1 files changed, 78 insertions, 0 deletions
diff --git a/editor/libeditor/JoinNodeTransaction.h b/editor/libeditor/JoinNodeTransaction.h
new file mode 100644
index 0000000000..db86b91411
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+++ b/editor/libeditor/JoinNodeTransaction.h
@@ -0,0 +1,78 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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 JoinNodeTransaction_h
+#define JoinNodeTransaction_h
+
+#include "mozilla/EditTransactionBase.h"  // for EditTransactionBase, etc.
+#include "nsCOMPtr.h"                     // for nsCOMPtr
+#include "nsCycleCollectionParticipant.h"
+#include "nsID.h"    // for REFNSIID
+#include "nscore.h"  // for NS_IMETHOD
+
+class nsIContent;
+class nsINode;
+
+namespace mozilla {
+
+class HTMLEditor;
+
+/**
+ * A transaction that joins two nodes E1 (left node) and E2 (right node) into a
+ * single node E.  The children of E are the children of E1 followed by the
+ * children of E2.  After DoTransaction() and RedoTransaction(), E1 is removed
+ * from the content tree and E2 remains.
+ */
+class JoinNodeTransaction final : public EditTransactionBase {
+ protected:
+  JoinNodeTransaction(HTMLEditor& aHTMLEditor, nsIContent& aLeftContent,
+                      nsIContent& aRightContent);
+
+ public:
+  /**
+   * Creates a join node transaction.  This returns nullptr if cannot join the
+   * nodes.
+   *
+   * @param aHTMLEditor     The provider of core editing operations.
+   * @param aLeftContent    The first of two nodes to join.
+   * @param aRightContent   The second of two nodes to join.
+   */
+  static already_AddRefed<JoinNodeTransaction> MaybeCreate(
+      HTMLEditor& aHTMLEditor, nsIContent& aLeftContent,
+      nsIContent& aRightContent);
+
+  /**
+   * CanDoIt() returns true if there are enough members and can join or
+   * restore the nodes.  Otherwise, false.
+   */
+  bool CanDoIt() const;
+
+  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(JoinNodeTransaction,
+                                           EditTransactionBase)
+  NS_IMETHOD QueryInterface(REFNSIID aIID, void** aInstancePtr) override;
+
+  NS_DECL_EDITTRANSACTIONBASE
+  NS_DECL_EDITTRANSACTIONBASE_GETASMETHODS_OVERRIDE(JoinNodeTransaction)
+
+ protected:
+  RefPtr<HTMLEditor> mHTMLEditor;
+
+  // The nodes to operate upon.  After the merge, mRightContent remains and
+  // mLeftContent is removed from the content tree.
+  nsCOMPtr<nsIContent> mLeftContent;
+  nsCOMPtr<nsIContent> mRightContent;
+
+  // The offset into mNode where the children of mElement are split (for
+  // undo). mOffset is the index of the first child in the right node.  -1
+  // means the left node had no children.
+  uint32_t mOffset;
+
+  // The parent node containing mLeftContent and mRightContent.
+  nsCOMPtr<nsINode> mParentNode;
+};
+
+}  // namespace mozilla
+
+#endif  // #ifndef JoinNodeTransaction_h