issue #1547 - Correct z-ordering for some table parts and add reftests

1 files changed, 5 insertions, 2 deletions

diff --git a/layout/tables/nsTableWrapperFrame.cpp b/layout/tables/nsTableWrapperFrame.cpp
index 476024e96..86f032218 100644
--- a/layout/tables/nsTableWrapperFrame.cpp
+++ b/layout/tables/nsTableWrapperFrame.cpp
@@ -187,8 +187,11 @@ nsTableWrapperFrame::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
   BuildDisplayListForChild(aBuilder, mCaptionFrames.FirstChild(), captionSet);
 
   // Now we have to sort everything by content order, since the caption
-  // may be somewhere inside the table
-  set.BlockBorderBackgrounds()->SortByContentOrder(GetContent());
+  // may be somewhere inside the table.
+  // We don't sort BlockBorderBackgrounds and BorderBackgrounds because the
+  // display items in those lists should stay out of content order in order to
+  // follow the rules in https://www.w3.org/TR/CSS21/zindex.html#painting-order
+  // and paint the caption background after all of the rest.
   set.Floats()->SortByContentOrder(GetContent());
   set.Content()->SortByContentOrder(GetContent());
   set.PositionedDescendants()->SortByContentOrder(GetContent());