LibWeb: Implement Document.rootElement (SVG2 extension to Document)

Author: https://github.com/awesomekling
Commit: 879cba762b
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/4775

Libraries/LibWeb/DOM/Document.cpp

@@ -151,6 +151,7 @@
 #include <LibWeb/ResizeObserver/ResizeObserverEntry.h>
 #include <LibWeb/SVG/SVGDecodedImageData.h>
 #include <LibWeb/SVG/SVGElement.h>
+#include <LibWeb/SVG/SVGSVGElement.h>
 #include <LibWeb/SVG/SVGStyleElement.h>
 #include <LibWeb/SVG/SVGTitleElement.h>
 #include <LibWeb/Selection/Selection.h>
@@ -892,6 +893,12 @@ Element const* Document::document_element() const
     return first_child_of_type<Element>();
 }
 
+// https://www.w3.org/TR/SVG2/struct.html#InterfaceDocumentExtensions
+GC::Ptr<SVG::SVGSVGElement> Document::root_element()
+{
+    return as_if<SVG::SVGSVGElement>(document_element());
+}
+
 // https://html.spec.whatwg.org/multipage/dom.html#the-html-element-2
 HTML::HTMLHtmlElement* Document::html_element()
 {

Libraries/LibWeb/DOM/Document.h

@@ -270,6 +270,9 @@ public:
     Element* document_element();
     Element const* document_element() const;
 
+    // https://www.w3.org/TR/SVG2/struct.html#InterfaceDocumentExtensions
+    GC::Ptr<SVG::SVGSVGElement> root_element();
+
     HTML::HTMLHtmlElement* html_element();
     HTML::HTMLHeadElement* head();
     GC::Ptr<HTML::HTMLTitleElement> title_element();

Libraries/LibWeb/DOM/Document.idl

@@ -156,6 +156,9 @@ interface Document : Node {
     // special event handler IDL attributes that only apply to Document objects
     [LegacyLenientThis] attribute EventHandler onreadystatechange;
     attribute EventHandler onvisibilitychange;
+
+    // https://www.w3.org/TR/SVG2/struct.html#InterfaceDocumentExtensions
+    readonly attribute SVGSVGElement? rootElement;
 };
 
 dictionary ElementCreationOptions {

Tests/LibWeb/Text/expected/wpt-import/svg/idlharness.window.txt

@@ -2,8 +2,8 @@ Harness status: OK
 
 Found 1781 tests
 
-873 Pass
-908 Fail
+874 Pass
+907 Fail
 Pass	idl_test setup
 Pass	idl_test validation
 Pass	Partial interface Document: original interface defined
@@ -1784,4 +1784,4 @@ Fail	SVGDiscardElement interface object name
 Fail	SVGDiscardElement interface: existence and properties of interface prototype object
 Fail	SVGDiscardElement interface: existence and properties of interface prototype object's "constructor" property
 Fail	SVGDiscardElement interface: existence and properties of interface prototype object's @@unscopables property
-Fail	Document interface: attribute rootElement
+Pass	Document interface: attribute rootElement