From ba5d192b11ac08f921f22fa181578268c0a85da4 Mon Sep 17 00:00:00 2001
From: Masayuki Nakano <masayuki@d-toybox.com>
Date: Mon, 7 Nov 2022 02:33:35 +0000
Subject: [PATCH] Bug 1798214 - Make
 `HTMLeditor::AdjustCaretPositionAndEnsurePaddingBRElement` invalidate child
 after inserting `<br>` element of the insertion point r=m_kato

It keeps using the insertion point after inserting `<br>` element for making
empty last line visible. Therefore, referring `IsStartOfContainer` in
`HTMLEditUtils::GetPreviousContent` causes the warning of mismating offset
and child node.

According to the old code [1], `HTMLEditRules` keeps scanning the DOM tree with
the offset of the insertion point.  Therefore, it should invalidate the child
after inserting `<br>` element.

1. https://searchfox.org/mozilla-central/rev/7b5f4b93ca3e96f9fb9b5793b58080c1e44bd4f6/editor/libeditor/HTMLEditRules.cpp#7606,7631

Differential Revision: https://phabricator.services.mozilla.com/D161246
---
 editor/libeditor/HTMLEditSubActionHandler.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/editor/libeditor/HTMLEditSubActionHandler.cpp b/editor/libeditor/HTMLEditSubActionHandler.cpp
index d0b174d8cded..c73fb09612b0 100644
--- a/editor/libeditor/HTMLEditSubActionHandler.cpp
+++ b/editor/libeditor/HTMLEditSubActionHandler.cpp
@@ -9431,6 +9431,7 @@ nsresult HTMLEditor::AdjustCaretPositionAndEnsurePaddingBRElement(
       if (HTMLEditUtils::IsInvisibleBRElement(*previousEditableContent) &&
           !EditorUtils::IsPaddingBRElementForEmptyLastLine(
               *previousEditableContent)) {
+        AutoEditorDOMPointChildInvalidator lockOffset(point);
         Result<CreateElementResult, nsresult> insertPaddingBRElementResult =
             InsertPaddingBRElementForEmptyLastLineWithTransaction(point);
         if (MOZ_UNLIKELY(insertPaddingBRElementResult.isErr())) {