Bug 773296 - Part 23: Support variables in CSSStyleDelcaration methods. r=dbaron

This adds support for custom properties on the remainder of the
CSSStyleDeclaration methods.

A shorthand that was specified using a variable reference is serialized
to its originally specified value, rather than by concatenating the
serializations of its longhand components.

A shorthand that was not specified using a variable references but which
has a component longhand that was is serialized to the empty string.

layout/style/Declaration.cpp

@@ -175,8 +175,15 @@ Declaration::GetValue(nsCSSProperty aProperty, nsAString& aValue) const
   // Since we're doing this check for 'inherit' and 'initial' up front,
   // we can also simplify the property serialization code by serializing
   // those values up front as well.
+  //
+  // Additionally, if a shorthand property was set using a value with a
+  // variable reference and none of its component longhand properties were
+  // then overridden on the declaration, we return the token stream
+  // assigned to the shorthand.
+  const nsCSSValue* tokenStream = nullptr;
   uint32_t totalCount = 0, importantCount = 0,
-           initialCount = 0, inheritCount = 0, unsetCount = 0;
+           initialCount = 0, inheritCount = 0, unsetCount = 0,
+           matchingTokenStreamCount = 0;
   CSSPROPS_FOR_SHORTHAND_SUBPROPERTIES(p, aProperty) {
     if (*p == eCSSProperty__x_system_font ||
          nsCSSProps::PropHasFlags(*p, CSS_PROPERTY_DIRECTIONAL_SOURCE)) {
@@ -201,6 +208,10 @@ Declaration::GetValue(nsCSSProperty aProperty, nsAString& aValue) const
       ++initialCount;
     } else if (val->GetUnit() == eCSSUnit_Unset) {
       ++unsetCount;
+    } else if (val->GetUnit() == eCSSUnit_TokenStream &&
+               val->GetTokenStreamValue()->mShorthandPropertyID == aProperty) {
+      tokenStream = val;
+      ++matchingTokenStreamCount;
     }
   }
   if (importantCount != 0 && importantCount != totalCount) {
@@ -226,6 +237,16 @@ Declaration::GetValue(nsCSSProperty aProperty, nsAString& aValue) const
     // Case (2): partially initial, inherit or unset.
     return;
   }
+  if (tokenStream) {
+    if (matchingTokenStreamCount == totalCount) {
+      // Shorthand was specified using variable references and all of its
+      // longhand components were set by the shorthand.
+      aValue.Append(tokenStream->GetTokenStreamValue()->mTokenStream);
+    } else {
+      // In all other cases, serialize to the empty string.
+    }
+    return;
+  }
 
   nsCSSCompressedDataBlock *data = importantCount ? mImportantData : mData;
   switch (aProperty) {
@@ -1210,7 +1231,8 @@ void
 Declaration::AddVariableDeclaration(const nsAString& aName,
                                     CSSVariableDeclarations::Type aType,
                                     const nsString& aValue,
-                                    bool aIsImportant)
+                                    bool aIsImportant,
+                                    bool aOverrideImportant)
 {
   MOZ_ASSERT(IsMutable());
 
@@ -1220,7 +1242,8 @@ Declaration::AddVariableDeclaration(const nsAString& aName,
     mVariableOrder.AppendElement(aName);
   }
 
-  if (!aIsImportant && mImportantVariables && mImportantVariables->Has(aName)) {
+  if (!aIsImportant && !aOverrideImportant &&
+      mImportantVariables && mImportantVariables->Has(aName)) {
     return;
   }
 
@@ -1234,6 +1257,9 @@ Declaration::AddVariableDeclaration(const nsAString& aName,
     }
     variables = mImportantVariables;
   } else {
+    if (mImportantVariables) {
+      mImportantVariables->Remove(aName);
+    }
     if (!mVariables) {
       mVariables = new CSSVariableDeclarations;
     }

layout/style/Declaration.h

@@ -78,11 +78,14 @@ public:
    * @param aValue The value of the variable, if aType is
    *   CSSVariableDeclarations::eTokenStream.
    * @param aIsImportant Whether the declaration is !important.
+   * @param aOverrideImportant When aIsImportant is false, whether an
+   *   existing !important declaration will be overridden.
    */
   void AddVariableDeclaration(const nsAString& aName,
                               CSSVariableDeclarations::Type aType,
                               const nsString& aValue,
-                              bool aIsImportant);
+                              bool aIsImportant,
+                              bool aOverrideImportant);
 
   /**
    * Removes a custom property declaration from this object.

layout/style/nsCSSParser.cpp

@@ -131,6 +131,15 @@ public:
                       nsMediaList* aMediaList,
                       bool aHTMLMode);
 
+  nsresult ParseVariable(const nsAString& aVariableName,
+                         const nsAString& aPropValue,
+                         nsIURI* aSheetURL,
+                         nsIURI* aBaseURL,
+                         nsIPrincipal* aSheetPrincipal,
+                         css::Declaration* aDeclaration,
+                         bool* aChanged,
+                         bool aIsImportant);
+
   bool ParseColorString(const nsSubstring& aBuffer,
                         nsIURI* aURL, // for error reporting
                         uint32_t aLineNumber, // for error reporting
@@ -1257,6 +1266,7 @@ CSSParserImpl::ParseRule(const nsAString&        aRule,
 #pragma warning( push )
 #pragma warning( disable : 4748 )
 #endif
+
 nsresult
 CSSParserImpl::ParseProperty(const nsCSSProperty aPropID,
                              const nsAString& aPropValue,
@@ -1331,6 +1341,63 @@ CSSParserImpl::ParseProperty(const nsCSSProperty aPropID,
   ReleaseScanner();
   return NS_OK;
 }
+
+nsresult
+CSSParserImpl::ParseVariable(const nsAString& aVariableName,
+                             const nsAString& aPropValue,
+                             nsIURI* aSheetURI,
+                             nsIURI* aBaseURI,
+                             nsIPrincipal* aSheetPrincipal,
+                             css::Declaration* aDeclaration,
+                             bool* aChanged,
+                             bool aIsImportant)
+{
+  NS_PRECONDITION(aSheetPrincipal, "Must have principal here!");
+  NS_PRECONDITION(aBaseURI, "need base URI");
+  NS_PRECONDITION(aDeclaration, "Need declaration to parse into!");
+  NS_PRECONDITION(nsLayoutUtils::CSSVariablesEnabled(),
+                  "expected Variables to be enabled");
+
+  mData.AssertInitialState();
+  mTempData.AssertInitialState();
+  aDeclaration->AssertMutable();
+
+  nsCSSScanner scanner(aPropValue, 0);
+  css::ErrorReporter reporter(scanner, mSheet, mChildLoader, aSheetURI);
+  InitScanner(scanner, reporter, aSheetURI, aBaseURI, aSheetPrincipal);
+  mSection = eCSSSection_General;
+
+  *aChanged = false;
+
+  CSSVariableDeclarations::Type variableType;
+  nsString variableValue;
+
+  bool parsedOK = ParseVariableDeclaration(&variableType, variableValue);
+
+  // We should now be at EOF
+  if (parsedOK && GetToken(true)) {
+    REPORT_UNEXPECTED_TOKEN(PEExpectEndValue);
+    parsedOK = false;
+  }
+
+  if (!parsedOK) {
+    REPORT_UNEXPECTED_P(PEValueParsingError, NS_LITERAL_STRING("var-") +
+                                             aVariableName);
+    REPORT_UNEXPECTED(PEDeclDropped);
+    OUTPUT_ERROR();
+  } else {
+    CLEAR_ERROR();
+    aDeclaration->AddVariableDeclaration(aVariableName, variableType,
+                                         variableValue, aIsImportant, true);
+    *aChanged = true;
+  }
+
+  mTempData.AssertInitialState();
+
+  ReleaseScanner();
+  return NS_OK;
+}
+
 #ifdef _MSC_VER
 #pragma warning( pop )
 #pragma optimize( "", on )
@@ -5541,6 +5608,7 @@ CSSParserImpl::ParseDeclaration(css::Declaration* aDeclaration,
   NS_PRECONDITION(aContext == eCSSContext_General ||
                   aContext == eCSSContext_Page,
                   "Must be page or general context");
+
   bool checkForBraces = (aFlags & eParseDeclaration_InBraces) != 0;
 
   mTempData.AssertInitialState();
@@ -5683,7 +5751,7 @@ CSSParserImpl::ParseDeclaration(css::Declaration* aDeclaration,
                          0, VAR_PREFIX_LENGTH).EqualsLiteral("var-"));
     nsDependentString varName(propertyName, VAR_PREFIX_LENGTH); // remove 'var-'
     aDeclaration->AddVariableDeclaration(varName, variableType, variableValue,
-                                         status == ePriority_Important);
+                                         status == ePriority_Important, false);
   } else {
     *aChanged |= mData.TransferFromBlock(mTempData, propID,
                                          status == ePriority_Important,
@@ -12667,6 +12735,21 @@ nsCSSParser::ParseProperty(const nsCSSProperty aPropID,
                   aIsImportant, aIsSVGMode);
 }
 
+nsresult
+nsCSSParser::ParseVariable(const nsAString&    aVariableName,
+                           const nsAString&    aPropValue,
+                           nsIURI*             aSheetURI,
+                           nsIURI*             aBaseURI,
+                           nsIPrincipal*       aSheetPrincipal,
+                           css::Declaration*   aDeclaration,
+                           bool*               aChanged,
+                           bool                aIsImportant)
+{
+  return static_cast<CSSParserImpl*>(mImpl)->
+    ParseVariable(aVariableName, aPropValue, aSheetURI, aBaseURI,
+                  aSheetPrincipal, aDeclaration, aChanged, aIsImportant);
+}
+
 void
 nsCSSParser::ParseMediaList(const nsSubstring& aBuffer,
                             nsIURI*            aURI,

layout/style/nsCSSParser.h

@@ -129,6 +129,15 @@ public:
                          bool                aIsImportant,
                          bool                aIsSVGMode = false);
 
+  // The same as ParseProperty but for a variable.
+  nsresult ParseVariable(const nsAString&    aVariableName,
+                         const nsAString&    aPropValue,
+                         nsIURI*             aSheetURL,
+                         nsIURI*             aBaseURL,
+                         nsIPrincipal*       aSheetPrincipal,
+                         mozilla::css::Declaration* aDeclaration,
+                         bool*               aChanged,
+                         bool                aIsImportant);
   /**
    * Parse aBuffer into a media list |aMediaList|, which must be
    * non-null, replacing its current contents.  If aHTMLMode is true,

layout/style/nsDOMCSSDeclaration.cpp

@@ -52,6 +52,26 @@ nsDOMCSSDeclaration::GetPropertyValue(const nsCSSProperty aPropID,
   return NS_OK;
 }
 
+// Length of the "var-" prefix of custom property names.
+#define VAR_PREFIX_LENGTH 4
+
+void
+nsDOMCSSDeclaration::GetCustomPropertyValue(const nsAString& aPropertyName,
+                                            nsAString& aValue)
+{
+  MOZ_ASSERT(Substring(aPropertyName,
+                       0, VAR_PREFIX_LENGTH).EqualsLiteral("var-"));
+
+  css::Declaration* decl = GetCSSDeclaration(false);
+  if (!decl) {
+    aValue.Truncate();
+    return;
+  }
+
+  decl->GetVariableDeclaration(Substring(aPropertyName, VAR_PREFIX_LENGTH),
+                               aValue);
+}
+
 NS_IMETHODIMP
 nsDOMCSSDeclaration::SetPropertyValue(const nsCSSProperty aPropID,
                                       const nsAString& aValue)
@@ -156,6 +176,11 @@ nsDOMCSSDeclaration::GetPropertyValue(const nsAString& aPropertyName,
     return NS_OK;
   }
 
+  if (propID == eCSSPropertyExtra_variable) {
+    GetCustomPropertyValue(aPropertyName, aReturn);
+    return NS_OK;
+  }
+
   return GetPropertyValue(propID, aReturn);
 }
 
@@ -189,19 +214,26 @@ nsDOMCSSDeclaration::SetProperty(const nsAString& aPropertyName,
     // If the new value of the property is an empty string we remove the
     // property.
     // XXX this ignores the priority string, should it?
+    if (propID == eCSSPropertyExtra_variable) {
+      return RemoveCustomProperty(aPropertyName);
+    }
     return RemoveProperty(propID);
   }
 
+  bool important;
   if (aPriority.IsEmpty()) {
-    return ParsePropertyValue(propID, aValue, false);
+    important = false;
+  } else if (aPriority.EqualsLiteral("important")) {
+    important = true;
+  } else {
+    // XXX silent failure?
+    return NS_OK;
   }
 
-  if (aPriority.EqualsLiteral("important")) {
-    return ParsePropertyValue(propID, aValue, true);
+  if (propID == eCSSPropertyExtra_variable) {
+    return ParseCustomPropertyValue(aPropertyName, aValue, important);
   }
-
-  // XXX silent failure?
-  return NS_OK;
+  return ParsePropertyValue(propID, aValue, important);
 }
 
 NS_IMETHODIMP
@@ -215,6 +247,11 @@ nsDOMCSSDeclaration::RemoveProperty(const nsAString& aPropertyName,
     return NS_OK;
   }
 
+  if (propID == eCSSPropertyExtra_variable) {
+    RemoveCustomProperty(aPropertyName);
+    return NS_OK;
+  }
+
   nsresult rv = GetPropertyValue(propID, aReturn);
   NS_ENSURE_SUCCESS(rv, rv);
 
@@ -278,6 +315,49 @@ nsDOMCSSDeclaration::ParsePropertyValue(const nsCSSProperty aPropID,
   return SetCSSDeclaration(decl);
 }
 
+nsresult
+nsDOMCSSDeclaration::ParseCustomPropertyValue(const nsAString& aPropertyName,
+                                              const nsAString& aPropValue,
+                                              bool aIsImportant)
+{
+  MOZ_ASSERT(nsCSSProps::IsCustomPropertyName(aPropertyName));
+
+  css::Declaration* olddecl = GetCSSDeclaration(true);
+  if (!olddecl) {
+    return NS_ERROR_FAILURE;
+  }
+
+  CSSParsingEnvironment env;
+  GetCSSParsingEnvironment(env);
+  if (!env.mPrincipal) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  // For nsDOMCSSAttributeDeclaration, SetCSSDeclaration will lead to
+  // Attribute setting code, which leads in turn to BeginUpdate.  We
+  // need to start the update now so that the old rule doesn't get used
+  // between when we mutate the declaration and when we set the new
+  // rule (see stack in bug 209575).
+  mozAutoDocConditionalContentUpdateBatch autoUpdate(DocToUpdate(), true);
+  css::Declaration* decl = olddecl->EnsureMutable();
+
+  nsCSSParser cssParser(env.mCSSLoader);
+  bool changed;
+  nsresult result = cssParser.ParseVariable(Substring(aPropertyName,
+                                                      VAR_PREFIX_LENGTH),
+                                            aPropValue, env.mSheetURI,
+                                            env.mBaseURI, env.mPrincipal, decl,
+                                            &changed, aIsImportant);
+  if (NS_FAILED(result) || !changed) {
+    if (decl != olddecl) {
+      delete decl;
+    }
+    return result;
+  }
+
+  return SetCSSDeclaration(decl);
+}
+
 nsresult
 nsDOMCSSDeclaration::RemoveProperty(const nsCSSProperty aPropID)
 {
@@ -297,3 +377,26 @@ nsDOMCSSDeclaration::RemoveProperty(const nsCSSProperty aPropID)
   decl->RemoveProperty(aPropID);
   return SetCSSDeclaration(decl);
 }
+
+nsresult
+nsDOMCSSDeclaration::RemoveCustomProperty(const nsAString& aPropertyName)
+{
+  MOZ_ASSERT(Substring(aPropertyName,
+                       0, VAR_PREFIX_LENGTH).EqualsLiteral("var-"));
+
+  css::Declaration* decl = GetCSSDeclaration(false);
+  if (!decl) {
+    return NS_OK; // no decl, so nothing to remove
+  }
+
+  // For nsDOMCSSAttributeDeclaration, SetCSSDeclaration will lead to
+  // Attribute setting code, which leads in turn to BeginUpdate.  We
+  // need to start the update now so that the old rule doesn't get used
+  // between when we mutate the declaration and when we set the new
+  // rule (see stack in bug 209575).
+  mozAutoDocConditionalContentUpdateBatch autoUpdate(DocToUpdate(), true);
+
+  decl = decl->EnsureMutable();
+  decl->RemoveVariableDeclaration(Substring(aPropertyName, VAR_PREFIX_LENGTH));
+  return SetCSSDeclaration(decl);
+}

layout/style/nsDOMCSSDeclaration.h

@@ -138,6 +138,12 @@ protected:
   // return the old value; it just does a straight removal.
   nsresult RemoveProperty(const nsCSSProperty aPropID);
 
+  void GetCustomPropertyValue(const nsAString& aPropertyName, nsAString& aValue);
+  nsresult RemoveCustomProperty(const nsAString& aPropertyName);
+  nsresult ParseCustomPropertyValue(const nsAString& aPropertyName,
+                                    const nsAString& aPropValue,
+                                    bool aIsImportant);
+
 protected:
   virtual ~nsDOMCSSDeclaration();
   nsDOMCSSDeclaration()