tor-browser

commit 97ef6bc71f79bce9f26f1076f8df1667a07a577f
parent e83327ce2280e6c0f44f1ec4a752c91aaedc99ff
Author: Botond Ballo <botond@mozilla.com>
Date:   Thu, 13 Nov 2025 04:59:04 +0000

Bug 1730749 - Use a distinct frame property for sticky ASRs. r=mstange

A frame can be both a scroll frame and sticky, in which case it has
two associated ASRs. Using distinct frame properties allows retaining
information about both.

Differential Revision: https://phabricator.services.mozilla.com/D254148

Diffstat:
M
layout/painting/nsDisplayList.cpp
 | 
9
++++++---
M
layout/painting/nsDisplayList.h
 | 
5
+++++

2 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/layout/painting/nsDisplayList.cpp b/layout/painting/nsDisplayList.cpp
@@ -200,7 +200,7 @@ ActiveScrolledRoot::CreateASRForStickyFrame(const ActiveScrolledRoot* aParent,
                                             bool aIsRetained) {
   RefPtr<ActiveScrolledRoot> asr;
   if (aIsRetained) {
-    asr = aStickyFrame->GetProperty(ActiveScrolledRootCache());
+    asr = aStickyFrame->GetProperty(StickyActiveScrolledRootCache());
   }
 
   if (!asr) {
@@ -208,7 +208,8 @@ ActiveScrolledRoot::CreateASRForStickyFrame(const ActiveScrolledRoot* aParent,
 
     if (aIsRetained) {
       RefPtr<ActiveScrolledRoot> ref = asr;
-      aStickyFrame->SetProperty(ActiveScrolledRootCache(), ref.forget().take());
+      aStickyFrame->SetProperty(StickyActiveScrolledRootCache(),
+                                ref.forget().take());
     }
   }
 
@@ -311,7 +312,9 @@ ScrollableLayerGuid::ViewID ActiveScrolledRoot::ComputeViewId() const {
 
 ActiveScrolledRoot::~ActiveScrolledRoot() {
   if (mFrame && mRetained) {
-    mFrame->RemoveProperty(ActiveScrolledRootCache());
+    mFrame->RemoveProperty(mKind == ASRKind::Sticky
+                               ? StickyActiveScrolledRootCache()
+                               : ActiveScrolledRootCache());
   }
 }
 
diff --git a/layout/painting/nsDisplayList.h b/layout/painting/nsDisplayList.h
@@ -260,6 +260,11 @@ struct ActiveScrolledRoot {
   }
   NS_DECLARE_FRAME_PROPERTY_WITH_DTOR(ActiveScrolledRootCache,
                                       ActiveScrolledRoot, DetachASR)
+  // We need a distinct frame property for storing the sticky ASR,
+  // because a single frame could be both a scroll frame and position:sticky
+  // and thus have two associated ASRs.
+  NS_DECLARE_FRAME_PROPERTY_WITH_DTOR(StickyActiveScrolledRootCache,
+                                      ActiveScrolledRoot, DetachASR)
 
   static uint32_t Depth(const ActiveScrolledRoot* aActiveScrolledRoot) {
     return aActiveScrolledRoot ? aActiveScrolledRoot->mDepth : 0;