LibWeb: Add a proper FocusEvent interface for "focus" and "blur" events

Userland/Libraries/LibWeb/UIEvents/FocusEvent.cpp

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/UIEvents/FocusEvent.h>
+
+namespace Web::UIEvents {
+
+FocusEvent::FocusEvent(FlyString const& event_name, FocusEventInit const& event_init)
+    : UIEvent(event_name)
+{
+    set_related_target(const_cast<DOM::EventTarget*>(event_init.related_target.ptr()));
+}
+
+FocusEvent::~FocusEvent()
+{
+}
+
+}

Userland/Libraries/LibWeb/UIEvents/FocusEvent.h

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibWeb/UIEvents/UIEvent.h>
+
+namespace Web::UIEvents {
+
+struct FocusEventInit : public UIEventInit {
+    RefPtr<DOM::EventTarget> related_target;
+};
+
+class FocusEvent final : public UIEvent {
+public:
+    using WrapperType = Bindings::FocusEventWrapper;
+
+    virtual ~FocusEvent() override;
+
+    static NonnullRefPtr<FocusEvent> create_with_global_object(Bindings::WindowObject&, FlyString const& event_name, FocusEventInit const& event_init)
+    {
+        return adopt_ref(*new FocusEvent(event_name, event_init));
+    }
+
+private:
+    FocusEvent(FlyString const& event_name, FocusEventInit const&);
+};
+
+}

Userland/Libraries/LibWeb/UIEvents/FocusEvent.idl

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+#import <UIEvents/UIEvent.idl>
+
+[Exposed=Window]
+interface FocusEvent : UIEvent {
+
+    constructor(DOMString type, optional FocusEventInit eventInitDict = {});
+    readonly attribute EventTarget? relatedTarget;
+
+};
+
+dictionary FocusEventInit : UIEventInit {
+
+    EventTarget? relatedTarget = null;
+
+};