LibHTML: Add Node::{next,previous}_element_sibling()

These helpers return the next/previous sibling Node that's actually an
element. This will be useful in the CSS engine since CSS doesn't care
about text nodes.

2 files changed, 22 insertions, 0 deletions

diff --git a/Libraries/LibHTML/DOM/Node.cpp b/Libraries/LibHTML/DOM/Node.cpp
index 700a26bcd7..ca9f874780 100644
--- a/Libraries/LibHTML/DOM/Node.cpp
+++ b/Libraries/LibHTML/DOM/Node.cpp
@@ -83,3 +83,21 @@ String Node::text_content() const
         builder.trim(1);
     return builder.to_string();
 }
+
+const Element* Node::next_element_sibling() const
+{
+    for (auto* node = next_sibling(); node; node = node->next_sibling()) {
+        if (node->is_element())
+            return static_cast<const Element*>(node);
+    }
+    return nullptr;
+}
+
+const Element* Node::previous_element_sibling() const
+{
+    for (auto* node = previous_sibling(); node; node = node->previous_sibling()) {
+        if (node->is_element())
+            return static_cast<const Element*>(node);
+    }
+    return nullptr;
+}
diff --git a/Libraries/LibHTML/DOM/Node.h b/Libraries/LibHTML/DOM/Node.h
index e43aa3b2f0..e9771eeb99 100644
--- a/Libraries/LibHTML/DOM/Node.h
+++ b/Libraries/LibHTML/DOM/Node.h
@@ -14,6 +14,7 @@ enum class NodeType : unsigned {
 };
 
 class Document;
+class Element;
 class HTMLElement;
 class HTMLAnchorElement;
 class ParentNode;
@@ -63,6 +64,9 @@ public:
 
     void set_layout_node(Badge<LayoutNode>, LayoutNode* layout_node) const { m_layout_node = layout_node; }
 
+    const Element* previous_element_sibling() const;
+    const Element* next_element_sibling() const;
+
 protected:
     Node(Document&, NodeType);