Cherry-pick 260286.14@webkit-2023.2-embargoed (0888aab). https://bugs…

….webkit.org/show_bug.cgi?id=245374

    Improve isInsideMulticolumnFlow lambda for top-layer elements
    https://bugs.webkit.org/show_bug.cgi?id=245374

    Reviewed by Alan Baradlay.

    Improve isInsideMulticolumnFlow lambda for top-layer elements.
    Top-layer elements can skip many ancestors since the containing
    block is the RenderView. So instead of checking the fragmentedFlowRoot
    boundary, check the containing block fragmented flow state.

    * Source/WebCore/rendering/RenderObject.cpp:
    (WebCore::RenderObject::setFragmentedFlowStateIncludingDescendants):
    (WebCore::RenderObject::initializeFragmentedFlowStateOnInsertion):
    (WebCore::RenderObject::resetFragmentedFlowStateOnRemoval):
    * Source/WebCore/rendering/RenderObject.h:

    Canonical link: https://commits.webkit.org/260286.14@webkit-2023.2-embargoed

Canonical link: https://commits.webkit.org/263022.6@webkit-2023.4-embargoed

Source/WebCore/rendering/RenderObject.cpp

@@ -223,7 +223,7 @@ bool RenderObject::isBlockContainer() const
         || display == DisplayType::TableCaption) && !isRenderReplaced();
 }
 
-void RenderObject::setFragmentedFlowStateIncludingDescendants(FragmentedFlowState state, const RenderElement* fragmentedFlowRoot, SkipDescendentFragmentedFlow skipDescendentFragmentedFlow)
+void RenderObject::setFragmentedFlowStateIncludingDescendants(FragmentedFlowState state, SkipDescendentFragmentedFlow skipDescendentFragmentedFlow)
 {
     setFragmentedFlowState(state);
 
@@ -234,22 +234,21 @@ void RenderObject::setFragmentedFlowStateIncludingDescendants(FragmentedFlowStat
         // If the child is a fragmentation context it already updated the descendants flag accordingly.
         if (child.isRenderFragmentedFlow() && skipDescendentFragmentedFlow == SkipDescendentFragmentedFlow::Yes)
             continue;
-        if (fragmentedFlowRoot && child.isOutOfFlowPositioned()) {
+        if (child.isOutOfFlowPositioned()) {
             // Fragmented status propagation stops at out-of-flow boundary.
             auto isInsideMulticolumnFlow = [&] {
                 auto* containingBlock = child.containingBlock();
                 if (!containingBlock) {
                     ASSERT_NOT_REACHED();
                     return false;
                 }
-                // It's ok to only check the first level containing block (as opposed to the containing block chain) as setFragmentedFlowStateIncludingDescendants is top to down.
-                return containingBlock->isDescendantOf(fragmentedFlowRoot);
+                return containingBlock->fragmentedFlowState() == InsideInFragmentedFlow;
             };
             if (!isInsideMulticolumnFlow())
                 continue;
         }
         ASSERT(skipDescendentFragmentedFlow == SkipDescendentFragmentedFlow::No || state != child.fragmentedFlowState());
-        child.setFragmentedFlowStateIncludingDescendants(state, fragmentedFlowRoot, skipDescendentFragmentedFlow);
+        child.setFragmentedFlowStateIncludingDescendants(state, skipDescendentFragmentedFlow);
     }
 }
 
@@ -291,8 +290,7 @@ void RenderObject::initializeFragmentedFlowStateOnInsertion()
     if (fragmentedFlowState() == computedState)
         return;
 
-    auto* enclosingFragmentedFlow = locateEnclosingFragmentedFlow();
-    setFragmentedFlowStateIncludingDescendants(computedState, enclosingFragmentedFlow ? enclosingFragmentedFlow->parent() : nullptr, SkipDescendentFragmentedFlow::No);
+    setFragmentedFlowStateIncludingDescendants(computedState, SkipDescendentFragmentedFlow::No);
 }
 
 void RenderObject::resetFragmentedFlowStateOnRemoval()
@@ -309,8 +307,7 @@ void RenderObject::resetFragmentedFlowStateOnRemoval()
     if (isRenderFragmentedFlow())
         return;
 
-    auto* enclosingFragmentedFlow = this->enclosingFragmentedFlow();
-    setFragmentedFlowStateIncludingDescendants(NotInsideFragmentedFlow, enclosingFragmentedFlow ? enclosingFragmentedFlow->parent() : nullptr);
+    setFragmentedFlowStateIncludingDescendants(NotInsideFragmentedFlow);
 }
 
 void RenderObject::setParent(RenderElement* parent)

Source/WebCore/rendering/RenderObject.h

@@ -298,7 +298,7 @@ class RenderObject : public CachedImageClient {
     };
 
     enum class SkipDescendentFragmentedFlow { No, Yes };
-    void setFragmentedFlowStateIncludingDescendants(FragmentedFlowState, const RenderElement* fragmentedFlowRoot, SkipDescendentFragmentedFlow = SkipDescendentFragmentedFlow::Yes);
+    void setFragmentedFlowStateIncludingDescendants(FragmentedFlowState, SkipDescendentFragmentedFlow = SkipDescendentFragmentedFlow::Yes);
 
     FragmentedFlowState fragmentedFlowState() const { return m_bitfields.fragmentedFlowState(); }
     void setFragmentedFlowState(FragmentedFlowState state) { m_bitfields.setFragmentedFlowState(state); }