Avoid heap allocation in SkPictureStateTree constructor

src/core/SkPictureStateTree.cpp

 
 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkPictureStateTree.h"
 #include "SkCanvas.h"
 
 SkPictureStateTree::SkPictureStateTree()
     : fAlloc(2048)
-    , fRoot(NULL)
     , fLastRestoredNode(NULL)
     , fStateStack(sizeof(Draw), 16) {
-    SkMatrix* identity = static_cast<SkMatrix*>(fAlloc.allocThrow(sizeof(SkMatrix)));
-    identity->reset();
-    fRoot = static_cast<Node*>(fAlloc.allocThrow(sizeof(Node)));
-    fRoot->fParent = NULL;
-    fRoot->fMatrix = identity;
-    fRoot->fFlags = Node::kSave_Flag;
-    fRoot->fOffset = 0;
-    fRoot->fLevel = 0;
-    fCurrentState.fNode = fRoot;
-    fCurrentState.fMatrix = identity;
+    fRootMatrix.reset();
+    fRoot.fParent = NULL;
+    fRoot.fMatrix = &fRootMatrix;
+    fRoot.fFlags = Node::kSave_Flag;
+    fRoot.fOffset = 0;
+    fRoot.fLevel = 0;
+    fCurrentState.fNode = &fRoot;
+    fCurrentState.fMatrix = &fRootMatrix;
     *static_cast<Draw*>(fStateStack.push_back()) = fCurrentState;
 }
 
 SkPictureStateTree::~SkPictureStateTree() {
 }
 
 SkPictureStateTree::Draw* SkPictureStateTree::appendDraw(uint32_t offset) {
     Draw* draw = static_cast<Draw*>(fAlloc.allocThrow(sizeof(Draw)));
     *draw = fCurrentState;
     draw->fOffset = offset;
@@ skipping 34 matching lines @@
     *m = trans;
     fCurrentState.fMatrix = m;
 }
 
 void SkPictureStateTree::appendClip(uint32_t offset) {
     this->appendNode(offset);
 }
 
 SkPictureStateTree::Iterator SkPictureStateTree::getIterator(const SkTDArray<void*>& draws,
                                                              SkCanvas* canvas) {
-    return Iterator(draws, canvas, fRoot);
+    return Iterator(draws, canvas, &fRoot);
 }
 
 void SkPictureStateTree::appendNode(uint32_t offset) {
     Node* n = static_cast<Node*>(fAlloc.allocThrow(sizeof(Node)));
     n->fOffset = offset;
     n->fFlags = 0;
     n->fParent = fCurrentState.fNode;
     n->fLevel = fCurrentState.fNode->fLevel + 1;
     n->fMatrix = fCurrentState.fMatrix;
     fCurrentState.fNode = n;
@@ skipping 88 matching lines @@
     if (fCurrentMatrix != draw->fMatrix) {
         SkMatrix tmp = *draw->fMatrix;
         tmp.postConcat(fPlaybackMatrix);
         fCanvas->setMatrix(tmp);
         fCurrentMatrix = draw->fMatrix;
     }
 
     ++fPlaybackIndex;
     return draw->fOffset;
 }