Issue #2045 - Part 5: Serialize shorthands using "revert" like those containing "unset"

layout/style/CSSVariableDeclarations.cpp

@@ -11,12 +11,13 @@
 #include "nsCSSScanner.h"
 #include "nsRuleData.h"
 
-// These three special string values are used to represent specified values of
+// These four special string values are used to represent specified values of
-// 'initial', 'inherit' and 'unset'.  (Note that none of these are valid
+// 'initial', 'inherit', 'unset', and 'revert'.  (Note that none of these are
-// variable values.)
+// valid variable values.)
 #define INITIAL_VALUE "!"
 #define INHERIT_VALUE ";"
 #define UNSET_VALUE   ")"
+#define REVERT_VALUE  ">"
 
 namespace mozilla {
 
@@ -83,6 +84,9 @@ CSSVariableDeclarations::Get(const nsAString& aName,
   } else if (value.EqualsLiteral(UNSET_VALUE)) {
     aType = eUnset;
     aTokenStream.Truncate();
+  } else if (value.EqualsLiteral(REVERT_VALUE)) {
+    aType = eRevert;
+    aTokenStream.Truncate();
   } else {
     aType = eTokenStream;
     aTokenStream = value;
@@ -96,7 +100,8 @@ CSSVariableDeclarations::PutTokenStream(const nsAString& aName,
 {
   MOZ_ASSERT(!aTokenStream.EqualsLiteral(INITIAL_VALUE) &&
              !aTokenStream.EqualsLiteral(INHERIT_VALUE) &&
-             !aTokenStream.EqualsLiteral(UNSET_VALUE));
+             !aTokenStream.EqualsLiteral(UNSET_VALUE) &&
+             !aTokenStream.EqualsLiteral(REVERT_VALUE));
   mVariables.Put(aName, aTokenStream);
 }
 
@@ -118,6 +123,12 @@ CSSVariableDeclarations::PutUnset(const nsAString& aName)
   mVariables.Put(aName, NS_LITERAL_STRING(UNSET_VALUE));
 }
 
+void
+CSSVariableDeclarations::PutRevert(const nsAString& aName)
+{
+  mVariables.Put(aName, NS_LITERAL_STRING(REVERT_VALUE));
+}
+
 void
 CSSVariableDeclarations::Remove(const nsAString& aName)
 {
@@ -160,12 +171,13 @@ CSSVariableDeclarations::AddVariablesToResolver(
                      eCSSTokenSerialization_Nothing,
                      false);
     } else if (value.EqualsLiteral(INHERIT_VALUE) ||
-               value.EqualsLiteral(UNSET_VALUE)) {
+               value.EqualsLiteral(UNSET_VALUE) ||
-      // Values of 'inherit' and 'unset' don't need any handling, since it means
+               value.EqualsLiteral(REVERT_VALUE)) {
-      // we just need to keep whatever value is currently in the resolver.  This
+      // Values of 'inherit', 'unset', and 'revert' don't need any handling,
-      // is because the specified variable declarations already have only the
+      // since it means we just need to keep whatever value is currently in
-      // winning declaration for the variable and no longer have any of the
+      // the resolver.  This is because the specified variable declarations
-      // others.
+      // already have only the winning declaration for the variable and no
+      // longer have any of the others.
     } else {
       // At this point, we don't know what token types are at the start and end
       // of the specified variable value.  These will be determined later during

layout/style/CSSVariableDeclarations.h

@@ -42,7 +42,8 @@ public:
     eTokenStream,  // a stream of CSS tokens (the usual type for variables)
     eInitial,      // 'initial'
     eInherit,      // 'inherit'
-    eUnset         // 'unset'
+    eUnset,        // 'unset'
+    eRevert        // 'revert'
   };
 
   /**
@@ -53,8 +54,8 @@ public:
    * @param aType Out parameter into which the type of the variable value will
    *   be stored.
    * @param aValue Out parameter into which the value of the variable will
-   *   be stored.  If the variable is 'initial', 'inherit' or 'unset', this will
+   *   be stored.  If the variable is 'initial', 'inherit', 'unset', or
-   *   be the empty string.
+   *   'revert', this will be the empty string.
    * @return Whether a variable with the given name was found.  When false
    *   is returned, aType and aValue will not be modified.
    */
@@ -87,6 +88,15 @@ public:
    */
   void PutUnset(const nsAString& aName);
 
+  /**
+   * Adds or modifies an existing entry in this set of variable declarations
+   * to have the value 'revert'.
+   *
+   * @param aName The variable name (not including any "--" prefix that would
+   *   be part of the custom property name) whose value is to be set.
+   */
+  void PutRevert(const nsAString& aName);
+
   /**
    * Adds or modifies an existing entry in this set of variable declarations
    * to have a token stream value.

layout/style/Declaration.cpp

@@ -558,9 +558,9 @@ Declaration::GetPropertyValueInternal(
   //   (1) Since a shorthand sets all sub-properties, if some of its
   //       subproperties were not specified, we must return the empty
   //       string.
-  //   (2) Since 'inherit', 'initial' and 'unset' can only be specified
+  //   (2) Since 'inherit', 'initial', 'unset', and 'revert' can only be
-  //       as the values for entire properties, we need to return the
+  //       specified as the values for entire properties, we need to return
-  //       empty string if some but not all of the subproperties have one
+  //       the empty string if some but not all of the subproperties have one
   //       of those values.
   //   (3) Since a single value only makes sense with or without
   //       !important, we return the empty string if some values are
@@ -575,7 +575,7 @@ Declaration::GetPropertyValueInternal(
   // 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, revertCount = 0,
            matchingTokenStreamCount = 0, nonMatchingTokenStreamCount = 0;
   CSSPROPS_FOR_SHORTHAND_SUBPROPERTIES(p, aProperty,
                                        CSSEnabledState::eForAllContent) {
@@ -601,6 +601,8 @@ Declaration::GetPropertyValueInternal(
       ++initialCount;
     } else if (val->GetUnit() == eCSSUnit_Unset) {
       ++unsetCount;
+    } else if (val->GetUnit() == eCSSUnit_Revert) {
+      ++revertCount;
     } else if (val->GetUnit() == eCSSUnit_TokenStream) {
       if (val->GetTokenStreamValue()->mShorthandPropertyID == aProperty) {
         tokenStream = val;
@@ -632,9 +634,15 @@ Declaration::GetPropertyValueInternal(
                                               nsCSSValue::eNormalized);
     return;
   }
-  if (initialCount != 0 || inheritCount != 0 ||
+  if (revertCount == totalCount) {
-      unsetCount != 0 || nonMatchingTokenStreamCount != 0) {
+    // Simplify serialization below by serializing revert up-front.
-    // Case (2): partially initial, inherit, unset or token stream.
+    nsCSSValue(eCSSUnit_Revert).AppendToString(eCSSProperty_UNKNOWN, aValue,
+                                              nsCSSValue::eNormalized);
+    return;
+  }
+  if (initialCount != 0 || inheritCount != 0 || unsetCount != 0 ||
+      revertCount != 0 || nonMatchingTokenStreamCount != 0) {
+    // Case (2): partially initial, inherit, unset, revert, or token stream.
     return;
   }
   if (tokenStream) {
@@ -1455,6 +1463,7 @@ Declaration::GetPropertyValueInternal(
           case eCSSUnit_Inherit:
           case eCSSUnit_Initial:
           case eCSSUnit_Unset:
+          case eCSSUnit_Revert:
             return true;
           case eCSSUnit_Enumerated:
             // return false if there is a fallback value or <overflow-position>
@@ -1563,10 +1572,10 @@ Declaration::GetPropertyValueInternal(
       break;
     }
     case eCSSProperty_all:
-      // If we got here, then we didn't have all "inherit" or "initial" or
+      // If we got here, then we didn't have all "inherit", "initial", "unset",
-      // "unset" values for all of the longhand property components of 'all'.
+      // or "revert" values for all of the longhand property components of
-      // There is no other possible value that is valid for all properties,
+      // 'all'. There is no other possible value that is valid for all
-      // so serialize as the empty string.
+      // properties, so serialize as the empty string.
       break;
     default:
       MOZ_ASSERT(false, "no other shorthands");
@@ -1663,6 +1672,10 @@ Declaration::AppendVariableAndValueToString(const nsAString& aName,
       aResult.AppendLiteral("unset");
       break;
 
+    case CSSVariableDeclarations::eRevert:
+      aResult.AppendLiteral("revert");
+      break;
+
     default:
       MOZ_ASSERT(false, "unexpected variable value type");
   }
@@ -1899,6 +1912,10 @@ Declaration::GetVariableValue(const nsAString& aName, nsAString& aValue) const
         aValue.AppendLiteral("unset");
         break;
 
+      case CSSVariableDeclarations::eRevert:
+        aValue.AppendLiteral("revert");
+        break;
+
       default:
         MOZ_ASSERT(false, "unexpected variable value type");
     }
@@ -1964,6 +1981,11 @@ Declaration::AddVariable(const nsAString& aName,
       variables->PutUnset(aName);
       break;
 
+    case CSSVariableDeclarations::eRevert:
+      MOZ_ASSERT(aValue.IsEmpty());
+      variables->PutRevert(aName);
+      break;
+
     default:
       MOZ_ASSERT(false, "unexpected aType value");
   }