Bug 1848491 - Handle private subtags in the lang attribute and :lang() selector. r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D186133

layout/style/nsStyleUtil.cpp

@@ -82,32 +82,82 @@ bool nsStyleUtil::LangTagCompare(const nsACString& aAttributeValue,
     return false;
   }
 
+  int32_t attrPriv = -1;
   AutoLangId attrLangId(aAttributeValue);
   if (!attrLangId.IsValid()) {
-    return false;
-  }
-
-  AutoLangId selectorId(aSelectorValue);
-  if (!selectorId.IsValid()) {
-    // If it was "invalid" because of a wildcard language subtag, replace that
-    // with 'und' and try again.
-    // XXX Should unic_langid_new handle the wildcard internally?
-    if (aSelectorValue[0] == '*') {
-      nsAutoCString temp(aSelectorValue);
-      temp.Replace(0, 1, "und");
-      selectorId.Reset(temp);
-      if (!selectorId.IsValid()) {
+    // If it was invalid due to private subtags, try stripping them and
+    // re-parsing what remains.
+    attrPriv = aAttributeValue.LowerCaseFindASCII("-x-");
+    if (attrPriv >= 0) {
+      nsAutoCString temp(aAttributeValue);
+      temp.Truncate(attrPriv);
+      attrLangId.Reset(temp);
+      if (!attrLangId.IsValid()) {
         return false;
       }
-      intl::ffi::unic_langid_clear_language(selectorId);
     } else {
       return false;
     }
   }
 
-  return intl::ffi::unic_langid_matches(attrLangId, selectorId,
-                                        /* match addrLangId as range */ false,
-                                        /* match selectorId as range */ true);
+  int32_t selPriv = -1;
+  AutoLangId selectorId(aSelectorValue);
+  if (!selectorId.IsValid()) {
+    // If it was "invalid" because of a wildcard language subtag, replace that
+    // with 'und' and try again.
+    // XXX Should unic_langid_new handle the wildcard internally?
+    bool wildcard = false;
+    if (aSelectorValue[0] == '*') {
+      wildcard = true;
+      nsAutoCString temp(aSelectorValue);
+      temp.Replace(0, 1, "und");
+      selectorId.Reset(temp);
+      if (selectorId.IsValid()) {
+        intl::ffi::unic_langid_clear_language(selectorId);
+      }
+    }
+    // If it was invalid due to private subtags, try stripping them.
+    if (!selectorId.IsValid()) {
+      selPriv = aSelectorValue.LowerCaseFindASCII("-x-");
+      if (selPriv >= 0) {
+        nsAutoCString temp(aSelectorValue);
+        temp.Truncate(selPriv);
+        // Also do the wildcard replacement if necessary.
+        if (wildcard) {
+          temp.Replace(0, 1, "und");
+        }
+        selectorId.Reset(temp);
+        if (!selectorId.IsValid()) {
+          return false;
+        }
+        if (wildcard) {
+          intl::ffi::unic_langid_clear_language(selectorId);
+        }
+      } else {
+        return false;
+      }
+    }
+  }
+
+  if (!intl::ffi::unic_langid_matches(attrLangId, selectorId,
+                                      /* match addrLangId as range */ false,
+                                      /* match selectorId as range */ true)) {
+    return false;
+  }
+
+  // If the selector included private subtags, we also require them to match.
+  // However, if the attribute has private subtags but the selector doesn't,
+  // they are ignored; the selector still matches the (non-private) subtags in
+  // the attribute.
+  if (selPriv >= 0) {
+    if (attrPriv < 0) {
+      return false;
+    }
+    return Substring(aAttributeValue, attrPriv)
+        .EqualsIgnoreCase(Substring(aSelectorValue, selPriv));
+  }
+
+  return true;
 }
 
 bool nsStyleUtil::ValueIncludes(const nsAString& aValueList,