Bug 454317. Improve GetClasses to not do virtual calls when not needed. r=smaug, sr=jst

content/base/public/nsIContent.h

@@ -62,8 +62,8 @@ class nsIDocShell;
 
 // IID for the nsIContent interface
 #define NS_ICONTENT_IID       \
-{ 0x0acd0482, 0x09a2, 0x42fd, \
+{ 0x2813b1d9, 0x7fe1, 0x496f, \
-  { 0xb6, 0x1b, 0x95, 0xa2, 0x01, 0x6a, 0x55, 0xd3 } }
+ { 0x85, 0x52, 0xa2, 0xc1, 0xc5, 0x6b, 0x15, 0x40 } }
 
 /**
  * A node of content in a document's content model. This interface
@@ -784,10 +784,15 @@ public:
   /**
    * Get the class list of this content node (this corresponds to the
    * value of the null-namespace attribute whose name is given by
-   * GetClassAttributeName().  This may be null if there are no
+   * GetClassAttributeName()).  This may be null if there are no
    * classes, but that's not guaranteed.
    */
-  virtual const nsAttrValue* GetClasses() const = 0;
+  const nsAttrValue* GetClasses() const {
+    if (HasFlag(NODE_MAY_HAVE_CLASS)) {
+      return DoGetClasses();
+    }
+    return nsnull;
+  }
 
   /**
    * Walk aRuleWalker over the content style rules (presentational
@@ -849,6 +854,14 @@ public:
    */
   virtual void SaveSubtreeState() = 0;
 
+private:
+  /**
+   * Hook for implementing GetClasses.  This is guaranteed to only be
+   * called if the NODE_MAY_HAVE_CLASS flag is set.
+   */
+  virtual const nsAttrValue* DoGetClasses() const = 0;
+
+public:
 #ifdef DEBUG
   /**
    * List the content (and anything it contains) out to the given

content/base/public/nsINode.h

@@ -95,6 +95,8 @@ enum {
   // Optimizations to quickly check whether element may have ID, class or style
   // attributes. Not all element implementations may use these!
   NODE_MAY_HAVE_ID =             0x00000200U,
+  // For all Element nodes, NODE_MAY_HAVE_CLASS is guaranteed to be set if the
+  // node in fact has a class, but may be set even if it doesn't.
   NODE_MAY_HAVE_CLASS =          0x00000400U,
   NODE_MAY_HAVE_STYLE =          0x00000800U,
 

content/base/src/nsGenericDOMDataNode.cpp

@@ -1217,8 +1217,9 @@ nsGenericDOMDataNode::GetID() const
 }
 
 const nsAttrValue*
-nsGenericDOMDataNode::GetClasses() const
+nsGenericDOMDataNode::DoGetClasses() const
 {
+  NS_NOTREACHED("Shouldn't ever be called");
   return nsnull;
 }
 

content/base/src/nsGenericDOMDataNode.h

@@ -248,7 +248,7 @@ public:
   virtual PRBool MayHaveFrame() const;
 
   virtual nsIAtom* GetID() const;
-  virtual const nsAttrValue* GetClasses() const;
+  virtual const nsAttrValue* DoGetClasses() const;
   NS_IMETHOD WalkContentStyleRules(nsRuleWalker* aRuleWalker);
   virtual nsICSSStyleRule* GetInlineStyleRule();
   NS_IMETHOD SetInlineStyleRule(nsICSSStyleRule* aStyleRule, PRBool aNotify);

content/base/src/nsGenericElement.cpp

@@ -2916,8 +2916,9 @@ nsGenericElement::GetID() const
 }
 
 const nsAttrValue*
-nsGenericElement::GetClasses() const
+nsGenericElement::DoGetClasses() const
 {
+  NS_NOTREACHED("Shouldn't ever be called");
   return nsnull;
 }
 

content/base/src/nsGenericElement.h

@@ -417,7 +417,7 @@ public:
 #endif
 
   virtual nsIAtom* GetID() const;
-  virtual const nsAttrValue* GetClasses() const;
+  virtual const nsAttrValue* DoGetClasses() const;
   NS_IMETHOD WalkContentStyleRules(nsRuleWalker* aRuleWalker);
   virtual nsICSSStyleRule* GetInlineStyleRule();
   NS_IMETHOD SetInlineStyleRule(nsICSSStyleRule* aStyleRule, PRBool aNotify);

content/base/src/nsStyledElement.cpp

@@ -71,11 +71,9 @@ nsStyledElement::GetIDAttributeName() const
 }
 
 const nsAttrValue*
-nsStyledElement::GetClasses() const
+nsStyledElement::DoGetClasses() const
 {
-  if (!HasFlag(NODE_MAY_HAVE_CLASS)) {
+  NS_ASSERTION(HasFlag(NODE_MAY_HAVE_CLASS), "Unexpected call");
-    return nsnull;
-  }
   return mAttrsAndChildren.GetAttr(nsGkAtoms::_class);
 }
 

content/base/src/nsStyledElement.h

@@ -67,7 +67,7 @@ public:
   // nsIContent interface methods for styling
   virtual nsIAtom* GetClassAttributeName() const;
   virtual nsIAtom* GetIDAttributeName() const;
-  virtual const nsAttrValue* GetClasses() const;
+  virtual const nsAttrValue* DoGetClasses() const;
 
   virtual nsICSSStyleRule* GetInlineStyleRule();
   NS_IMETHOD SetInlineStyleRule(nsICSSStyleRule* aStyleRule, PRBool aNotify);

content/svg/content/src/nsSVGStylableElement.cpp

@@ -60,7 +60,8 @@ NS_INTERFACE_MAP_END_INHERITING(nsSVGStylableElementBase)
 nsSVGStylableElement::nsSVGStylableElement(nsINodeInfo *aNodeInfo)
   : nsSVGStylableElementBase(aNodeInfo)
 {
-
+  // We never know when we might have a class
+  SetFlags(NODE_MAY_HAVE_CLASS);
 }
 
 nsresult
@@ -88,7 +89,7 @@ nsSVGStylableElement::Init()
 // nsIContent methods
 
 const nsAttrValue*
-nsSVGStylableElement::GetClasses() const
+nsSVGStylableElement::DoGetClasses() const
 {
   return mClassName->GetAttrValue();
 }

content/svg/content/src/nsSVGStylableElement.h

@@ -60,7 +60,7 @@ public:
   NS_DECL_NSIDOMSVGSTYLABLE
 
   // nsIContent
-  virtual const nsAttrValue* GetClasses() const;
+  virtual const nsAttrValue* DoGetClasses() const;
 
 protected:
   nsRefPtr<nsSVGClassValue> mClassName;

content/xtf/src/nsXTFElementWrapper.cpp

@@ -73,6 +73,8 @@ nsXTFElementWrapper::nsXTFElementWrapper(nsINodeInfo* aNodeInfo,
       mTmpAttrName(nsGkAtoms::_asterix) // XXX this is a hack, but names
                                             // have to have a value
 {
+  // We never know when we might have a class
+  SetFlags(NODE_MAY_HAVE_CLASS);
 }
 
 nsXTFElementWrapper::~nsXTFElementWrapper()
@@ -931,7 +933,7 @@ nsXTFElementWrapper::GetClassAttributeName() const
 }
 
 const nsAttrValue*
-nsXTFElementWrapper::GetClasses() const
+nsXTFElementWrapper::DoGetClasses() const
 {
   const nsAttrValue* val = nsnull;
   nsIAtom* clazzAttr = GetClassAttributeName();

content/xtf/src/nsXTFElementWrapper.h

@@ -109,7 +109,7 @@ public:
   virtual nsresult DoneAddingChildren(PRBool aHaveNotified);
 
   virtual nsIAtom *GetClassAttributeName() const;
-  virtual const nsAttrValue* GetClasses() const;
+  virtual const nsAttrValue* DoGetClasses() const;
 
   virtual void PerformAccesskey(PRBool aKeyCausesActivation,
                                 PRBool aIsTrustedEvent);

content/xul/content/src/nsXULElement.cpp

@@ -1830,11 +1830,9 @@ nsXULElement::GetID() const
 }
 
 const nsAttrValue*
-nsXULElement::GetClasses() const
+nsXULElement::DoGetClasses() const
 {
-    if (!HasFlag(NODE_MAY_HAVE_CLASS)) {
+    NS_ASSERTION(HasFlag(NODE_MAY_HAVE_CLASS), "Unexpected call");
-        return nsnull;
-    }
     return FindLocalOrProtoAttr(kNameSpaceID_None, nsGkAtoms::_class);
 }
 

content/xul/content/src/nsXULElement.h

@@ -592,7 +592,7 @@ public:
     virtual PRBool IsNodeOfType(PRUint32 aFlags) const;
     virtual PRBool IsFocusable(PRInt32 *aTabIndex = nsnull);
     virtual nsIAtom* GetID() const;
-    virtual const nsAttrValue* GetClasses() const;
+    virtual const nsAttrValue* DoGetClasses() const;
 
     NS_IMETHOD WalkContentStyleRules(nsRuleWalker* aRuleWalker);
     virtual nsICSSStyleRule* GetInlineStyleRule();