Bug 2002340 - Store class attribute as array of nsAtoms. r=Jamie

DOM class names are meant to be repeated in elements. Therefore, this
should be an array of atoms. DOM's nsAttrValue stores them like this as
well.

Differential Revision: https://phabricator.services.mozilla.com/D274629

accessible/base/AccAttributes.cpp

@@ -119,6 +119,20 @@ void AccAttributes::StringFromValueAndName(nsAtom* aAttrName,
       },
       [&aValueString](const WritingMode& val) {
         aValueString.AppendPrintf("WritingModes: %x", val.GetBits());
+      },
+      [&aValueString](const nsTArray<RefPtr<nsAtom>>& val) {
+        if (const size_t len = val.Length()) {
+          for (size_t i = 0; i < len - 1; i++) {
+            aValueString.Append(val[i]->GetUTF16String());
+            aValueString.Append(u" ");
+          }
+          aValueString.Append(val[len - 1]->GetUTF16String());
+        } else {
+          // The array is empty
+          NS_WARNING(
+              "Hmm, should we have used a DeleteEntry() for this instead?");
+          aValueString.Append(u"");
+        }
       });
 }
 
@@ -255,6 +269,11 @@ void AccAttributes::CopyTo(AccAttributes* aDest, bool aOnlyMissing) const {
         },
         [&iter, &aDest](const WritingMode& val) {
           aDest->mData.InsertOrUpdate(iter.Key(), AsVariant(val));
+        },
+        [](const nsTArray<RefPtr<nsAtom>>& val) {
+          // We don't copy arrays.
+          MOZ_ASSERT_UNREACHABLE(
+              "Trying to copy an AccAttributes containing an array");
         });
   }
 }
@@ -301,6 +320,9 @@ size_t AccAttributes::Entry::SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) {
   } else if (mValue->is<nsTArray<uint64_t>>()) {
     size += mValue->as<nsTArray<uint64_t>>().ShallowSizeOfExcludingThis(
         aMallocSizeOf);
+  } else if (mValue->is<nsTArray<RefPtr<nsAtom>>>()) {
+    size += mValue->as<nsTArray<RefPtr<nsAtom>>>().ShallowSizeOfExcludingThis(
+        aMallocSizeOf);
   } else {
     // This type is stored directly and already counted or is an atom and
     // stored and counted in the atoms table.

accessible/base/AccAttributes.h

@@ -108,7 +108,8 @@ class AccAttributes {
               CSSCoord, FontSize, Color, DeleteEntry, UniquePtr<nsString>,
               RefPtr<AccAttributes>, uint64_t, UniquePtr<AccGroupInfo>,
               UniquePtr<gfx::Matrix4x4>, nsTArray<uint64_t>,
-              nsTArray<TextOffsetAttribute>, WritingMode>;
+              nsTArray<TextOffsetAttribute>, WritingMode,
+              nsTArray<RefPtr<nsAtom>>>;
   static_assert(sizeof(AttrValueType) <= 16);
   using AtomVariantMap = nsTHashMap<RefPtr<nsAtom>, AttrValueType>;
 
@@ -197,7 +198,8 @@ class AccAttributes {
   template <typename T>
   Maybe<T&> GetMutableAttribute(nsAtom* aAttrName) const {
     static_assert(std::is_same_v<nsTArray<int32_t>, T> ||
-                      std::is_same_v<nsTArray<uint64_t>, T>,
+                      std::is_same_v<nsTArray<uint64_t>, T> ||
+                      std::is_same_v<nsTArray<RefPtr<nsAtom>>, T>,
                   "Only arrays should be mutable attributes");
     if (auto value = mData.Lookup(aAttrName)) {
       if (value->is<T>()) {

accessible/generic/LocalAccessible.cpp

@@ -3922,12 +3922,19 @@ already_AddRefed<AccAttributes> LocalAccessible::BundleFieldsForCache(
     } else if (IsUpdatePush(CacheDomain::DOMNodeIDAndClass)) {
       fields->SetAttribute(CacheKey::DOMNodeID, DeleteEntry());
     }
-    nsString className;
-    DOMNodeClass(className);
-    if (!className.IsEmpty()) {
-      fields->SetAttribute(CacheKey::DOMNodeClass, std::move(className));
-    } else if (IsUpdatePush(CacheDomain::DOMNodeIDAndClass)) {
-      fields->SetAttribute(CacheKey::DOMNodeClass, DeleteEntry());
+
+    if (dom::Element* el = Elm()) {
+      nsTArray<RefPtr<nsAtom>> classes;
+      if (const nsAttrValue* attr = el->GetClasses()) {
+        for (uint32_t i = 0; i < attr->GetAtomCount(); i++) {
+          classes.AppendElement(attr->AtomAt(i));
+        }
+      }
+      if (!classes.IsEmpty()) {
+        fields->SetAttribute(CacheKey::DOMNodeClass, std::move(classes));
+      } else if (IsUpdatePush(CacheDomain::DOMNodeIDAndClass)) {
+        fields->SetAttribute(CacheKey::DOMNodeClass, DeleteEntry());
+      }
     }
   }