Bug 1792387 - part 3-1: Make `HTMLEditor::DoSplitNode()` adjust selection for both split node directions r=m_kato

This patch adds new path to adjust selection for the new split node direction.
So this does not change any behavior of the existing path.

Differential Revision: https://phabricator.services.mozilla.com/D158100

editor/libeditor/HTMLEditor.cpp

@@ -4853,7 +4853,8 @@ SplitNodeResult HTMLEditor::SplitNodeDeepWithTransaction(
 }
 
 SplitNodeResult HTMLEditor::DoSplitNode(const EditorDOMPoint& aStartOfRightNode,
-                                        nsIContent& aNewNode) {
+                                        nsIContent& aNewNode,
+                                        SplitNodeDirection aDirection) {
   // Ensure computing the offset if it's intialized with a child content node.
   Unused << aStartOfRightNode.Offset();
 
@@ -4999,30 +5000,45 @@ SplitNodeResult HTMLEditor::DoSplitNode(const EditorDOMPoint& aStartOfRightNode,
       continue;
     }
 
-    // Split the selection into existing node and new node.
-    if (savedRange.mStartContainer == aStartOfRightNode.GetContainer()) {
-      if (savedRange.mStartOffset < aStartOfRightNode.Offset()) {
-        savedRange.mStartContainer = &aNewNode;
-      } else if (savedRange.mStartOffset >= aStartOfRightNode.Offset()) {
-        savedRange.mStartOffset -= aStartOfRightNode.Offset();
-      } else {
-        NS_WARNING(
-            "The stored start offset was smaller than the right node offset");
-        savedRange.mStartOffset = 0u;
+    auto AdjustDOMPoint = [&](nsCOMPtr<nsINode>& aContainer,
+                              uint32_t& aOffset) {
+      if (aContainer != aStartOfRightNode.GetContainer()) {
+        return;
       }
-    }
 
-    if (savedRange.mEndContainer == aStartOfRightNode.GetContainer()) {
-      if (savedRange.mEndOffset < aStartOfRightNode.Offset()) {
-        savedRange.mEndContainer = &aNewNode;
-      } else if (savedRange.mEndOffset >= aStartOfRightNode.Offset()) {
-        savedRange.mEndOffset -= aStartOfRightNode.Offset();
-      } else {
-        NS_WARNING(
-            "The stored end offset was smaller than the right node offset");
-        savedRange.mEndOffset = 0u;
+      if (aDirection == SplitNodeDirection::LeftNodeIsNewOne) {
+        // If the container is the right node and offset is before the split
+        // point, the content was moved into aNewNode.  So, just changing the
+        // container will point proper position.
+        if (aOffset < aStartOfRightNode.Offset()) {
+          aContainer = &aNewNode;
+          return;
+        }
+
+        // If the container is the right node and offset equals or is larger
+        // than the split point, we need to decrease the offset since some
+        // content before the split point was moved to aNewNode.
+        if (aOffset >= aStartOfRightNode.Offset()) {
+          aOffset -= aStartOfRightNode.Offset();
+          return;
+        }
+
+        NS_WARNING("The stored offset was smaller than the right node offset");
+        aOffset = 0u;
+        return;
       }
-    }
+
+      // If the container is the left node and offset is after the split
+      // point, the content was moved from the right node to aNewNode.
+      // So, we need to change the container to aNewNode and decrease the
+      // offset.
+      if (aOffset >= aStartOfRightNode.Offset()) {
+        aContainer = &aNewNode;
+        aOffset -= aStartOfRightNode.Offset();
+      }
+    };
+    AdjustDOMPoint(savedRange.mStartContainer, savedRange.mStartOffset);
+    AdjustDOMPoint(savedRange.mEndContainer, savedRange.mEndOffset);
 
     RefPtr<nsRange> newRange =
         nsRange::Create(savedRange.mStartContainer, savedRange.mStartOffset,
@@ -5066,12 +5082,12 @@ SplitNodeResult HTMLEditor::DoSplitNode(const EditorDOMPoint& aStartOfRightNode,
 
   DebugOnly<nsresult> rvIgnored = RangeUpdaterRef().SelAdjSplitNode(
       *aStartOfRightNode.ContainerAs<nsIContent>(), aStartOfRightNode.Offset(),
-      aNewNode, GetSplitNodeDirection());
+      aNewNode, aDirection);
   NS_WARNING_ASSERTION(NS_SUCCEEDED(rvIgnored),
                        "RangeUpdater::SelAdjSplitNode() failed, but ignored");
 
   return SplitNodeResult(aNewNode, *aStartOfRightNode.ContainerAs<nsIContent>(),
-                         GetSplitNodeDirection());
+                         aDirection);
 }
 
 JoinNodesResult HTMLEditor::JoinNodesWithTransaction(

editor/libeditor/HTMLEditor.h

@@ -978,20 +978,20 @@ class HTMLEditor final : public EditorBase,
   [[nodiscard]] MOZ_CAN_RUN_SCRIPT nsresult OnModifyDocument();
 
   /**
-   * DoSplitNode() inserts aNewNode (left node before the container of
-   * aStartOfRightNode (right node), and moves all content before
+   * DoSplitNode() inserts aNewNode and moves all content before or after
    * aStartOfRightNode to aNewNode.
    *
-   * @param aStartOfRightNode   The point to split.  Its container will be
-   *                            the right node, i.e., becomes aNewNode's
-   *                            next sibling.  And the point will be start
-   *                            of the right node.
-   * @param aNewNode            The new node called as left node, so, this
-   *                            becomes the container of all previous content
-   *                            before aPointToSplit.
+   * @param aStartOfRightNode   The point to split.  The container will keep
+   *                            having following or previous content of this.
+   * @param aNewNode            The new node called.  The previous or following
+   *                            content of aStartOfRightNode will be moved into
+   *                            this node.
+   * @param aDirection          Whether aNewNode will have previous or following
+   *                            content of aStartOfRightNode.
    */
   MOZ_CAN_RUN_SCRIPT SplitNodeResult
-  DoSplitNode(const EditorDOMPoint& aStartOfRightNode, nsIContent& aNewNode);
+  DoSplitNode(const EditorDOMPoint& aStartOfRightNode, nsIContent& aNewNode,
+              SplitNodeDirection aDirection);
 
   /**
    * DoJoinNodes() merges contents in aContentToRemove to aContentToKeep and

editor/libeditor/JoinNodesTransaction.cpp

@@ -177,7 +177,7 @@ NS_IMETHODIMP JoinNodesTransaction::UndoTransaction() {
   const SplitNodeResult splitNodeResult = htmlEditor->DoSplitNode(
       EditorDOMPoint(mKeepingContent,
                      std::min(mJoinedOffset, mKeepingContent->Length())),
-      removedContent);
+      removedContent, GetSplitNodeDirection());
   NS_WARNING_ASSERTION(splitNodeResult.isOk(),
                        "HTMLEditor::DoSplitNode() failed");
   // When adding caret suggestion to SplitNodeResult, here didn't change

editor/libeditor/SelectionState.cpp

@@ -334,7 +334,7 @@ nsresult RangeUpdater::SelAdjSplitNode(nsIContent& aOriginalContent,
       }
     } else if (aOffset >= aSplitOffset) {
       aContainer = &aNewContent;
-      aOffset = aSplitOffset - aOffset;
+      aOffset -= aSplitOffset;
     }
   };
 

editor/libeditor/SplitNodeTransaction.cpp

@@ -154,7 +154,7 @@ SplitNodeResult SplitNodeTransaction::DoTransactionInternal(
   SplitNodeResult splitNodeResult = aHTMLEditor.DoSplitNode(
       EditorDOMPoint(&aSplittingContent,
                      std::min(aSplitOffset, aSplittingContent.Length())),
-      aNewContent);
+      aNewContent, GetSplitNodeDirection());
   NS_WARNING_ASSERTION(splitNodeResult.isOk(),
                        "HTMLEditor::DoSplitNode() failed");
   // When adding caret suggestion to SplitNodeResult, here didn't change