Compile-time initialize special SkMatrices.

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 "SkFloatBits.h"
-#include "SkLazyPtr.h"
 #include "SkString.h"
 
 // In a few places, we performed the following
 //      a * b + c * d + e
 // as
 //      a * b + (c * d + e)
 //
 // sdot and scross are indended to capture these compound operations into a
 // function, with an eye toward considering upscaling the intermediates to
 // doubles for more precision (as we do in concat and invert).
@@ skipping 1532 matching lines @@
         return -1;
     }
 }
 
 bool SkMatrix::getMinMaxScales(SkScalar scaleFactors[2]) const {
     return get_scale_factor<kBoth_MinMaxOrBoth>(this->getType(), fMat, scaleFactors);
 }
 
 namespace {
 
-SkMatrix* create_identity() {
-    SkMatrix* m = SkNEW(SkMatrix);
-    m->reset();
-    return m;
-}
+struct PODMatrix {
+    SkScalar matrix[9];
+    uint32_t typemask;
 
-SkMatrix* create_invalid() {
-    SkMatrix* m = SkNEW(SkMatrix);
-    m->setAll(SK_ScalarMax, SK_ScalarMax, SK_ScalarMax,
-              SK_ScalarMax, SK_ScalarMax, SK_ScalarMax,
-              SK_ScalarMax, SK_ScalarMax, SK_ScalarMax);
-    m->getType();  // Force the type to be computed.
-    return m;
-}
+    const SkMatrix& asSkMatrix() const { return *reinterpret_cast<const SkMatrix*>(this); }
+};
+SK_COMPILE_ASSERT(sizeof(PODMatrix) == sizeof(SkMatrix), PODMatrixSizeMismatch);

[bungeman-skia, 2014/06/02 16:35:15]

In addition to this, it would be nice for SkMatrix to SK_COMPILE_ASSERT that the
offsetof its matrix and typemask are where an equivalent POD would put them. 

 
 }  // namespace
 
 const SkMatrix& SkMatrix::I() {
-    SK_DECLARE_STATIC_LAZY_PTR(SkMatrix, identity, create_identity);
-    return *identity.get();
+    static const PODMatrix identity = { {SK_Scalar1, 0, 0,
+                                         0, SK_Scalar1, 0,
+                                         0, 0, SK_Scalar1 },
+                                       kIdentity_Mask | kRectStaysRect_Mask};
+    SkASSERT(identity.asSkMatrix().isIdentity());
+    return identity.asSkMatrix();
 }
 
 const SkMatrix& SkMatrix::InvalidMatrix() {
-    SK_DECLARE_STATIC_LAZY_PTR(SkMatrix, invalid, create_invalid);
-    return *invalid.get();
+    static const PODMatrix invalid =
+        { {SK_ScalarMax, SK_ScalarMax, SK_ScalarMax,
+           SK_ScalarMax, SK_ScalarMax, SK_ScalarMax,
+           SK_ScalarMax, SK_ScalarMax, SK_ScalarMax },
+         kTranslate_Mask | kScale_Mask | kAffine_Mask | kPerspective_Mask };
+    return invalid.asSkMatrix();
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 size_t SkMatrix::writeToMemory(void* buffer) const {
     // TODO write less for simple matrices
     static const size_t sizeInMemory = 9 * sizeof(SkScalar);
     if (buffer) {
         memcpy(buffer, fMat, sizeInMemory);
     }
@@ skipping 174 matching lines @@
         rotation1->fX = cos1;
         rotation1->fY = sin1;
     }
     if (NULL != rotation2) {
         rotation2->fX = cos2;
         rotation2->fY = sin2;
     }
 
     return true;
 }