Bug 1824933 - Avoid some copying in SVGLengthList and co. r=longsonr

Differential Revision: https://phabricator.services.mozilla.com/D174371

dom/svg/SVGAnimatedLengthList.cpp

@@ -20,10 +20,7 @@ using namespace dom;
 
 nsresult SVGAnimatedLengthList::SetBaseValueString(const nsAString& aValue) {
   SVGLengthList newBaseValue;
-  nsresult rv = newBaseValue.SetValueFromString(aValue);
-  if (NS_FAILED(rv)) {
-    return rv;
-  }
+  MOZ_TRY(newBaseValue.SetValueFromString(aValue));
 
   DOMSVGAnimatedLengthList* domWrapper =
       DOMSVGAnimatedLengthList::GetDOMWrapperIfExists(this);
@@ -39,14 +36,8 @@ nsresult SVGAnimatedLengthList::SetBaseValueString(const nsAString& aValue) {
   // We don't need to call DidChange* here - we're only called by
   // SVGElement::ParseAttribute under Element::SetAttr,
   // which takes care of notifying.
-
-  rv = mBaseVal.CopyFrom(newBaseValue);
-  if (NS_FAILED(rv) && domWrapper) {
-    // Attempting to increase mBaseVal's length failed - reduce domWrapper
-    // back to the same length:
-    domWrapper->InternalBaseValListWillChangeTo(mBaseVal);
-  }
-  return rv;
+  mBaseVal.SwapWith(newBaseValue);
+  return NS_OK;
 }
 
 void SVGAnimatedLengthList::ClearBaseValue(uint32_t aAttrEnum) {

dom/svg/SVGAnimatedNumberList.cpp

@@ -19,10 +19,7 @@ namespace mozilla {
 
 nsresult SVGAnimatedNumberList::SetBaseValueString(const nsAString& aValue) {
   SVGNumberList newBaseValue;
-  nsresult rv = newBaseValue.SetValueFromString(aValue);
-  if (NS_FAILED(rv)) {
-    return rv;
-  }
+  MOZ_TRY(newBaseValue.SetValueFromString(aValue));
 
   DOMSVGAnimatedNumberList* domWrapper =
       DOMSVGAnimatedNumberList::GetDOMWrapperIfExists(this);
@@ -40,13 +37,8 @@ nsresult SVGAnimatedNumberList::SetBaseValueString(const nsAString& aValue) {
   // which takes care of notifying.
 
   mIsBaseSet = true;
-  rv = mBaseVal.CopyFrom(newBaseValue);
-  if (NS_FAILED(rv) && domWrapper) {
-    // Attempting to increase mBaseVal's length failed - reduce domWrapper
-    // back to the same length:
-    domWrapper->InternalBaseValListWillChangeTo(mBaseVal);
-  }
-  return rv;
+  mBaseVal.SwapWith(newBaseValue);
+  return NS_OK;
 }
 
 void SVGAnimatedNumberList::ClearBaseValue(uint32_t aAttrEnum) {

dom/svg/SVGAnimatedPathSegList.cpp

@@ -25,7 +25,6 @@ nsresult SVGAnimatedPathSegList::SetBaseValueString(const nsAString& aValue) {
   // The spec says that the path data is parsed and accepted up to the first
   // error encountered, so we don't return early if an error occurs. However,
   // we do want to throw any error code from setAttribute if there's a problem.
-
   nsresult rv = newBaseValue.SetValueFromString(aValue);
 
   // We must send these notifications *before* changing mBaseVal! Our baseVal's
@@ -56,20 +55,7 @@ nsresult SVGAnimatedPathSegList::SetBaseValueString(const nsAString& aValue) {
   // SVGElement::ParseAttribute under Element::SetAttr,
   // which takes care of notifying.
 
-  nsresult rv2 = mBaseVal.CopyFrom(newBaseValue);
-  if (NS_FAILED(rv2)) {
-    if (StaticPrefs::dom_svg_pathSeg_enabled()) {
-      // Attempting to increase mBaseVal's length failed (mBaseVal is left
-      // unmodified). We MUST keep any DOM wrappers in sync:
-      if (baseValWrapper) {
-        baseValWrapper->InternalListWillChangeTo(mBaseVal);
-      }
-      if (animValWrapper) {
-        animValWrapper->InternalListWillChangeTo(mBaseVal);
-      }
-    }
-    return rv2;
-  }
+  mBaseVal.SwapWith(newBaseValue);
   return rv;
 }
 
@@ -177,7 +163,7 @@ SMILValue SVGAnimatedPathSegList::SMILAnimatedPathSegList::GetBaseValue()
   SMILValue val;
 
   SMILValue tmp(SVGPathSegListSMILType::Singleton());
-  SVGPathDataAndInfo* list = static_cast<SVGPathDataAndInfo*>(tmp.mU.mPtr);
+  auto* list = static_cast<SVGPathDataAndInfo*>(tmp.mU.mPtr);
   nsresult rv = list->CopyFrom(mVal->mBaseVal);
   if (NS_SUCCEEDED(rv)) {
     list->SetElement(mElement);

dom/svg/SVGAnimatedPointList.cpp

@@ -54,18 +54,7 @@ nsresult SVGAnimatedPointList::SetBaseValueString(const nsAString& aValue) {
   // SVGElement::ParseAttribute under Element::SetAttr,
   // which takes care of notifying.
 
-  nsresult rv2 = mBaseVal.CopyFrom(newBaseValue);
-  if (NS_FAILED(rv2)) {
-    // Attempting to increase mBaseVal's length failed (mBaseVal is left
-    // unmodified). We MUST keep any DOM wrappers in sync:
-    if (baseValWrapper) {
-      baseValWrapper->InternalListWillChangeTo(mBaseVal);
-    }
-    if (animValWrapper) {
-      animValWrapper->InternalListWillChangeTo(mBaseVal);
-    }
-    return rv2;
-  }
+  mBaseVal.SwapWith(newBaseValue);
   return rv;
 }
 
@@ -165,7 +154,7 @@ SMILValue SVGAnimatedPointList::SMILAnimatedPointList::GetBaseValue() const {
   SMILValue val;
 
   SMILValue tmp(&SVGPointListSMILType::sSingleton);
-  SVGPointListAndInfo* list = static_cast<SVGPointListAndInfo*>(tmp.mU.mPtr);
+  auto* list = static_cast<SVGPointListAndInfo*>(tmp.mU.mPtr);
   nsresult rv = list->CopyFrom(mVal->mBaseVal);
   if (NS_SUCCEEDED(rv)) {
     list->SetInfo(mElement);

dom/svg/SVGLengthList.cpp

@@ -56,7 +56,8 @@ nsresult SVGLengthList::SetValueFromString(const nsAString& aValue) {
   if (tokenizer.separatorAfterCurrentToken()) {
     return NS_ERROR_DOM_SYNTAX_ERR;  // trailing comma
   }
-  return CopyFrom(temp);
+  mLengths = std::move(temp.mLengths);
+  return NS_OK;
 }
 
 bool SVGLengthList::operator==(const SVGLengthList& rhs) const {

dom/svg/SVGLengthList.h

@@ -85,7 +85,10 @@ class SVGLengthList {
    * This may fail on OOM if the internal capacity needs to be increased, in
    * which case the list will be left unmodified.
    */
-  nsresult CopyFrom(const SVGLengthList& rhs);
+  nsresult CopyFrom(const SVGLengthList&);
+  void SwapWith(SVGLengthList& aOther) {
+    mLengths.SwapElements(aOther.mLengths);
+  }
 
   SVGLength& operator[](uint32_t aIndex) { return mLengths[aIndex]; }
 

dom/svg/SVGNumberList.cpp

@@ -58,7 +58,8 @@ nsresult SVGNumberList::SetValueFromString(const nsAString& aValue) {
   if (tokenizer.separatorAfterCurrentToken()) {
     return NS_ERROR_DOM_SYNTAX_ERR;  // trailing comma
   }
-  return CopyFrom(temp);
+  mNumbers = std::move(temp.mNumbers);
+  return NS_OK;
 }
 
 }  // namespace mozilla

dom/svg/SVGNumberList.h

@@ -84,6 +84,7 @@ class SVGNumberList {
    * which case the list will be left unmodified.
    */
   nsresult CopyFrom(const SVGNumberList& rhs);
+  void SwapWith(SVGNumberList& aRhs) { mNumbers.SwapElements(aRhs.mNumbers); }
 
   float& operator[](uint32_t aIndex) { return mNumbers[aIndex]; }
 

dom/svg/SVGPathData.h

@@ -213,6 +213,7 @@ class SVGPathData {
    * which case the list will be left unmodified.
    */
   nsresult CopyFrom(const SVGPathData& rhs);
+  void SwapWith(SVGPathData& aRhs) { mData.SwapElements(aRhs.mData); }
 
   float& operator[](uint32_t aIndex) { return mData[aIndex]; }
 

dom/svg/SVGPointList.h

@@ -81,6 +81,7 @@ class SVGPointList {
    * which case the list will be left unmodified.
    */
   nsresult CopyFrom(const SVGPointList& rhs);
+  void SwapWith(SVGPointList& aRhs) { mItems.SwapElements(aRhs.mItems); }
 
   SVGPoint& operator[](uint32_t aIndex) { return mItems[aIndex]; }