From 3ba0b10bb48450351343ad8c6e0d32a759e25d6a Mon Sep 17 00:00:00 2001
From: Francis Dominic Fajardo <fofajardo@up.edu.ph>
Date: Thu, 26 Jun 2025 21:15:50 +0800
Subject: [PATCH] Issue #2765 - Part 3: Make scrollbar width checks use the
 originating non-NAC style context

---
 layout/generic/nsGfxScrollFrame.cpp | 4 +++-
 widget/windows/nsNativeThemeWin.cpp | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/layout/generic/nsGfxScrollFrame.cpp b/layout/generic/nsGfxScrollFrame.cpp
index e718315731..6197cf94c3 100644
--- a/layout/generic/nsGfxScrollFrame.cpp
+++ b/layout/generic/nsGfxScrollFrame.cpp
@@ -1058,7 +1058,9 @@ nsHTMLScrollFrame::Reflow(nsPresContext* aPresContext,
     // This is only needed for root element because scrollbars of non-
     // root elements with "scrollbar-width: none" is already suppressed
     // in ScrollFrameHelper::CreateAnonymousContent.
-    if (this->StyleUIReset()->mScrollbarWidth == StyleScrollbarWidth::None) {
+    nsStyleContext* scrollbarStyle = nsLayoutUtils::GetNonAnonymousStyleContext(this);
+    auto scrollbarWidth = scrollbarStyle->StyleUIReset()->mScrollbarWidth;
+    if (scrollbarWidth == StyleScrollbarWidth::None) {
       state.mVScrollbar = ShowScrollbar::Never;
       state.mHScrollbar = ShowScrollbar::Never;
     }
diff --git a/widget/windows/nsNativeThemeWin.cpp b/widget/windows/nsNativeThemeWin.cpp
index 5aab75de26..3250fec5c9 100644
--- a/widget/windows/nsNativeThemeWin.cpp
+++ b/widget/windows/nsNativeThemeWin.cpp
@@ -1572,7 +1572,9 @@ GetThemeDpiScaleFactor(nsIFrame* aFrame)
 static bool
 IsScrollbarWidthThin(nsIFrame* aFrame)
 {
-  return aFrame->StyleUIReset()->mScrollbarWidth == StyleScrollbarWidth::Thin;
+  nsStyleContext* styleContext = nsLayoutUtils::GetNonAnonymousStyleContext(aFrame);
+  auto scrollbarWidth = styleContext->StyleUIReset()->mScrollbarWidth;
+  return scrollbarWidth == StyleScrollbarWidth::Thin;
 }
 
 NS_IMETHODIMP