Bug 1755604: Add Accessible::IsBefore/IsAncestorOf. r=eeejay

Differential Revision: https://phabricator.services.mozilla.com/D138743

accessible/base/TextLeafRange.cpp

@@ -375,39 +375,7 @@ bool TextLeafPoint::operator<(const TextLeafPoint& aPoint) const {
   if (mAcc == aPoint.mAcc) {
     return mOffset < aPoint.mOffset;
   }
-
-  // Build the chain of parents.
-  Accessible* thisP = mAcc;
-  Accessible* otherP = aPoint.mAcc;
-  AutoTArray<Accessible*, 30> thisParents, otherParents;
-  do {
-    thisParents.AppendElement(thisP);
-    thisP = thisP->Parent();
-  } while (thisP);
-  do {
-    otherParents.AppendElement(otherP);
-    otherP = otherP->Parent();
-  } while (otherP);
-
-  // Find where the parent chain differs.
-  uint32_t thisPos = thisParents.Length(), otherPos = otherParents.Length();
-  for (uint32_t len = std::min(thisPos, otherPos); len > 0; --len) {
-    Accessible* thisChild = thisParents.ElementAt(--thisPos);
-    Accessible* otherChild = otherParents.ElementAt(--otherPos);
-    if (thisChild != otherChild) {
-      return thisChild->IndexInParent() < otherChild->IndexInParent();
-    }
-  }
-
-  // If the ancestries are the same length (both thisPos and otherPos are 0),
-  // we should have returned by now.
-  MOZ_ASSERT(thisPos != 0 || otherPos != 0);
-  // At this point, one of the ancestries is a superset of the other, so one of
-  // thisPos or otherPos should be 0.
-  MOZ_ASSERT(thisPos != otherPos);
-  // If the other Accessible is deeper than this one (otherPos > 0), this
-  // Accessible comes before the other.
-  return otherPos > 0;
+  return mAcc->IsBefore(aPoint.mAcc);
 }
 
 bool TextLeafPoint::IsEmptyLastLine() const {

accessible/basetypes/Accessible.cpp

@@ -33,6 +33,41 @@ void Accessible::StaticAsserts() const {
       "Accessible::mGenericType was oversized by eLastAccGenericType!");
 }
 
+bool Accessible::IsBefore(const Accessible* aAcc) const {
+  // Build the chain of parents.
+  const Accessible* thisP = this;
+  const Accessible* otherP = aAcc;
+  AutoTArray<const Accessible*, 30> thisParents, otherParents;
+  do {
+    thisParents.AppendElement(thisP);
+    thisP = thisP->Parent();
+  } while (thisP);
+  do {
+    otherParents.AppendElement(otherP);
+    otherP = otherP->Parent();
+  } while (otherP);
+
+  // Find where the parent chain differs.
+  uint32_t thisPos = thisParents.Length(), otherPos = otherParents.Length();
+  for (uint32_t len = std::min(thisPos, otherPos); len > 0; --len) {
+    const Accessible* thisChild = thisParents.ElementAt(--thisPos);
+    const Accessible* otherChild = otherParents.ElementAt(--otherPos);
+    if (thisChild != otherChild) {
+      return thisChild->IndexInParent() < otherChild->IndexInParent();
+    }
+  }
+
+  // If the ancestries are the same length (both thisPos and otherPos are 0),
+  // we should have returned by now.
+  MOZ_ASSERT(thisPos != 0 || otherPos != 0);
+  // At this point, one of the ancestries is a superset of the other, so one of
+  // thisPos or otherPos should be 0.
+  MOZ_ASSERT(thisPos != otherPos);
+  // If the other Accessible is deeper than this one (otherPos > 0), this
+  // Accessible comes before the other.
+  return otherPos > 0;
+}
+
 const nsRoleMapEntry* Accessible::ARIARoleMap() const {
   return aria::GetRoleMapFromIndex(mRoleMapEntryIndex);
 }

accessible/basetypes/Accessible.h

@@ -101,6 +101,21 @@ class Accessible {
     return childCount ? ChildAt(childCount - 1) : nullptr;
   }
 
+  /**
+   * Return true if this Accessible is before another Accessible in the tree.
+   */
+  bool IsBefore(const Accessible* aAcc) const;
+
+  bool IsAncestorOf(const Accessible* aAcc) const {
+    for (const Accessible* parent = aAcc->Parent(); parent;
+         parent = parent->Parent()) {
+      if (parent == this) {
+        return true;
+      }
+    }
+    return false;
+  }
+
   /**
    * Used by ChildAtPoint() method to get direct or deepest child at point.
    */