Cherry-pick c1353df. rdar://123854267

    text-wrap balance should consider line-clamp when balancing
    https://bugs.webkit.org/show_bug.cgi?id=268302
    rdar://121858978

    Reviewed by Alan Baradlay.

    According to spec resolution [1], if line-clamp
    is defined, text-wrap: balance should balance
    only within the clamped lines.

    Up to this patch, we would balance taking into
    consideration all the lines and we would clamp
    it after balance.

    This patches makes InlineContentBalancer::initialize()
    take the maximum number of visible lines into account,
    based into the line-clamp property.

    Also, this allows for a small optimization:
    If line-clamp clamps to 1 line, we can skip balacing.

    [1] w3c/csswg-drafts#9310

    * LayoutTests/TestExpectations:
    * Source/WebCore/layout/formattingContexts/block/BlockLayoutState.h:
    (WebCore::Layout::BlockLayoutState::LineClamp::allowedLineCount const):
    * Source/WebCore/layout/formattingContexts/inline/InlineContentBalancer.cpp:
    (WebCore::Layout::InlineContentBalancer::initialize):
    (WebCore::Layout::InlineContentBalancer::computeBalanceConstraints):
    * Source/WebCore/layout/formattingContexts/inline/InlineContentBalancer.h:
    * Source/WebCore/layout/formattingContexts/inline/InlineFormattingContext.cpp:
    (WebCore::Layout::InlineFormattingContext::createDisplayContentForInlineContent):

    Canonical link: https://commits.webkit.org/273800@main

Canonical link: https://commits.webkit.org/272448.662@safari-7618-branch

Author: vitorroriz

LayoutTests/TestExpectations

@@ -3071,7 +3071,6 @@ webkit.org/b/257049 imported/w3c/web-platform-tests/css/css-text/white-space/ful
 webkit.org/b/257049 imported/w3c/web-platform-tests/css/css-text/white-space/seg-break-transformation-018.tentative.html [ ImageOnlyFailure ]
 webkit.org/b/257049 imported/w3c/web-platform-tests/css/css-text/white-space/seg-break-transformation-019.tentative.html [ ImageOnlyFailure ]
 webkit.org/b/257049 imported/w3c/web-platform-tests/css/css-text/white-space/tab-bidi-001.html [ ImageOnlyFailure ]
-webkit.org/b/257049 imported/w3c/web-platform-tests/css/css-text/white-space/text-wrap-balance-line-clamp-001.html [ ImageOnlyFailure ]
 imported/w3c/web-platform-tests/css/css-text/white-space/text-wrap-balance-float-001.html [ ImageOnlyFailure ]
 imported/w3c/web-platform-tests/css/css-text/white-space/text-wrap-balance-float-002.html [ ImageOnlyFailure ]
 imported/w3c/web-platform-tests/css/css-text/white-space/text-wrap-balance-float-003.html [ ImageOnlyFailure ]

Source/WebCore/layout/formattingContexts/block/BlockLayoutState.h

@@ -33,10 +33,11 @@ namespace Layout {
 
 class BlockFormattingContext;
 
-// This class holds block level information shared across child inline formatting contexts. 
+// This class holds block level information shared across child inline formatting contexts.
 class BlockLayoutState {
 public:
     struct LineClamp {
+        size_t allowedLineCount() const { return std::max(maximumLineCount - currentLineCount, 0lu); }
         size_t maximumLineCount { 0 };
         size_t currentLineCount { 0 };
     };

Source/WebCore/layout/formattingContexts/inline/InlineContentBalancer.cpp

@@ -110,11 +110,20 @@ InlineContentBalancer::InlineContentBalancer(InlineFormattingContext& inlineForm
 
 void InlineContentBalancer::initialize()
 {
+    auto lineClamp = m_inlineFormattingContext.layoutState().parentBlockLayoutState().lineClamp();
+    auto numberOfVisibleLinesAllowed = lineClamp ? std::make_optional(lineClamp->allowedLineCount()) : std::nullopt;
+
     if (!m_inlineFormattingContext.layoutState().placedFloats().isEmpty()) {
         m_cannotBalanceContent = true;
         return;
     }
 
+    // if we have a single line content, we don't have anything to be balanced.
+    if (numberOfVisibleLinesAllowed == 1) {
+        m_hasSingleLineVisibleContent = true;
+        return;
+    }
+
     m_numberOfInlineItems = m_inlineItemList.size();
     m_maximumLineWidth = m_horizontalConstraints.logicalWidth;
 
@@ -153,6 +162,10 @@ void InlineContentBalancer::initialize()
         auto textIndent = m_inlineFormattingContext.formattingUtils().computedTextIndent(InlineFormattingUtils::IsIntrinsicWidthMode::No, previousLineEndsWithLineBreak, m_maximumLineWidth);
         m_originalLineWidths.append(textIndent + lineSlidingWidth.width());
 
+        // If next line count would match (or exceed) the number of visible lines due to line-clamp, we can bail out early.
+        if (numberOfVisibleLinesAllowed && (lineIndex + 1 >= numberOfVisibleLinesAllowed))
+            break;
+
         layoutRange.start = InlineFormattingUtils::leadingInlineItemPositionForNextLine(lineLayoutResult.inlineItemRange.end, previousLineEnd, layoutRange.end);
         previousLineEnd = layoutRange.start;
         previousLine = PreviousLine { lineIndex, lineLayoutResult.contentGeometry.trailingOverflowingContentWidth, !lineLayoutResult.inlineContent.isEmpty() && lineLayoutResult.inlineContent.last().isLineBreak(), !lineLayoutResult.inlineContent.isEmpty(), lineLayoutResult.directionality.inlineBaseDirection, WTFMove(lineLayoutResult.floatContent.suspendedFloats) };
@@ -164,7 +177,7 @@ void InlineContentBalancer::initialize()
 
 std::optional> InlineContentBalancer::computeBalanceConstraints()
 {
-    if (m_cannotBalanceContent)
+    if (m_cannotBalanceContent || m_hasSingleLineVisibleContent)
         return std::nullopt;
 
     // If forced line breaks exist, then we can balance each forced-break-delimited

Source/WebCore/layout/formattingContexts/inline/InlineContentBalancer.h

@@ -63,6 +63,7 @@ class InlineContentBalancer {
     size_t m_numberOfInlineItems { 0 };
     double m_maximumLineWidth { 0 };
     bool m_cannotBalanceContent { false };
+    bool m_hasSingleLineVisibleContent { false };
 
     struct SlidingWidth {
         SlidingWidth(const InlineContentBalancer&, const InlineItemList&, size_t start, size_t end, bool useFirstLineStyle, bool isFirstLineInChunk);

Source/WebCore/layout/formattingContexts/inline/InlineFormattingContext.cpp

@@ -314,11 +314,8 @@ void InlineFormattingContext::updateBoxGeometryForPlacedFloats(const LineLayoutR
 
 InlineRect InlineFormattingContext::createDisplayContentForInlineContent(const LineBox& lineBox, const LineLayoutResult& lineLayoutResult, const ConstraintsForInlineContent& constraints, InlineDisplay::Content& displayContent, size_t numberOfPreviousLinesWithInlineContent)
 {
-    auto numberOfVisibleLinesAllowed = [&] () -> std::optional<size_t> {
-        if (auto lineClamp = layoutState().parentBlockLayoutState().lineClamp())
-            return lineClamp->maximumLineCount > lineClamp->currentLineCount ? lineClamp->maximumLineCount - lineClamp->currentLineCount : 0;
-        return { };
-    }();
+    auto numberOfVisibleLinesAllowed = layoutState().parentBlockLayoutState().lineClamp() ? std::make_optional(layoutState().parentBlockLayoutState().lineClamp()->allowedLineCount()) : std::nullopt;
+
     auto numberOfLinesWithInlineContent = numberOfPreviousLinesWithInlineContent + (!lineLayoutResult.inlineContent.isEmpty() ? 1 : 0);
     auto lineIsFullyTruncatedInBlockDirection = numberOfVisibleLinesAllowed && numberOfLinesWithInlineContent > *numberOfVisibleLinesAllowed;
     auto displayLine = InlineDisplayLineBuilder { *this, constraints }.build(lineLayoutResult, lineBox, lineIsFullyTruncatedInBlockDirection);