LibHTML: Move layout tree building to a LayoutTreeBuilder class

Building a whole layout tree shouldn't be a concern of Node, so this
patch moves it to a separate class.

Libraries/LibHTML/DOM/Document.cpp

@@ -11,6 +11,7 @@
 #include <LibHTML/DOM/HTMLTitleElement.h>
 #include <LibHTML/Frame.h>
 #include <LibHTML/Layout/LayoutDocument.h>
+#include <LibHTML/Layout/LayoutTreeBuilder.h>
 #include <stdio.h>
 
 Document::Document()
@@ -153,8 +154,10 @@ URL Document::complete_url(const String& string) const
 
 void Document::layout()
 {
-    if (!m_layout_root)
-        m_layout_root = create_layout_tree(style_resolver(), nullptr);
+    if (!m_layout_root) {
+        LayoutTreeBuilder tree_builder;
+        m_layout_root = tree_builder.build(*this);
+    }
     m_layout_root->layout();
 }
 
@@ -209,4 +212,3 @@ void Document::set_hovered_node(Node* node)
     if (m_hovered_node)
         m_hovered_node->invalidate_style();
 }
-

Libraries/LibHTML/DOM/Node.cpp

@@ -19,41 +19,6 @@ Node::~Node()
 {
 }
 
-RefPtr<LayoutNode> Node::create_layout_tree(const StyleResolver& resolver, const StyleProperties* parent_style) const
-{
-    auto layout_node = create_layout_node(resolver, parent_style);
-    if (!layout_node)
-        return nullptr;
-
-    if (!has_children())
-        return layout_node;
-
-    Vector<RefPtr<LayoutNode>> layout_children;
-    bool have_inline_children = false;
-    bool have_block_children = false;
-
-    static_cast<const ParentNode&>(*this).for_each_child([&](const Node& child) {
-        auto layout_child = child.create_layout_tree(resolver, &layout_node->style());
-        if (!layout_child)
-            return;
-        if (!layout_child->is_block())
-            have_inline_children = true;
-        if (layout_child->is_block())
-            have_block_children = true;
-        layout_children.append(move(layout_child));
-    });
-
-    for (auto layout_child : layout_children)
-        if (have_block_children && have_inline_children && !layout_child->is_block()) {
-            if (layout_child->is_text() && static_cast<const LayoutText&>(*layout_child).text_for_style(*parent_style) == " ")
-                continue;
-            layout_node->inline_wrapper().append_child(*layout_child);
-        } else {
-            layout_node->append_child(*layout_child);
-        }
-    return layout_node;
-}
-
 const HTMLAnchorElement* Node::enclosing_link_element() const
 {
     return first_ancestor_of_type<HTMLAnchorElement>();

Libraries/LibHTML/DOM/Node.h

@@ -38,7 +38,6 @@ public:
     bool is_parent_node() const { return is_element() || is_document(); }
 
     virtual RefPtr<LayoutNode> create_layout_node(const StyleResolver&, const StyleProperties* parent_style) const;
-    RefPtr<LayoutNode> create_layout_tree(const StyleResolver&, const StyleProperties* parent_style) const;
 
     virtual String tag_name() const = 0;
 

Libraries/LibHTML/Layout/LayoutTreeBuilder.cpp

@@ -0,0 +1,51 @@
+#include <LibHTML/DOM/Document.h>
+#include <LibHTML/DOM/ParentNode.h>
+#include <LibHTML/Layout/LayoutNode.h>
+#include <LibHTML/Layout/LayoutText.h>
+#include <LibHTML/Layout/LayoutTreeBuilder.h>
+
+LayoutTreeBuilder::LayoutTreeBuilder()
+{
+}
+
+static RefPtr<LayoutNode> create_layout_tree(Node& node, const StyleProperties* parent_style)
+{
+    auto layout_node = node.create_layout_node(node.document().style_resolver(), parent_style);
+    if (!layout_node)
+        return nullptr;
+
+    if (!node.has_children())
+        return layout_node;
+
+    NonnullRefPtrVector<LayoutNode> layout_children;
+    bool have_inline_children = false;
+    bool have_block_children = false;
+
+    to<ParentNode>(node).for_each_child([&](Node& child) {
+        auto layout_child = create_layout_tree(child, &layout_node->style());
+        if (!layout_child)
+            return;
+        if (layout_child->is_inline())
+            have_inline_children = true;
+        if (layout_child->is_block())
+            have_block_children = true;
+        layout_children.append(layout_child.release_nonnull());
+    });
+
+    for (auto& layout_child : layout_children)
+        if (have_block_children && have_inline_children && !layout_child.is_block()) {
+            if (is<LayoutText>(layout_child) && to<LayoutText>(layout_child).text_for_style(*parent_style) == " ")
+                continue;
+            layout_node->inline_wrapper().append_child(layout_child);
+        } else {
+            layout_node->append_child(layout_child);
+        }
+    return layout_node;
+}
+
+RefPtr<LayoutNode> LayoutTreeBuilder::build(Node& node)
+{
+    // FIXME: Support building partial trees.
+    ASSERT(is<Document>(node));
+    return create_layout_tree(node, nullptr);
+}

Libraries/LibHTML/Layout/LayoutTreeBuilder.h

@@ -0,0 +1,13 @@
+#pragma once
+
+#include <AK/RefPtr.h>
+
+class Node;
+class LayoutNode;
+
+class LayoutTreeBuilder {
+public:
+    LayoutTreeBuilder();
+
+    RefPtr<LayoutNode> build(Node&);
+};

Libraries/LibHTML/Makefile.shared

@@ -46,6 +46,7 @@ LIBHTML_OBJS = \
     Layout/BoxModelMetrics.o \
     Layout/LineBox.o \
     Layout/LineBoxFragment.o \
+    Layout/LayoutTreeBuilder.o \
     ResourceLoader.o \
     HtmlView.o \
     Frame.o \