LibWeb: Lay out the fieldset's rendered legend

Author: https://github.com/kostyafarber
Commit: 81f8866606
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2546
Reviewed-by: https://github.com/tcl3 ✅

Libraries/LibWeb/Layout/BlockFormattingContext.cpp

@@ -12,7 +12,9 @@
 #include <LibWeb/Layout/BlockContainer.h>
 #include <LibWeb/Layout/BlockFormattingContext.h>
 #include <LibWeb/Layout/Box.h>
+#include <LibWeb/Layout/FieldSetBox.h>
 #include <LibWeb/Layout/InlineFormattingContext.h>
+#include <LibWeb/Layout/LegendBox.h>
 #include <LibWeb/Layout/LineBuilder.h>
 #include <LibWeb/Layout/ListItemBox.h>
 #include <LibWeb/Layout/ListItemMarkerBox.h>
@@ -73,6 +75,38 @@ void BlockFormattingContext::run(AvailableSpace const& available_space)
         return;
     }
 
+    if (is<FieldSetBox>(root())) {
+        if (root().children_are_inline())
+            layout_inline_children(root(), available_space);
+        else
+            layout_block_level_children(root(), available_space);
+
+        auto const& fieldset_box = verify_cast<FieldSetBox>(root());
+        if (!(fieldset_box.has_rendered_legend())) {
+            return;
+        }
+
+        auto const* legend = root().first_child_of_type<LegendBox>();
+        auto& legend_state = m_state.get_mutable(*legend);
+        auto& fieldset_state = m_state.get_mutable(root());
+
+        // The element is expected to be positioned in the block-flow direction such that
+        // its border box is centered over the border on the block-start side of the fieldset element.
+        // FIXME: this should take writing modes into consideration.
+        auto legend_height = legend_state.border_box_height();
+        auto new_y = -((legend_height) / 2) - fieldset_state.padding_top;
+        legend_state.set_content_offset({ legend_state.offset.x(), new_y });
+
+        // If the computed value of 'inline-size' is 'auto',
+        // then the used value is the fit-content inline size.
+        if (legend->computed_values().width().is_auto()) {
+            auto width = calculate_fit_content_width(*legend, available_space);
+            legend_state.set_content_width(width);
+        }
+
+        return;
+    }
+
     if (root().children_are_inline())
         layout_inline_children(root(), available_space);
     else

Libraries/LibWeb/Layout/FieldSetBox.cpp

@@ -7,6 +7,8 @@
 #include <LibWeb/Forward.h>
 #include <LibWeb/HTML/HTMLLegendElement.h>
 #include <LibWeb/Layout/FieldSetBox.h>
+#include <LibWeb/Layout/LegendBox.h>
+#include <LibWeb/Painting/FieldSetPaintable.h>
 
 namespace Web::Layout {
 
@@ -22,13 +24,27 @@ FieldSetBox::~FieldSetBox() = default;
 bool FieldSetBox::has_rendered_legend() const
 {
     // https://html.spec.whatwg.org/#rendered-legend
-    if (this->has_children() && this->first_child()->is_legend_box()) {
-        auto* first_child = this->first_child();
-        return first_child->computed_values().float_() == CSS::Float::None
-            && first_child->computed_values().position() != CSS::Positioning::Absolute
-            && first_child->computed_values().position() != CSS::Positioning::Fixed;
+    bool has_rendered_legend = false;
+    if (has_children()) {
+        for_each_child_of_type<Box>([&](Box const& child) {
+            if (child.is_anonymous())
+                return IterationDecision::Continue;
+
+            if (!child.is_legend_box())
+                return IterationDecision::Break;
+
+            has_rendered_legend = child.computed_values().float_() == CSS::Float::None
+                && child.computed_values().position() != CSS::Positioning::Absolute
+                && child.computed_values().position() != CSS::Positioning::Fixed;
+            return IterationDecision::Break;
+        });
     }
-    return false;
+    return has_rendered_legend;
+}
+
+GC::Ptr<Painting::Paintable> FieldSetBox::create_paintable() const
+{
+    return Painting::FieldSetPaintable::create(*this);
 }
 
 }

Libraries/LibWeb/Layout/FieldSetBox.h

@@ -8,7 +8,7 @@
 
 #include <LibWeb/Forward.h>
 #include <LibWeb/Layout/BlockContainer.h>
-
+#include <LibWeb/Painting/FieldSetPaintable.h>
 namespace Web::Layout {
 
 class FieldSetBox final : public BlockContainer {
@@ -22,10 +22,10 @@ public:
     DOM::Element& dom_node() { return static_cast<DOM::Element&>(*BlockContainer::dom_node()); }
     DOM::Element const& dom_node() const { return static_cast<DOM::Element const&>(*BlockContainer::dom_node()); }
 
-    void layout_legend() const;
+    bool has_rendered_legend() const;
+    virtual GC::Ptr<Painting::Paintable> create_paintable() const override;
 
 private:
-    bool has_rendered_legend() const;
     virtual bool is_fieldset_box() const final
     {
         return true;

Libraries/LibWeb/Layout/TreeBuilder.cpp

@@ -23,6 +23,7 @@
 #include <LibWeb/HTML/HTMLLIElement.h>
 #include <LibWeb/HTML/HTMLOListElement.h>
 #include <LibWeb/HTML/HTMLSlotElement.h>
+#include <LibWeb/Layout/FieldSetBox.h>
 #include <LibWeb/Layout/ListItemBox.h>
 #include <LibWeb/Layout/ListItemMarkerBox.h>
 #include <LibWeb/Layout/Node.h>
@@ -76,6 +77,9 @@ static Layout::Node& insertion_parent_for_inline_node(Layout::NodeWithStyle& lay
         return *layout_parent.last_child();
     };
 
+    if (is<FieldSetBox>(layout_parent))
+        return last_child_creating_anonymous_wrapper_if_needed(layout_parent);
+
     if (layout_parent.display().is_inline_outside() && layout_parent.display().is_flow_inside())
         return layout_parent;