LibWeb: Start working on DOM event support

This patch adds the EventTarget class and makes Node inherit from it.

You can register event listeners on an EventTarget, and when you call
dispatch_event() on it, the event listeners will get invoked.

An event listener is basically a wrapper around a JS::Function*.

This is pretty far from how DOM events should eventually work, but it's
a place to start and we'll build more on top of this. :^)

Libraries/LibWeb/Bindings/DocumentWrapper.h

@@ -40,7 +40,7 @@ public:
     const Document& node() const;
 
 private:
-    virtual const char* class_name() const override { return "Document"; }
+    virtual const char* class_name() const override { return "DocumentWrapper"; }
 };
 
 }

Libraries/LibWeb/Bindings/EventListenerWrapper.cpp

@@ -0,0 +1,24 @@
+#include <LibJS/Runtime/Function.h>
+#include <LibWeb/Bindings/EventListenerWrapper.h>
+#include <LibWeb/DOM/EventListener.h>
+
+namespace Web {
+namespace Bindings {
+
+EventListenerWrapper::EventListenerWrapper(EventListener& impl)
+    : m_impl(impl)
+{
+}
+
+EventListenerWrapper::~EventListenerWrapper()
+{
+}
+
+void EventListenerWrapper::visit_children(JS::Cell::Visitor& visitor)
+{
+    Wrapper::visit_children(visitor);
+    visitor.visit(impl().function());
+}
+
+}
+}

Libraries/LibWeb/Bindings/EventListenerWrapper.h

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <LibWeb/Bindings/Wrapper.h>
+
+namespace Web {
+namespace Bindings {
+
+class EventListenerWrapper final : public Wrapper {
+public:
+    explicit EventListenerWrapper(EventListener&);
+    virtual ~EventListenerWrapper() override;
+
+    EventListener& impl() { return *m_impl; }
+    const EventListener& impl() const { return *m_impl; }
+
+private:
+    virtual const char* class_name() const override { return "EventListenerWrapper"; }
+    virtual void visit_children(JS::Cell::Visitor&) override;
+
+    NonnullRefPtr<EventListener> m_impl;
+};
+
+}
+}

Libraries/LibWeb/Bindings/EventTargetWrapper.cpp

@@ -0,0 +1,33 @@
+#include <AK/Function.h>
+#include <LibJS/Runtime/Function.h>
+#include <LibWeb/Bindings/EventListenerWrapper.h>
+#include <LibWeb/Bindings/EventTargetWrapper.h>
+#include <LibWeb/DOM/EventListener.h>
+#include <LibWeb/DOM/EventTarget.h>
+
+namespace Web {
+namespace Bindings {
+
+EventTargetWrapper::EventTargetWrapper(EventTarget& impl)
+    : m_impl(impl)
+{
+    put_native_function("addEventListener", [](Object* this_object, const Vector<JS::Value>& arguments) {
+        if (arguments.size() < 2)
+            return JS::js_undefined();
+
+        auto event_name = arguments[0].to_string();
+        ASSERT(arguments[1].is_object());
+        ASSERT(arguments[1].as_object()->is_function());
+        auto listener = adopt(*new EventListener(static_cast<JS::Function*>(const_cast<Object*>(arguments[1].as_object()))));
+        wrap(this_object->heap(), *listener);
+        static_cast<EventTargetWrapper*>(this_object)->impl().add_event_listener(event_name, move(listener));
+        return JS::js_undefined();
+    });
+}
+
+EventTargetWrapper::~EventTargetWrapper()
+{
+}
+
+}
+}

Libraries/LibWeb/Bindings/EventTargetWrapper.h

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <LibWeb/Bindings/Wrapper.h>
+
+namespace Web {
+namespace Bindings {
+
+class EventTargetWrapper : public Wrapper {
+public:
+    explicit EventTargetWrapper(EventTarget&);
+    virtual ~EventTargetWrapper() override;
+
+    EventTarget& impl() { return *m_impl; }
+    const EventTarget& impl() const { return *m_impl; }
+
+private:
+    virtual const char* class_name() const override { return "EventTargetWrapper"; }
+
+    NonnullRefPtr<EventTarget> m_impl;
+};
+
+}
+}

Libraries/LibWeb/Bindings/NodeWrapper.cpp

@@ -33,7 +33,7 @@ namespace Web {
 namespace Bindings {
 
 NodeWrapper::NodeWrapper(Node& node)
-    : m_node(node)
+    : EventTargetWrapper(node)
 {
     put("nodeName", JS::js_string(heap(), node.tag_name()));
 }
@@ -42,5 +42,15 @@ NodeWrapper::~NodeWrapper()
 {
 }
 
+Node& NodeWrapper::node()
+{
+    return static_cast<Node&>(EventTargetWrapper::impl());
+}
+
+const Node& NodeWrapper::node() const
+{
+    return static_cast<const Node&>(EventTargetWrapper::impl());
+}
+
 }
 }

Libraries/LibWeb/Bindings/NodeWrapper.h

@@ -26,23 +26,21 @@
 
 #pragma once
 
-#include <LibWeb/Bindings/Wrapper.h>
+#include <LibWeb/Bindings/EventTargetWrapper.h>
 
 namespace Web {
 namespace Bindings {
 
-class NodeWrapper : public Wrapper {
+class NodeWrapper : public EventTargetWrapper {
 public:
     explicit NodeWrapper(Node&);
     virtual ~NodeWrapper() override;
 
-    Node& node() { return *m_node; }
-    const Node& node() const { return *m_node; }
+    Node& node();
+    const Node& node() const;
 
 private:
-    virtual const char* class_name() const override { return "Node"; }
-
-    NonnullRefPtr<Node> m_node;
+    virtual const char* class_name() const override { return "NodeWrapper"; }
 };
 
 }