Attachment 358143 Details for Bug 192625 – Patch

[patch] Patch

bug-192625-20181229182305.patch (text/plain), 83.76 KB, created by zalan on 2018-12-29 18:23:12 PST

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Creator: zalan

Created: 2018-12-29 18:23:12 PST

Size: 83.76 KB

patch

obsolete

>Subversion Revision: 239540
>diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
>index 8ecfee1d2c9f6197df758209640135c8423828f2..f2efd609450db4e2e30f105fdd853dde777257b5 100644
>--- a/Source/WebCore/ChangeLog
>+++ b/Source/WebCore/ChangeLog
>@@ -1,3 +1,117 @@
>+2018-12-29  Zalan Bujtas  <zalan@apple.com>
>+
>+        [LFC][BFC][MarginCollapsing] Add support for peculiar cases.
>+        https://bugs.webkit.org/show_bug.cgi?id=192625
>+
>+        Reviewed by NOBODY (OOPS!).
>+
>+        Implement some of the more peculiar cases like margin collpasing through multiple boxes etc.
>+        Add ~100 new passing cases.
>+
>+        * Sources.txt:
>+        * WebCore.xcodeproj/project.pbxproj:
>+        * layout/FormattingContext.cpp:
>+        (WebCore::Layout::FormattingContext::FormattingContext):
>+        (WebCore::Layout::FormattingContext::formattingState const): Deleted.
>+        * layout/FormattingContext.h:
>+        * layout/FormattingContextGeometry.cpp:
>+        (WebCore::Layout::FormattingContext::Geometry::computedMinHeight):
>+        (WebCore::Layout::FormattingContext::Geometry::floatingNonReplacedWidthAndMargin):
>+        (WebCore::Layout::FormattingContext::Geometry::floatingReplacedWidthAndMargin):
>+        (WebCore::Layout::FormattingContext::Geometry::inlineReplacedHeightAndMargin):
>+        (WebCore::Layout::FormattingContext::Geometry::computedNonCollapsedHorizontalMargin):
>+        (WebCore::Layout::FormattingContext::Geometry::computedNonCollapsedVerticalMargin):
>+        (WebCore::Layout::FormattingContext::Geometry::computedNonCollapsedHorizontalMarginValue): Deleted.
>+        (WebCore::Layout::FormattingContext::Geometry::computedNonCollapsedVerticalMarginValue): Deleted.
>+        * layout/FormattingContextQuirks.cpp:
>+        (WebCore::Layout::FormattingContext::Quirks::heightValueOfNearestContainingBlockWithFixedHeight):
>+        * layout/LayoutState.h:
>+        (WebCore::Layout::LayoutState::hasFormattingState const):
>+        * layout/MarginTypes.h:
>+        * layout/blockformatting/BlockFormattingContext.cpp:
>+        (WebCore::Layout::BlockFormattingContext::formattingState const):
>+        (WebCore::Layout::BlockFormattingContext::computeEstimatedMarginBefore const):
>+        (WebCore::Layout::BlockFormattingContext::computeEstimatedMarginBeforeForAncestors const):
>+        (WebCore::Layout::hasPrecomputedMarginBefore):
>+        (WebCore::Layout::BlockFormattingContext::computeFloatingPosition const):
>+        (WebCore::Layout::BlockFormattingContext::computePositionToAvoidFloats const):
>+        (WebCore::Layout::BlockFormattingContext::computeVerticalPositionForFloatClear const):
>+        (WebCore::Layout::BlockFormattingContext::computeHeightAndMargin const):
>+        (WebCore::Layout::BlockFormattingContext::adjustedVerticalPositionAfterMarginCollapsing const):
>+        * layout/blockformatting/BlockFormattingContext.h:
>+        (WebCore::Layout::BlockFormattingContext::Geometry::inFlowNonReplacedHeightAndMargin):
>+        (WebCore::Layout::BlockFormattingContext::Geometry::inFlowNonReplacedWidthAndMargin):
>+        (WebCore::Layout::BlockFormattingContext::Geometry::inFlowReplacedWidthAndMargin):
>+        * layout/blockformatting/BlockFormattingContextGeometry.cpp:
>+        (WebCore::Layout::BlockFormattingContext::Geometry::inFlowNonReplacedHeightAndMargin):
>+        (WebCore::Layout::BlockFormattingContext::Geometry::inFlowHeightAndMargin):
>+        (WebCore::Layout::BlockFormattingContext::Geometry::estimatedMarginBefore): Deleted.
>+        (WebCore::Layout::BlockFormattingContext::Geometry::estimatedMarginAfter): Deleted.
>+        * layout/blockformatting/BlockFormattingContextQuirks.cpp:
>+        (WebCore::Layout::BlockFormattingContext::Quirks::stretchedInFlowHeight):
>+        (WebCore::Layout::BlockFormattingContext::Quirks::shouldIgnoreMarginAfter):
>+        (WebCore::Layout::BlockFormattingContext::Quirks::stretchedHeight): Deleted.
>+        * layout/blockformatting/BlockFormattingState.h:
>+        (WebCore::Layout::BlockFormattingState::setPositiveAndNegativeVerticalMargin):
>+        (WebCore::Layout::BlockFormattingState::hasPositiveAndNegativeVerticalMargin const):
>+        (WebCore::Layout::BlockFormattingState::positiveAndNegativeVerticalMargin const):
>+        (WebCore::Layout::BlockFormattingState::setHasEstimatedMarginBefore):
>+        (WebCore::Layout::BlockFormattingState::clearHasEstimatedMarginBefore):
>+        (WebCore::Layout::BlockFormattingState::hasEstimatedMarginBefore const):
>+        * layout/blockformatting/BlockMargin.cpp: Added.
>+        (WebCore::Layout::hasBorder):
>+        (WebCore::Layout::hasPadding):
>+        (WebCore::Layout::hasBorderBefore):
>+        (WebCore::Layout::hasBorderAfter):
>+        (WebCore::Layout::hasPaddingBefore):
>+        (WebCore::Layout::hasPaddingAfter):
>+        (WebCore::Layout::hasClearance):
>+        (WebCore::Layout::establishesBlockFormattingContext):
>+        (WebCore::Layout::BlockFormattingContext::Margin::marginBeforeCollapsesWithParentMarginAfter):
>+        (WebCore::Layout::BlockFormattingContext::Margin::marginBeforeCollapsesWithParentMarginBefore):
>+        (WebCore::Layout::BlockFormattingContext::Margin::marginBeforeCollapsesWithPreviousSiblingMarginAfter):
>+        (WebCore::Layout::BlockFormattingContext::Margin::marginBeforeCollapsesWithFirstInFlowChildMarginBefore):
>+        (WebCore::Layout::BlockFormattingContext::Margin::marginAfterCollapsesWithSiblingMarginBeforeWithClearance):
>+        (WebCore::Layout::BlockFormattingContext::Margin::marginAfterCollapsesWithParentMarginBefore):
>+        (WebCore::Layout::BlockFormattingContext::Margin::marginAfterCollapsesWithParentMarginAfter):
>+        (WebCore::Layout::BlockFormattingContext::Margin::marginAfterCollapsesWithLastInFlowChildMarginAfter):
>+        (WebCore::Layout::BlockFormattingContext::Margin::marginAfterCollapsesWithNextSiblingMarginBefore):
>+        (WebCore::Layout::BlockFormattingContext::Margin::marginsCollapseThrough):
>+        (WebCore::Layout::computedPositiveAndNegativeMargin):
>+        (WebCore::Layout::marginValue):
>+        (WebCore::Layout::BlockFormattingContext::Margin::updateCollapsedMarginAfter):
>+        (WebCore::Layout::BlockFormattingContext::Margin::positiveNegativeValues):
>+        (WebCore::Layout::BlockFormattingContext::Margin::positiveNegativeMarginBefore):
>+        (WebCore::Layout::BlockFormattingContext::Margin::positiveNegativeMarginAfter):
>+        (WebCore::Layout::BlockFormattingContext::Margin::estimatedMarginBefore):
>+        (WebCore::Layout::BlockFormattingContext::Margin::vertical):
>+        * layout/blockformatting/BlockMarginCollapse.cpp: Removed.
>+        * layout/displaytree/DisplayBox.cpp:
>+        (WebCore::Display::Box::Box):
>+        * layout/displaytree/DisplayBox.h:
>+        (WebCore::Display::Box::hasClearance const):
>+        (WebCore::Display::Box::setEstimatedMarginBefore):
>+        (WebCore::Display::Box::estimatedMarginBefore const):
>+        (WebCore::Display::Box::setHasClearance):
>+        (WebCore::Display::Box::invalidateEstimatedMarginBefore):
>+        (WebCore::Display::Box::setVerticalMargin):
>+        (WebCore::Display::Box::rectWithMargin const):
>+        * layout/floats/FloatingContext.cpp:
>+        (WebCore::Layout::FloatingContext::verticalPositionWithClearance const):
>+        * layout/inlineformatting/InlineFormattingContext.cpp:
>+        (WebCore::Layout::InlineFormattingContext::formattingState const):
>+        (WebCore::Layout::InlineFormattingContext::splitInlineRunIfNeeded const):
>+        (WebCore::Layout::InlineFormattingContext::createFinalRuns const):
>+        (WebCore::Layout::InlineFormattingContext::postProcessInlineRuns const):
>+        (WebCore::Layout::InlineFormattingContext::layoutInlineContent const):
>+        (WebCore::Layout::InlineFormattingContext::placeInFlowPositionedChildren const):
>+        (WebCore::Layout::InlineFormattingContext::collectInlineContentForSubtree const):
>+        (WebCore::Layout::InlineFormattingContext::instrinsicWidthConstraints const):
>+        * layout/inlineformatting/InlineFormattingContext.h:
>+        (WebCore::Layout::InlineFormattingContext::inlineFormattingState const): Deleted.
>+        * layout/inlineformatting/InlineFormattingContextGeometry.cpp:
>+        (WebCore::Layout::InlineFormattingContext::Geometry::inlineBlockWidthAndMargin):
>+
> 2018-12-22  Carlos Garcia Campos  <cgarcia@igalia.com>
> 
>         [HarfBuzz] Width not correctly reported as 0 for zero font size
>diff --git a/Source/WebCore/Sources.txt b/Source/WebCore/Sources.txt
>index e7d934ad27f1bfa91231e1d86df0b7419d838b90..e6fb284caf77e1ebfffa75d0bc858d83cb1cd778 100644
>--- a/Source/WebCore/Sources.txt
>+++ b/Source/WebCore/Sources.txt
>@@ -1278,7 +1278,7 @@ layout/blockformatting/BlockFormattingContext.cpp
> layout/blockformatting/BlockFormattingContextGeometry.cpp
> layout/blockformatting/BlockFormattingContextQuirks.cpp
> layout/blockformatting/BlockFormattingState.cpp
>-layout/blockformatting/BlockMarginCollapse.cpp
>+layout/blockformatting/BlockMargin.cpp
> layout/blockformatting/BlockInvalidation.cpp
> layout/displaytree/DisplayBox.cpp
> layout/floats/FloatAvoider.cpp
>diff --git a/Source/WebCore/WebCore.xcodeproj/project.pbxproj b/Source/WebCore/WebCore.xcodeproj/project.pbxproj
>index de452c062a6ba26f47327077fc1f99acfcfd8ceb..bd3f77087b89ab297dedc6b96f83920f924abb38 100644
>--- a/Source/WebCore/WebCore.xcodeproj/project.pbxproj
>+++ b/Source/WebCore/WebCore.xcodeproj/project.pbxproj
>@@ -5882,7 +5882,7 @@
> 		115CFA81208B8EDA001E6991 /* FloatingState.cpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.cpp; path = FloatingState.cpp; sourceTree = "<group>"; };
> 		115CFA84208B9066001E6991 /* FloatingContext.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = FloatingContext.h; sourceTree = "<group>"; };
> 		115CFA85208B9066001E6991 /* FloatingContext.cpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.cpp; path = FloatingContext.cpp; sourceTree = "<group>"; };
>-		115CFA89208B921A001E6991 /* BlockMarginCollapse.cpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.cpp; path = BlockMarginCollapse.cpp; sourceTree = "<group>"; };
>+		115CFA89208B921A001E6991 /* BlockMargin.cpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.cpp; path = BlockMargin.cpp; sourceTree = "<group>"; };
> 		115CFA95208B952B001E6991 /* LayoutBox.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = LayoutBox.h; sourceTree = "<group>"; };
> 		115CFA96208B952B001E6991 /* LayoutBox.cpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.cpp; path = LayoutBox.cpp; sourceTree = "<group>"; };
> 		115F7805209CBCBD00739C13 /* Invalidation.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = Invalidation.h; sourceTree = "<group>"; };
>@@ -16210,7 +16210,7 @@
> 				115CFA78208B8D9D001E6991 /* BlockFormattingState.h */,
> 				1123AFDA209ABB2000736ACC /* BlockInvalidation.cpp */,
> 				1123AFD9209ABB2000736ACC /* BlockInvalidation.h */,
>-				115CFA89208B921A001E6991 /* BlockMarginCollapse.cpp */,
>+				115CFA89208B921A001E6991 /* BlockMargin.cpp */,
> 			);
> 			path = blockformatting;
> 			sourceTree = "<group>";
>diff --git a/Source/WebCore/layout/FormattingContextQuirks.cpp b/Source/WebCore/layout/FormattingContextQuirks.cpp
>index b4f44a825ef3aa58ad2b36a0e2ad21475f2e87d5..fa1d0a80bc092c1909a163361a421976bfcd90fe 100644
>--- a/Source/WebCore/layout/FormattingContextQuirks.cpp
>+++ b/Source/WebCore/layout/FormattingContextQuirks.cpp
>@@ -51,7 +51,7 @@ LayoutUnit FormattingContext::Quirks::heightValueOfNearestContainingBlockWithFix
>         if (containingBlock->isBodyBox() || containingBlock->isDocumentBox()) {
>             auto& displayBox = layoutState.displayBoxForLayoutBox(*containingBlock);
> 
>-            auto verticalMargin = FormattingContext::Geometry::computedNonCollapsedVerticalMarginValue(layoutState, *containingBlock);
>+            auto verticalMargin = Geometry::computedNonCollapsedVerticalMarginValue(layoutState, *containingBlock);
>             auto verticalPadding = displayBox.paddingTop().valueOr(0) + displayBox.paddingBottom().valueOr(0);
>             auto verticalBorder = displayBox.borderTop() + displayBox.borderBottom();
>             bodyAndDocumentVerticalMarginPaddingAndBorder += verticalMargin.before + verticalMargin.after + verticalPadding + verticalBorder;
>diff --git a/Source/WebCore/layout/LayoutState.h b/Source/WebCore/layout/LayoutState.h
>index 04775ab2bb668fc226a3fc1324042dbcf12fb33f..28446cf9add3e79869861c9cc79c6985bcd9f7ae 100644
>--- a/Source/WebCore/layout/LayoutState.h
>+++ b/Source/WebCore/layout/LayoutState.h
>@@ -75,6 +75,7 @@ public:
> 
>     FormattingState& formattingStateForBox(const Box&) const;
>     FormattingState& establishedFormattingState(const Box& formattingRoot) const;
>+    bool hasFormattingState(const Box& formattingRoot) const { return m_formattingStates.contains(&formattingRoot); }
>     FormattingState& createFormattingStateForFormattingRootIfNeeded(const Box& formattingRoot);
> 
>     Display::Box& displayBoxForLayoutBox(const Box& layoutBox) const;
>diff --git a/Source/WebCore/layout/MarginTypes.h b/Source/WebCore/layout/MarginTypes.h
>index 85ffed6596867893f7d6e7df586524d687c31497..449ab4f6019fa2490d3abdff456f1736506182c2 100644
>--- a/Source/WebCore/layout/MarginTypes.h
>+++ b/Source/WebCore/layout/MarginTypes.h
>@@ -39,10 +39,11 @@ struct VerticalMargin {
>     };
>     ComputedValues usedValues() const;
>     ComputedValues nonCollapsedValues() const { return m_nonCollapsed; }
>-    
>+
>     struct CollapsedValues {
>         Optional<LayoutUnit> before;
>         Optional<LayoutUnit> after;
>+        bool isCollapsedThrough { false };
>     };
>     Optional<CollapsedValues> collapsedValues() const { return m_collapsed; }
>     void setCollapsedValues(CollapsedValues collapsedValues) { m_collapsed = collapsedValues; }
>@@ -51,6 +52,7 @@ struct VerticalMargin {
> 
>     VerticalMargin() = default;
>     ~VerticalMargin() = default;
>+
> private:
>     ComputedValues m_nonCollapsed;
>     Optional<CollapsedValues> m_collapsed;
>@@ -70,6 +72,10 @@ struct PositiveAndNegativeVerticalMargin {
>     Values after;
> };
> 
>+struct EstimatedMarginBefore {
>+    LayoutUnit computedValue;
>+};
>+
> inline VerticalMargin::VerticalMargin(VerticalMargin::ComputedValues nonCollapsed, Optional<VerticalMargin::CollapsedValues> collapsed)
>     : m_nonCollapsed(nonCollapsed)
>     , m_collapsed(collapsed)
>diff --git a/Source/WebCore/layout/blockformatting/BlockFormattingContext.cpp b/Source/WebCore/layout/blockformatting/BlockFormattingContext.cpp
>index 429c0a9811a48dbf4551a4be92130f250143a38b..934bc78b00c4cb25477510b2bbf67672e0dac3e9 100644
>--- a/Source/WebCore/layout/blockformatting/BlockFormattingContext.cpp
>+++ b/Source/WebCore/layout/blockformatting/BlockFormattingContext.cpp
>@@ -186,12 +186,14 @@ void BlockFormattingContext::computeStaticPosition(const Box& layoutBox) const
> 
> void BlockFormattingContext::computeEstimatedMarginBefore(const Box& layoutBox) const
> {
>-    auto& layoutState = this->layoutState();
>-    auto estimatedMarginBefore = Geometry::estimatedMarginBefore(layoutState, layoutBox);
>+    auto estimatedMarginBefore = Margin::estimatedMarginBefore(layoutState(), layoutBox);
>+    blockFormattingState().setHasEstimatedMarginBefore(layoutBox);
> 
>-    auto& displayBox = layoutState.displayBoxForLayoutBox(layoutBox);
>+    auto& displayBox = layoutState().displayBoxForLayoutBox(layoutBox);
>+#if !ASSERT_DISABLED
>     displayBox.setEstimatedMarginBefore(estimatedMarginBefore);
>-    displayBox.moveVertically(estimatedMarginBefore);
>+#endif
>+    displayBox.setTop(adjustedVerticalPositionAfterMarginCollapsing(layoutBox, estimatedMarginBefore.computedValue));
> }
> 
> void BlockFormattingContext::computeEstimatedMarginBeforeForAncestors(const Box& layoutBox) const
>@@ -208,12 +210,11 @@ void BlockFormattingContext::computeEstimatedMarginBeforeForAncestors(const Box&
>     // So when we get to the point where we intersect the box with the float to decide if the box needs to move, we don't yet have the final vertical position.
>     //
>     // The idea here is that as long as we don't cross the block formatting context boundary, we should be able to pre-compute the final top margin.
>-    auto& layoutState = this->layoutState();
>+    auto& formattingState = blockFormattingState();
> 
>     for (auto* ancestor = layoutBox.containingBlock(); ancestor && !ancestor->establishesBlockFormattingContext(); ancestor = ancestor->containingBlock()) {
>-        auto& displayBox = layoutState.displayBoxForLayoutBox(*ancestor);
>         // FIXME: with incremental layout, we might actually have a valid (non-estimated) margin top as well.
>-        if (displayBox.estimatedMarginBefore())
>+        if (formattingState.hasEstimatedMarginBefore(*ancestor))
>             return;
> 
>         computeEstimatedMarginBefore(*ancestor);
>@@ -238,10 +239,10 @@ void BlockFormattingContext::precomputeVerticalPositionForFormattingRootIfNeeded
> }
> 
> #ifndef NDEBUG
>-static bool hasPrecomputedMarginBefore(const LayoutState& layoutState, const Box& layoutBox)
>+static bool hasPrecomputedMarginBefore(const BlockFormattingState& formattingState, const Box& layoutBox)
> {
>     for (auto* ancestor = layoutBox.containingBlock(); ancestor && !ancestor->establishesBlockFormattingContext(); ancestor = ancestor->containingBlock()) {
>-        if (layoutState.displayBoxForLayoutBox(*ancestor).estimatedMarginBefore())
>+        if (formattingState.hasEstimatedMarginBefore(*ancestor))
>             continue;
>         return false;
>     }
>@@ -253,7 +254,7 @@ void BlockFormattingContext::computeFloatingPosition(const FloatingContext& floa
> {
>     auto& layoutState = this->layoutState();
>     ASSERT(layoutBox.isFloatingPositioned());
>-    ASSERT(hasPrecomputedMarginBefore(layoutState, layoutBox));
>+    ASSERT(hasPrecomputedMarginBefore(blockFormattingState(), layoutBox));
> 
>     auto& displayBox = layoutState.displayBoxForLayoutBox(layoutBox);
>     // 8.3.1 Collapsing margins
>@@ -273,7 +274,7 @@ void BlockFormattingContext::computePositionToAvoidFloats(const FloatingContext&
>     ASSERT(layoutBox.establishesBlockFormattingContext());
>     ASSERT(!layoutBox.isFloatingPositioned());
>     ASSERT(!layoutBox.hasFloatClear());
>-    ASSERT(hasPrecomputedMarginBefore(layoutState, layoutBox));
>+    ASSERT(hasPrecomputedMarginBefore(blockFormattingState(), layoutBox));
> 
>     if (floatingContext.floatingState().isEmpty())
>         return;
>@@ -292,7 +293,7 @@ void BlockFormattingContext::computeVerticalPositionForFloatClear(const Floating
>     // For formatting roots, we already precomputed final position.
>     if (!layoutBox.establishesFormattingContext())
>         computeEstimatedMarginBeforeForAncestors(layoutBox);
>-    ASSERT(hasPrecomputedMarginBefore(layoutState, layoutBox));
>+    ASSERT(hasPrecomputedMarginBefore(blockFormattingState(), layoutBox));
> 
>     if (auto verticalPositionWithClearance = floatingContext.verticalPositionWithClearance(layoutBox))
>         layoutState.displayBoxForLayoutBox(layoutBox).setTop(*verticalPositionWithClearance);
>@@ -372,12 +373,15 @@ void BlockFormattingContext::computeHeightAndMargin(const Box& layoutBox) const
>     }
> 
>     auto& displayBox = layoutState.displayBoxForLayoutBox(layoutBox);
>+    auto& formattingState = this->blockFormattingState();
>+    if (formattingState.hasEstimatedMarginBefore(layoutBox)) {
>+        formattingState.clearHasEstimatedMarginBefore(layoutBox);
>+        ASSERT(layoutState.displayBoxForLayoutBox(layoutBox).estimatedMarginBefore()->computedValue == heightAndMargin.margin.usedValues().before);
>+    } else
>+        displayBox.setTop(adjustedVerticalPositionAfterMarginCollapsing(layoutBox, heightAndMargin.margin.usedValues().before));
>+
>     displayBox.setContentBoxHeight(heightAndMargin.height);
>     displayBox.setVerticalMargin(heightAndMargin.margin);
>-
>-    // If this box has already been moved by the estimated vertical margin, no need to move it again.
>-    if (layoutBox.isFloatingPositioned() || !displayBox.estimatedMarginBefore())
>-        displayBox.moveVertically(heightAndMargin.margin.usedValues().before);
> }
> 
> FormattingContext::InstrinsicWidthConstraints BlockFormattingContext::instrinsicWidthConstraints() const
>@@ -444,6 +448,37 @@ FormattingContext::InstrinsicWidthConstraints BlockFormattingContext::instrinsic
>     return instrinsicWidthConstraints;
> }
> 
>+LayoutUnit BlockFormattingContext::adjustedVerticalPositionAfterMarginCollapsing(const Box& layoutBox, LayoutUnit marginBefore) const
>+{
>+    // Now that we've computed the final margin before, let's shift the box's vertical position.
>+    // 1. Check if the margin before collapses with the previous box's margin after. if not -> return previous box's bottom inlcuding margin after + marginBefore
>+    // 2. Check if the previous box's margins collapse through. If not -> return previous box' bottom excluding margin after + marginBefore (they are supposed to be equal)
>+    // 3. Go to previous box and start from step #1 until we hit the parent box.
>+    auto& layoutState = this->layoutState();
>+    auto* currentLayoutBox = &layoutBox;
>+    while (currentLayoutBox) {
>+        if (!currentLayoutBox->previousInFlowSibling())
>+            break;
>+        auto& previousInFlowSibling = *currentLayoutBox->previousInFlowSibling();
>+        if (!Margin::marginBeforeCollapsesWithPreviousSiblingMarginAfter(layoutState, *currentLayoutBox)) {
>+            auto& previousDisplayBox = layoutState.displayBoxForLayoutBox(previousInFlowSibling);
>+            return previousDisplayBox.rectWithMargin().bottom() + marginBefore;
>+        }
>+
>+        if (!Margin::marginsCollapseThrough(layoutState, previousInFlowSibling)) {
>+            auto& previousDisplayBox = layoutState.displayBoxForLayoutBox(previousInFlowSibling);
>+            return previousDisplayBox.bottom() + marginBefore;
>+        }
>+        currentLayoutBox = &previousInFlowSibling;
>+    }
>+
>+    auto containingBlockContentBoxTop = layoutState.displayBoxForLayoutBox(*layoutBox.containingBlock()).contentBoxTop();
>+    if (Margin::marginBeforeCollapsesWithParentMarginBefore(layoutState, layoutBox) || Margin::marginBeforeCollapsesWithParentMarginAfter(layoutState, layoutBox))
>+        return containingBlockContentBoxTop;
>+
>+    return containingBlockContentBoxTop + marginBefore;
>+}
>+
> }
> }
> 
>diff --git a/Source/WebCore/layout/blockformatting/BlockFormattingContext.h b/Source/WebCore/layout/blockformatting/BlockFormattingContext.h
>index 68041d4908567fb889340d6b53b7e3f2082ec180..9a412ae402695fce1b957332c3685508edf34214 100644
>--- a/Source/WebCore/layout/blockformatting/BlockFormattingContext.h
>+++ b/Source/WebCore/layout/blockformatting/BlockFormattingContext.h
>@@ -50,6 +50,8 @@ public:
>     void layout() const override;
> 
> private:
>+    BlockFormattingState& blockFormattingState() const { return downcast<BlockFormattingState>(formattingState()); }
>+
>     void layoutFormattingContextRoot(FloatingContext&, const Box&) const;
>     void placeInFlowPositionedChildren(const Container&) const;
> 
>@@ -67,6 +69,7 @@ private:
>     void precomputeVerticalPositionForFormattingRootIfNeeded(const Box&) const;
> 
>     InstrinsicWidthConstraints instrinsicWidthConstraints() const override;
>+    LayoutUnit adjustedVerticalPositionAfterMarginCollapsing(const Box&, LayoutUnit marginBefore) const;
> 
>     // This class implements positioning and sizing for boxes participating in a block formatting context.
>     class Geometry : public FormattingContext::Geometry {
>@@ -79,49 +82,47 @@ private:
>         static bool instrinsicWidthConstraintsNeedChildrenWidth(const Box&);
>         static InstrinsicWidthConstraints instrinsicWidthConstraints(const LayoutState&, const Box&);
> 
>-        static LayoutUnit estimatedMarginBefore(const LayoutState&, const Box&);
>-        static LayoutUnit estimatedMarginAfter(const LayoutState&, const Box&);
>-
>     private:
>-        // This class implements margin collapsing for block formatting context.
>-        class MarginCollapse {
>-        public:
>-            static LayoutUnit marginBefore(const LayoutState&, const Box&);
>-            static LayoutUnit marginAfter(const LayoutState&, const Box&);
>+        static HeightAndMargin inFlowNonReplacedHeightAndMargin(const LayoutState&, const Box&, Optional<LayoutUnit> usedHeight = { });
>+        static WidthAndMargin inFlowNonReplacedWidthAndMargin(const LayoutState&, const Box&, Optional<LayoutUnit> usedWidth = { });
>+        static WidthAndMargin inFlowReplacedWidthAndMargin(const LayoutState&, const Box&, Optional<LayoutUnit> usedWidth = { });
>+        static Point staticPositionForOutOfFlowPositioned(const LayoutState&, const Box&);
>+    };
> 
>-            static bool marginBeforeCollapsesWithParentMarginAfter(const LayoutState&, const Box&);
>-            static bool marginAfterCollapsesWithParentMarginAfter(const LayoutState&, const Box&);
>+    class Margin {
>+    public:
>+        static VerticalMargin vertical(const LayoutState&, const Box&);
> 
>-        private:
>-            static LayoutUnit collapsedMarginAfterFromLastChild(const LayoutState&, const Box&);
>-            static LayoutUnit nonCollapsedMarginAfter(const LayoutState&, const Box&);
>+        static EstimatedMarginBefore estimatedMarginBefore(const LayoutState&, const Box&);
>+        static void updateCollapsedMarginAfter(const LayoutState&, const Box&, const VerticalMargin& nextSiblingVerticalMargin);
> 
>-            static LayoutUnit computedNonCollapsedMarginBefore(const LayoutState&, const Box&);
>-            static LayoutUnit computedNonCollapsedMarginAfter(const LayoutState&, const Box&);
>+        static bool marginBeforeCollapsesWithParentMarginBefore(const LayoutState&, const Box&);
>+        static bool marginBeforeCollapsesWithFirstInFlowChildMarginBefore(const LayoutState&, const Box&);
>+        static bool marginBeforeCollapsesWithParentMarginAfter(const LayoutState&, const Box&);
>+        static bool marginBeforeCollapsesWithPreviousSiblingMarginAfter(const LayoutState&, const Box&);
> 
>-            static LayoutUnit collapsedMarginBeforeFromFirstChild(const LayoutState&, const Box&);
>-            static LayoutUnit nonCollapsedMarginBefore(const LayoutState&, const Box&);
>+        static bool marginAfterCollapsesWithParentMarginAfter(const LayoutState&, const Box&);
>+        static bool marginAfterCollapsesWithLastInFlowChildMarginAfter(const LayoutState&, const Box&);
>+        static bool marginAfterCollapsesWithParentMarginBefore(const LayoutState&, const Box&);
>+        static bool marginAfterCollapsesWithNextSiblingMarginBefore(const LayoutState&, const Box&);
>+        static bool marginAfterCollapsesWithSiblingMarginBeforeWithClearance(const LayoutState&, const Box&);
> 
>-            static bool marginBeforeCollapsesWithParentMarginBefore(const LayoutState&, const Box&);
>-            static bool marginBeforeCollapsesWithPreviousSibling(const Box&);
>-            static bool marginAfterCollapsesWithNextSibling(const Box&);
>-            static bool marginAfterCollapsesWithSiblingMarginBeforeWithClearance(const LayoutState&, const Box&);
>-            static bool marginAfterCollapsesWithParentMarginBefore(const LayoutState&, const Box&);
>-            static bool marginsCollapseThrough(const LayoutState&, const Box&);
>-        };
>+        static bool marginsCollapseThrough(const LayoutState&, const Box&);
> 
>-        static HeightAndMargin inFlowNonReplacedHeightAndMargin(const LayoutState&, const Box&, Optional<LayoutUnit> usedHeight = { });
>-        static WidthAndMargin inFlowNonReplacedWidthAndMargin(const LayoutState&, const Box&, Optional<LayoutUnit> usedWidth = { });
>-        static WidthAndMargin inFlowReplacedWidthAndMargin(const LayoutState&, const Box&, Optional<LayoutUnit> usedWidth = { });
>-        static Point staticPositionForOutOfFlowPositioned(const LayoutState&, const Box&);
>+    private:
>+        enum class MarginType { Before, After };
>+        static PositiveAndNegativeVerticalMargin::Values positiveNegativeValues(const LayoutState&, const Box&, MarginType);
>+        static PositiveAndNegativeVerticalMargin::Values positiveNegativeMarginBefore(const LayoutState&, const Box&);
>+        static PositiveAndNegativeVerticalMargin::Values positiveNegativeMarginAfter(const LayoutState&, const Box&);
>     };
> 
>     class Quirks {
>     public:
>         static bool needsStretching(const LayoutState&, const Box&);
>-        static HeightAndMargin stretchedHeight(const LayoutState&, const Box&, HeightAndMargin);
>+        static HeightAndMargin stretchedInFlowHeight(const LayoutState&, const Box&, HeightAndMargin);
> 
>         static bool shouldIgnoreMarginBefore(const LayoutState&, const Box&);
>+        static bool shouldIgnoreMarginAfter(const LayoutState&, const Box&);
>     };
> };
> 
>diff --git a/Source/WebCore/layout/blockformatting/BlockFormattingContextGeometry.cpp b/Source/WebCore/layout/blockformatting/BlockFormattingContextGeometry.cpp
>index ee43872eab6e500be8ac72b15af9010beebf8106..007f72a3044c1cc3da18369e279bb5ab502c4332 100644
>--- a/Source/WebCore/layout/blockformatting/BlockFormattingContextGeometry.cpp
>+++ b/Source/WebCore/layout/blockformatting/BlockFormattingContextGeometry.cpp
>@@ -57,13 +57,9 @@ HeightAndMargin BlockFormattingContext::Geometry::inFlowNonReplacedHeightAndMarg
>         // Only children in the normal flow are taken into account (i.e., floating boxes and absolutely positioned boxes are ignored,
>         // and relatively positioned boxes are considered without their offset). Note that the child box may be an anonymous block box.
> 
>-        auto& style = layoutBox.style();
>-        auto containingBlockWidth = layoutState.displayBoxForLayoutBox(*layoutBox.containingBlock()).contentBoxWidth();
>         auto& displayBox = layoutState.displayBoxForLayoutBox(layoutBox);
>-
>-        auto nonCollapsedMargin = VerticalMargin::ComputedValues { computedValueIfNotAuto(style.marginBefore(), containingBlockWidth).valueOr(0),
>-            computedValueIfNotAuto(style.marginAfter(), containingBlockWidth).valueOr(0) }; 
>-        auto collapsedMargin = VerticalMargin::CollapsedValues { MarginCollapse::marginBefore(layoutState, layoutBox), MarginCollapse::marginAfter(layoutState, layoutBox) };
>+        auto nonCollapsedMargin = computedNonCollapsedVerticalMarginValue(layoutState, layoutBox);
>+        auto collapsedMargin = Margin::vertical(layoutState, layoutBox).collapsedValues();
>         auto borderAndPaddingTop = displayBox.borderTop() + displayBox.paddingTop().valueOr(0);
> 
>         auto height = usedHeight ? usedHeight.value() : computedHeightValue(layoutState, layoutBox, HeightType::Normal);
>@@ -84,14 +80,14 @@ HeightAndMargin BlockFormattingContext::Geometry::inFlowNonReplacedHeightAndMarg
>         // 2. the bottom edge of the bottom (possibly collapsed) margin of its last in-flow child, if the child's bottom margin...
>         auto* lastInFlowChild = downcast<Container>(layoutBox).lastInFlowChild();
>         ASSERT(lastInFlowChild);
>-        if (!MarginCollapse::marginAfterCollapsesWithParentMarginAfter(layoutState, *lastInFlowChild)) {
>+        if (!Margin::marginAfterCollapsesWithParentMarginAfter(layoutState, *lastInFlowChild)) {
>             auto& lastInFlowDisplayBox = layoutState.displayBoxForLayoutBox(*lastInFlowChild);
>             return { lastInFlowDisplayBox.bottom() + lastInFlowDisplayBox.marginAfter() - borderAndPaddingTop, { nonCollapsedMargin, collapsedMargin } };
>         }
> 
>         // 3. the bottom border edge of the last in-flow child whose top margin doesn't collapse with the element's bottom margin
>         auto* inFlowChild = lastInFlowChild;
>-        while (inFlowChild && MarginCollapse::marginBeforeCollapsesWithParentMarginAfter(layoutState, *inFlowChild))
>+        while (inFlowChild && Margin::marginBeforeCollapsesWithParentMarginAfter(layoutState, *inFlowChild))
>             inFlowChild = inFlowChild->previousInFlowSibling();
>         if (inFlowChild) {
>             auto& inFlowDisplayBox = layoutState.displayBoxForLayoutBox(*inFlowChild);
>@@ -103,6 +99,9 @@ HeightAndMargin BlockFormattingContext::Geometry::inFlowNonReplacedHeightAndMarg
>     };
> 
>     auto heightAndMargin = compute();
>+    // Adjust the previous sibling's margin bottom now that this box's vertical margin is computed.
>+    if (Margin::marginBeforeCollapsesWithPreviousSiblingMarginAfter(layoutState, layoutBox))
>+        Margin::updateCollapsedMarginAfter(layoutState, *layoutBox.previousInFlowSibling(), heightAndMargin.margin);
> 
>     LOG_WITH_STREAM(FormattingContextLayout, stream << "[Height][Margin] -> inflow non-replaced -> height(" << heightAndMargin.height << "px) margin(" << heightAndMargin.margin.usedValues().before << "px, " << heightAndMargin.margin.usedValues().after << "px) -> layoutBox(" << &layoutBox << ")");
>     return heightAndMargin;
>@@ -261,7 +260,7 @@ HeightAndMargin BlockFormattingContext::Geometry::inFlowHeightAndMargin(const La
>     if (!Quirks::needsStretching(layoutState, layoutBox))
>         return heightAndMargin;
> 
>-    heightAndMargin = Quirks::stretchedHeight(layoutState, layoutBox, heightAndMargin);
>+    heightAndMargin = Quirks::stretchedInFlowHeight(layoutState, layoutBox, heightAndMargin);
> 
>     LOG_WITH_STREAM(FormattingContextLayout, stream << "[Height][Margin] -> inflow non-replaced -> streched to viewport -> height(" << heightAndMargin.height << "px) margin(" << heightAndMargin.margin.usedValues().before << "px, " << heightAndMargin.margin.usedValues().after << "px) -> layoutBox(" << &layoutBox << ")");
>     return heightAndMargin;
>@@ -322,30 +321,6 @@ FormattingContext::InstrinsicWidthConstraints BlockFormattingContext::Geometry::
>     return { minimumIntrinsicWidth, maximumIntrinsicWidth };
> }
> 
>-LayoutUnit BlockFormattingContext::Geometry::estimatedMarginBefore(const LayoutState& layoutState, const Box& layoutBox)
>-{
>-    ASSERT(layoutBox.isBlockLevelBox());
>-    // Can't estimate vertical margins for out of flow boxes (and we shouldn't need to do it for float boxes).
>-    ASSERT(layoutBox.isInFlow());
>-    // Can't cross block formatting context boundary.
>-    ASSERT(!layoutBox.establishesBlockFormattingContext());
>-
>-    // Let's just use the normal path for now.
>-    return MarginCollapse::marginBefore(layoutState, layoutBox);
>-}
>-
>-LayoutUnit BlockFormattingContext::Geometry::estimatedMarginAfter(const LayoutState& layoutState, const Box& layoutBox)
>-{
>-    ASSERT(layoutBox.isBlockLevelBox());
>-    // Can't estimate vertical margins for out of flow boxes (and we shouldn't need to do it for float boxes).
>-    ASSERT(layoutBox.isInFlow());
>-    // Can't cross block formatting context boundary.
>-    ASSERT(!layoutBox.establishesBlockFormattingContext());
>-
>-    // Let's just use the normal path for now.
>-    return MarginCollapse::marginAfter(layoutState, layoutBox);
>-}
>-
> }
> }
> 
>diff --git a/Source/WebCore/layout/blockformatting/BlockFormattingContextQuirks.cpp b/Source/WebCore/layout/blockformatting/BlockFormattingContextQuirks.cpp
>index 4606f9dc6628ee03f30c7a95f439fb13e740709d..b03c23a0ea55d2cd383dfe0e7765187c75c16575 100644
>--- a/Source/WebCore/layout/blockformatting/BlockFormattingContextQuirks.cpp
>+++ b/Source/WebCore/layout/blockformatting/BlockFormattingContextQuirks.cpp
>@@ -66,8 +66,9 @@ bool BlockFormattingContext::Quirks::needsStretching(const LayoutState& layoutSt
>     return layoutBox.style().logicalHeight().isAuto();
> }
> 
>-HeightAndMargin BlockFormattingContext::Quirks::stretchedHeight(const LayoutState& layoutState, const Box& layoutBox, HeightAndMargin heightAndMargin)
>+HeightAndMargin BlockFormattingContext::Quirks::stretchedInFlowHeight(const LayoutState& layoutState, const Box& layoutBox, HeightAndMargin heightAndMargin)
> {
>+    ASSERT(layoutBox.isInFlow());
>     ASSERT(layoutBox.isDocumentBox() || layoutBox.isBodyBox());
> 
>     auto& documentBox = layoutBox.isDocumentBox() ? layoutBox : *layoutBox.parent();
>@@ -88,12 +89,10 @@ HeightAndMargin BlockFormattingContext::Quirks::stretchedHeight(const LayoutStat
>         // Here is the quirky part for body box:
>         // Stretch the body using the initial containing block's height and shrink it with document box's margin/border/padding.
>         // This looks extremely odd when html has non-auto height.
>-        auto verticalMargin = Geometry::estimatedMarginBefore(layoutState, documentBox) + Geometry::estimatedMarginAfter(layoutState, documentBox);
>-        strechedHeight -= verticalMargin;
>+        auto documentBoxVerticalMargin = Geometry::computedNonCollapsedVerticalMarginValue(layoutState, documentBox);
>+        strechedHeight -= (documentBoxVerticalMargin.before + documentBoxVerticalMargin.after);
> 
>-        // This quirk happens when the body height is 0 which means its vertical margins collapse through (top and bottom margins are adjoining).
>-        // However now that we stretch the body they don't collapse through anymore, so we need to use the non-collapsed values instead.
>-        auto bodyBoxVerticalMargin = heightAndMargin.height ? heightAndMargin.margin.usedValues() : heightAndMargin.margin.nonCollapsedValues();
>+        auto bodyBoxVerticalMargin = heightAndMargin.margin.usedValues(); 
>         totalVerticalMargin = bodyBoxVerticalMargin.before + bodyBoxVerticalMargin.after;
>     }
> 
>@@ -112,6 +111,20 @@ bool BlockFormattingContext::Quirks::shouldIgnoreMarginBefore(const LayoutState&
>     return layoutState.inQuirksMode() && isQuirkContainer(*layoutBox.parent()) && hasMarginBeforeQuirkValue(layoutBox);
> }
> 
>+bool BlockFormattingContext::Quirks::shouldIgnoreMarginAfter(const LayoutState& layoutState, const Box& layoutBox)
>+{
>+    // Ignore maring after when the ignored margin before collapses through.
>+    if (!shouldIgnoreMarginBefore(layoutState, layoutBox))
>+        return false;
>+
>+    ASSERT(layoutBox.parent());
>+    auto& parent = *layoutBox.parent();
>+    if (parent.firstInFlowOrFloatingChild() != &layoutBox || parent.firstInFlowOrFloatingChild() != parent.lastInFlowOrFloatingChild())
>+        return false;
>+
>+    return Margin::marginsCollapseThrough(layoutState, layoutBox);
>+}
>+
> }
> }
> 
>diff --git a/Source/WebCore/layout/blockformatting/BlockFormattingState.h b/Source/WebCore/layout/blockformatting/BlockFormattingState.h
>index bb9669390ff9a2876fe714dc8544b01df6deaa84..bb456b5927fefe45c637831d5b24f717092bad2a 100644
>--- a/Source/WebCore/layout/blockformatting/BlockFormattingState.h
>+++ b/Source/WebCore/layout/blockformatting/BlockFormattingState.h
>@@ -28,6 +28,7 @@
> #if ENABLE(LAYOUT_FORMATTING_CONTEXT)
> 
> #include "FormattingState.h"
>+#include "MarginTypes.h"
> #include <wtf/IsoMalloc.h>
> 
> namespace WebCore {
>@@ -42,6 +43,18 @@ public:
>     virtual ~BlockFormattingState();
> 
>     std::unique_ptr<FormattingContext> createFormattingContext(const Box& formattingContextRoot) override;
>+
>+    void setPositiveAndNegativeVerticalMargin(const Box& layoutBox, PositiveAndNegativeVerticalMargin verticalMargin) { m_positiveAndNegativeVerticalMargin.set(&layoutBox, verticalMargin); }
>+    bool hasPositiveAndNegativeVerticalMargin(const Box& layoutBox) const { return m_positiveAndNegativeVerticalMargin.contains(&layoutBox); }
>+    PositiveAndNegativeVerticalMargin positiveAndNegativeVerticalMargin(const Box& layoutBox) const { return m_positiveAndNegativeVerticalMargin.get(&layoutBox); }
>+
>+    void setHasEstimatedMarginBefore(const Box& layoutBox) { m_estimatedMarginBeforeList.add(&layoutBox); }
>+    void clearHasEstimatedMarginBefore(const Box& layoutBox) { m_estimatedMarginBeforeList.remove(&layoutBox); }
>+    bool hasEstimatedMarginBefore(const Box& layoutBox) const { return m_estimatedMarginBeforeList.contains(&layoutBox); }
>+
>+private:
>+    HashMap<const Box*, PositiveAndNegativeVerticalMargin> m_positiveAndNegativeVerticalMargin;
>+    HashSet<const Box*> m_estimatedMarginBeforeList;
> };
> 
> }
>diff --git a/Source/WebCore/layout/blockformatting/BlockMarginCollapse.cpp b/Source/WebCore/layout/blockformatting/BlockMarginCollapse.cpp
>deleted file mode 100644
>index 567708745394a785b84d97c82f5f48135a3f8d50..0000000000000000000000000000000000000000
>--- a/Source/WebCore/layout/blockformatting/BlockMarginCollapse.cpp
>+++ /dev/null
>@@ -1,465 +0,0 @@
>-/*
>- * Copyright (C) 2018 Apple Inc. All rights reserved.
>- *
>- * Redistribution and use in source and binary forms, with or without
>- * modification, are permitted provided that the following conditions
>- * are met:
>- * 1. Redistributions of source code must retain the above copyright
>- *    notice, this list of conditions and the following disclaimer.
>- * 2. Redistributions in binary form must reproduce the above copyright
>- *    notice, this list of conditions and the following disclaimer in the
>- *    documentation and/or other materials provided with the distribution.
>- *
>- * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
>- * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
>- * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
>- * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
>- * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
>- * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
>- * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
>- * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
>- * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
>- * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
>- * THE POSSIBILITY OF SUCH DAMAGE.
>- */
>-
>-#include "config.h"
>-#include "BlockFormattingContext.h"
>-
>-#if ENABLE(LAYOUT_FORMATTING_CONTEXT)
>-
>-#include "InlineFormattingState.h"
>-#include "LayoutBox.h"
>-#include "LayoutContainer.h"
>-#include "LayoutUnit.h"
>-#include "RenderStyle.h"
>-
>-namespace WebCore {
>-namespace Layout {
>-
>-static bool hasBorder(const BorderValue& borderValue)
>-{
>-    if (borderValue.style() == BorderStyle::None || borderValue.style() == BorderStyle::Hidden)
>-        return false;
>-    return !!borderValue.width();
>-}
>-
>-static bool hasPadding(const Length& paddingValue)
>-{
>-    // FIXME: Check if percent value needs to be resolved.
>-    return !paddingValue.isZero();
>-}
>-
>-static bool hasBorderBefore(const Box& layoutBox)
>-{
>-    return hasBorder(layoutBox.style().borderBefore());
>-}
>-
>-static bool hasBorderAfter(const Box& layoutBox)
>-{
>-    return hasBorder(layoutBox.style().borderAfter());
>-}
>-
>-static bool hasPaddingBefore(const Box& layoutBox)
>-{
>-    return hasPadding(layoutBox.style().paddingBefore());
>-}
>-
>-static bool hasPaddingAfter(const Box& layoutBox)
>-{
>-    return hasPadding(layoutBox.style().paddingAfter());
>-}
>-
>-static bool hasClearance(const Box& layoutBox)
>-{
>-    if (!layoutBox.hasFloatClear())
>-        return false;
>-    // FIXME
>-    return false;
>-}
>-
>-static bool establishesBlockFormattingContext(const Box& layoutBox)
>-{
>-    // WebKit treats the document element renderer as a block formatting context root. It probably only impacts margin collapsing, so let's not do
>-    // a layout wide quirk on this for now.
>-    if (layoutBox.isDocumentBox())
>-        return true;
>-    return layoutBox.establishesBlockFormattingContext();
>-}
>-
>-static LayoutUnit marginValue(LayoutUnit currentMarginValue, LayoutUnit candidateMarginValue)
>-{
>-    if (!candidateMarginValue)
>-        return currentMarginValue;
>-    if (!currentMarginValue)
>-        return candidateMarginValue;
>-    // Both margins are positive.
>-    if (candidateMarginValue > 0 && currentMarginValue > 0)
>-        return std::max(candidateMarginValue, currentMarginValue);
>-    // Both margins are negative.
>-    if (candidateMarginValue < 0 && currentMarginValue < 0)
>-        return 0 - std::max(std::abs(candidateMarginValue.toFloat()), std::abs(currentMarginValue.toFloat()));
>-    // One of the margins is negative.
>-    return currentMarginValue + candidateMarginValue;
>-}
>-
>-LayoutUnit BlockFormattingContext::Geometry::MarginCollapse::computedNonCollapsedMarginBefore(const LayoutState& layoutState, const Box& layoutBox)
>-{
>-    ASSERT(layoutBox.isBlockLevelBox());
>-
>-    return computedNonCollapsedVerticalMarginValue(layoutState, layoutBox).before;
>-}
>-
>-LayoutUnit BlockFormattingContext::Geometry::MarginCollapse::computedNonCollapsedMarginAfter(const LayoutState& layoutState, const Box& layoutBox)
>-{
>-    ASSERT(layoutBox.isBlockLevelBox());
>-
>-    return computedNonCollapsedVerticalMarginValue(layoutState, layoutBox).after;
>-}
>-
>-LayoutUnit BlockFormattingContext::Geometry::MarginCollapse::nonCollapsedMarginBefore(const LayoutState& layoutState, const Box& layoutBox)
>-{
>-    ASSERT(layoutBox.isBlockLevelBox());
>-
>-    // Non collapsed margin top includes collapsed margin from inflow first child.
>-    return marginValue(computedNonCollapsedMarginBefore(layoutState, layoutBox), collapsedMarginBeforeFromFirstChild(layoutState, layoutBox));
>-}
>-
>-LayoutUnit BlockFormattingContext::Geometry::MarginCollapse::nonCollapsedMarginAfter(const LayoutState& layoutState, const Box& layoutBox)
>-{
>-    ASSERT(layoutBox.isBlockLevelBox());
>-
>-    // Non collapsed margin bottom includes collapsed margin from inflow last child.
>-    return marginValue(computedNonCollapsedMarginAfter(layoutState, layoutBox), collapsedMarginAfterFromLastChild(layoutState, layoutBox));
>-}
>-
>-LayoutUnit BlockFormattingContext::Geometry::MarginCollapse::collapsedMarginBeforeFromFirstChild(const LayoutState& layoutState, const Box& layoutBox)
>-{
>-    ASSERT(layoutBox.isBlockLevelBox());
>-
>-    // Check if the first child collapses its margin top.
>-    if (!is<Container>(layoutBox) || !downcast<Container>(layoutBox).hasInFlowChild())
>-        return 0;
>-
>-    // Do not collapse margin with a box from a non-block formatting context <div><span>foobar</span></div>.
>-    if (layoutBox.establishesFormattingContext() && !layoutBox.establishesBlockFormattingContextOnly())
>-        return 0;
>-
>-    // FIXME: Take collapsed through margin into account.
>-    auto& firstInFlowChild = *downcast<Container>(layoutBox).firstInFlowChild();
>-    if (!marginBeforeCollapsesWithParentMarginBefore(layoutState, firstInFlowChild))
>-        return 0;
>-    // Collect collapsed margin top recursively.
>-    return marginValue(computedNonCollapsedMarginBefore(layoutState, firstInFlowChild), collapsedMarginBeforeFromFirstChild(layoutState, firstInFlowChild));
>-}
>-
>-LayoutUnit BlockFormattingContext::Geometry::MarginCollapse::collapsedMarginAfterFromLastChild(const LayoutState& layoutState, const Box& layoutBox)
>-{
>-    ASSERT(layoutBox.isBlockLevelBox());
>-
>-    // Check if the last child propagates its margin bottom.
>-    if (!is<Container>(layoutBox) || !downcast<Container>(layoutBox).hasInFlowChild())
>-        return 0;
>-
>-    // Do not collapse margin with a box from a non-block formatting context <div><span>foobar</span></div>.
>-    if (layoutBox.establishesFormattingContext() && !layoutBox.establishesBlockFormattingContextOnly())
>-        return 0;
>-
>-    // FIXME: Check for collapsed through margin.
>-    auto& lastInFlowChild = *downcast<Container>(layoutBox).lastInFlowChild();
>-    if (!marginAfterCollapsesWithParentMarginAfter(layoutState, lastInFlowChild))
>-        return 0;
>-
>-    // Collect collapsed margin bottom recursively.
>-    return marginValue(computedNonCollapsedMarginAfter(layoutState, lastInFlowChild), collapsedMarginAfterFromLastChild(layoutState, lastInFlowChild));
>-}
>-
>-bool BlockFormattingContext::Geometry::MarginCollapse::marginBeforeCollapsesWithParentMarginAfter(const LayoutState& layoutState, const Box& layoutBox)
>-{
>-    // 1. This is the last in-flow child and its margins collapse through and the margin after collapses with parent's margin after or
>-    // 2. This box's margin after collapses with the next sibling's margin before and that sibling collapses through and
>-    // we can get to the last in-flow child like that.
>-    auto* lastInFlowChild = layoutBox.parent()->lastInFlowChild();
>-    for (auto* currentBox = &layoutBox; currentBox; currentBox = currentBox->nextInFlowSibling()) {
>-        if (!marginsCollapseThrough(layoutState, *currentBox))
>-            return false;
>-        if (currentBox == lastInFlowChild)
>-            return marginAfterCollapsesWithParentMarginAfter(layoutState, *currentBox); 
>-        if (!marginAfterCollapsesWithNextSibling(*currentBox))
>-            return false;
>-    }
>-    ASSERT_NOT_REACHED();
>-    return false;
>-}
>-
>-bool BlockFormattingContext::Geometry::MarginCollapse::marginBeforeCollapsesWithParentMarginBefore(const LayoutState& layoutState, const Box& layoutBox)
>-{
>-    // The first inflow child could propagate its top margin to parent.
>-    // https://www.w3.org/TR/CSS21/box.html#collapsing-margins
>-    if (layoutBox.isAnonymous())
>-        return false;
>-
>-    ASSERT(layoutBox.isBlockLevelBox());
>-
>-    // Margins between a floated box and any other box do not collapse.
>-    if (layoutBox.isFloatingPositioned())
>-        return false;
>-
>-    // Margins of absolutely positioned boxes do not collapse.
>-    if (layoutBox.isOutOfFlowPositioned())
>-        return false;
>-
>-    // Margins of inline-block boxes do not collapse.
>-    if (layoutBox.isInlineBlockBox())
>-        return false;
>-
>-    // Only the first inlflow child collapses with parent.
>-    if (layoutBox.previousInFlowSibling())
>-        return false;
>-
>-    auto& parent = *layoutBox.parent();
>-    // Margins of elements that establish new block formatting contexts do not collapse with their in-flow children
>-    if (establishesBlockFormattingContext(parent))
>-        return false;
>-
>-    if (hasBorderBefore(parent))
>-        return false;
>-
>-    if (hasPaddingBefore(parent))
>-        return false;
>-
>-    // ...and the child has no clearance.
>-    if (hasClearance(layoutBox))
>-        return false;
>-
>-    if (BlockFormattingContext::Quirks::shouldIgnoreMarginBefore(layoutState, layoutBox))
>-        return false;
>-
>-    return true;
>-}
>-
>-bool BlockFormattingContext::Geometry::MarginCollapse::marginAfterCollapsesWithSiblingMarginBeforeWithClearance(const LayoutState& layoutState, const Box& layoutBox)
>-{
>-    // If the top and bottom margins of an element with clearance are adjoining, its margins collapse with the adjoining margins
>-    // of following siblings but that resulting margin does not collapse with the bottom margin of the parent block.
>-    if (!marginsCollapseThrough(layoutState, layoutBox))
>-        return false;
>-
>-    for (auto* previousSibling = layoutBox.previousInFlowSibling(); previousSibling; previousSibling = previousSibling->previousInFlowSibling()) {
>-        if (!marginsCollapseThrough(layoutState, *previousSibling))
>-            return false;
>-        if (hasClearance(*previousSibling))
>-            return true;
>-    }
>-    return false;
>-}
>-
>-bool BlockFormattingContext::Geometry::MarginCollapse::marginAfterCollapsesWithParentMarginBefore(const LayoutState& layoutState, const Box& layoutBox)
>-{
>-    // 1. This is the first in-flow child and its margins collapse through and the margin before collapses with parent's margin before or
>-    // 2. This box's margin before collapses with the previous sibling's margin after and that sibling collapses through and
>-    // we can get to the first in-flow child like that.
>-    auto* firstInFlowChild = layoutBox.parent()->firstInFlowChild();
>-    for (auto* currentBox = &layoutBox; currentBox; currentBox = currentBox->previousInFlowSibling()) {
>-        if (!marginsCollapseThrough(layoutState, *currentBox))
>-            return false;
>-        if (currentBox == firstInFlowChild)
>-            return marginBeforeCollapsesWithParentMarginBefore(layoutState, *currentBox); 
>-        if (!marginBeforeCollapsesWithPreviousSibling(*currentBox))
>-            return false;
>-    }
>-    ASSERT_NOT_REACHED();
>-    return false;
>-}
>-
>-bool BlockFormattingContext::Geometry::MarginCollapse::marginAfterCollapsesWithParentMarginAfter(const LayoutState& layoutState, const Box& layoutBox)
>-{
>-    if (layoutBox.isAnonymous())
>-        return false;
>-
>-    ASSERT(layoutBox.isBlockLevelBox());
>-
>-    // Margins between a floated box and any other box do not collapse.
>-    if (layoutBox.isFloatingPositioned())
>-        return false;
>-
>-    // Margins of absolutely positioned boxes do not collapse.
>-    if (layoutBox.isOutOfFlowPositioned())
>-        return false;
>-
>-    // Margins of inline-block boxes do not collapse.
>-    if (layoutBox.isInlineBlockBox())
>-        return false;
>-
>-    // Only the last inlflow child collapses with parent.
>-    if (layoutBox.nextInFlowSibling())
>-        return false;
>-
>-    auto& parent = *layoutBox.parent();
>-    // Margins of elements that establish new block formatting contexts do not collapse with their in-flow children.
>-    if (establishesBlockFormattingContext(parent))
>-        return false;
>-
>-    // The bottom margin of an in-flow block box with a 'height' of 'auto' collapses with its last in-flow block-level child's bottom margin, if:
>-    if (!parent.style().height().isAuto())
>-        return false;
>-
>-    // the box has no bottom padding, and
>-    if (hasPaddingBefore(parent))
>-        return false;
>-
>-    // the box has no bottom border, and
>-    if (hasBorderBefore(parent))
>-        return false;
>-
>-    // the child's bottom margin neither collapses with a top margin that has clearance...
>-    if (marginAfterCollapsesWithSiblingMarginBeforeWithClearance(layoutState, layoutBox))
>-        return false;
>-
>-    // nor (if the box's min-height is non-zero) with the box's top margin.
>-    auto computedMinHeight = parent.style().logicalMinHeight();
>-    if (!computedMinHeight.isAuto() && computedMinHeight.value() && marginAfterCollapsesWithParentMarginBefore(layoutState, layoutBox))
>-        return false;
>-
>-    return true;
>-}
>-
>-bool BlockFormattingContext::Geometry::MarginCollapse::marginBeforeCollapsesWithPreviousSibling(const Box& layoutBox)
>-{
>-    ASSERT(layoutBox.isBlockLevelBox());
>-
>-    if (!layoutBox.previousInFlowSibling())
>-        return false;
>-
>-    auto& previousInFlowSibling = *layoutBox.previousInFlowSibling();
>-
>-    // Margins between a floated box and any other box do not collapse.
>-    if (layoutBox.isFloatingPositioned() || previousInFlowSibling.isFloatingPositioned())
>-        return false;
>-
>-    // Margins of absolutely positioned boxes do not collapse.
>-    if ((layoutBox.isOutOfFlowPositioned() && !layoutBox.style().top().isAuto())
>-        || (previousInFlowSibling.isOutOfFlowPositioned() && !previousInFlowSibling.style().bottom().isAuto()))
>-        return false;
>-
>-    // Margins of inline-block boxes do not collapse.
>-    if (layoutBox.isInlineBlockBox() || previousInFlowSibling.isInlineBlockBox())
>-        return false;
>-
>-    // The bottom margin of an in-flow block-level element always collapses with the top margin of
>-    // its next in-flow block-level sibling, unless that sibling has clearance.
>-    if (hasClearance(layoutBox))
>-        return false;
>-
>-    return true;
>-}
>-
>-bool BlockFormattingContext::Geometry::MarginCollapse::marginAfterCollapsesWithNextSibling(const Box& layoutBox)
>-{
>-    ASSERT(layoutBox.isBlockLevelBox());
>-
>-    if (!layoutBox.nextInFlowSibling())
>-        return false;
>-
>-    return marginBeforeCollapsesWithPreviousSibling(*layoutBox.nextInFlowSibling());
>-}
>-
>-bool BlockFormattingContext::Geometry::MarginCollapse::marginsCollapseThrough(const LayoutState& layoutState, const Box& layoutBox)
>-{
>-    ASSERT(layoutBox.isBlockLevelBox());
>-
>-    // A box's own margins collapse if the 'min-height' property is zero, and it has neither top or bottom borders nor top or bottom padding,
>-    // and it has a 'height' of either 0 or 'auto', and it does not contain a line box, and all of its in-flow children's margins (if any) collapse.
>-    if (hasBorderBefore(layoutBox) || hasBorderAfter(layoutBox))
>-        return false;
>-
>-    if (hasPaddingBefore(layoutBox) || hasPaddingAfter(layoutBox))
>-        return false;
>-
>-    // FIXME: Check for computed 0 height.
>-    if (!layoutBox.style().height().isAuto())
>-        return false;
>-
>-    // FIXME: Check for computed 0 height.
>-    if (!layoutBox.style().minHeight().isAuto())
>-        return false;
>-
>-    if (!is<Container>(layoutBox))
>-        return true;
>-
>-    if (layoutBox.establishesInlineFormattingContext()) {
>-        if (downcast<InlineFormattingState>(layoutState.establishedFormattingState(layoutBox)).inlineRuns().isEmpty())
>-            return false;
>-    } else {
>-        for (auto* inflowChild = downcast<Container>(layoutBox).firstInFlowChild(); inflowChild; inflowChild = inflowChild->nextInFlowSibling()) {
>-            if (!marginsCollapseThrough(layoutState, *inflowChild))
>-                return true;
>-        }
>-    }
>-
>-    return true;
>-}
>-
>-LayoutUnit BlockFormattingContext::Geometry::MarginCollapse::marginBefore(const LayoutState& layoutState, const Box& layoutBox)
>-{
>-    if (layoutBox.isAnonymous())
>-        return 0;
>-
>-    ASSERT(layoutBox.isBlockLevelBox());
>-
>-    // TODO: take _hasAdjoiningMarginBeforeAndAfter() into account.
>-    if (marginBeforeCollapsesWithParentMarginBefore(layoutState, layoutBox))
>-        return 0;
>-
>-    // FIXME: Find out the logic behind this.
>-    if (BlockFormattingContext::Quirks::shouldIgnoreMarginBefore(layoutState, layoutBox))
>-        return 0;
>-
>-    if (!marginBeforeCollapsesWithPreviousSibling(layoutBox)) {
>-        if (!marginsCollapseThrough(layoutState, layoutBox))
>-            return nonCollapsedMarginBefore(layoutState, layoutBox);
>-        // Compute the collapsed through value.
>-        auto marginBefore = nonCollapsedMarginBefore(layoutState, layoutBox);
>-        auto marginAfter = nonCollapsedMarginAfter(layoutState, layoutBox); 
>-        return marginValue(marginBefore, marginAfter);
>-    }
>-
>-    // The bottom margin of an in-flow block-level element always collapses with the top margin of its next in-flow block-level sibling,
>-    // unless that sibling has clearance.
>-    auto* previousInFlowSibling = layoutBox.previousInFlowSibling();
>-    if (!previousInFlowSibling)
>-        return nonCollapsedMarginBefore(layoutState, layoutBox);
>-
>-    auto previousSiblingMarginAfter = nonCollapsedMarginAfter(layoutState, *previousInFlowSibling);
>-    auto marginBefore = nonCollapsedMarginBefore(layoutState, layoutBox);
>-    return marginValue(marginBefore, previousSiblingMarginAfter);
>-}
>-
>-LayoutUnit BlockFormattingContext::Geometry::MarginCollapse::marginAfter(const LayoutState& layoutState, const Box& layoutBox)
>-{
>-    if (layoutBox.isAnonymous())
>-        return 0;
>-
>-    ASSERT(layoutBox.isBlockLevelBox());
>-
>-    // TODO: take _hasAdjoiningMarginBeforeAndBottom() into account.
>-    if (marginAfterCollapsesWithParentMarginAfter(layoutState, layoutBox))
>-        return 0;
>-
>-    if (marginsCollapseThrough(layoutState, layoutBox))
>-        return 0;
>-
>-    // Floats and out of flow positioned boxes do not collapse their margins.
>-    if (!marginAfterCollapsesWithNextSibling(layoutBox))
>-        return nonCollapsedMarginAfter(layoutState, layoutBox);
>-
>-    // The bottom margin of an in-flow block-level element always collapses with the top margin of its next in-flow block-level sibling,
>-    // unless that sibling has clearance.
>-    if (layoutBox.nextInFlowSibling())
>-        return 0;
>-    return nonCollapsedMarginAfter(layoutState, layoutBox);
>-}
>-
>-}
>-}
>-#endif
>diff --git a/Source/WebCore/layout/displaytree/DisplayBox.cpp b/Source/WebCore/layout/displaytree/DisplayBox.cpp
>index 027b434bbc6d4c2f5510afce9c507839e649e244..6db7dedb37ac9e38fb945682969e87d6be43eede 100644
>--- a/Source/WebCore/layout/displaytree/DisplayBox.cpp
>+++ b/Source/WebCore/layout/displaytree/DisplayBox.cpp
>@@ -60,7 +60,7 @@ Box::Box(const Box& other)
>     , m_horizontalMargin(other.m_horizontalMargin)
>     , m_verticalMargin(other.m_verticalMargin)
>     , m_horizontalNonComputedMargin(other.m_horizontalNonComputedMargin)
>-    , m_estimatedMarginBefore(other.m_estimatedMarginBefore)
>+    , m_hasClearance(other.m_hasClearance)
>     , m_border(other.m_border)
>     , m_padding(other.m_padding)
> #if !ASSERT_DISABLED
>@@ -74,6 +74,7 @@ Box::Box(const Box& other)
>     , m_hasValidPadding(other.m_hasValidPadding)
>     , m_hasValidContentHeight(other.m_hasValidContentHeight)
>     , m_hasValidContentWidth(other.m_hasValidContentWidth)
>+    , m_estimatedMarginBefore(other.m_estimatedMarginBefore)
> #endif
> {
> }
>diff --git a/Source/WebCore/layout/displaytree/DisplayBox.h b/Source/WebCore/layout/displaytree/DisplayBox.h
>index 56392f47ee79e30d3f0e21894d3f14bb875d7e89..5acb087ffab49204f6cb6767d157d33070999d2f 100644
>--- a/Source/WebCore/layout/displaytree/DisplayBox.h
>+++ b/Source/WebCore/layout/displaytree/DisplayBox.h
>@@ -136,21 +136,20 @@ public:
>     LayoutUnit width() const { return borderLeft() + paddingLeft().valueOr(0) + contentBoxWidth() + paddingRight().valueOr(0) + borderRight(); }
>     LayoutUnit height() const { return borderTop() + paddingTop().valueOr(0) + contentBoxHeight() + paddingBottom().valueOr(0) + borderBottom(); }
>     Rect rect() const { return { top(), left(), width(), height() }; }
>-    Rect rectWithMargin() const { return { top() - marginBefore(), left() - marginStart(), marginStart() + width() + marginEnd(), marginBefore() + height() + marginAfter() }; }
>+    Rect rectWithMargin() const;
> 
>     Layout::VerticalMargin verticalMargin() const;
>     LayoutUnit marginBefore() const;
>     LayoutUnit marginStart() const;
>     LayoutUnit marginAfter() const;
>     LayoutUnit marginEnd() const;
>+    bool hasClearance() const { return m_hasClearance; }
> 
>     LayoutUnit nonCollapsedMarginBefore() const;
>     LayoutUnit nonCollapsedMarginAfter() const;
>     LayoutUnit nonComputedMarginStart() const;
>     LayoutUnit nonComputedMarginEnd() const;
> 
>-    Optional<LayoutUnit> estimatedMarginBefore() const { return m_estimatedMarginBefore; }
>-
>     LayoutUnit borderTop() const;
>     LayoutUnit borderLeft() const;
>     LayoutUnit borderBottom() const;
>@@ -175,6 +174,11 @@ public:
>     Rect paddingBox() const;
>     Rect contentBox() const;
> 
>+#if !ASSERT_DISABLED
>+    void setEstimatedMarginBefore(Layout::EstimatedMarginBefore marginBefore) { m_estimatedMarginBefore = marginBefore; }
>+    Optional<Layout::EstimatedMarginBefore> estimatedMarginBefore() const { return m_estimatedMarginBefore; }
>+#endif
>+
> private:
>     struct Style {
>         Style(const RenderStyle&);
>@@ -194,7 +198,7 @@ private:
>     void setHorizontalMargin(Layout::HorizontalMargin);
>     void setVerticalMargin(Layout::VerticalMargin);
>     void setHorizontalNonComputedMargin(Layout::HorizontalMargin);
>-    void setEstimatedMarginBefore(LayoutUnit marginBefore) { m_estimatedMarginBefore = marginBefore; }
>+    void setHasClearance() { m_hasClearance = true; }
> 
>     void setBorder(Layout::Edges);
>     void setPadding(Optional<Layout::Edges>);
>@@ -203,6 +207,7 @@ private:
>     void invalidateMargin();
>     void invalidateBorder() { m_hasValidBorder = false; }
>     void invalidatePadding() { m_hasValidPadding = false; }
>+    void invalidateEstimatedMarginBefore() { m_estimatedMarginBefore = { }; }
> 
>     void setHasValidTop() { m_hasValidTop = true; }
>     void setHasValidLeft() { m_hasValidLeft = true; }
>@@ -227,7 +232,7 @@ private:
>     Layout::HorizontalMargin m_horizontalMargin;
>     Layout::VerticalMargin m_verticalMargin;
>     Layout::HorizontalMargin m_horizontalNonComputedMargin;
>-    Optional<LayoutUnit> m_estimatedMarginBefore;
>+    bool m_hasClearance;
> 
>     Layout::Edges m_border;
>     Optional<Layout::Edges> m_padding;
>@@ -243,6 +248,7 @@ private:
>     bool m_hasValidPadding { false };
>     bool m_hasValidContentHeight { false };
>     bool m_hasValidContentWidth { false };
>+    Optional<Layout::EstimatedMarginBefore> m_estimatedMarginBefore;
> #endif
> };
> 
>@@ -520,8 +526,8 @@ inline void Box::setVerticalMargin(Layout::VerticalMargin margin)
> #if !ASSERT_DISABLED
>     setHasValidVerticalMargin();
>     setHasValidVerticalNonCollapsedMargin();
>+    invalidateEstimatedMarginBefore();
> #endif
>-    ASSERT(!m_estimatedMarginBefore || *m_estimatedMarginBefore == margin.usedValues().before);
>     m_verticalMargin = margin;
> }
> 
>@@ -549,6 +555,14 @@ inline void Box::setPadding(Optional<Layout::Edges> padding)
>     m_padding = padding;
> }
> 
>+inline Box::Rect Box::rectWithMargin() const
>+{
>+    auto marginAfter = this->marginAfter();
>+    if (m_verticalMargin.collapsedValues() && m_verticalMargin.collapsedValues()->isCollapsedThrough)
>+        marginAfter = 0;
>+    return { top() - marginBefore(), left() - marginStart(), marginStart() + width() + marginEnd(), marginBefore() + height() + marginAfter };
>+}
>+
> inline Layout::VerticalMargin Box::verticalMargin() const
> {
>     ASSERT(m_hasValidVerticalMargin);
>diff --git a/Source/WebCore/layout/floats/FloatingContext.cpp b/Source/WebCore/layout/floats/FloatingContext.cpp
>index 71fc0606522780dbad23a98f5994a8538ca32e39..fcdb5077e6cd8f533bcafbd111a7c80254579b88 100644
>--- a/Source/WebCore/layout/floats/FloatingContext.cpp
>+++ b/Source/WebCore/layout/floats/FloatingContext.cpp
>@@ -183,34 +183,32 @@ Optional<Position> FloatingContext::verticalPositionWithClearance(const Box& lay
>         if (clearance <= 0)
>             return { };
> 
>+        displayBox.setHasClearance();
>         // Clearance inhibits margin collapsing. Let's reset the relevant adjoining margins.
>         if (auto* previousInFlowSibling = layoutBox.previousInFlowSibling()) {
>             auto& previousInFlowDisplayBox = layoutState.displayBoxForLayoutBox(*previousInFlowSibling);
>+            // Does this box with clearance actually collapse its margin before with the previous inflow box's margin after? 
>+            auto verticalMargin = displayBox.verticalMargin();
>+            if (verticalMargin.collapsedValues() && verticalMargin.collapsedValues()->before) {
>+                // Reset previous bottom after and current margin before to non-collapsing.
>+                auto previousVerticalMargin = previousInFlowDisplayBox.verticalMargin();
>+                ASSERT(previousVerticalMargin.collapsedValues() && previousVerticalMargin.collapsedValues()->after);
> 
>-            // Since the previous inflow sibling has already been laid out, its margin is collapsed by now.
>-            ASSERT(!previousInFlowDisplayBox.marginAfter());
>-            auto collapsedMargin = displayBox.marginBefore();
>-
>-            // Reset previous bottom and current top margins to non-collapsing.
>-            auto previousVerticalMargin = previousInFlowDisplayBox.verticalMargin();
>-            if (previousVerticalMargin.collapsedValues() && previousVerticalMargin.collapsedValues()->after) {
>+                auto collapsedMargin = *verticalMargin.collapsedValues()->before;
>                 previousVerticalMargin.setCollapsedValues({ previousVerticalMargin.collapsedValues()->before, { } });
>                 previousInFlowDisplayBox.setVerticalMargin(previousVerticalMargin);
>-            }
>-            // FIXME: check if collapsing through has anything to do with this.
>-            auto verticalMargin = displayBox.verticalMargin();
>-            if (verticalMargin.collapsedValues() && verticalMargin.collapsedValues()->before) {
>+
>                 verticalMargin.setCollapsedValues({ { }, verticalMargin.collapsedValues()->after });
>                 displayBox.setVerticalMargin(verticalMargin);
>-            }
> 
>-            auto nonCollapsedMargin = previousInFlowDisplayBox.marginAfter() + displayBox.marginBefore();
>-            auto marginOffset = nonCollapsedMargin - collapsedMargin;
>-            // Move the box to the position where it would be with non-collapsed margins.
>-            rootRelativeTop += marginOffset;
>+                auto nonCollapsedMargin = previousVerticalMargin.usedValues().after + verticalMargin.usedValues().before;
>+                auto marginDifference = nonCollapsedMargin - collapsedMargin;
>+                // Move the box to the position where it would be with non-collapsed margins.
>+                rootRelativeTop += marginDifference;
> 
>-            // Having negative clearance is also normal. It just means that the box with the non-collapsed margins is now lower than it needs to be.
>-            clearance -= marginOffset;
>+                // Having negative clearance is also normal. It just means that the box with the non-collapsed margins is now lower than it needs to be.
>+                clearance -= marginDifference;
>+            }
>         }
>         // Now adjust the box's position with the clearance.
>         rootRelativeTop += clearance;
>diff --git a/Tools/ChangeLog b/Tools/ChangeLog
>index 8dcee1e52700fae0a737c5008d5a85f0f1a8f060..c6d38d6b73757239c3a55f81a36864e6bab3b85b 100644
>--- a/Tools/ChangeLog
>+++ b/Tools/ChangeLog
>@@ -1,3 +1,12 @@
>+2018-12-29  Zalan Bujtas  <zalan@apple.com>
>+
>+        [LFC][BFC][MarginCollapsing] Add support for peculiar cases.
>+        https://bugs.webkit.org/show_bug.cgi?id=192625
>+
>+        Reviewed by NOBODY (OOPS!).
>+
>+        * LayoutReloaded/misc/LFC-passing-tests.txt:
>+
> 2018-12-22  Carlos Garcia Campos  <cgarcia@igalia.com>
> 
>         WebDriver: warn about non existing tests when parsing expectations
>diff --git a/Tools/LayoutReloaded/misc/LFC-passing-tests.txt b/Tools/LayoutReloaded/misc/LFC-passing-tests.txt
>index ff5eb38154b72ef8c8817fb2945f350ebb5d1012..225b7475da83aa5caae191ea591aa6251e69cf68 100644
>--- a/Tools/LayoutReloaded/misc/LFC-passing-tests.txt
>+++ b/Tools/LayoutReloaded/misc/LFC-passing-tests.txt
>@@ -4,23 +4,66 @@ fast/block/block-only/absolute-left-auto.html
> fast/block/block-only/absolute-left-right-top-bottom-auto.html
> fast/block/block-only/absolute-nested2.html
> fast/block/block-only/absolute-nested.html
>+fast/block/block-only/absolute-position-min-max-height.html
>+fast/block/block-only/absolute-position-min-max-width.html
>+fast/block/block-only/absolute-position-when-containing-block-is-not-in-the-formatting-context2.html
> fast/block/block-only/absolute-position-when-containing-block-is-not-in-the-formatting-context.html
> fast/block/block-only/absolute-simple.html
> fast/block/block-only/absolute-width-shrink-to-fit.html
> fast/block/block-only/absolute-width-stretch.html
> fast/block/block-only/absolute-with-static-block-position-nested.html
>+fast/block/block-only/almost-intruding-left-float-simple.html
>+fast/block/block-only/body-height-with-auto-html-height-quirk2.html
>+fast/block/block-only/body-height-with-auto-html-height-quirk.html
>+fast/block/block-only/body-height-with-non-auto-html-height-quirk2.html
>+fast/block/block-only/body-height-with-non-auto-html-height-quirk.html
> fast/block/block-only/border-simple.html
>+fast/block/block-only/collapsed-margin-with-min-height.html
> fast/block/block-only/fixed-nested.html
>+fast/block/block-only/float-and-siblings-with-margins.html
>+fast/block/block-only/float-avoider-multiple-roots.html
>+fast/block/block-only/float-avoider-simple-left.html
>+fast/block/block-only/float-avoider-simple-right.html
>+fast/block/block-only/float-avoider-with-margins.html
>+fast/block/block-only/float-left-when-container-has-padding-margin.html
>+fast/block/block-only/float-min-max-height.html
>+fast/block/block-only/float-min-max-width.html
>+fast/block/block-only/floating-and-next-previous-inflow-with-margin-with-no-border.html
>+fast/block/block-only/floating-and-next-previous-inflow-with-margin.html
>+fast/block/block-only/floating-box-clear-both-simple.html
>+fast/block/block-only/floating-box-clear-right-simple.html
>+fast/block/block-only/floating-box-left-and-right-multiple-with-top-offset.html
>+fast/block/block-only/floating-box-left-and-right-multiple.html
>+fast/block/block-only/floating-box-right-simple.html
>+fast/block/block-only/floating-box-with-clear-siblings.html
>+fast/block/block-only/floating-box-with-clear-simple.html
>+fast/block/block-only/floating-box-with-new-formatting-context.html
>+fast/block/block-only/floating-box-with-relative-positioned-sibling.html
>+fast/block/block-only/floating-left-and-right-with-clearance.html
>+fast/block/block-only/floating-left-right-simple.html
>+fast/block/block-only/floating-left-right-with-all-margins.html
>+fast/block/block-only/floating-lefts-and-rights-simple.html
>+fast/block/block-only/floating-multiple-lefts-in-body.html
>+fast/block/block-only/floating-multiple-lefts-multiple-lines.html
>+fast/block/block-only/floating-multiple-lefts.html
>+fast/block/block-only/floating-with-new-block-formatting-context.html
>+fast/block/block-only/inflow-min-max-height.html
>+fast/block/block-only/inflow-min-max-width.html
> fast/block/block-only/margin-collapse-bottom-bottom.html
> fast/block/block-only/margin-collapse-bottom-nested.html
>+fast/block/block-only/margin-collapse-first-last-are-floating.html
> fast/block/block-only/margin-collapse-simple.html
> fast/block/block-only/margin-collapse-top-nested.html
> fast/block/block-only/margin-collapse-when-child-has-padding-border.html
>+fast/block/block-only/margin-collapse-with-block-formatting-context2.html
>+fast/block/block-only/margin-collapse-with-block-formatting-context.html
>+fast/block/block-only/margin-collapse-with-clearance.html
> fast/block/block-only/margin-left-right-sizing-out-of-flow.html
> fast/block/block-only/margin-left-right-sizing.html
> fast/block/block-only/margin-propagation-simple-content-height.html
> fast/block/block-only/margin-sibling-collapse-propagated.html
> fast/block/block-only/margin-simple.html
>+fast/block/block-only/min-max-height-percentage.html
> fast/block/block-only/negative-margin-simple.html
> fast/block/block-only/padding-nested.html
> fast/block/block-only/padding-simple.html
>@@ -31,80 +74,49 @@ fast/block/block-only/relative-position-when-containing-block-is-not-in-the-form
> fast/block/block-only/relative-right.html
> fast/block/block-only/relative-siblings.html
> fast/block/block-only/relative-simple.html
>-fast/block/block-only/absolute-position-when-containing-block-is-not-in-the-formatting-context2.html
>-fast/block/block-only/margin-collapse-with-block-formatting-context.html
>-fast/block/block-only/margin-collapse-with-block-formatting-context2.html
>-fast/block/block-only/float-left-when-container-has-padding-margin.html
>-fast/block/block-only/floating-box-left-and-right-multiple-with-top-offset.html
>-fast/block/block-only/floating-box-left-and-right-multiple.html
>-fast/block/block-only/floating-box-right-simple.html
>-fast/block/block-only/floating-box-with-new-formatting-context.html
>-fast/block/block-only/floating-box-with-relative-positioned-sibling.html
>-fast/block/block-only/floating-left-right-simple.html
>-fast/block/block-only/floating-left-right-with-all-margins.html
>-fast/block/block-only/floating-lefts-and-rights-simple.html
>-fast/block/block-only/floating-multiple-lefts-in-body.html
>-fast/block/block-only/floating-multiple-lefts-multiple-lines.html
>-fast/block/block-only/floating-multiple-lefts.html
>-fast/block/block-only/floating-and-next-previous-inflow-with-margin.html
>-fast/block/block-only/floating-and-next-previous-inflow-with-margin-with-no-border.html
>-fast/block/block-only/floating-left-and-right-with-clearance.html
>-fast/block/block-only/float-and-siblings-with-margins.html
>-fast/block/block-only/margin-collapse-with-clearance.html
>-fast/block/block-only/float-avoider-simple-left.html
>-fast/block/block-only/float-avoider-simple-right.html
>-fast/block/block-only/float-avoider-multiple-roots.html
>-fast/block/block-only/float-avoider-with-margins.html
>-fast/block/block-only/inflow-min-max-width.html
>-fast/block/block-only/absolute-position-min-max-width.html
>-fast/block/block-only/float-min-max-width.html
>-fast/block/block-only/inflow-min-max-height.html
>-fast/block/block-only/absolute-position-min-max-height.html
>-fast/block/block-only/float-min-max-height.html
>-fast/block/block-only/min-max-height-percentage.html
>-fast/block/block-only/body-height-with-non-auto-html-height-quirk.html
>-fast/block/block-only/body-height-with-non-auto-html-height-quirk2.html
>-fast/block/block-only/body-height-with-auto-html-height-quirk.html
>-fast/block/block-only/body-height-with-auto-html-height-quirk2.html
>-fast/block/block-only/collapsed-margin-with-min-height.html
>+fast/block/basic/002.html
>+fast/block/basic/003.html
>+fast/block/basic/006.html
>+fast/block/basic/007.html
>+fast/block/basic/008.html
>+fast/block/basic/009.html
>+fast/block/basic/012.html
>+fast/block/basic/child-block-level-box-with-height-percent.html
>+fast/block/basic/height-percentage-simple.html
> fast/block/basic/inline-content-with-floating-image.html
> fast/block/basic/inline-content-with-floating-images2.html
>-fast/inline/simple-intruding-float1.html
>-fast/inline/simple-intruding-floats2.html
>-fast/inline/simple-intruding-floats3.html
>-fast/inline/simple-inline-block.html
>-fast/inline/simple-shrink-to-fit-inline-block.html
>-fast/inline/simple-inline-inflow-positioned.html
>-fast/inline/simple-inline-with-out-of-flow-descendant.html
>-fast/inline/simple-inline-with-out-of-flow-descendant2.html
>-fast/inline/inline-content-with-padding-left-right.html
>-fast/inline/inline-content-with-border-left-right.html
>-fast/inline/inline-content-with-margin-left-right.html
>-fast/inline/inline-content-and-nested-formatting-root-with-margin-left-right.html
>-fast/inline/inline-content-with-image-simple.html
>-fast/inline/inline-content-with-float-and-margin.html
>-fast/block/basic/height-percentage-simple.html
>-fast/block/basic/child-block-level-box-with-height-percent.html
>+fast/block/basic/percent-height-inside-anonymous-block.html
> fast/block/basic/quirk-mode-percent-height.html
>+fast/block/basic/quirk-percent-height-grandchild.html
> fast/block/float/001.html
> fast/block/float/007.html
> fast/block/float/008.html
> fast/block/float/009.html
> fast/block/float/013.html
> fast/block/float/019.html
>-fast/block/basic/002.html
>-fast/block/basic/003.html
>-fast/block/basic/006.html
>-fast/block/basic/007.html
>-fast/block/basic/008.html
>-fast/block/basic/009.html
>-fast/block/basic/012.html
>+fast/block/float/negative-margin-clear.html
>+fast/block/float/overhanging-after-height-decrease-offsets.html
>+fast/block/float/overhanging-after-height-decrease.html
>+fast/block/float/overlapping-floats-with-overflow-hidden.html
>+fast/block/float/previous-sibling-abspos-002.html
>+fast/block/float/relative-painted-twice.html
>+fast/block/float/avoidance-rtl.html
>+fast/block/float/br-with-clear.html
>+fast/block/float/clamped-right-float.html
>+fast/block/float/float-on-zero-height-line.html
>+fast/block/float/float-overhangs-root.html
>+fast/block/float/float-with-anonymous-previous-sibling.html
>+fast/block/float/floats-not-cleared-crash.html
> fast/block/margin-collapse/002.html
> fast/block/margin-collapse/003.html
> fast/block/margin-collapse/026.html
> fast/block/margin-collapse/027.html
>+fast/block/margin-collapse/028.html
>+fast/block/margin-collapse/029.html
>+fast/block/margin-collapse/035.html
> fast/block/margin-collapse/039.html
> fast/block/margin-collapse/040.html
>+fast/block/positioning/003.html
> fast/block/positioning/004.html
> fast/block/positioning/005.html
> fast/block/positioning/006.html
>@@ -145,8 +157,29 @@ fast/block/positioning/046.html
> fast/block/positioning/049.html
> fast/block/positioning/052.html
> fast/block/positioning/054.html
>+fast/block/positioning/060.html
>+fast/block/positioning/absolute-positioning-no-scrollbar.html
>+fast/block/positioning/change-containing-block-for-absolute-positioned.html
>+fast/block/positioning/change-containing-block-for-fixed-positioned.html
>+fast/block/positioning/complex-positioned-movement.html
>+fast/block/positioning/fixed-position-detached-frame.html
>+fast/block/positioning/fixed-position-stacking-context2.html
>+fast/block/positioning/fixed-position-stacking-context.html
>+fast/block/positioning/hiding-inside-relpositioned-inline.html
>+fast/block/positioning/insert-positioned-in-anonymous-crash.html
>+fast/block/positioning/leftmargin-topmargin.html
>+fast/block/positioning/negative-rel-position.html
>+fast/block/positioning/abs-inside-inline-rel.html
>+fast/block/positioning/pref-width-change.html
>+fast/block/positioning/relative-overflow-replaced-float.html
>+fast/block/positioning/static-inline-position-dynamic.html
> fast/block/inside-inlines/basic-float-intrusion.html
> fast/block/inside-inlines/crash-on-first-line-change.html
>+fast/block/lineboxcontain/replaced.html
>+fast/block/collapse-anon-block-with-float-siblings-only.html
>+fast/block/crash-when-anonymous-blocks-are-merged-with-simple-line-layout.html
>+fast/block/crash-when-subtree-is-still-attached.html
>+fast/block/geometry-map-assertion-with-tall-content.html
> fast/borders/0px-borders-no-line-height.html
> fast/borders/0px-borders.html
> fast/borders/block-mask-overlay-image-outset.html
>@@ -156,11 +189,8 @@ fast/borders/border-image-scaled-gradient.html
> fast/borders/border-image-slice-omission.html
> fast/borders/border-left-right-same-bottom-different-color.html
> fast/borders/border-painting-dashed-at-all.html
>-fast/borders/border-painting-dashed.html
> fast/borders/border-painting-dotted-at-all.html
>-fast/borders/border-painting-dotted.html
> fast/borders/border-painting-double-at-all.html
>-fast/borders/border-painting-double.html
> fast/borders/border-painting-groove-at-all.html
> fast/borders/border-painting-inset-at-all.html
> fast/borders/border-painting-inset.html
>@@ -169,4 +199,86 @@ fast/borders/border-painting-outset.html
> fast/borders/border-painting-ridge-at-all.html
> fast/borders/border-painting-solid-at-all.html
> fast/borders/border-painting-solid.html
>-fast/inline-block/004.html
>+fast/borders/border-radius-inset-outset.html
>+fast/borders/border-radius-on-html.html
>+fast/borders/border-radius-on-subpixel-position-non-hidpi.html
>+fast/borders/border-radius-percent.html
>+fast/borders/border-radius-valid-border-clipping.html
>+fast/borders/border-radius-wide-border-01.html
>+fast/borders/border-radius-with-box-shadow-01.html
>+fast/borders/border-radius-with-box-shadow.html
>+fast/borders/border-shadow-large-radius.html
>+fast/borders/borderRadiusAllStylesAllCorners.html
>+fast/borders/borderRadiusArcs01.html
>+fast/borders/borderRadiusDashed01.html
>+fast/borders/borderRadiusDashed02.html
>+fast/borders/borderRadiusDashed03.html
>+fast/borders/borderRadiusDotted01.html
>+fast/borders/borderRadiusDotted02.html
>+fast/borders/borderRadiusDotted03.html
>+fast/borders/borderRadiusDouble01.html
>+fast/borders/borderRadiusDouble02.html
>+fast/borders/borderRadiusDouble03.html
>+fast/borders/borderRadiusGroove01.html
>+fast/borders/borderRadiusGroove02.html
>+fast/borders/borderRadiusInset01.html
>+fast/borders/borderRadiusInvalidColor.html
>+fast/borders/borderRadiusOutset01.html
>+fast/borders/borderRadiusRidge01.html
>+fast/borders/borderRadiusSolid01.html
>+fast/borders/borderRadiusSolid02.html
>+fast/borders/borderRadiusSolid03.html
>+fast/borders/borderRadiusSolid04.html
>+fast/borders/dashed-border-on-subpixel-position.html
>+fast/borders/dotted-border-on-subpixel-position.html
>+fast/borders/double-1px-border-assert.html
>+fast/borders/empty-drawrect-assert-after-pixelsnap.html
>+fast/borders/empty-outline-border-assert.html
>+fast/borders/hidpi-3x-input-hairline-border.html
>+fast/borders/hidpi-border-clipping-right-after-move.html
>+fast/borders/hidpi-border-painting-groove.html
>+fast/borders/hidpi-border-painting-ridge.html
>+fast/borders/hidpi-border-radius-outer-border-goes-rectangle.html
>+fast/borders/hidpi-border-radius-with-subpixel-margin-not-renderable.html
>+fast/borders/hidpi-border-width-flooring.html
>+fast/borders/hidpi-outline-hairline-painting.html
>+fast/borders/hidpi-outline-on-subpixel-position.html
>+fast/borders/hidpi-rounded-border-on-subpixel-position.html
>+fast/borders/hidpi-simple-hairline-border-painting.html
>+fast/borders/mixed-border-style2.html
>+fast/borders/negative-border-width.html
>+fast/borders/outline-offset-min-assert.html
>+fast/borders/outline-offset-overflow.html
>+fast/borders/webkit-border-radius.html
>+fast/inline/absolute-positioned-block-in-centred-block.html
>+fast/inline/absolute-positioned-inline-in-centred-block.html
>+fast/inline/anonymous-block-with-empty-inline.html
>+fast/inline/hidpi-outline-auto-negative-offset-with-border-radius.html
>+fast/inline/hidpi-outline-auto-with-fractional-radius.html
>+fast/inline/hidpi-outline-auto-with-one-focusring-rect.html
>+fast/inline/hidpi-pixel-gap-between-adjacent-selection-inlines.html
>+fast/inline/hidpi-select-inline-on-subpixel-position.html
>+fast/inline/hidpi-selection-gap-on-subpixel-position.html
>+fast/inline/hidpi-selection-gap-overlaps-inline-selection.html
>+fast/inline/inline-body-with-scrollbar-crash.html
>+fast/inline/inline-child-height-width-calc-crash.html
>+fast/inline/inline-content-with-border-left-right.html
>+fast/inline/inline-content-with-float-and-margin.html
>+fast/inline/inline-content-with-image-simple.html
>+fast/inline/inline-content-with-margin-left-right.html
>+fast/inline/inline-content-with-padding-left-right.html
>+fast/inline/inline-marquee-crash.html
>+fast/inline/inline-padding-disables-text-quirk.html
>+fast/inline/new-float-needs-layout-when-line-is-dirty.html
>+fast/inline/percentage-margins.html
>+fast/inline/simple-inline-block.html
>+fast/inline/simple-inline-inflow-positioned.html
>+fast/inline/simple-inline-with-out-of-flow-descendant2.html
>+fast/inline/simple-inline-with-out-of-flow-descendant.html
>+fast/inline/simple-intruding-float1.html
>+fast/inline/simple-intruding-floats2.html
>+fast/inline/simple-intruding-floats3.html
>+fast/inline/simple-line-layout-16bit-content.html
>+fast/inline/simple-shrink-to-fit-inline-block.html
>+fast/inline/skipped-whitespace-boundingBox.html
>+fast/inline/skipped-whitespace-client-rect.html

Actions: View | Formatted Diff | Diff

Attachments on bug 192625: 357130 | 357423 | 358137 | 358138 | 358142 | 358143 | 358144 | 358455 | 358479 | 358589 | 358670