1 files changed, 112 insertions, 0 deletions
diff --git a/editor/libeditor/JoinNodesTransaction.h b/editor/libeditor/JoinNodesTransaction.h
new file mode 100644
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+++ b/editor/libeditor/JoinNodesTransaction.h
@@ -0,0 +1,112 @@
+/* -*- 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 JoinNodesTransaction_h
+#define JoinNodesTransaction_h
+
+#include "EditTransactionBase.h"  // for EditTransactionBase, etc.
+
+#include "EditorDOMPoint.h"  // for EditorDOMPoint, etc.
+#include "EditorForwards.h"
+
+#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 {
+
+/**
+ * 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 JoinNodesTransaction final : public EditTransactionBase {
+ protected:
+  JoinNodesTransaction(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<JoinNodesTransaction> 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(JoinNodesTransaction,
+                                           EditTransactionBase)
+  NS_IMETHOD QueryInterface(REFNSIID aIID, void** aInstancePtr) override;
+
+  NS_DECL_EDITTRANSACTIONBASE
+  NS_DECL_EDITTRANSACTIONBASE_GETASMETHODS_OVERRIDE(JoinNodesTransaction)
+
+  MOZ_CAN_RUN_SCRIPT NS_IMETHOD RedoTransaction() override;
+
+  // Note that we don't support join/split node direction switching per
+  // transaction.
+  [[nodiscard]] SplitNodeDirection GetSplitNodeDirection() const;
+  [[nodiscard]] JoinNodesDirection GetJoinNodesDirection() const;
+
+  /**
+   * GetExistingContent() and GetRemovedContent() never returns nullptr
+   * unless the cycle collector clears them out.
+   */
+  nsIContent* GetExistingContent() const { return mKeepingContent; }
+  nsIContent* GetRemovedContent() const { return mRemovedContent; }
+  nsINode* GetParentNode() const { return mParentNode; }
+
+  template <typename EditorDOMPointType>
+  EditorDOMPointType CreateJoinedPoint() const {
+    if (MOZ_UNLIKELY(!mKeepingContent)) {
+      return EditorDOMPointType();
+    }
+    return EditorDOMPointType(
+        mKeepingContent, std::min(mJoinedOffset, mKeepingContent->Length()));
+  }
+
+  friend std::ostream& operator<<(std::ostream& aStream,
+                                  const JoinNodesTransaction& aTransaction);
+
+ protected:
+  virtual ~JoinNodesTransaction() = default;
+
+  enum class RedoingTransaction { No, Yes };
+  MOZ_CAN_RUN_SCRIPT nsresult DoTransactionInternal(RedoingTransaction);
+
+  RefPtr<HTMLEditor> mHTMLEditor;
+
+  // The original parent of the left/right nodes.
+  nsCOMPtr<nsINode> mParentNode;
+
+  // Removed content after joined.
+  nsCOMPtr<nsIContent> mRemovedContent;
+
+  // The keeping content node which contains ex-children of mRemovedContent.
+  nsCOMPtr<nsIContent> mKeepingContent;
+
+  // Offset where the original first content is in mKeepingContent after
+  // doing or redoing.
+  uint32_t mJoinedOffset = 0u;
+};
+
+}  // namespace mozilla
+
+#endif  // #ifndef JoinNodesTransaction_h