LibWeb: Make the Window object "inherit" from EventTarget :^)

Since Web::Bindings::WindowObject inherits from JS::GlobalObject, it
cannot also inherit from Web::Bindings::EventTargetWrapper.

However, that's not actually necessary. Instead, we simply set the
Window object's prototype to the EventTargetPrototype, and add a little
extra branch in the impl_from() function that turns the JS "this" value
into a DOM::EventTarget*.

With this, you can now call window.addEventListener()! Very cool :^)

Fixes #4758.

Userland/Libraries/LibWeb/Bindings/EventTargetWrapperFactory.cpp

@@ -29,7 +29,7 @@
 
 namespace Web::Bindings {
 
-EventTargetWrapper* wrap(JS::GlobalObject& global_object, DOM::EventTarget& target)
+JS::Object* wrap(JS::GlobalObject& global_object, DOM::EventTarget& target)
 {
     return target.create_wrapper(global_object);
 }

Userland/Libraries/LibWeb/Bindings/EventTargetWrapperFactory.h

@@ -31,6 +31,6 @@
 
 namespace Web::Bindings {
 
-EventTargetWrapper* wrap(JS::GlobalObject&, DOM::EventTarget&);
+JS::Object* wrap(JS::GlobalObject&, DOM::EventTarget&);
 
 }

Userland/Libraries/LibWeb/Bindings/WindowObject.cpp

@@ -67,6 +67,8 @@ void WindowObject::initialize()
 {
     GlobalObject::initialize();
 
+    set_prototype(&ensure_web_prototype<EventTargetPrototype>("EventTarget"));
+
     define_property("window", this, JS::Attribute::Enumerable);
     define_property("frames", this, JS::Attribute::Enumerable);
     define_property("self", this, JS::Attribute::Enumerable);

Userland/Libraries/LibWeb/CodeGenerators/WrapperGenerator.cpp

@@ -840,6 +840,7 @@ void generate_prototype_implementation(const IDL::Interface& interface)
 #include <LibWeb/Bindings/WindowObject.h>
 #include <LibWeb/DOM/Element.h>
 #include <LibWeb/DOM/EventListener.h>
+#include <LibWeb/DOM/Window.h>
 #include <LibWeb/HTML/HTMLElement.h>
 #include <LibWeb/Origin.h>
 
@@ -927,9 +928,18 @@ static @fully_qualified_name@* impl_from(JS::VM& vm, JS::GlobalObject& global_ob
     auto* this_object = vm.this_value(global_object).to_object(global_object);
     if (!this_object)
         return {};
+)~~~");
+
+        if (interface.name == "EventTarget") {
+            generator.append(R"~~~(
+    if (is<WindowObject>(this_object)) {
+        return &static_cast<WindowObject*>(this_object)->impl();
+    }
+)~~~");
+        }
+
+        generator.append(R"~~~(
     if (!is<@wrapper_class@>(this_object)) {
-        dbgln("expected @wrapper_class@ but got {}", this_object->class_name());
-        ASSERT_NOT_REACHED();
         vm.throw_exception<JS::TypeError>(global_object, JS::ErrorType::NotA, "@fully_qualified_name@");
         return nullptr;
     }

Userland/Libraries/LibWeb/DOM/EventTarget.h

@@ -51,7 +51,7 @@ public:
     void remove_from_event_listener_list(NonnullRefPtr<EventListener>);
 
     virtual bool dispatch_event(NonnullRefPtr<Event>) = 0;
-    virtual Bindings::EventTargetWrapper* create_wrapper(JS::GlobalObject&) = 0;
+    virtual JS::Object* create_wrapper(JS::GlobalObject&) = 0;
     Bindings::ScriptExecutionContext* script_execution_context() { return m_script_execution_context; }
 
     virtual EventTarget* get_parent(const Event&) { return nullptr; }

Userland/Libraries/LibWeb/DOM/Node.cpp

@@ -213,7 +213,7 @@ bool Node::is_editable() const
     return parent() && parent()->is_editable();
 }
 
-Bindings::EventTargetWrapper* Node::create_wrapper(JS::GlobalObject& global_object)
+JS::Object* Node::create_wrapper(JS::GlobalObject& global_object)
 {
     return wrap(global_object, *this);
 }

Userland/Libraries/LibWeb/DOM/Node.h

@@ -61,7 +61,7 @@ public:
     virtual void ref_event_target() final { ref(); }
     virtual void unref_event_target() final { unref(); }
     virtual bool dispatch_event(NonnullRefPtr<Event>) final;
-    virtual Bindings::EventTargetWrapper* create_wrapper(JS::GlobalObject&) override;
+    virtual JS::Object* create_wrapper(JS::GlobalObject&) override;
 
     virtual ~Node();
 

Userland/Libraries/LibWeb/DOM/Window.cpp

@@ -169,9 +169,9 @@ bool Window::dispatch_event(NonnullRefPtr<Event> event)
     return EventDispatcher::dispatch(*this, event, true);
 }
 
-Bindings::EventTargetWrapper* Window::create_wrapper(JS::GlobalObject&)
+JS::Object* Window::create_wrapper(JS::GlobalObject& global_object)
 {
-    ASSERT_NOT_REACHED();
+    return &global_object;
 }
 
 }

Userland/Libraries/LibWeb/DOM/Window.h

@@ -50,7 +50,7 @@ public:
     virtual void ref_event_target() override { RefCounted::ref(); }
     virtual void unref_event_target() override { RefCounted::unref(); }
     virtual bool dispatch_event(NonnullRefPtr<Event>) override;
-    virtual Bindings::EventTargetWrapper* create_wrapper(JS::GlobalObject&) override;
+    virtual JS::Object* create_wrapper(JS::GlobalObject&) override;
 
     const Document& document() const { return m_document; }
     Document& document() { return m_document; }

Userland/Libraries/LibWeb/DOM/XMLHttpRequest.cpp

@@ -113,7 +113,7 @@ bool XMLHttpRequest::dispatch_event(NonnullRefPtr<DOM::Event> event)
     return DOM::EventDispatcher::dispatch(*this, move(event));
 }
 
-Bindings::EventTargetWrapper* XMLHttpRequest::create_wrapper(JS::GlobalObject& global_object)
+JS::Object* XMLHttpRequest::create_wrapper(JS::GlobalObject& global_object)
 {
     return wrap(global_object, *this);
 }

Userland/Libraries/LibWeb/DOM/XMLHttpRequest.h

@@ -66,7 +66,7 @@ private:
     virtual void ref_event_target() override { ref(); }
     virtual void unref_event_target() override { unref(); }
     virtual bool dispatch_event(NonnullRefPtr<DOM::Event>) override;
-    virtual Bindings::EventTargetWrapper* create_wrapper(JS::GlobalObject&) override;
+    virtual JS::Object* create_wrapper(JS::GlobalObject&) override;
 
     void set_ready_state(ReadyState);
 

Userland/Libraries/LibWeb/HighResolutionTime/Performance.cpp

@@ -65,7 +65,7 @@ bool Performance::dispatch_event(NonnullRefPtr<DOM::Event> event)
     return DOM::EventDispatcher::dispatch(*this, event);
 }
 
-Bindings::EventTargetWrapper* Performance::create_wrapper(JS::GlobalObject& global_object)
+JS::Object* Performance::create_wrapper(JS::GlobalObject& global_object)
 {
     return Bindings::wrap(global_object, *this);
 }

Userland/Libraries/LibWeb/HighResolutionTime/Performance.h

@@ -50,7 +50,7 @@ public:
     virtual void unref_event_target() override;
 
     virtual bool dispatch_event(NonnullRefPtr<DOM::Event>) override;
-    virtual Bindings::EventTargetWrapper* create_wrapper(JS::GlobalObject&) override;
+    virtual JS::Object* create_wrapper(JS::GlobalObject&) override;
 
 private:
     DOM::Window& m_window;