Bug 774169, patch 3: Treat -moz-transform as a shorthand rather than an alias so the parsing function can know whether it is parsing a prefixed transform. r=bzbarsky

layout/style/Declaration.cpp

@@ -818,6 +818,15 @@ Declaration::GetValue(nsCSSProperty aProperty, nsAString& aValue) const
       break;
     }
 #endif // MOZ_FLEXBOX
+    case eCSSProperty__moz_transform: {
+      // shorthands that are just aliases with different parsing rules
+      const nsCSSProperty* subprops =
+        nsCSSProps::SubpropertyEntryFor(aProperty);
+      NS_ABORT_IF_FALSE(subprops[1] == eCSSProperty_UNKNOWN,
+                        "must have exactly one subproperty");
+      AppendValueToString(subprops[0], aValue);
+      break;
+    }
     default:
       NS_ABORT_IF_FALSE(false, "no other shorthands");
       break;

layout/style/nsCSSParser.cpp

@@ -509,7 +509,7 @@ protected:
   bool ParseListStyle();
   bool ParseMargin();
   bool ParseMarks(nsCSSValue& aValue);
-  bool ParseTransform();
+  bool ParseTransform(bool aIsPrefixed);
   bool ParseOutline();
   bool ParseOverflow();
   bool ParsePadding();
@@ -6109,7 +6109,9 @@ CSSParserImpl::ParsePropertyByFunction(nsCSSProperty aPropID)
   case eCSSProperty_text_decoration:
     return ParseTextDecoration();
   case eCSSProperty_transform:
-    return ParseTransform();
+    return ParseTransform(false);
+  case eCSSProperty__moz_transform:
+    return ParseTransform(true);
   case eCSSProperty_transform_origin:
     return ParseTransformOrigin(false);
   case eCSSProperty_perspective_origin:
@@ -8575,7 +8577,7 @@ CSSParserImpl::ParseSingleTransform(nsCSSValue& aValue, bool& aIs3D)
 /* Parses a transform property list by continuously reading in properties
  * and constructing a matrix from it.
  */
-bool CSSParserImpl::ParseTransform()
+bool CSSParserImpl::ParseTransform(bool aIsPrefixed)
 {
   nsCSSValue value;
   if (ParseVariant(value, VARIANT_INHERIT | VARIANT_NONE, nullptr)) {

layout/style/nsCSSPropAliasList.h

@@ -35,7 +35,6 @@
 
  ******/
 
-CSS_PROP_ALIAS(-moz-transform, transform, MozTransform, "")
 CSS_PROP_ALIAS(-moz-transform-origin, transform_origin, MozTransformOrigin, "")
 CSS_PROP_ALIAS(-moz-perspective-origin, perspective_origin, MozPerspectiveOrigin, "")
 CSS_PROP_ALIAS(-moz-perspective, perspective, MozPerspective, "")

layout/style/nsCSSPropList.h

@@ -3358,6 +3358,16 @@ CSS_PROP_SVGRESET(
     offsetof(nsStyleSVGReset, mVectorEffect),
     eStyleAnimType_EnumU8)
 
+// The shorthands below are essentially aliases, but they require different
+// parsing rules, and are therefore implemented as shorthands.
+CSS_PROP_SHORTHAND(
+    -moz-transform,
+    _moz_transform,
+    MozTransform,
+    CSS_PROPERTY_PARSE_FUNCTION |
+        CSS_PROPERTY_IS_ALIAS,
+    "")
+
 #ifndef CSS_PROP_LIST_EXCLUDE_INTERNAL
 // We have a few properties that are in style structs but are not stored
 // in style sheets (or nsCSS* structs).  Some fields in these property

layout/style/nsCSSProps.cpp

@@ -219,6 +219,11 @@ nsCSSProps::BuildShorthandsContainingTable()
       subpropCounts[shorthand - eCSSProperty_COUNT_no_shorthands];
     subpropCountsEntry.property = shorthand;
     subpropCountsEntry.count = 0;
+    if (nsCSSProps::PropHasFlags(shorthand, CSS_PROPERTY_IS_ALIAS)) {
+      // Don't put shorthands that are acting as aliases in the
+      // shorthands-containing lists.
+      continue;
+    }
     for (const nsCSSProperty* subprops = SubpropertyEntryFor(shorthand);
          *subprops != eCSSProperty_UNKNOWN;
          ++subprops) {
@@ -279,6 +284,12 @@ nsCSSProps::BuildShorthandsContainingTable()
            shorthandAndCount->count,
            nsCSSProps::GetStringValue(shorthandAndCount->property).get());
 #endif
+    if (nsCSSProps::PropHasFlags(shorthandAndCount->property,
+                                 CSS_PROPERTY_IS_ALIAS)) {
+      // Don't put shorthands that are acting as aliases in the
+      // shorthands-containing lists.
+      continue;
+    }
     for (const nsCSSProperty* subprops =
            SubpropertyEntryFor(shorthandAndCount->property);
          *subprops != eCSSProperty_UNKNOWN;
@@ -307,6 +318,11 @@ nsCSSProps::BuildShorthandsContainingTable()
   for (nsCSSProperty shorthand = eCSSProperty_COUNT_no_shorthands;
        shorthand < eCSSProperty_COUNT;
        shorthand = nsCSSProperty(shorthand + 1)) {
+    if (nsCSSProps::PropHasFlags(shorthand, CSS_PROPERTY_IS_ALIAS)) {
+      // Don't put shorthands that are acting as aliases in the
+      // shorthands-containing lists.
+      continue;
+    }
     for (const nsCSSProperty* subprops = SubpropertyEntryFor(shorthand);
          *subprops != eCSSProperty_UNKNOWN;
          ++subprops) {
@@ -2243,6 +2259,13 @@ static const nsCSSProperty gMarkerSubpropTable[] = {
   eCSSProperty_UNKNOWN
 };
 
+// Subproperty tables for shorthands that are just aliases with
+// different parsing rules.
+static const nsCSSProperty gMozTransformSubpropTable[] = {
+  eCSSProperty_transform,
+  eCSSProperty_UNKNOWN
+};
+
 const nsCSSProperty *const
 nsCSSProps::kSubpropertyTable[eCSSProperty_COUNT - eCSSProperty_COUNT_no_shorthands] = {
 #define CSS_PROP_DOMPROP_PREFIXED(prop_) prop_

layout/style/nsCSSProps.h

@@ -98,6 +98,9 @@ MOZ_STATIC_ASSERT((CSS_PROPERTY_PARSE_PROPERTY_MASK &
 // Does this property suppor the unitless length quirk in quirks mode?
 #define CSS_PROPERTY_UNITLESS_LENGTH_QUIRK        (1<<16)
 
+// Is this property (which must be a shorthand) really an alias?
+#define CSS_PROPERTY_IS_ALIAS                     (1<<17)
+
 /**
  * Types of animatable values.
  */

layout/style/nsComputedDOMStyle.cpp

@@ -405,6 +405,18 @@ nsComputedDOMStyle::GetPropertyCSSValue(const nsAString& aPropertyName,
   nsCSSProperty prop = nsCSSProps::LookupProperty(aPropertyName,
                                                   nsCSSProps::eEnabled);
 
+  // We don't (for now, anyway, though it may make sense to change it
+  // for all aliases, including those in nsCSSPropAliasList) want
+  // aliases to be enumerable (via GetLength and IndexedGetter), so
+  // handle them here rather than adding entries to
+  // GetQueryablePropertyMap.
+  if (nsCSSProps::PropHasFlags(prop, CSS_PROPERTY_IS_ALIAS)) {
+    const nsCSSProperty* subprops = nsCSSProps::SubpropertyEntryFor(prop);
+    NS_ABORT_IF_FALSE(subprops[1] == eCSSProperty_UNKNOWN,
+                      "must have list of length 1");
+    prop = subprops[0];
+  }
+
   const ComputedStyleMapEntry* propEntry = nullptr;
   {
     uint32_t length = 0;