LibWeb/SVG: Implement SVGElement.ownerSVGElement

Author: https://github.com/jamierocks
Commit: https://github.com/LadybirdBrowser/ladybird/commit/6f3c5f5ae9
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/666

Tests/LibWeb/Text/expected/SVG/svg-ownerSVGElement-attribute.txt

@@ -0,0 +1,3 @@
+    svg.ownerSVGElement = 'null'
+linearGradient.ownerSVGElement = '[object SVGSVGElement]'
+linearGradient.ownerSVGElement == svg = 'true'

Tests/LibWeb/Text/input/SVG/svg-ownerSVGElement-attribute.html

@@ -0,0 +1,14 @@
+<script src="../include.js"></script>
+<svg xmlns="http://www.w3.org/2000/svg" id="svg-element">
+    <linearGradient id="linear-gradient-element" />
+</svg>
+<script>
+    test(() => {
+        const svgElement = document.getElementById("svg-element");
+        println(`svg.ownerSVGElement = '${svgElement.ownerSVGElement}'`);
+
+        const linearGradientElement = document.getElementById("linear-gradient-element");
+        println(`linearGradient.ownerSVGElement = '${linearGradientElement.ownerSVGElement}'`);
+        println(`linearGradient.ownerSVGElement == svg = '${linearGradientElement.ownerSVGElement === svgElement}'`);
+    });
+</script>

Userland/Libraries/LibWeb/SVG/SVGElement.cpp

@@ -13,6 +13,7 @@
 #include <LibWeb/DOM/ShadowRoot.h>
 #include <LibWeb/HTML/DOMStringMap.h>
 #include <LibWeb/SVG/SVGElement.h>
+#include <LibWeb/SVG/SVGSVGElement.h>
 #include <LibWeb/SVG/SVGUseElement.h>
 
 namespace Web::SVG {
@@ -125,6 +126,15 @@ JS::NonnullGCPtr<SVGAnimatedString> SVGElement::class_name()
     return *m_class_name_animated_string;
 }
 
+// https://svgwg.org/svg2-draft/types.html#__svg__SVGElement__ownerSVGElement
+JS::GCPtr<SVGSVGElement> SVGElement::owner_svg_element()
+{
+    // The ownerSVGElement IDL attribute represents the nearest ancestor ‘svg’ element.
+    // On getting ownerSVGElement, the nearest ancestor ‘svg’ element is returned;
+    // if the current element is the outermost svg element, then null is returned.
+    return first_ancestor_of_type<SVGSVGElement>();
+}
+
 JS::NonnullGCPtr<SVGAnimatedLength> SVGElement::svg_animated_length_for_property(CSS::PropertyID property) const
 {
     // FIXME: Create a proper animated value when animations are supported.

Userland/Libraries/LibWeb/SVG/SVGElement.h

@@ -32,6 +32,7 @@ public:
     void blur();
 
     JS::NonnullGCPtr<SVGAnimatedString> class_name();
+    JS::GCPtr<SVGSVGElement> owner_svg_element();
 
 protected:
     SVGElement(DOM::Document&, DOM::QualifiedName);

Userland/Libraries/LibWeb/SVG/SVGElement.idl

@@ -3,6 +3,7 @@
 #import <HTML/HTMLElement.idl>
 #import <HTML/DOMStringMap.idl>
 #import <SVG/SVGAnimatedString.idl>
+#import <SVG/SVGSVGElement.idl>
 
 // https://svgwg.org/svg2-draft/types.html#InterfaceSVGElement
 [Exposed=Window]
@@ -10,7 +11,7 @@ interface SVGElement : Element {
 
     [SameObject] readonly attribute SVGAnimatedString className;
 
-    [FIXME] readonly attribute SVGSVGElement? ownerSVGElement;
+    readonly attribute SVGSVGElement? ownerSVGElement;
     [FIXME] readonly attribute SVGElement? viewportElement;
 };