LibWeb: Add initial support for CustomEvent

This is used surprisingly often. For example, it is used by a core
YouTube library called Structured Page Fragments.

It allows you to manually dispatch an event with arbitrary data
attached to it.

The only thing missing from this implementation is the constructor.
This is because WrapperGenerator is currently missing dictionary
capabilities.

Userland/Libraries/LibWeb/Bindings/EventWrapperFactory.cpp

@@ -1,10 +1,12 @@
 /*
  * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2021, Luke Wilde <lukew@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
 #include <LibWeb/Bindings/CloseEventWrapper.h>
+#include <LibWeb/Bindings/CustomEventWrapper.h>
 #include <LibWeb/Bindings/EventWrapper.h>
 #include <LibWeb/Bindings/EventWrapperFactory.h>
 #include <LibWeb/Bindings/MessageEventWrapper.h>
@@ -17,6 +19,8 @@ namespace Web::Bindings {
 
 EventWrapper* wrap(JS::GlobalObject& global_object, DOM::Event& event)
 {
+    if (is<DOM::CustomEvent>(event))
+        return static_cast<CustomEventWrapper*>(wrap_impl(global_object, static_cast<DOM::CustomEvent&>(event)));
     if (is<HTML::CloseEvent>(event))
         return static_cast<CloseEventWrapper*>(wrap_impl(global_object, static_cast<HTML::CloseEvent&>(event)));
     if (is<HTML::MessageEvent>(event))

Userland/Libraries/LibWeb/Bindings/WindowObjectHelper.h

@@ -22,6 +22,8 @@
 #include <LibWeb/Bindings/CloseEventPrototype.h>
 #include <LibWeb/Bindings/CommentConstructor.h>
 #include <LibWeb/Bindings/CommentPrototype.h>
+#include <LibWeb/Bindings/CustomEventConstructor.h>
+#include <LibWeb/Bindings/CustomEventPrototype.h>
 #include <LibWeb/Bindings/DOMExceptionConstructor.h>
 #include <LibWeb/Bindings/DOMExceptionPrototype.h>
 #include <LibWeb/Bindings/DOMImplementationConstructor.h>
@@ -265,6 +267,7 @@
     ADD_WINDOW_OBJECT_INTERFACE(CharacterData)             \
     ADD_WINDOW_OBJECT_INTERFACE(CloseEvent)                \
     ADD_WINDOW_OBJECT_INTERFACE(Comment)                   \
+    ADD_WINDOW_OBJECT_INTERFACE(CustomEvent)               \
     ADD_WINDOW_OBJECT_INTERFACE(CSSStyleSheet)             \
     ADD_WINDOW_OBJECT_INTERFACE(DocumentFragment)          \
     ADD_WINDOW_OBJECT_INTERFACE(Document)                  \

Userland/Libraries/LibWeb/CMakeLists.txt

@@ -45,6 +45,7 @@ set(SOURCES
     DOM/CharacterData.cpp
     DOM/CharacterData.idl
     DOM/Comment.cpp
+    DOM/CustomEvent.cpp
     DOM/DOMImplementation.cpp
     DOM/Document.cpp
     DOM/DocumentFragment.cpp
@@ -328,6 +329,7 @@ libweb_js_wrapper(DOM/AbortController)
 libweb_js_wrapper(DOM/AbortSignal)
 libweb_js_wrapper(DOM/CharacterData)
 libweb_js_wrapper(DOM/Comment)
+libweb_js_wrapper(DOM/CustomEvent)
 libweb_js_wrapper(DOM/Document)
 libweb_js_wrapper(DOM/DocumentFragment)
 libweb_js_wrapper(DOM/DocumentType)

Userland/Libraries/LibWeb/DOM/CustomEvent.cpp

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2021, Luke Wilde <lukew@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/DOM/CustomEvent.h>
+
+namespace Web::DOM {
+
+CustomEvent::CustomEvent(FlyString const& event_name)
+    : Event(event_name)
+{
+}
+
+CustomEvent::~CustomEvent()
+{
+}
+
+void CustomEvent::visit_edges(JS::Cell::Visitor& visitor)
+{
+    visitor.visit(m_detail);
+}
+
+// https://dom.spec.whatwg.org/#dom-customevent-initcustomevent
+void CustomEvent::init_custom_event(String const& type, bool bubbles, bool cancelable, JS::Value detail)
+{
+    // 1. If this’s dispatch flag is set, then return.
+    if (dispatched())
+        return;
+
+    // 2. Initialize this with type, bubbles, and cancelable.
+    initialize(type, bubbles, cancelable);
+
+    // 3. Set this’s detail attribute to detail.
+    m_detail = detail;
+}
+
+}

Userland/Libraries/LibWeb/DOM/CustomEvent.h

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2021, Luke Wilde <lukew@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibWeb/DOM/Event.h>
+
+namespace Web::DOM {
+
+// https://dom.spec.whatwg.org/#customevent
+class CustomEvent : public Event {
+public:
+    using WrapperType = Bindings::CustomEventWrapper;
+
+    static NonnullRefPtr<CustomEvent> create(FlyString const& event_name)
+    {
+        return adopt_ref(*new CustomEvent(event_name));
+    }
+
+    virtual ~CustomEvent() override;
+
+    // https://dom.spec.whatwg.org/#dom-customevent-detail
+    JS::Value detail() const { return m_detail; }
+
+    void visit_edges(JS::Cell::Visitor&);
+
+    void init_custom_event(String const& type, bool bubbles, bool cancelable, JS::Value detail);
+
+private:
+    CustomEvent(FlyString const&);
+
+    // https://dom.spec.whatwg.org/#dom-customevent-initcustomevent-type-bubbles-cancelable-detail-detail
+    JS::Value m_detail { JS::js_null() };
+};
+
+}

Userland/Libraries/LibWeb/DOM/CustomEvent.idl

@@ -0,0 +1,8 @@
+[Exposed=(Window,Worker), CustomVisit]
+interface CustomEvent : Event {
+    // FIXME: constructor(DOMString type, optional CustomEventInit eventInitDict = {});
+
+    readonly attribute any detail;
+
+    undefined initCustomEvent(DOMString type, optional boolean bubbles = false, optional boolean cancelable = false, optional any detail = null);
+};

Userland/Libraries/LibWeb/DOM/Document.cpp

@@ -18,6 +18,7 @@
 #include <LibWeb/CSS/StyleComputer.h>
 #include <LibWeb/Cookie/ParsedCookie.h>
 #include <LibWeb/DOM/Comment.h>
+#include <LibWeb/DOM/CustomEvent.h>
 #include <LibWeb/DOM/DOMException.h>
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/DOM/DocumentFragment.h>
@@ -739,7 +740,7 @@ NonnullRefPtr<Event> Document::create_event(const String& interface)
     } else if (interface_lowercase == "compositionevent") {
         event = Event::create(""); // FIXME: Create CompositionEvent
     } else if (interface_lowercase == "customevent") {
-        event = Event::create(""); // FIXME: Create CustomEvent
+        event = CustomEvent::create("");
     } else if (interface_lowercase == "devicemotionevent") {
         event = Event::create(""); // FIXME: Create DeviceMotionEvent
     } else if (interface_lowercase == "deviceorientationevent") {

Userland/Libraries/LibWeb/Forward.h

@@ -62,6 +62,7 @@ class AbortController;
 class AbortSignal;
 class CharacterData;
 class Comment;
+class CustomEvent;
 class Document;
 class DocumentFragment;
 class DocumentLoadEventDelayer;
@@ -261,6 +262,7 @@ class CanvasRenderingContext2DWrapper;
 class CharacterDataWrapper;
 class CloseEventWrapper;
 class CommentWrapper;
+class CustomEventWrapper;
 class DocumentFragmentWrapper;
 class DocumentTypeWrapper;
 class DocumentWrapper;