Bug 1113238 - Part 2: Only maintain the pre level status which can be potentially expensive if we may end up using it; r=bzbarsky

This patch ensures that we check ShouldMaintainPreLevel() before attempting
to modify or read mPreLevel in order to avoid wasting time to compute
mPreLevel for elements without frames needlessly.  Computing this value for
such elements can incur expensive style calculations.

dom/base/nsHTMLContentSerializer.cpp

@@ -192,7 +192,7 @@ nsHTMLContentSerializer::AppendElementStart(Element* aElement,
 
   bool lineBreakBeforeOpen = LineBreakBeforeOpen(ns, name);
 
-  if ((mDoFormat || forceFormat) && !mPreLevel && !mDoRaw) {
+  if ((mDoFormat || forceFormat) && !mDoRaw && !PreLevel()) {
     if (mColPos && lineBreakBeforeOpen) {
       AppendNewLineToString(aStr);
     }
@@ -225,7 +225,7 @@ nsHTMLContentSerializer::AppendElementStart(Element* aElement,
   MaybeEnterInPreContent(content);
 
   // for block elements, we increase the indentation
-  if ((mDoFormat || forceFormat) && !mPreLevel && !mDoRaw)
+  if ((mDoFormat || forceFormat) && !mDoRaw && !PreLevel())
     IncrIndentation(name);
 
   // Need to keep track of OL and LI elements in order to get ordinal number 
@@ -280,8 +280,8 @@ nsHTMLContentSerializer::AppendElementStart(Element* aElement,
     ++mDisableEntityEncoding;
   }
 
-  if ((mDoFormat || forceFormat) && !mPreLevel &&
-    !mDoRaw && LineBreakAfterOpen(ns, name)) {
+  if ((mDoFormat || forceFormat) && !mDoRaw && !PreLevel() &&
+    LineBreakAfterOpen(ns, name)) {
     AppendNewLineToString(aStr);
   }
 
@@ -312,18 +312,18 @@ nsHTMLContentSerializer::AppendElementEnd(Element* aElement,
   bool forceFormat = !(mFlags & nsIDocumentEncoder::OutputIgnoreMozDirty) &&
                      content->HasAttr(kNameSpaceID_None, nsGkAtoms::mozdirty);
 
-  if ((mDoFormat || forceFormat) && !mPreLevel && !mDoRaw) {
+  if ((mDoFormat || forceFormat) && !mDoRaw && !PreLevel()) {
     DecrIndentation(name);
   }
 
   if (name == nsGkAtoms::script) {
     nsCOMPtr<nsIScriptElement> script = do_QueryInterface(aElement);
 
-    if (script && script->IsMalformed()) {
+    if (ShouldMaintainPreLevel() && script && script->IsMalformed()) {
       // We're looking at a malformed script tag. This means that the end tag
       // was missing in the source. Imitate that here by not serializing the end
       // tag.
-      --mPreLevel;
+      --PreLevel();
       return NS_OK;
     }
   }
@@ -351,7 +351,7 @@ nsHTMLContentSerializer::AppendElementEnd(Element* aElement,
     }
   }
 
-  if ((mDoFormat || forceFormat) && !mPreLevel && !mDoRaw) {
+  if ((mDoFormat || forceFormat) && !mDoRaw && !PreLevel()) {
 
     bool lineBreakBeforeClose = LineBreakBeforeClose(ns, name);
 
@@ -377,8 +377,8 @@ nsHTMLContentSerializer::AppendElementEnd(Element* aElement,
 
   MaybeLeaveFromPreContent(content);
 
-  if ((mDoFormat || forceFormat) && !mPreLevel
-      && !mDoRaw && LineBreakAfterClose(ns, name)) {
+  if ((mDoFormat || forceFormat)&& !mDoRaw  && !PreLevel()
+      && LineBreakAfterClose(ns, name)) {
     AppendNewLineToString(aStr);
   }
   else {

dom/base/nsXHTMLContentSerializer.cpp

@@ -133,7 +133,7 @@ nsXHTMLContentSerializer::AppendText(nsIContent* aText,
   if (NS_FAILED(rv))
     return NS_ERROR_FAILURE;
 
-  if (mPreLevel > 0 || mDoRaw) {
+  if (mDoRaw || PreLevel() > 0) {
     AppendToStringConvertLF(data, aStr);
   }
   else if (mDoFormat) {
@@ -537,8 +537,9 @@ nsXHTMLContentSerializer::CheckElementStart(nsIContent * aContent,
   int32_t namespaceID = aContent->GetNameSpaceID();
 
   if (namespaceID == kNameSpaceID_XHTML) {
-    if (name == nsGkAtoms::br && mPreLevel > 0 && 
-        (mFlags & nsIDocumentEncoder::OutputNoFormattingInPre)) {
+    if (name == nsGkAtoms::br &&
+        (mFlags & nsIDocumentEncoder::OutputNoFormattingInPre) &&
+        PreLevel() > 0) {
       AppendNewLineToString(aStr);
       return false;
     }
@@ -845,8 +846,8 @@ nsXHTMLContentSerializer::LineBreakAfterClose(int32_t aNamespaceID, nsIAtom* aNa
 void
 nsXHTMLContentSerializer::MaybeEnterInPreContent(nsIContent* aNode)
 {
-
-  if (aNode->GetNameSpaceID() != kNameSpaceID_XHTML) {
+  if (!ShouldMaintainPreLevel() ||
+      aNode->GetNameSpaceID() != kNameSpaceID_XHTML) {
     return;
   }
 
@@ -858,14 +859,15 @@ nsXHTMLContentSerializer::MaybeEnterInPreContent(nsIContent* aNode)
       name == nsGkAtoms::noscript ||
       name == nsGkAtoms::noframes
       ) {
-    mPreLevel++;
+    PreLevel()++;
   }
 }
 
 void
 nsXHTMLContentSerializer::MaybeLeaveFromPreContent(nsIContent* aNode)
 {
-  if (aNode->GetNameSpaceID() != kNameSpaceID_XHTML) {
+  if (!ShouldMaintainPreLevel() ||
+      aNode->GetNameSpaceID() != kNameSpaceID_XHTML) {
     return;
   }
 
@@ -876,13 +878,15 @@ nsXHTMLContentSerializer::MaybeLeaveFromPreContent(nsIContent* aNode)
       name == nsGkAtoms::noscript ||
       name == nsGkAtoms::noframes
     ) {
-    --mPreLevel;
+    --PreLevel();
   }
 }
 
 bool
 nsXHTMLContentSerializer::IsElementPreformatted(nsIContent* aNode)
 {
+  MOZ_ASSERT(ShouldMaintainPreLevel(), "We should not be calling this needlessly");
+
   if (!aNode->IsElement()) {
     return false;
   }

dom/base/nsXMLContentSerializer.cpp

@@ -187,7 +187,7 @@ nsXMLContentSerializer::AppendText(nsIContent* aText,
   if (NS_FAILED(rv))
     return NS_ERROR_FAILURE;
 
-  if (mPreLevel > 0 || mDoRaw) {
+  if (mDoRaw || PreLevel() > 0) {
     AppendToStringConvertLF(data, aStr);
   }
   else if (mDoFormat) {
@@ -214,7 +214,7 @@ nsXMLContentSerializer::AppendCDATASection(nsIContent* aCDATASection,
 
   NS_NAMED_LITERAL_STRING(cdata , "<![CDATA[");
 
-  if (mPreLevel > 0 || mDoRaw) {
+  if (mDoRaw || PreLevel() > 0) {
     AppendToString(cdata, aStr);
   }
   else if (mDoFormat) {
@@ -260,7 +260,7 @@ nsXMLContentSerializer::AppendProcessingInstruction(nsIContent* aPI,
   start.AppendLiteral("<?");
   start.Append(target);
 
-  if (mPreLevel > 0 || mDoRaw) {
+  if (mDoRaw || PreLevel() > 0) {
     AppendToString(start, aStr);
   }
   else if (mDoFormat) {
@@ -318,7 +318,7 @@ nsXMLContentSerializer::AppendComment(nsIContent* aComment,
 
   NS_NAMED_LITERAL_STRING(startComment, "<!--");
 
-  if (mPreLevel > 0 || mDoRaw) {
+  if (mDoRaw || PreLevel() > 0) {
     AppendToString(startComment, aStr);
   }
   else if (mDoFormat) {
@@ -693,7 +693,7 @@ nsXMLContentSerializer::SerializeAttr(const nsAString& aPrefix,
     attrString.Append(sValue);
     attrString.Append(cDelimiter);
   }
-  if (mPreLevel > 0 || mDoRaw) {
+  if (mDoRaw || PreLevel() > 0) {
     AppendToStringConvertLF(attrString, aStr);
   }
   else if (mDoFormat) {
@@ -898,7 +898,7 @@ nsXMLContentSerializer::AppendElementStart(Element* aElement,
   nsIAtom *name = content->Tag();
   bool lineBreakBeforeOpen = LineBreakBeforeOpen(content->GetNameSpaceID(), name);
 
-  if ((mDoFormat || forceFormat) && !mPreLevel && !mDoRaw) {
+  if ((mDoFormat || forceFormat) && !mDoRaw && !PreLevel()) {
     if (mColPos && lineBreakBeforeOpen) {
       AppendNewLineToString(aStr);
     }
@@ -939,7 +939,7 @@ nsXMLContentSerializer::AppendElementStart(Element* aElement,
 
   MaybeEnterInPreContent(content);
 
-  if ((mDoFormat || forceFormat) && !mPreLevel && !mDoRaw) {
+  if ((mDoFormat || forceFormat) && !mDoRaw && !PreLevel()) {
     IncrIndentation(name);
   }
 
@@ -949,8 +949,8 @@ nsXMLContentSerializer::AppendElementStart(Element* aElement,
   AppendEndOfElementStart(aOriginalElement, name, content->GetNameSpaceID(),
                           aStr);
 
-  if ((mDoFormat || forceFormat) && !mPreLevel 
-    && !mDoRaw && LineBreakAfterOpen(content->GetNameSpaceID(), name)) {
+  if ((mDoFormat || forceFormat) && !mDoRaw && !PreLevel()
+    && LineBreakAfterOpen(content->GetNameSpaceID(), name)) {
     AppendNewLineToString(aStr);
   }
 
@@ -987,7 +987,7 @@ nsXMLContentSerializer::AppendElementEnd(Element* aElement,
 
   nsIAtom *name = content->Tag();
 
-  if ((mDoFormat || forceFormat) && !mPreLevel && !mDoRaw) {
+  if ((mDoFormat || forceFormat) && !mDoRaw && !PreLevel()) {
     DecrIndentation(name);
   }
 
@@ -1009,7 +1009,7 @@ nsXMLContentSerializer::AppendElementEnd(Element* aElement,
   ConfirmPrefix(tagPrefix, tagNamespaceURI, aElement, false);
   NS_ASSERTION(!debugNeedToPushNamespace, "Can't push namespaces in closing tag!");
 
-  if ((mDoFormat || forceFormat) && !mPreLevel && !mDoRaw) {
+  if ((mDoFormat || forceFormat) && !mDoRaw && !PreLevel()) {
 
     bool lineBreakBeforeClose = LineBreakBeforeClose(content->GetNameSpaceID(), name);
 
@@ -1041,8 +1041,8 @@ nsXMLContentSerializer::AppendElementEnd(Element* aElement,
 
   MaybeLeaveFromPreContent(content);
 
-  if ((mDoFormat || forceFormat) && !mPreLevel
-      && !mDoRaw && LineBreakAfterClose(content->GetNameSpaceID(), name)) {
+  if ((mDoFormat || forceFormat) && !mDoRaw && !PreLevel()
+      && LineBreakAfterClose(content->GetNameSpaceID(), name)) {
     AppendNewLineToString(aStr);
   }
   else {
@@ -1217,11 +1217,12 @@ void
 nsXMLContentSerializer::MaybeEnterInPreContent(nsIContent* aNode)
 {
   // support of the xml:space attribute
-  if (aNode->HasAttr(kNameSpaceID_XML, nsGkAtoms::space)) {
+  if (ShouldMaintainPreLevel() &&
+      aNode->HasAttr(kNameSpaceID_XML, nsGkAtoms::space)) {
     nsAutoString space;
     aNode->GetAttr(kNameSpaceID_XML, nsGkAtoms::space, space);
     if (space.EqualsLiteral("preserve"))
-      ++mPreLevel;
+      ++PreLevel();
   }
 }
 
@@ -1229,11 +1230,12 @@ void
 nsXMLContentSerializer::MaybeLeaveFromPreContent(nsIContent* aNode)
 {
   // support of the xml:space attribute
-  if (aNode->HasAttr(kNameSpaceID_XML, nsGkAtoms::space)) {
+  if (ShouldMaintainPreLevel() &&
+      aNode->HasAttr(kNameSpaceID_XML, nsGkAtoms::space)) {
     nsAutoString space;
     aNode->GetAttr(kNameSpaceID_XML, nsGkAtoms::space, space);
     if (space.EqualsLiteral("preserve"))
-      --mPreLevel;
+      --PreLevel();
   }
 }
 
@@ -1442,7 +1444,7 @@ nsXMLContentSerializer::AppendWrapped_NonWhitespaceSequence(
       colPos = mColPos;
     }
     else {
-      if (mDoFormat && !mPreLevel && !onceAgainBecauseWeAddedBreakInFront) {
+      if (mDoFormat && !mDoRaw && !PreLevel() && !onceAgainBecauseWeAddedBreakInFront) {
         colPos = mIndent.Length();
       }
       else
@@ -1711,3 +1713,10 @@ nsXMLContentSerializer::AppendToStringWrapped(const nsASingleFragmentString& aSt
     }
   }
 }
+
+bool
+nsXMLContentSerializer::ShouldMaintainPreLevel() const
+{
+  // Only attempt to maintain the pre level for consumers who care about it.
+  return !mDoRaw || (mFlags & nsIDocumentEncoder::OutputNoFormattingInPre);
+}

dom/base/nsXMLContentSerializer.h

@@ -294,6 +294,16 @@ class nsXMLContentSerializer : public nsIContentSerializer {
   virtual void MaybeEnterInPreContent(nsIContent* aNode);
   virtual void MaybeLeaveFromPreContent(nsIContent* aNode);
 
+  bool ShouldMaintainPreLevel() const;
+  int32_t PreLevel() const {
+    MOZ_ASSERT(ShouldMaintainPreLevel());
+    return mPreLevel;
+  }
+  int32_t& PreLevel() {
+    MOZ_ASSERT(ShouldMaintainPreLevel());
+    return mPreLevel;
+  }
+
   int32_t mPrefixIndex;
 
   struct NameSpaceDecl {
@@ -361,6 +371,7 @@ class nsXMLContentSerializer : public nsIContentSerializer {
   bool          mBodyOnly;
   int32_t       mInBody;
 
+private:
   // number of nested elements which have preformated content
   int32_t       mPreLevel;
 };