Bug 1730096 part 1: Add AccAttributes::Equal to compare attributes in two instances. r=eeejay

This will be used later to check whether text attributes are different between two Accessibles.
I added this as a method instead of operator== because callers always hold a pointer to AccAttributes, and *a1 == *a2 is weird and will probably lead to mistakes.
This required adding operator== for our value structs.

Differential Revision: https://phabricator.services.mozilla.com/D129467

accessible/base/AccAttributes.cpp

@@ -71,3 +71,27 @@ void AccAttributes::Update(AccAttributes* aOther) {
     iter.Remove();
   }
 }
+
+bool AccAttributes::Equal(const AccAttributes* aOther) const {
+  if (Count() != aOther->Count()) {
+    return false;
+  }
+  for (auto iter = mData.ConstIter(); !iter.Done(); iter.Next()) {
+    const auto otherEntry = aOther->mData.Lookup(iter.Key());
+    if (iter.Data().is<UniquePtr<nsString>>()) {
+      // Because we store nsString in a UniquePtr, we must handle it specially
+      // so we compare the string and not the pointer.
+      if (!otherEntry->is<UniquePtr<nsString>>()) {
+        return false;
+      }
+      const auto& thisStr = iter.Data().as<UniquePtr<nsString>>();
+      const auto& otherStr = otherEntry->as<UniquePtr<nsString>>();
+      if (*thisStr != *otherStr) {
+        return false;
+      }
+    } else if (!otherEntry || iter.Data() != otherEntry.Data()) {
+      return false;
+    }
+  }
+  return true;
+}

accessible/base/AccAttributes.h

@@ -29,10 +29,22 @@ namespace a11y {
 
 struct FontSize {
   int32_t mValue;
+
+  bool operator==(const FontSize& aOther) const {
+    return mValue == aOther.mValue;
+  }
+
+  bool operator!=(const FontSize& aOther) const {
+    return mValue != aOther.mValue;
+  }
 };
 
 struct Color {
   nscolor mValue;
+
+  bool operator==(const Color& aOther) const { return mValue == aOther.mValue; }
+
+  bool operator!=(const Color& aOther) const { return mValue != aOther.mValue; }
 };
 
 // A special type. If an entry has a value of this type, it instructs the
@@ -40,6 +52,10 @@ struct Color {
 struct DeleteEntry {
   DeleteEntry() : mValue(true) {}
   bool mValue;
+
+  bool operator==(const DeleteEntry& aOther) const { return true; }
+
+  bool operator!=(const DeleteEntry& aOther) const { return false; }
 };
 
 class AccAttributes {
@@ -112,6 +128,12 @@ class AccAttributes {
   // will be emptied.
   void Update(AccAttributes* aOther);
 
+  /**
+   * Return true if all the attributes in this instance are equal to all the
+   * attributes in another instance.
+   */
+  bool Equal(const AccAttributes* aOther) const;
+
   // An entry class for our iterator.
   class Entry {
    public: