Make Block and inline-block have the same baseline when overflow: hidden

alanbaradlay · alanbaradlay · commit 9a017d08c0cd · 2026-02-17T12:30:45.000-08:00
https://bugs.webkit.org/show_bug.cgi?id=307965 Reviewed by Antti Koivisto. Just because a child box's baseline is its margin box, it does not necessarily mean it is not a valid baseline. e.g. <div style="display: inline-block"> <div style="overflow: hidden">text</div> </div> Due to 'overflow: hidden', the inner box's baseline is its margin box and not 'text', but it is still a valid baseline candidate box when computing the baseline for outer. * LayoutTests/TestExpectations: * Source/WebCore/layout/integration/LayoutIntegrationBoxGeometryUpdater.cpp: (WebCore::LayoutIntegration::lastInflowBoxBaseline): Do not use 'shouldUseMarginBoxAsBaseline' to decided whether a child box is a candidate for baseline computation. Canonical link: https://commits.webkit.org/307718@main
diff --git a/LayoutTests/TestExpectations b/LayoutTests/TestExpectations
@@ -8184,7 +8184,6 @@ imported/w3c/web-platform-tests/css/CSS2/visudet/replaced-elements-min-width-80.
 
 imported/w3c/web-platform-tests/css/CSS2/abspos/remove-block-between-inline-and-abspos.html [ ImageOnlyFailure ]
 
-imported/w3c/web-platform-tests/css/CSS2/linebox/baseline-block-with-overflow-001.html [ ImageOnlyFailure ]
 imported/w3c/web-platform-tests/css/CSS2/linebox/inline-formatting-context-023.xht [ ImageOnlyFailure ]
 imported/w3c/web-platform-tests/css/CSS2/linebox/vertical-align-117a.xht [ ImageOnlyFailure ]
 imported/w3c/web-platform-tests/css/CSS2/linebox/vertical-align-118a.xht [ ImageOnlyFailure ]
diff --git a/Source/WebCore/layout/integration/LayoutIntegrationBoxGeometryUpdater.cpp b/Source/WebCore/layout/integration/LayoutIntegrationBoxGeometryUpdater.cpp
@@ -365,13 +365,26 @@ static std::optional<LayoutUnit> lastInflowBoxBaseline(const RenderBlock& blockC
 {
     auto* lastInFlowChild = blockContainer.lastInFlowChildBox();
     for (auto* inflowBox = lastInFlowChild; inflowBox; inflowBox = inflowBox->previousInFlowSiblingBox()) {
-        if (inflowBox->isWritingModeRoot())
-            continue;
 
-        if (inflowBox->shouldApplyLayoutContainment())
-            continue;
+        auto isBaselineCanididate = [&](auto& inflowChildBox) {
+            if (inflowChildBox.isWritingModeRoot() || inflowChildBox.shouldApplyLayoutContainment() || is<RenderTable>(inflowChildBox))
+                return false;
+
+            if (CheckedPtr scrollableArea = inflowChildBox.layer() ? inflowChildBox.layer()->scrollableArea() : nullptr) {
+                if (scrollableArea->marquee())
+                    return false;
+
+                auto isScrollable = blockContainer.writingMode().isHorizontal() ? (scrollableArea->verticalScrollbar() || scrollableArea->scrollOffset().y()) : (scrollableArea->horizontalScrollbar() || scrollableArea->scrollOffset().x());
+                return !isScrollable;
+            }
+            if (CheckedPtr blockFlow = dynamicDowncast<RenderBlockFlow>(inflowChildBox)) {
+                auto hasValidBaseline = !blockFlow->childrenInline() || blockFlow->hasContentfulInlineOrBlockLine() || blockFlow->hasLineIfEmpty();
+                return hasValidBaseline;
+            }
+            return true;
+        };
 
-        if (shouldUseMarginBoxAsBaseline(*inflowBox)) {
+        if (!isBaselineCanididate(*inflowBox)) {
             // We need to find a better candidate for baseline.
             continue;
         }
