Bug 1569252 Part 2 - Let mHasColumnSpanSiblings propagate to all the continuations. r=dbaron

We want mHasColumnSpanSiblings to propagate to all the
continuations (both fixed ones or fluid ones) in nsFrame::Init() so that
we don't need to traverse all the way to FirstInFlow() for the bit in
nsBlockFrame::ComputeFinalBSize().

For the last ColumnSet or the last non-column-span wrapper, we'll need
to unset the bit for them manually after constructing them.

Differential Revision: https://phabricator.services.mozilla.com/D40761

--HG--
extra : moz-landing-system : lando

layout/base/nsCSSFrameConstructor.cpp

@@ -10785,11 +10785,13 @@ void nsCSSFrameConstructor::FinishBuildingColumns(
                  prevColumnSet->GetParent() == aColumnSetWrapper,
              "Should have established column hierarchy!");
 
+  // Tag the first ColumnSet to have column-span siblings so that the bit can
+  // propagate to all the continuations. We don't want the last ColumnSet to
+  // have this bit, so we will unset the bit for it at the end of this function.
+  prevColumnSet->SetHasColumnSpanSiblings(true);
+
   nsFrameList finalList;
   while (aColumnContentSiblings.NotEmpty()) {
-    // Tag every ColumnSet except the last one.
-    prevColumnSet->SetHasColumnSpanSiblings(true);
-
     nsIFrame* f = aColumnContentSiblings.RemoveFirstChild();
     if (f->IsColumnSpan()) {
       // Do nothing for column-span wrappers. Just move it to the final
@@ -10799,6 +10801,9 @@ void nsCSSFrameConstructor::FinishBuildingColumns(
       auto* continuingColumnSet = static_cast<nsContainerFrame*>(
           CreateContinuingFrame(mPresShell->GetPresContext(), prevColumnSet,
                                 aColumnSetWrapper, false));
+      MOZ_ASSERT(continuingColumnSet->HasColumnSpanSiblings(),
+                 "The bit should propagate to the next continuation!");
+
       f->SetParent(continuingColumnSet);
       SetInitialSingleChild(continuingColumnSet, f);
       finalList.AppendFrame(aColumnSetWrapper, continuingColumnSet);
@@ -10806,6 +10811,9 @@ void nsCSSFrameConstructor::FinishBuildingColumns(
     }
   }
 
+  // Unset the bit because the last ColumnSet has no column-span siblings.
+  prevColumnSet->SetHasColumnSpanSiblings(false);
+
   aColumnSetWrapper->AppendFrames(kPrincipalList, finalList);
 }
 
@@ -10843,14 +10851,17 @@ nsFrameList nsCSSFrameConstructor::CreateColumnSpanSiblings(
 
   nsFrameList siblings;
   nsContainerFrame* lastNonColumnSpanWrapper = aInitialBlock;
+
+  // Tag the first non-column-span wrapper to have column-span siblings so that
+  // the bit can propagate to all the continuations. We don't want the last
+  // wrapper to have this bit, so we will unset the bit for it at the end of
+  // this function.
+  lastNonColumnSpanWrapper->SetHasColumnSpanSiblings(true);
   do {
     MOZ_ASSERT(aChildList.NotEmpty(), "Why call this if child list is empty?");
     MOZ_ASSERT(aChildList.FirstChild()->IsColumnSpan(),
                "Must have the child starting with column-span!");
 
-    // Tag every non-column-span wrapper except the last one.
-    lastNonColumnSpanWrapper->SetHasColumnSpanSiblings(true);
-
     // Grab the consecutive column-span kids, and reparent them into a
     // block frame.
     RefPtr<ComputedStyle> columnSpanWrapperStyle =
@@ -10879,6 +10890,8 @@ nsFrameList nsCSSFrameConstructor::CreateColumnSpanSiblings(
                               lastNonColumnSpanWrapper, parentFrame, false));
     nonColumnSpanWrapper->AddStateBits(NS_FRAME_HAS_MULTI_COLUMN_ANCESTOR |
                                        NS_FRAME_CAN_HAVE_ABSPOS_CHILDREN);
+    MOZ_ASSERT(nonColumnSpanWrapper->HasColumnSpanSiblings(),
+               "The bit should propagate to the next continuation!");
 
     if (aChildList.NotEmpty()) {
       nsFrameList nonColumnSpanKids =
@@ -10897,6 +10910,10 @@ nsFrameList nsCSSFrameConstructor::CreateColumnSpanSiblings(
     lastNonColumnSpanWrapper = nonColumnSpanWrapper;
   } while (aChildList.NotEmpty());
 
+  // Unset the bit because the last non-column-span wrapper has no column-span
+  // siblings.
+  lastNonColumnSpanWrapper->SetHasColumnSpanSiblings(false);
+
   return siblings;
 }
 

layout/generic/nsBlockFrame.cpp

@@ -7427,7 +7427,7 @@ nscoord nsBlockFrame::ComputeFinalBSize(const ReflowInput& aReflowInput,
     return finalBSize;
   }
 
-  if (FirstInFlow()->HasColumnSpanSiblings()) {
+  if (HasColumnSpanSiblings()) {
     MOZ_ASSERT(LastInFlow()->GetNextContinuation(),
                "Frame constructor should've created column-span siblings!");
 

layout/generic/nsFrame.cpp

@@ -630,6 +630,9 @@ void nsFrame::Init(nsIContent* aContent, nsContainerFrame* aParent,
                   NS_FRAME_MAY_BE_TRANSFORMED |
                   NS_FRAME_HAS_MULTI_COLUMN_ANCESTOR));
     // clang-format on
+
+    // Copy other bits in nsIFrame from prev-in-flow.
+    mHasColumnSpanSiblings = aPrevInFlow->HasColumnSpanSiblings();
   } else {
     PresContext()->ConstructedFrame();
   }