LibWeb: Don't create unwanted layout nodes when recomputing style

When recomputing the style for an element that previously didn't have
a corresponding layout node, it may become necessary to create a layout
node for it.

However, we should not do this if it's within a subtree that can't have
layout children. Nor should we do it for elements who have an ancestor
with display:none.

1 files changed, 11 insertions, 1 deletions

diff --git a/Userland/Libraries/LibWeb/DOM/Element.cpp b/Userland/Libraries/LibWeb/DOM/Element.cpp
index 323f50d888..7cbf512ed2 100644
--- a/Userland/Libraries/LibWeb/DOM/Element.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Element.cpp
@@ -304,9 +304,19 @@ void Element::recompute_style()
     auto new_specified_css_values = document().style_computer().compute_style(*this);
     m_specified_css_values = new_specified_css_values;
     if (!layout_node()) {
+        // This element doesn't have a corresponding layout node.
+
+        // If the new style is display:none, bail.
         if (new_specified_css_values->display().is_none())
             return;
-        // We need a new layout tree here!
+
+        // If we're inside a display:none ancestor or an ancestor that can't have children, bail.
+        for (auto* ancestor = parent_element(); ancestor; ancestor = ancestor->parent_element()) {
+            if (!ancestor->layout_node() || !ancestor->layout_node()->can_have_children())
+                return;
+        }
+
+        // Okay, we need a new layout subtree here.
         Layout::TreeBuilder tree_builder;
         (void)tree_builder.build(*this);
         return;