LibWeb: Implement HTMLDialogElement::close() for non-modal dialogs

Tests/LibWeb/Text/expected/close-non-modal-dialog.txt

@@ -0,0 +1,3 @@
+  dialog.open state before close(): true
+dialog.open state after close(): false
+dialog.returnValue state after close(): after-close

Tests/LibWeb/Text/input/close-non-modal-dialog.html

@@ -0,0 +1,14 @@
+<script src="./include.js"></script>
+<dialog id="test-dialog" open></dialog>
+<script>
+    asyncTest((done) => {
+        const dialog = document.getElementById("test-dialog");
+        println(`dialog.open state before close(): ${dialog.open}`);
+        dialog.addEventListener("close", (event) => {
+            println(`dialog.open state after close(): ${dialog.open}`);
+            println(`dialog.returnValue state after close(): ${dialog.returnValue}`);
+            done();
+        });
+        dialog.close("after-close");
+    });
+</script>

Userland/Libraries/LibWeb/HTML/HTMLDialogElement.cpp

@@ -5,6 +5,7 @@
  */
 
 #include <LibWeb/Bindings/Intrinsics.h>
+#include <LibWeb/DOM/Event.h>
 #include <LibWeb/HTML/HTMLDialogElement.h>
 
 namespace Web::HTML {
@@ -37,9 +38,11 @@ void HTMLDialogElement::show_modal()
 }
 
 // https://html.spec.whatwg.org/multipage/interactive-elements.html#dom-dialog-close
-void HTMLDialogElement::close(Optional<String>)
+void HTMLDialogElement::close(Optional<String> return_value)
 {
-    dbgln("(STUBBED) HTMLDialogElement::close()");
+    // 1. If returnValue is not given, then set it to null.
+    // 2. Close the dialog this with returnValue.
+    close_the_dialog(move(return_value));
 }
 
 // https://html.spec.whatwg.org/multipage/interactive-elements.html#dom-dialog-returnvalue
@@ -54,4 +57,39 @@ void HTMLDialogElement::set_return_value(String return_value)
     m_return_value = move(return_value);
 }
 
+// https://html.spec.whatwg.org/multipage/interactive-elements.html#close-the-dialog
+void HTMLDialogElement::close_the_dialog(Optional<String> result)
+{
+    // 1. If subject does not have an open attribute, then return.
+    if (!has_attribute(AttributeNames::open))
+        return;
+
+    // 2. Remove subject's open attribute.
+    remove_attribute(AttributeNames::open);
+
+    // FIXME: 3. If the is modal flag of subject is true, then request an element to be removed from the top layer given subject.
+    // FIXME: 4. Let wasModal be the value of subject's is modal flag.
+    // FIXME: 5. Set the is modal flag of subject to false.
+
+    // 6. If result is not null, then set the returnValue attribute to result.
+    if (result.has_value())
+        set_return_value(result.release_value());
+
+    // FIXME: 7. If subject's previously focused element is not null, then:
+    //           1. Let element be subject's previously focused element.
+    //           2. Set subject's previously focused element to null.
+    //           3. If subject's node document's focused area of the document's DOM anchor is a shadow-including inclusive descendant of element,
+    //              or wasModal is true, then run the focusing steps for element; the viewport should not be scrolled by doing this step.
+
+    // 8. Queue an element task on the user interaction task source given the subject element to fire an event named close at subject.
+    queue_an_element_task(HTML::Task::Source::UserInteraction, [this] {
+        auto close_event = DOM::Event::create(realm(), HTML::EventNames::close);
+        dispatch_event(close_event);
+    });
+
+    // FIXME: 9. If subject's close watcher is not null, then:
+    //           1. Destroy subject's close watcher.
+    //           2. Set subject's close watcher to null.
+}
+
 }

Userland/Libraries/LibWeb/HTML/HTMLDialogElement.h

@@ -33,6 +33,8 @@ private:
 
     virtual void initialize(JS::Realm&) override;
 
+    void close_the_dialog(Optional<String> result);
+
     String m_return_value;
 };