1 files changed, 98 insertions, 0 deletions
diff --git a/accessible/base/Relation.h b/accessible/base/Relation.h
new file mode 100644
index 0000000000..7b7f521eaf
--- /dev/null
+++ b/accessible/base/Relation.h
@@ -0,0 +1,98 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_a11y_relation_h_
+#define mozilla_a11y_relation_h_
+
+#include "AccIterator.h"
+
+#include <memory>
+
+namespace mozilla {
+namespace a11y {
+
+/**
+ * A collection of relation targets of a certain type.  Targets are computed
+ * lazily while enumerating.
+ */
+class Relation {
+ public:
+  Relation() : mFirstIter(nullptr), mLastIter(nullptr) {}
+
+  explicit Relation(AccIterable* aIter) : mFirstIter(aIter), mLastIter(aIter) {}
+
+  explicit Relation(Accessible* aAcc)
+      : mFirstIter(nullptr), mLastIter(nullptr) {
+    AppendTarget(aAcc);
+  }
+
+  Relation(DocAccessible* aDocument, nsIContent* aContent)
+      : mFirstIter(nullptr), mLastIter(nullptr) {
+    AppendTarget(aDocument, aContent);
+  }
+
+  Relation(Relation&& aOther)
+      : mFirstIter(std::move(aOther.mFirstIter)), mLastIter(aOther.mLastIter) {
+    aOther.mLastIter = nullptr;
+  }
+
+  Relation& operator=(Relation&& aRH) {
+    mFirstIter = std::move(aRH.mFirstIter);
+    mLastIter = aRH.mLastIter;
+    aRH.mLastIter = nullptr;
+    return *this;
+  }
+
+  inline void AppendIter(AccIterable* aIter) {
+    if (mLastIter)
+      mLastIter->mNextIter.reset(aIter);
+    else
+      mFirstIter.reset(aIter);
+
+    mLastIter = aIter;
+  }
+
+  /**
+   * Append the given accessible to the set of related accessibles.
+   */
+  inline void AppendTarget(Accessible* aAcc) {
+    if (aAcc) AppendIter(new SingleAccIterator(aAcc));
+  }
+
+  /**
+   * Append the one accessible for this content node to the set of related
+   * accessibles.
+   */
+  void AppendTarget(DocAccessible* aDocument, nsIContent* aContent) {
+    if (aContent) AppendTarget(aDocument->GetAccessible(aContent));
+  }
+
+  /**
+   * compute and return the next related accessible.
+   */
+  inline Accessible* Next() {
+    Accessible* target = nullptr;
+
+    while (mFirstIter && !(target = mFirstIter->Next()))
+      mFirstIter = std::move(mFirstIter->mNextIter);
+
+    if (!mFirstIter) mLastIter = nullptr;
+
+    return target;
+  }
+
+ private:
+  Relation& operator=(const Relation&) = delete;
+  Relation(const Relation&) = delete;
+
+  std::unique_ptr<AccIterable> mFirstIter;
+  AccIterable* mLastIter;
+};
+
+}  // namespace a11y
+}  // namespace mozilla
+
+#endif