From a69e82b0d7d0617ba1e02257bb92491cafe9470a Mon Sep 17 00:00:00 2001
From: FranklinDM <mrmineshafter17@gmail.com>
Date: Sat, 4 Mar 2023 02:23:31 +0800
Subject: Issue #2135 - Bug 1413102 (Follow-up): Ignore current target because
 of shadow DOM retargeting

Based on https://bugzilla.mozilla.org/show_bug.cgi?id=1466581
---
 dom/base/FragmentOrElement.cpp |  4 ++--
 dom/events/EventDispatcher.cpp |  7 ++++++-
 dom/events/EventDispatcher.h   | 11 ++++++++++-
 3 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/dom/base/FragmentOrElement.cpp b/dom/base/FragmentOrElement.cpp
index 7f287cb58d..412031f98a 100644
--- a/dom/base/FragmentOrElement.cpp
+++ b/dom/base/FragmentOrElement.cpp
@@ -991,7 +991,7 @@ nsIContent::GetEventTargetParent(EventChainPreVisitor& aVisitor)
             // Step 4.
             // "If target is relatedTarget and target is not event's
             //  relatedTarget, then return true."
-            aVisitor.IgnoreCurrentTarget();
+            aVisitor.IgnoreCurrentTargetBecauseOfShadowDOMRetargeting();
             // Old code relies on mTarget to point to the first element which
             // was not added to the event target chain because of mCanHandle
             // being false, but in Shadow DOM case mTarget really should
@@ -1030,7 +1030,7 @@ nsIContent::GetEventTargetParent(EventChainPreVisitor& aVisitor)
             // Step 11.5
             // "Otherwise, if parent and relatedTarget are identical, then set
             //  parent to null."
-            aVisitor.IgnoreCurrentTarget();
+            aVisitor.IgnoreCurrentTargetBecauseOfShadowDOMRetargeting();
             // Old code relies on mTarget to point to the first element which
             // was not added to the event target chain because of mCanHandle
             // being false, but in Shadow DOM case mTarget really should
diff --git a/dom/events/EventDispatcher.cpp b/dom/events/EventDispatcher.cpp
index 9a48ca2a90..e2b5699241 100644
--- a/dom/events/EventDispatcher.cpp
+++ b/dom/events/EventDispatcher.cpp
@@ -872,6 +872,7 @@ EventDispatcher::Dispatch(nsISupports* aTarget,
         preVisitor.mTargetInKnownToBeHandledScope = preVisitor.mEvent->mTarget;
         topEtci = parentEtci;
       } else {
+        bool ignoreBecauseOfShadowDOM = preVisitor.mIgnoreBecauseOfShadowDOM;
         nsCOMPtr<nsINode> disabledTarget = do_QueryInterface(parentTarget);
         parentEtci = MayRetargetToChromeIfCanNotHandleEvent(chain,
                                                             preVisitor,
@@ -882,7 +883,11 @@ EventDispatcher::Dispatch(nsISupports* aTarget,
           preVisitor.mTargetInKnownToBeHandledScope = preVisitor.mEvent->mTarget;
           EventTargetChainItem* item =
             EventTargetChainItem::GetFirstCanHandleEventTarget(chain);
-          item->SetNewTarget(parentTarget);
+          if (!ignoreBecauseOfShadowDOM) {
+            // If we ignored the target because of Shadow DOM retargeting, we
+            // shouldn't treat the target to be in the event path at all.
+            item->SetNewTarget(parentTarget);
+          }
           topEtci = parentEtci;
           continue;
         }
diff --git a/dom/events/EventDispatcher.h b/dom/events/EventDispatcher.h
index 529240d0ac..403c472c5c 100644
--- a/dom/events/EventDispatcher.h
+++ b/dom/events/EventDispatcher.h
@@ -128,6 +128,7 @@ public:
     , mParentIsSlotInClosedTree(false)
     , mParentIsChromeHandler(false)
     , mRelatedTargetRetargetedInCurrentScope(false)
+    , mIgnoreBecauseOfShadowDOM(false)
     , mParentTarget(nullptr)
     , mEventTargetAtParent(nullptr)
     , mRetargetedRelatedTarget(nullptr)
@@ -151,6 +152,7 @@ public:
     // Note, we don't clear mRelatedTargetRetargetedInCurrentScope explicitly,
     // since it is used during event path creation to indicate whether
     // relatedTarget may need to be retargeted.
+    mIgnoreBecauseOfShadowDOM = false;
     mParentTarget = nullptr;
     mEventTargetAtParent = nullptr;
     mRetargetedRelatedTarget = nullptr;
@@ -169,9 +171,10 @@ public:
     }
   }
 
-  void IgnoreCurrentTarget()
+  void IgnoreCurrentTargetBecauseOfShadowDOMRetargeting()
   {
     mCanHandle = false;
+    mIgnoreBecauseOfShadowDOM = true;
     SetParentTarget(nullptr, false);
     mEventTargetAtParent = nullptr;
   }
@@ -251,6 +254,12 @@ public:
    */
   bool mRelatedTargetRetargetedInCurrentScope;
 
+  /**
+   * True if Shadow DOM relatedTarget retargeting causes the current item
+   * to not show up in the event path.
+   */
+  bool mIgnoreBecauseOfShadowDOM;
+
 private:
   /**
    * Parent item in the event target chain.
-- 
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