SK_ONCE for SkMatrix::I()

src/core/SkMatrix.cpp

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkMatrix.h"
 #include "Sk64.h"
 #include "SkFloatBits.h"
+#include "SkOnce.h"
 #include "SkScalarCompare.h"
 #include "SkString.h"
 
 #ifdef SK_SCALAR_IS_FLOAT
     #define kMatrix22Elem   SK_Scalar1
 
     static inline float SkDoubleToFloat(double x) {
         return static_cast<float>(x);
     }
 #else
@@ skipping 1865 matching lines @@
         largerRoot = SkMaxScalar(a, c);
     } else {
         SkScalar aminusc = a - c;
         SkScalar apluscdiv2 = SkScalarHalf(a + c);
         SkScalar x = SkScalarHalf(SkScalarSqrt(SkScalarMul(aminusc, aminusc) + 4 * bSqd));
         largerRoot = apluscdiv2 + x;
     }
     return SkScalarSqrt(largerRoot);
 }
 
+DEF_SK_ONCE(reset_identity_matrix, SkMatrix* identity) {
+    identity->reset();
+}
+
 const SkMatrix& SkMatrix::I() {
+    // If you can use C++11 now, you might consider replacing this with a constexpr constructor.
     static SkMatrix gIdentity;
-    static bool gOnce;
-    if (!gOnce) {
-        gIdentity.reset();
-        gOnce = true;
-    }
+    SK_ONCE(reset_identity_matrix, &gIdentity);
     return gIdentity;
 }
 
 const SkMatrix& SkMatrix::InvalidMatrix() {
     static SkMatrix gInvalid;
     static bool gOnce;
     if (!gOnce) {
         gInvalid.setAll(SK_ScalarMax, SK_ScalarMax, SK_ScalarMax,
                         SK_ScalarMax, SK_ScalarMax, SK_ScalarMax,
                         SK_ScalarMax, SK_ScalarMax, SK_ScalarMax);
@@ skipping 187 matching lines @@
         rotation1->fX = cos1;
         rotation1->fY = sin1;
     }
     if (NULL != rotation2) {
         rotation2->fX = cos2;
         rotation2->fY = sin2;
     }
 
     return true;
 }