tor-browser

commit eade387da45eb7b220989935c9b587b2cf4d2141
parent bd367a8e2912a1d7e436676a545241551390c494
Author: Timothy Nikkel <tnikkel@gmail.com>
Date:   Fri, 14 Nov 2025 14:19:16 +0000

Bug 1999697. If we are "creating" an ASR for the second time during a paint, assert that we aren't changing any fields. r=layout-reviewers,emilio

When the anchor pos code gets the ASR for the anchor it will cause a second call to these functions. We want to make sure that we aren't changing ASR the second time as that would indicate a problem.

Differential Revision: https://phabricator.services.mozilla.com/D272250

Diffstat:
M
layout/painting/nsDisplayList.cpp
 | 
54
+++++++++++++++++++++++++++++++++++++++++++++++++-----
M
layout/painting/nsDisplayList.h
 | 
14
++++++++++++--

2 files changed, 61 insertions(+), 7 deletions(-)
diff --git a/layout/painting/nsDisplayList.cpp b/layout/painting/nsDisplayList.cpp
@@ -168,10 +168,27 @@ void InitializeHitTestInfo(nsDisplayListBuilder* aBuilder,
 /* static */
 already_AddRefed<ActiveScrolledRoot> ActiveScrolledRoot::CreateASRForFrame(
     const ActiveScrolledRoot* aParent,
-    ScrollContainerFrame* aScrollContainerFrame) {
+    ScrollContainerFrame* aScrollContainerFrame
+#ifdef DEBUG
+    ,
+    const nsTArray<RefPtr<ActiveScrolledRoot>>& aActiveScrolledRoots
+#endif
+) {
   RefPtr<ActiveScrolledRoot> asr =
       aScrollContainerFrame->GetProperty(ActiveScrolledRootCache());
 
+#ifdef DEBUG
+  if (asr && aActiveScrolledRoots.Contains(asr)) {
+    // This is the second time we are "creating" this ASR in this paint. Assert
+    // that we aren't changing any of the values. (The values can change
+    // *between* paints, but not during one paint.)
+    MOZ_ASSERT(asr->mParent == aParent);
+    MOZ_ASSERT(asr->mFrame == aScrollContainerFrame);
+    MOZ_ASSERT(asr->mKind == ASRKind::Scroll);
+    MOZ_ASSERT(asr->mDepth == (aParent ? aParent->mDepth + 1 : 1));
+  }
+#endif
+
   if (!asr) {
     asr = new ActiveScrolledRoot();
 
@@ -189,13 +206,30 @@ already_AddRefed<ActiveScrolledRoot> ActiveScrolledRoot::CreateASRForFrame(
 
 /* static */
 already_AddRefed<ActiveScrolledRoot>
-ActiveScrolledRoot::CreateASRForStickyFrame(const ActiveScrolledRoot* aParent,
-                                            nsIFrame* aStickyFrame) {
+ActiveScrolledRoot::CreateASRForStickyFrame(
+    const ActiveScrolledRoot* aParent, nsIFrame* aStickyFrame
+#ifdef DEBUG
+    ,
+    const nsTArray<RefPtr<ActiveScrolledRoot>>& aActiveScrolledRoots
+#endif
+) {
   aStickyFrame = aStickyFrame->FirstContinuation();
 
   RefPtr<ActiveScrolledRoot> asr =
       aStickyFrame->GetProperty(StickyActiveScrolledRootCache());
 
+#ifdef DEBUG
+  if (asr && aActiveScrolledRoots.Contains(asr)) {
+    // This is the second time we are "creating" this ASR in this paint. Assert
+    // that we aren't changing any of the values. (The values can change
+    // *between* paints, but not during one paint.)
+    MOZ_ASSERT(asr->mParent == aParent);
+    MOZ_ASSERT(asr->mFrame == aStickyFrame);
+    MOZ_ASSERT(asr->mKind == ASRKind::Sticky);
+    MOZ_ASSERT(asr->mDepth == (aParent ? aParent->mDepth + 1 : 1));
+  }
+#endif
+
   if (!asr) {
     asr = new ActiveScrolledRoot();
 
@@ -1507,7 +1541,12 @@ ActiveScrolledRoot* nsDisplayListBuilder::AllocateActiveScrolledRoot(
     const ActiveScrolledRoot* aParent,
     ScrollContainerFrame* aScrollContainerFrame) {
   RefPtr<ActiveScrolledRoot> asr =
-      ActiveScrolledRoot::CreateASRForFrame(aParent, aScrollContainerFrame);
+      ActiveScrolledRoot::CreateASRForFrame(aParent, aScrollContainerFrame
+#ifdef DEBUG
+                                            ,
+                                            mActiveScrolledRoots
+#endif
+      );
   mActiveScrolledRoots.AppendElement(asr);
   return asr;
 }
@@ -1515,7 +1554,12 @@ ActiveScrolledRoot* nsDisplayListBuilder::AllocateActiveScrolledRoot(
 ActiveScrolledRoot* nsDisplayListBuilder::AllocateActiveScrolledRootForSticky(
     const ActiveScrolledRoot* aParent, nsIFrame* aStickyFrame) {
   RefPtr<ActiveScrolledRoot> asr =
-      ActiveScrolledRoot::CreateASRForStickyFrame(aParent, aStickyFrame);
+      ActiveScrolledRoot::CreateASRForStickyFrame(aParent, aStickyFrame
+#ifdef DEBUG
+                                                  ,
+                                                  mActiveScrolledRoots
+#endif
+      );
   mActiveScrolledRoots.AppendElement(asr);
   return asr;
 }
diff --git a/layout/painting/nsDisplayList.h b/layout/painting/nsDisplayList.h
@@ -187,9 +187,19 @@ struct ActiveScrolledRoot {
   // TODO: Just have one function with an extra ASRKind parameter
   static already_AddRefed<ActiveScrolledRoot> CreateASRForFrame(
       const ActiveScrolledRoot* aParent,
-      ScrollContainerFrame* aScrollContainerFrame);
+      ScrollContainerFrame* aScrollContainerFrame
+#ifdef DEBUG
+      ,
+      const nsTArray<RefPtr<ActiveScrolledRoot>>& aActiveScrolledRoots
+#endif
+  );
   static already_AddRefed<ActiveScrolledRoot> CreateASRForStickyFrame(
-      const ActiveScrolledRoot* aParent, nsIFrame* aStickyFrame);
+      const ActiveScrolledRoot* aParent, nsIFrame* aStickyFrame
+#ifdef DEBUG
+      ,
+      const nsTArray<RefPtr<ActiveScrolledRoot>>& aActiveScrolledRoots
+#endif
+  );
 
   static const ActiveScrolledRoot* PickAncestor(
       const ActiveScrolledRoot* aOne, const ActiveScrolledRoot* aTwo) {