LibWeb: Implement HTMLTableElement thead attributes

* tHead - Getter for the thead element
  The setter is not currently implemented
* createTHead - If necessary, creates a new thead element
  and add it to the table after any caption or colgroup elements,
  but before anything else
* deleteTHead - If a thead element exists in the table, delete it

Userland/Libraries/LibWeb/CodeGenerators/WrapperGenerator.cpp

@@ -873,6 +873,7 @@ void generate_implementation(const IDL::Interface& interface)
 #include <LibWeb/Bindings/HTMLHeadElementWrapper.h>
 #include <LibWeb/Bindings/HTMLImageElementWrapper.h>
 #include <LibWeb/Bindings/HTMLTableCaptionElementWrapper.h>
+#include <LibWeb/Bindings/HTMLTableSectionElementWrapper.h>
 #include <LibWeb/Bindings/ImageDataWrapper.h>
 #include <LibWeb/Bindings/NodeWrapperFactory.h>
 #include <LibWeb/Bindings/TextWrapper.h>
@@ -1219,6 +1220,7 @@ void generate_prototype_implementation(const IDL::Interface& interface)
 #include <LibWeb/Bindings/HTMLHeadElementWrapper.h>
 #include <LibWeb/Bindings/HTMLImageElementWrapper.h>
 #include <LibWeb/Bindings/HTMLTableCaptionElementWrapper.h>
+#include <LibWeb/Bindings/HTMLTableSectionElementWrapper.h>
 #include <LibWeb/Bindings/ImageDataWrapper.h>
 #include <LibWeb/Bindings/NodeWrapperFactory.h>
 #include <LibWeb/Bindings/PerformanceTimingWrapper.h>

Userland/Libraries/LibWeb/HTML/HTMLTableElement.cpp

@@ -7,6 +7,7 @@
 #include <LibWeb/CSS/Parser/DeprecatedCSSParser.h>
 #include <LibWeb/DOM/ElementFactory.h>
 #include <LibWeb/DOM/HTMLCollection.h>
+#include <LibWeb/HTML/HTMLTableColElement.h>
 #include <LibWeb/HTML/HTMLTableElement.h>
 #include <LibWeb/HTML/HTMLTableRowElement.h>
 #include <LibWeb/Namespace.h>
@@ -78,6 +79,90 @@ void HTMLTableElement::delete_caption()
     }
 }
 
+RefPtr<HTMLTableSectionElement> HTMLTableElement::t_head()
+{
+    for (auto* child = first_child(); child; child = child->next_sibling()) {
+        if (is<HTMLTableSectionElement>(*child)) {
+            auto table_section_element = &downcast<HTMLTableSectionElement>(*child);
+            if (table_section_element->tag_name() == TagNames::thead)
+                return table_section_element;
+        }
+    }
+
+    return nullptr;
+}
+
+DOM::ExceptionOr<void> HTMLTableElement::set_t_head(HTMLTableSectionElement& thead)
+{
+    if (thead.tag_name() != TagNames::thead)
+        return DOM::HierarchyRequestError::create("Element is not thead");
+
+    // FIXME: The spec requires deleting the current thead if thead is null
+    //        Currently the wrapper generator doesn't send us a nullable value
+    delete_t_head();
+
+    // We insert the new thead after any <caption> or <colgroup> elements
+    DOM::Node* child_to_append_after = nullptr;
+    for (auto* child = first_child(); child; child = child->next_sibling()) {
+        if (!is<HTMLElement>(*child))
+            continue;
+        if (is<HTMLTableCaptionElement>(*child))
+            continue;
+        if (is<HTMLTableColElement>(*child)) {
+            auto table_col_element = &downcast<HTMLTableColElement>(*child);
+            if (table_col_element->tag_name() == TagNames::colgroup)
+                continue;
+        }
+
+        // We have found an element which is not a <caption> or <colgroup>, we'll insert before this
+        child_to_append_after = child;
+        break;
+    }
+
+    pre_insert(thead, child_to_append_after);
+
+    return {};
+}
+
+NonnullRefPtr<HTMLTableSectionElement> HTMLTableElement::create_t_head()
+{
+    auto maybe_thead = t_head();
+    if (maybe_thead)
+        return *maybe_thead;
+
+    auto thead = DOM::create_element(document(), TagNames::thead, Namespace::HTML);
+
+    // We insert the new thead after any <caption> or <colgroup> elements
+    DOM::Node* child_to_append_after = nullptr;
+    for (auto* child = first_child(); child; child = child->next_sibling()) {
+        if (!is<HTMLElement>(*child))
+            continue;
+        if (is<HTMLTableCaptionElement>(*child))
+            continue;
+        if (is<HTMLTableColElement>(*child)) {
+            auto table_col_element = &downcast<HTMLTableColElement>(*child);
+            if (table_col_element->tag_name() == TagNames::colgroup)
+                continue;
+        }
+
+        // We have found an element which is not a <caption> or <colgroup>, we'll insert before this
+        child_to_append_after = child;
+        break;
+    }
+
+    pre_insert(thead, child_to_append_after);
+
+    return thead;
+}
+
+void HTMLTableElement::delete_t_head()
+{
+    auto maybe_thead = t_head();
+    if (maybe_thead) {
+        maybe_thead->remove(false);
+    }
+}
+
 NonnullRefPtr<DOM::HTMLCollection> HTMLTableElement::rows()
 {
     HTMLTableElement* table_node = this;

Userland/Libraries/LibWeb/HTML/HTMLTableElement.h

@@ -10,6 +10,7 @@
 #include <LibWeb/HTML/HTMLElement.h>
 #include <LibWeb/HTML/HTMLTableCaptionElement.h>
 #include <LibWeb/HTML/HTMLTableRowElement.h>
+#include <LibWeb/HTML/HTMLTableSectionElement.h>
 
 namespace Web::HTML {
 
@@ -25,6 +26,11 @@ public:
     NonnullRefPtr<HTMLTableCaptionElement> create_caption();
     void delete_caption();
 
+    RefPtr<HTMLTableSectionElement> t_head();
+    DOM::ExceptionOr<void> set_t_head(HTMLTableSectionElement& thead);
+    NonnullRefPtr<HTMLTableSectionElement> create_t_head();
+    void delete_t_head();
+
     NonnullRefPtr<DOM::HTMLCollection> rows();
     DOM::ExceptionOr<NonnullRefPtr<HTMLTableRowElement>> insert_row(long index);
     DOM::ExceptionOr<void> delete_row(long index);

Userland/Libraries/LibWeb/HTML/HTMLTableElement.idl

@@ -4,6 +4,10 @@ interface HTMLTableElement : HTMLElement {
     HTMLTableCaptionElement createCaption();
     undefined deleteCaption();
 
+    attribute HTMLTableSectionElement? tHead;
+    HTMLTableSectionElement createTHead();
+    undefined deleteTHead();
+
     readonly attribute HTMLCollection rows;
     HTMLTableRowElement insertRow(optional long index = -1);
     undefined deleteRow(long index);