Bug 1765615 - Introduce NS_BLOCK_DYNAMIC_BFC state bit. r=layout-reviewers,emilio

After D198523, NS_BLOCK_FLOAT_MGR and NS_BLOCK_MARGIN_ROOT are always
set simultaneously when initiating a frame, so we can merge them into a
single NS_BLOCK_STATIC_BFC flag. The freed bit is used to define a new
NS_BLOCK_DYNAMIC_BFC flag that has the same effect and is now used for
frames with paint/layout containment so that in D197043 they can be
updated later without having to reconstruct the frame tree. Finally
NS_BLOCK_BFC_STATE_BITS is the bitwise union of these BFC flags.

The following changes are made and cause no behavior changes:

- Instead of testing whether NS_BLOCK_FLOAT_MGR or NS_BLOCK_MARGIN_ROOT
  is set, or whether all of the bits from
  NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS are set, we test whether any
  of the NS_BLOCK_BFC_STATE_BITS is set.

- Instead of adding NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS when
  constructing a frame, we add NS_BLOCK_STATIC_BFC. The exception is
  for frame with paint/layout containment, for which we set
  NS_BLOCK_DYNAMIC_BFC instead.

Differential Revision: https://phabricator.services.mozilla.com/D198530

layout/base/nsCSSFrameConstructor.cpp

@@ -320,7 +320,7 @@ static bool ShouldSuppressColumnSpanDescendants(nsIFrame* aFrame) {
   }
 
   if (!aFrame->IsBlockFrameOrSubclass() ||
-      aFrame->HasAnyStateBits(NS_BLOCK_FLOAT_MGR | NS_FRAME_OUT_OF_FLOW) ||
+      aFrame->HasAnyStateBits(NS_BLOCK_BFC_STATE_BITS | NS_FRAME_OUT_OF_FLOW) ||
       aFrame->IsFixedPosContainingBlock()) {
     // Need to suppress column-span if we:
     // - Are a different block formatting context,
@@ -4602,7 +4602,7 @@ nsIFrame* nsCSSFrameConstructor::ConstructNonScrollableBlock(
        aDisplay->DisplayInside() == StyleDisplayInside::FlowRoot ||
        clipPaginatedOverflow) &&
       !aParentFrame->IsInSVGTextSubtree()) {
-    flags = NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS;
+    flags = NS_BLOCK_STATIC_BFC;
     if (clipPaginatedOverflow) {
       flags |= NS_BLOCK_CLIP_PAGINATED_OVERFLOW;
     }
@@ -10738,7 +10738,7 @@ nsBlockFrame* nsCSSFrameConstructor::BeginBuildingColumns(
   aColumnContent->SetComputedStyleWithoutNotification(blockStyle);
   InitAndRestoreFrame(aState, aContent, columnSet, aColumnContent);
   aColumnContent->AddStateBits(NS_FRAME_HAS_MULTI_COLUMN_ANCESTOR |
-                               NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS);
+                               NS_BLOCK_STATIC_BFC);
 
   // Set up the parent-child chain.
   SetInitialSingleChild(columnSetWrapper, columnSet);

layout/forms/nsComboboxControlFrame.cpp

@@ -82,7 +82,7 @@ nsComboboxControlFrame* NS_NewComboboxControlFrame(PresShell* aPresShell,
       nsComboboxControlFrame(aStyle, aPresShell->GetPresContext());
 
   if (it) {
-    it->AddStateBits(NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS);
+    it->AddStateBits(NS_BLOCK_STATIC_BFC);
   }
 
   return it;

layout/forms/nsFieldSetFrame.cpp

@@ -788,7 +788,7 @@ void nsFieldSetFrame::SetInitialChildList(ChildListID aListID,
   if (nsBlockFrame* legend = do_QueryFrame(GetLegend())) {
     // A rendered legend always establish a new formatting context.
     // https://html.spec.whatwg.org/multipage/rendering.html#rendered-legend
-    legend->AddStateBits(NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS);
+    legend->AddStateBits(NS_BLOCK_STATIC_BFC);
   }
   MOZ_ASSERT(
       aListID != FrameChildListID::Principal || GetInner() || GetLegend(),
@@ -819,7 +819,7 @@ void nsFieldSetFrame::InsertFrames(ChildListID aListID, nsIFrame* aPrevFrame,
   if (nsBlockFrame* legend = do_QueryFrame(GetLegend())) {
     // A rendered legend always establish a new formatting context.
     // https://html.spec.whatwg.org/multipage/rendering.html#rendered-legend
-    legend->AddStateBits(NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS);
+    legend->AddStateBits(NS_BLOCK_STATIC_BFC);
   }
 }
 

layout/forms/nsFileControlFrame.cpp

@@ -49,7 +49,7 @@ NS_IMPL_FRAMEARENA_HELPERS(nsFileControlFrame)
 nsFileControlFrame::nsFileControlFrame(ComputedStyle* aStyle,
                                        nsPresContext* aPresContext)
     : nsBlockFrame(aStyle, aPresContext, kClassID) {
-  AddStateBits(NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS);
+  AddStateBits(NS_BLOCK_STATIC_BFC);
 }
 
 void nsFileControlFrame::Init(nsIContent* aContent, nsContainerFrame* aParent,

layout/forms/nsSelectsAreaFrame.cpp

@@ -18,9 +18,9 @@ nsContainerFrame* NS_NewSelectsAreaFrame(PresShell* aShell,
   nsSelectsAreaFrame* it =
       new (aShell) nsSelectsAreaFrame(aStyle, aShell->GetPresContext());
 
-  // We need NS_BLOCK_FLOAT_MGR to ensure that the options inside the select
+  // We need NS_BLOCK_STATIC_BFC to ensure that the options inside the select
   // aren't expanded by right floats outside the select.
-  it->AddStateBits(NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS);
+  it->AddStateBits(NS_BLOCK_STATIC_BFC);
 
   return it;
 }

layout/generic/BlockReflowState.h

@@ -41,16 +41,16 @@ class BlockReflowState {
           mCanHaveOverflowMarkers(false) {}
 
     // Set in the BlockReflowState constructor when reflowing a "block margin
-    // root" frame (i.e. a frame with the NS_BLOCK_MARGIN_ROOT flag set, for
-    // which margins apply by default).
+    // root" frame (i.e. a frame with any of the NS_BLOCK_BFC_STATE_BITS flag
+    // set, for which margins apply by default).
     //
     // The flag is also set when reflowing a frame whose computed BStart border
     // padding is non-zero.
     bool mIsBStartMarginRoot : 1;
 
     // Set in the BlockReflowState constructor when reflowing a "block margin
-    // root" frame (i.e. a frame with the NS_BLOCK_MARGIN_ROOT flag set, for
-    // which margins apply by default).
+    // root" frame (i.e. a frame with any of the NS_BLOCK_BFC_STATE_BITS flag
+    // set, for which margins apply by default).
     //
     // The flag is also set when reflowing a frame whose computed BEnd border
     // padding is non-zero.
@@ -79,7 +79,7 @@ class BlockReflowState {
     // Set when mLineAdjacentToTop is valid.
     bool mHasLineAdjacentToTop : 1;
 
-    // Set when the block has the equivalent of NS_BLOCK_FLOAT_MGR.
+    // Set when the block has the equivalent of NS_BLOCK_*_BFC.
     bool mBlockNeedsFloatManager : 1;
 
     // Set when nsLineLayout::LineIsEmpty was true at the end of reflowing

layout/generic/ColumnSetWrapperFrame.cpp

@@ -23,7 +23,7 @@ nsBlockFrame* NS_NewColumnSetWrapperFrame(PresShell* aPresShell,
   // CSS Multi-column level 1 section 2: A multi-column container
   // establishes a new block formatting context, as per CSS 2.1 section
   // 9.4.1.
-  frame->AddStateBits(aStateFlags | NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS);
+  frame->AddStateBits(aStateFlags | NS_BLOCK_STATIC_BFC);
   return frame;
 }
 

layout/generic/nsBlockFrame.cpp

@@ -92,7 +92,7 @@ static void MarkAllDescendantLinesDirty(nsBlockFrame* aBlock) {
 
 static void MarkSameFloatManagerLinesDirty(nsBlockFrame* aBlock) {
   nsBlockFrame* blockWithFloatMgr = aBlock;
-  while (!blockWithFloatMgr->HasAnyStateBits(NS_BLOCK_FLOAT_MGR)) {
+  while (!blockWithFloatMgr->HasAnyStateBits(NS_BLOCK_BFC_STATE_BITS)) {
     nsBlockFrame* bf = do_QueryFrame(blockWithFloatMgr->GetParent());
     if (!bf) {
       break;
@@ -446,7 +446,7 @@ nsBlockFrame* NS_NewBlockFrame(PresShell* aPresShell, ComputedStyle* aStyle) {
 nsBlockFrame* NS_NewBlockFormattingContext(PresShell* aPresShell,
                                            ComputedStyle* aComputedStyle) {
   nsBlockFrame* blockFrame = NS_NewBlockFrame(aPresShell, aComputedStyle);
-  blockFrame->AddStateBits(NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS);
+  blockFrame->AddStateBits(NS_BLOCK_STATIC_BFC);
   return blockFrame;
 }
 
@@ -1191,7 +1191,7 @@ static LogicalSize CalculateContainingBlockSizeForAbsolutes(
  */
 static const nsBlockFrame* GetAsLineClampDescendant(const nsIFrame* aFrame) {
   if (const nsBlockFrame* block = do_QueryFrame(aFrame)) {
-    if (!block->HasAllStateBits(NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS)) {
+    if (!block->HasAnyStateBits(NS_BLOCK_BFC_STATE_BITS)) {
       return block;
     }
   }
@@ -1208,7 +1208,7 @@ static bool IsLineClampRoot(const nsBlockFrame* aFrame) {
     return false;
   }
 
-  if (!aFrame->HasAllStateBits(NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS)) {
+  if (!aFrame->HasAnyStateBits(NS_BLOCK_BFC_STATE_BITS)) {
     return false;
   }
 
@@ -3855,7 +3855,7 @@ bool nsBlockFrame::IsSelfEmpty() {
   // Blocks which are margin-roots (including inline-blocks) cannot be treated
   // as empty for margin-collapsing and other purposes. They're more like
   // replaced elements.
-  if (HasAnyStateBits(NS_BLOCK_MARGIN_ROOT)) {
+  if (HasAnyStateBits(NS_BLOCK_BFC_STATE_BITS)) {
     return false;
   }
 
@@ -5161,7 +5161,7 @@ void nsBlockFrame::SplitFloat(BlockReflowState& aState, nsIFrame* aFloat,
   }
 
   aState.AppendPushedFloatChain(nextInFlow);
-  if (MOZ_LIKELY(!HasAnyStateBits(NS_BLOCK_FLOAT_MGR)) ||
+  if (MOZ_LIKELY(!HasAnyStateBits(NS_BLOCK_BFC_STATE_BITS)) ||
       MOZ_UNLIKELY(IsTrueOverflowContainer())) {
     aState.mReflowStatus.SetOverflowIncomplete();
   } else {
@@ -7714,10 +7714,9 @@ void nsBlockFrame::Init(nsIContent* aContent, nsContainerFrame* aParent,
   // the prev-in-flow to a newly created next-in-flow, except for the
   // NS_BLOCK_FLAGS_NON_INHERITED_MASK bits below.
   constexpr nsFrameState NS_BLOCK_FLAGS_MASK =
-      NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS |
-      NS_BLOCK_CLIP_PAGINATED_OVERFLOW | NS_BLOCK_HAS_FIRST_LETTER_STYLE |
-      NS_BLOCK_FRAME_HAS_OUTSIDE_MARKER | NS_BLOCK_HAS_FIRST_LETTER_CHILD |
-      NS_BLOCK_FRAME_HAS_INSIDE_MARKER;
+      NS_BLOCK_BFC_STATE_BITS | NS_BLOCK_CLIP_PAGINATED_OVERFLOW |
+      NS_BLOCK_HAS_FIRST_LETTER_STYLE | NS_BLOCK_FRAME_HAS_OUTSIDE_MARKER |
+      NS_BLOCK_HAS_FIRST_LETTER_CHILD | NS_BLOCK_FRAME_HAS_INSIDE_MARKER;
 
   // This is the subset of NS_BLOCK_FLAGS_MASK that is NOT inherited
   // by default.  They should only be set on the first-in-flow.
@@ -7757,12 +7756,16 @@ void nsBlockFrame::Init(nsIContent* aContent, nsContainerFrame* aParent,
             GetParent()->GetWritingMode().GetBlockDir() ||
         GetWritingMode().IsVerticalSideways() !=
             GetParent()->GetWritingMode().IsVerticalSideways())) ||
-      StyleDisplay()->IsContainPaint() || StyleDisplay()->IsContainLayout() ||
       IsColumnSpan()) {
-    AddStateBits(NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS);
+    AddStateBits(NS_BLOCK_STATIC_BFC);
   }
 
-  if (HasAllStateBits(NS_FRAME_FONT_INFLATION_CONTAINER | NS_BLOCK_FLOAT_MGR)) {
+  if (StyleDisplay()->IsContainPaint() || StyleDisplay()->IsContainLayout()) {
+    AddStateBits(NS_BLOCK_DYNAMIC_BFC);
+  }
+
+  if (HasAnyStateBits(NS_FRAME_FONT_INFLATION_CONTAINER) &&
+      HasAnyStateBits(NS_BLOCK_BFC_STATE_BITS)) {
     AddStateBits(NS_FRAME_FONT_INFLATION_FLOW_ROOT);
   }
 }
@@ -7818,7 +7821,7 @@ void nsBlockFrame::SetMarkerFrameForListItem(nsIFrame* aMarkerFrame) {
     if (nsBlockFrame* marker = do_QueryFrame(aMarkerFrame)) {
       // An outside ::marker needs to be an independent formatting context
       // to avoid being influenced by the float manager etc.
-      marker->AddStateBits(NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS);
+      marker->AddStateBits(NS_BLOCK_STATIC_BFC);
     }
     SetProperty(OutsideMarkerProperty(),
                 new (PresShell()) nsFrameList(aMarkerFrame, aMarkerFrame));
@@ -8020,7 +8023,7 @@ void nsBlockFrame::CheckFloats(BlockReflowState& aState) {
 void nsBlockFrame::IsMarginRoot(bool* aBStartMarginRoot,
                                 bool* aBEndMarginRoot) {
   nsIFrame* parent = GetParent();
-  if (!HasAnyStateBits(NS_BLOCK_MARGIN_ROOT)) {
+  if (!HasAnyStateBits(NS_BLOCK_BFC_STATE_BITS)) {
     if (!parent || parent->IsFloatContainingBlock()) {
       *aBStartMarginRoot = false;
       *aBEndMarginRoot = false;
@@ -8047,14 +8050,14 @@ bool nsBlockFrame::BlockNeedsFloatManager(nsIFrame* aBlock) {
   NS_ASSERTION(aBlock->IsBlockFrameOrSubclass(), "aBlock must be a block");
 
   nsIFrame* parent = aBlock->GetParent();
-  return aBlock->HasAnyStateBits(NS_BLOCK_FLOAT_MGR) ||
+  return aBlock->HasAnyStateBits(NS_BLOCK_BFC_STATE_BITS) ||
          (parent && !parent->IsFloatContainingBlock());
 }
 
 /* static */
 bool nsBlockFrame::BlockCanIntersectFloats(nsIFrame* aFrame) {
   return aFrame->IsBlockFrameOrSubclass() && !aFrame->IsReplaced() &&
-         !aFrame->HasAnyStateBits(NS_BLOCK_FLOAT_MGR);
+         !aFrame->HasAnyStateBits(NS_BLOCK_BFC_STATE_BITS);
 }
 
 // Note that this width can vary based on the vertical position.

layout/generic/nsBlockReflowContext.cpp

@@ -275,7 +275,7 @@ void nsBlockReflowContext::ReflowBlock(const LogicalRect& aSpace,
     tI = space.LineLeft(mWritingMode, mContainerSize);
     tB = mBCoord;
 
-    if (!mFrame->HasAnyStateBits(NS_BLOCK_FLOAT_MGR)) {
+    if (!mFrame->HasAnyStateBits(NS_BLOCK_BFC_STATE_BITS)) {
       aFrameRI.mBlockDelta =
           mOuterReflowInput.mBlockDelta + mBCoord - aLine->BStart();
     }

layout/generic/nsFloatManager.h

@@ -70,7 +70,7 @@ struct nsFlowAreaRect {
 /**
  * nsFloatManager is responsible for implementing CSS's rules for
  * positioning floats. An nsFloatManager object is created during reflow for
- * any block with NS_BLOCK_FLOAT_MGR. During reflow, the float manager for
+ * any block with NS_BLOCK_BFC_STATE_BITS. During reflow, the float manager for
  * the nearest such ancestor block is found in ReflowInput::mFloatManager.
  *
  * According to the line-relative mappings in CSS Writing Modes spec [1],

layout/generic/nsFrameStateBits.h

@@ -528,24 +528,28 @@ FRAME_STATE_BIT(Block, 20, NS_BLOCK_NEEDS_BIDI_RESOLUTION)
 
 FRAME_STATE_BIT(Block, 21, NS_BLOCK_HAS_PUSHED_FLOATS)
 
-// This indicates that this is a frame from which child margins can be
+// This indicates that the frame establishes a block formatting context i.e.
+//
+// 1. This indicates that this is a frame from which child margins can be
 // calculated. The absence of this flag implies that child margin calculations
 // should ignore the frame and look further up the parent chain. Used in
 // nsBlockReflowContext::ComputeCollapsedBStartMargin() via
 // nsBlockFrame::IsMarginRoot().
-//
 // This causes the BlockReflowState's constructor to set the
 // mIsBStartMarginRoot and mIsBEndMarginRoot flags.
-FRAME_STATE_BIT(Block, 22, NS_BLOCK_MARGIN_ROOT)
+//
+// 2. This indicates that a block frame should create its own float manager.
+// This is required by each block frame that can contain floats. The float
+// manager is used to reserve space for the floated frames.
+FRAME_STATE_BIT(Block, 22, NS_BLOCK_STATIC_BFC)
 
-// This indicates that a block frame should create its own float manager. This
-// is required by each block frame that can contain floats. The float manager is
-// used to reserve space for the floated frames.
-FRAME_STATE_BIT(Block, 23, NS_BLOCK_FLOAT_MGR)
+// This is the same as NS_BLOCK_STATIC_BFC but can be updated dynamically after
+// the frame construction (e.g. paint/layout containment).
+// FIXME(bug 1874823): Try and merge this and NS_BLOCK_STATIC_BFC.
+FRAME_STATE_BIT(Block, 23, NS_BLOCK_DYNAMIC_BFC)
 
-// For setting the relevant bits on a block formatting context:
-#define NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS \
-(NS_BLOCK_FLOAT_MGR | NS_BLOCK_MARGIN_ROOT)
+// For testing the relevant bits on a block formatting context:
+#define NS_BLOCK_BFC_STATE_BITS (NS_BLOCK_STATIC_BFC | NS_BLOCK_DYNAMIC_BFC)
 
 FRAME_STATE_BIT(Block, 24, NS_BLOCK_HAS_LINE_CURSOR)
 

layout/generic/nsIFrame.cpp

@@ -2473,8 +2473,7 @@ bool nsIFrame::CanBeDynamicReflowRoot() const {
 
   // If we participate in a container's block reflow context, or margins
   // can collapse through us, we can't be a dynamic reflow root.
-  if (IsBlockFrameOrSubclass() &&
-      !HasAllStateBits(NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS)) {
+  if (IsBlockFrameOrSubclass() && !HasAnyStateBits(NS_BLOCK_BFC_STATE_BITS)) {
     return false;
   }
 

layout/generic/test/test_dynamic_reflow_root_disallowal.html

@@ -641,7 +641,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=1508420
 
     // We use 'display:block' on the candidate (overriding 'display:flow-root')
     // so that it won't be a block formatting context. (See usage/definition of
-    // NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS in our c++ layout code.)
+    // NS_BLOCK_BFC_STATE_BITS in our c++ layout code.)
     let cand = createStyledDiv(gReflowRootCandidateStyles +
                                "display: block; \
                                 background: purple;");
@@ -679,7 +679,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=1508420
 
     // We use 'display:block' on the candidate (overriding 'display:flow-root')
     // so that it won't be a block formatting context. (See usage/definition of
-    // NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS in our c++ layout code.)
+    // NS_BLOCK_BFC_STATE_BITS in our c++ layout code.)
     // This allows floats inside the candidate to affect the position of
     // inline-level content outside of it.
     let cand = createStyledDiv(gReflowRootCandidateStyles +

layout/mathml/nsMathMLContainerFrame.cpp

@@ -1444,7 +1444,7 @@ nsContainerFrame* NS_NewMathMLmathBlockFrame(PresShell* aPresShell,
                                              ComputedStyle* aStyle) {
   auto newFrame = new (aPresShell)
       nsMathMLmathBlockFrame(aStyle, aPresShell->GetPresContext());
-  newFrame->AddStateBits(NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS);
+  newFrame->AddStateBits(NS_BLOCK_STATIC_BFC);
   return newFrame;
 }
 

layout/mathml/nsMathMLContainerFrame.h

@@ -432,8 +432,8 @@ class nsMathMLmathBlockFrame final : public nsBlockFrame {
       : nsBlockFrame(aStyle, aPresContext, kClassID) {
     // We should always have a float manager.  Not that things can really try
     // to float out of us anyway, but we need one for line layout.
-    // Bug 1301881: Do we still need to set NS_BLOCK_FLOAT_MGR?
-    // AddStateBits(NS_BLOCK_FLOAT_MGR);
+    // Bug 1301881: Do we still need to set NS_BLOCK_STATIC_BFC?
+    // AddStateBits(NS_BLOCK_STATIC_BFC);
   }
   virtual ~nsMathMLmathBlockFrame() = default;
 };