tor-browser

commit d92b01bce062eb01a32599393d62fc625652f725
parent cfcfba76dec6d8785a9d50903d3f0d95d2aea206
Author: David Shin <dshin@mozilla.com>
Date:   Fri,  7 Nov 2025 17:57:07 +0000

Bug 1996832: Check margin rect of abspos frame for overflowing. r=layout-anchor-positioning-reviewers,layout-reviewers,emilio

Differential Revision: https://phabricator.services.mozilla.com/D271231

Diffstat:
M
layout/base/AnchorPositioningUtils.cpp
 | 
38
+++++++++++++++++++++++++++++++++-----
M
layout/base/AnchorPositioningUtils.h
 | 
22
+++++++++++++++++++---
M
layout/base/PresShell.cpp
 | 
11
+++++------
M
layout/generic/AbsoluteContainingBlock.cpp
 | 
5
+++--

4 files changed, 60 insertions(+), 16 deletions(-)
diff --git a/layout/base/AnchorPositioningUtils.cpp b/layout/base/AnchorPositioningUtils.cpp
@@ -822,12 +822,40 @@ const nsIFrame* AnchorPositioningUtils::GetAnchorPosImplicitAnchor(
              : pseudoRootFrame->GetParent();
 }
 
+AnchorPositioningUtils::ContainingBlockInfo
+AnchorPositioningUtils::ContainingBlockInfo::ExplicitCBFrameSize(
+    const nsRect& aContainingBlockRect) {
+  // TODO(dshin, bug 1989292): Ideally, this takes both local containing rect +
+  // scrollable containing rect, and one is picked here.
+  return ContainingBlockInfo{aContainingBlockRect};
+}
+
+AnchorPositioningUtils::ContainingBlockInfo
+AnchorPositioningUtils::ContainingBlockInfo::UseCBFrameSize(
+    const nsIFrame* aPositioned) {
+  // TODO(dshin, bug 1989292): This just gets local containing block.
+  const auto* cb = aPositioned->GetParent();
+  MOZ_ASSERT(cb);
+  if (cb->Style()->GetPseudoType() == PseudoStyleType::scrolledContent) {
+    cb = aPositioned->GetParent();
+  }
+  return ContainingBlockInfo{cb->GetPaddingRectRelativeToSelf()};
+}
+
 bool AnchorPositioningUtils::FitsInContainingBlock(
-    const nsRect& aOverflowCheckRect,
-    const nsRect& aOriginalContainingBlockSize, const nsRect& aRect) {
-  return aOverflowCheckRect.Intersect(aOriginalContainingBlockSize)
-      .Union(aOriginalContainingBlockSize)
-      .Contains(aRect);
+    const ContainingBlockInfo& aContainingBlockInfo,
+    const nsIFrame* aPositioned, const AnchorPosReferenceData* aReferenceData) {
+  MOZ_ASSERT(aPositioned->GetProperty(nsIFrame::AnchorPosReferences()) ==
+             aReferenceData);
+  const auto originalContainingBlockRect =
+      aContainingBlockInfo.GetContainingBlockRect();
+  const auto overflowCheckRect = aReferenceData->mContainingBlockRect -
+                                 aReferenceData->mDefaultScrollShift;
+  const auto rect = aPositioned->GetMarginRect();
+
+  return overflowCheckRect.Intersect(originalContainingBlockRect)
+      .Union(originalContainingBlockRect)
+      .Contains(rect);
 }
 
 }  // namespace mozilla
diff --git a/layout/base/AnchorPositioningUtils.h b/layout/base/AnchorPositioningUtils.h
@@ -291,9 +291,25 @@ struct AnchorPositioningUtils {
       PhysicalAxes aAxes, const nsIFrame* aPositioned,
       const AnchorPosDefaultAnchorCache& aDefaultAnchorCache);
 
-  static bool FitsInContainingBlock(const nsRect& aOverflowCheckRect,
-                                    const nsRect& aOriginalContainingBlockSize,
-                                    const nsRect& aRect);
+  struct ContainingBlockInfo {
+    // Provide an explicit containing block size, for during reflow when
+    // its `mRect` has not yet been set.
+    static ContainingBlockInfo ExplicitCBFrameSize(
+        const nsRect& aContainingBlockRect);
+    // Provide the positioned frame, to query  its containing block rect.
+    static ContainingBlockInfo UseCBFrameSize(const nsIFrame* aPositioned);
+
+    nsRect GetContainingBlockRect() const { return mRect; }
+
+   private:
+    explicit ContainingBlockInfo(const nsRect& aRect) : mRect{aRect} {}
+    nsRect mRect;
+  };
+
+  static bool FitsInContainingBlock(
+      const ContainingBlockInfo& aContainingBlockInfo,
+      const nsIFrame* aPositioned,
+      const AnchorPosReferenceData* aReferenceData);
 };
 
 }  // namespace mozilla
diff --git a/layout/base/PresShell.cpp b/layout/base/PresShell.cpp
@@ -11901,7 +11901,7 @@ static Maybe<FindScrollCompensatedAnchorResult> FindScrollCompensatedAnchor(
   return Nothing{};
 }
 
-static bool CheckOverflow(nsIFrame* aPositioned, const nsPoint& aOffset,
+static bool CheckOverflow(nsIFrame* aPositioned,
                           const AnchorPosReferenceData& aData) {
   const auto* stylePos = aPositioned->StylePosition();
   const auto hasFallbacks = !stylePos->mPositionTryFallbacks._0.IsEmpty();
@@ -11910,11 +11910,10 @@ static bool CheckOverflow(nsIFrame* aPositioned, const nsPoint& aOffset,
   if (!hasFallbacks && !visibilityDependsOnOverflow) {
     return false;
   }
-  const auto* cb = aPositioned->GetParent();
-  MOZ_ASSERT(cb);
   const auto overflows = !AnchorPositioningUtils::FitsInContainingBlock(
-      aData.mContainingBlockRect - aOffset, cb->GetPaddingRect(),
-      aPositioned->GetRect());
+      AnchorPositioningUtils::ContainingBlockInfo{
+          static_cast<const nsIFrame*>(aPositioned->GetParent())},
+      aPositioned, &aData);
   aPositioned->AddOrRemoveStateBits(NS_FRAME_POSITION_VISIBILITY_HIDDEN,
                                     visibilityDependsOnOverflow && overflows);
   return hasFallbacks && overflows;
@@ -11958,7 +11957,7 @@ void PresShell::UpdateAnchorPosForScroll(
       nsContainerFrame::PlaceFrameView(positioned);
       positioned->GetParent()->UpdateOverflow();
       referenceData.mDefaultScrollShift = offset;
-      if (CheckOverflow(positioned, offset, referenceData)) {
+      if (CheckOverflow(positioned, referenceData)) {
 #ifdef ACCESSIBILITY
         if (nsAccessibilityService* accService = GetAccService()) {
           accService->NotifyAnchorPositionedScrollUpdate(this, positioned);
diff --git a/layout/generic/AbsoluteContainingBlock.cpp b/layout/generic/AbsoluteContainingBlock.cpp
@@ -1439,8 +1439,9 @@ void AbsoluteContainingBlock::ReflowAbsoluteFrame(
         aAnchorPosResolutionCache->mReferenceData->mContainingBlockRect =
             overflowCheckRect;
         return AnchorPositioningUtils::FitsInContainingBlock(
-            overflowCheckRect, aOriginalContainingBlockRect,
-            aKidFrame->GetRect());
+            AnchorPositioningUtils::ContainingBlockInfo::ExplicitCBFrameSize(
+                aOriginalContainingBlockRect),
+            aKidFrame, aAnchorPosResolutionCache->mReferenceData);
       }
       return overflowCheckRect.Contains(aKidFrame->GetRect());
     }();