LibWeb: Factor out conditions for creation of inline continuation

Having one big `if` to determine whether or not we should restructure an
inline layout node became a bit unwieldy. This extracts the logic into a
separate method.

Libraries/LibWeb/Layout/Node.cpp

@@ -30,6 +30,7 @@
 #include <LibWeb/Layout/TableWrapper.h>
 #include <LibWeb/Layout/TextNode.h>
 #include <LibWeb/Layout/Viewport.h>
+#include <LibWeb/SVG/SVGForeignObjectElement.h>
 
 namespace Web::Layout {
 
@@ -1210,6 +1211,30 @@ CSS::UserSelect Node::user_select_used_value() const
     return computed_value;
 }
 
+bool NodeWithStyleAndBoxModelMetrics::should_create_inline_continuation() const
+{
+    // This node must have an inline parent.
+    if (!parent())
+        return false;
+    auto const& parent_display = parent()->display();
+    if (!parent_display.is_inline_outside() || !parent_display.is_flow_inside())
+        return false;
+
+    // This node must not be inline itself or out of flow (which gets handled separately).
+    if (display().is_inline_outside() || is_out_of_flow())
+        return false;
+
+    // This node must not have `display: contents`; inline continuation gets handled by its children.
+    if (display().is_contents())
+        return false;
+
+    // Parent element must not be <foreignObject>
+    if (is<SVG::SVGForeignObjectElement>(parent()->dom_node()))
+        return false;
+
+    return true;
+}
+
 void NodeWithStyleAndBoxModelMetrics::propagate_style_along_continuation(CSS::ComputedProperties const& computed_style) const
 {
     auto continuation = continuation_of_node();

Libraries/LibWeb/Layout/Node.h

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2018-2023, Andreas Kling <andreas@ladybird.org>
+ * Copyright (c) 2025, Jelle Raaijmakers <jelle@ladybird.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -265,6 +266,8 @@ public:
     GC::Ptr<NodeWithStyleAndBoxModelMetrics> continuation_of_node() const { return m_continuation_of_node; }
     void set_continuation_of_node(Badge<TreeBuilder>, GC::Ptr<NodeWithStyleAndBoxModelMetrics> node) { m_continuation_of_node = node; }
 
+    bool should_create_inline_continuation() const;
+
     void propagate_style_along_continuation(CSS::ComputedProperties const&) const;
 
     virtual void visit_edges(Cell::Visitor& visitor) override;

Libraries/LibWeb/Layout/TreeBuilder.cpp

@@ -32,7 +32,6 @@
 #include <LibWeb/Layout/TextNode.h>
 #include <LibWeb/Layout/TreeBuilder.h>
 #include <LibWeb/Layout/Viewport.h>
-#include <LibWeb/SVG/SVGForeignObjectElement.h>
 
 namespace Web::Layout {
 
@@ -609,11 +608,9 @@ void TreeBuilder::update_layout_tree(DOM::Node& dom_node, TreeBuilder::Context&
         // If we completely finished inserting a block level element into an inline parent, we need to fix up the tree so
         // that we can maintain the invariant that all children are either inline or non-inline. We can't do this earlier,
         // because the restructuring adds new children after this node that become part of the ancestor stack.
-        auto* layout_parent = layout_node->parent();
-        if (layout_parent && layout_parent->display().is_inline_outside() && !display.is_contents()
-            && !is<SVG::SVGForeignObjectElement>(layout_parent->dom_node())
-            && !display.is_inline_outside() && layout_parent->display().is_flow_inside() && !layout_node->is_out_of_flow())
-            restructure_block_node_in_inline_parent(static_cast<NodeWithStyleAndBoxModelMetrics&>(*layout_node));
+        if (auto node_with_metrics = as_if<NodeWithStyleAndBoxModelMetrics>(*layout_node);
+            node_with_metrics && node_with_metrics->should_create_inline_continuation())
+            restructure_block_node_in_inline_parent(*node_with_metrics);
     }
 
     // https://www.w3.org/TR/css-contain-2/#containment-style