From 9a071f3b7af7461168e0b80cdea8f4ff7f64780b Mon Sep 17 00:00:00 2001
From: FranklinDM <mrmineshafter17@gmail.com>
Date: Sun, 19 Mar 2023 23:43:34 +0800
Subject: [PATCH] Issue #1592 - Part 9: Post a restyle event after changing the
 slot of a slottable

---
 dom/base/ShadowRoot.cpp | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/dom/base/ShadowRoot.cpp b/dom/base/ShadowRoot.cpp
index d432c96e41..8482da5e99 100644
--- a/dom/base/ShadowRoot.cpp
+++ b/dom/base/ShadowRoot.cpp
@@ -9,6 +9,7 @@
 #include "mozilla/dom/DocumentFragment.h"
 #include "ChildIterator.h"
 #include "nsContentUtils.h"
+#include "nsLayoutUtils.h"
 #include "nsDOMClassInfoID.h"
 #include "nsIDOMHTMLElement.h"
 #include "nsIStyleSheetLinkingElement.h"
@@ -162,6 +163,16 @@ ShadowRoot::AddSlot(HTMLSlotElement* aSlot)
 
       oldSlot->RemoveAssignedNode(assignedNode);
       currentSlot->AppendAssignedNode(assignedNode);
+      Element* restyleElement;
+      if (assignedNode->IsElement()) {
+        restyleElement = assignedNode->AsElement();
+      } else {
+        // This is likely a text node. Use the host instead.
+        restyleElement = GetHost();
+      }
+      nsLayoutUtils::PostRestyleEvent(
+        restyleElement, eRestyle_Subtree, nsChangeHint(0));
+
       doEnqueueSlotChange = true;
     }