commit e787eae82043d0ad011ca6b5f1691ebe4faf5158
parent 1e94bab72bde8214b27fc3cd45d2a814d77a555d
Author: Emilio Cobos Álvarez <emilio@crisal.io>
Date: Fri, 14 Nov 2025 01:36:02 +0000
Bug 1958206 - Allow subgrids to be containing blocks again. r=TYLin,layout-reviewers
Instead, ensure we end up with a reasonable containing block reflow
input for subgrid to avoid regressing the parent.
Differential Revision: https://phabricator.services.mozilla.com/D272370
Diffstat:
4 files changed, 63 insertions(+), 16 deletions(-)
diff --git a/layout/generic/ReflowInput.cpp b/layout/generic/ReflowInput.cpp
@@ -603,29 +603,23 @@ static bool MightBeContainingBlockFor(nsIFrame* aMaybeContainingBlock,
}
void ReflowInput::InitCBReflowInput() {
- if (!mParentReflowInput) {
- mCBReflowInput = nullptr;
+ mCBReflowInput = mParentReflowInput;
+ if (!mCBReflowInput || mParentReflowInput->mFlags.mDummyParentReflowInput) {
return;
}
- if (mParentReflowInput->mFlags.mDummyParentReflowInput) {
- mCBReflowInput = mParentReflowInput;
- return;
- }
-
// To avoid a long walk up the frame tree check if the parent frame can be a
// containing block for mFrame.
- if (MightBeContainingBlockFor(mParentReflowInput->mFrame, mFrame,
+ if (MightBeContainingBlockFor(mCBReflowInput->mFrame, mFrame,
mStyleDisplay) &&
- mParentReflowInput->mFrame ==
- mFrame->GetContainingBlock(0, mStyleDisplay)) {
+ mCBReflowInput->mFrame == mFrame->GetContainingBlock(0, mStyleDisplay)) {
// Inner table frames need to use the containing block of the outer
// table frame.
if (mFrame->IsTableFrame()) {
+ MOZ_ASSERT(mParentReflowInput->mCBReflowInput,
+ "Inner table frames shouldn't be reflow roots");
mCBReflowInput = mParentReflowInput->mCBReflowInput;
- } else {
- mCBReflowInput = mParentReflowInput;
}
- } else {
+ } else if (mParentReflowInput->mCBReflowInput) {
mCBReflowInput = mParentReflowInput->mCBReflowInput;
}
}
diff --git a/layout/generic/nsIFrame.cpp b/layout/generic/nsIFrame.cpp
@@ -8681,9 +8681,8 @@ bool nsIFrame::IsBlockContainer() const {
//
// If we ever start skipping table row groups from being containing blocks,
// you need to remove the StickyScrollContainer hack referencing bug 1421660.
- return !IsLineParticipant() && !IsBlockWrapper() && !IsSubgrid() &&
- // Table rows are not containing blocks either
- !IsTableRowFrame();
+ // Table rows are not containing blocks either
+ return !IsLineParticipant() && !IsBlockWrapper() && !IsTableRowFrame();
}
nsIFrame* nsIFrame::GetContainingBlock(
diff --git a/testing/web-platform/tests/css/css-grid/subgrid/sticky-subgrid-item-ref.html b/testing/web-platform/tests/css/css-grid/subgrid/sticky-subgrid-item-ref.html
@@ -0,0 +1,11 @@
+<!doctype html>
+<meta charset="utf-8">
+<title>sticky inside subgrid</title>
+<style>
+body { margin: 0 }
+div {
+ border: 10px solid orange;
+ height: 400px;
+}
+</style>
+<div></div>
diff --git a/testing/web-platform/tests/css/css-grid/subgrid/sticky-subgrid-item.html b/testing/web-platform/tests/css/css-grid/subgrid/sticky-subgrid-item.html
@@ -0,0 +1,43 @@
+<!doctype html>
+<meta charset="utf-8">
+<title>sticky inside subgrid</title>
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1958206">
+<link rel="help" href="https://drafts.csswg.org/css-grid-2">
+<link rel="author" href="mailto:emilio@crisal.io" title="Emilio Cobos Álvarez">
+<link rel="author" href="https://mozilla.com" title="Mozilla">
+<link rel="match" href="sticky-subgrid-item-ref.html">
+<style>
+:root { scrollbar-width: none }
+body { margin: 0 }
+.grid {
+ display: grid;
+ grid-template-columns: 1fr;
+ margin-bottom: 100vh;
+}
+
+.subgrid {
+ border: 10px solid orange;
+ display: grid;
+ grid-template-columns: subgrid;
+ height: 400px;
+ margin-bottom: 100px;
+}
+
+.sticky {
+ background: red;
+ position: sticky;
+ top: 10px;
+ height: 200px;
+}
+</style>
+<div class="grid">
+ <div class="subgrid">
+ <div class="sticky">
+ This should not be visible.
+ </div>
+ </div>
+ <div class="subgrid" id="target"></div>
+</div>
+<script>
+ target.scrollIntoView({ block: "start" });
+</script>
