
21     } else if (0 == a) {
22         c = 0;
23         s = -SkScalarCopySign(SK_Scalar1, b);
24         //r = SkScalarAbs(b);
25     } else if (SkScalarAbs(b) > SkScalarAbs(a)) {
26         SkScalar t = a / b;
27         SkScalar u = SkScalarCopySign(SkScalarSqrt(SK_Scalar1 + t*t), b);
28         s = -SK_Scalar1 / u;
29         c = -s * t;
30         //r = b * u;
31     } else {
32         SkScalar t = b / a;
33         SkScalar u = SkScalarCopySign(SkScalarSqrt(SK_Scalar1 + t*t), a);
34         c = SK_Scalar1 / u;
35         s = -c * t;
36         //r = a * u;
37     }
38 
39     G->setSinCos(s, c);
40 }
41