Issue mcp-graveyard/UXP%146 - Part 5: Treat table row groups as containing blocks.

This aligns our behavior with Gecko/Blink.

2 files changed, 11 insertions, 0 deletions

diff --git a/layout/generic/StickyScrollContainer.cpp b/layout/generic/StickyScrollContainer.cpp
index ca68992c3..ff8ebcfef 100644
--- a/layout/generic/StickyScrollContainer.cpp
+++ b/layout/generic/StickyScrollContainer.cpp
@@ -176,6 +176,14 @@ StickyScrollContainer::ComputeStickyLimits(nsIFrame* aFrame, nsRect* aStick,
   nsRect rect =
     nsLayoutUtils::GetAllInFlowRectsUnion(aFrame, aFrame->GetParent());
 
+  // Note: Table row groups aren't supposed to be containing blocks, but we treat
+  // them as such anyway.
+  // Not having this basically disables position:sticky on table cells, which
+  // would be really unfortunate, and doesn't match what other browsers do.
+  if (cbFrame != scrolledFrame && cbFrame->GetType() == nsGkAtoms::tableRowGroupFrame) {
+    cbFrame = cbFrame->GetContainingBlock();
+  }
+
   // Containing block limits for the position of aFrame relative to its parent.
   // The margin box of the sticky element stays within the content box of the
   // contaning-block element.
diff --git a/layout/generic/nsFrame.cpp b/layout/generic/nsFrame.cpp
index a531dea07..d4bcf22ed 100644
--- a/layout/generic/nsFrame.cpp
+++ b/layout/generic/nsFrame.cpp
@@ -6629,6 +6629,9 @@ GetNearestBlockContainer(nsIFrame* frame)
   // Since the parent of such a block is either a normal block or
   // another such pseudo, this shouldn't cause anything bad to happen.
   // Also the anonymous blocks inside table cells are not containing blocks.
+  //
+  // If we ever start skipping table row groups from being containing blocks,
+  // we need to remove the containing block assignment in StickyScrollContainer .
   while (frame->IsFrameOfType(nsIFrame::eLineParticipant) ||
          frame->IsBlockWrapper() ||
          // Table rows are not containing blocks either