LibWeb+WebWorker: Move worker execution into a new WebWorker process

We now create a WorkerAgent for the parent context, which is currently
only a Window. Note that Workers can have Workers per the spec.

The WorkerAgent spawns a WebWorker process to hold the actual
script execution of the Worker. This is modeled with the
DedicatedWorkerHost object in the WebWorker process.
A start_dedicated_worker IPC method in the WebWorker IPC creates the
WorkerHost object. Future different worker types may use different IPC
messages to create their WorkerHost instance.

This implementation cannot yet postMessage between the parent and the
child processes.

Co-Authored-By: Andreas Kling <kling@serenityos.org>

Base/home/anon/.config/SystemServer.ini

@@ -33,6 +33,15 @@ SystemModes=text,graphical
 MultiInstance=true
 AcceptSocketConnections=true
 
+[WebWorker]
+Socket=/tmp/session/%sid/portal/webworker
+SocketPermissions=600
+Lazy=true
+Priority=low
+SystemModes=text,graphical
+MultiInstance=true
+AcceptSocketConnections=true
+
 [FileSystemAccessServer]
 Socket=/tmp/session/%sid/portal/filesystemaccess
 SocketPermissions=660

Ladybird/CMakeLists.txt

@@ -215,7 +215,8 @@ add_subdirectory(SQLServer)
 add_subdirectory(WebContent)
 add_subdirectory(WebDriver)
 add_subdirectory(WebSocket)
-add_dependencies(ladybird ImageDecoder RequestServer SQLServer WebContent WebDriver WebSocketServer headless-browser)
+add_subdirectory(WebWorker)
+add_dependencies(ladybird ImageDecoder RequestServer SQLServer WebContent WebDriver WebSocketServer WebWorker headless-browser)
 
 function(create_ladybird_bundle target_name)
     set_target_properties(${target_name} PROPERTIES
@@ -240,6 +241,7 @@ function(create_ladybird_bundle target_name)
             COMMAND "${CMAKE_COMMAND}" -E copy_if_different "$<TARGET_FILE:WebContent>" "${app_dir}"
             COMMAND "${CMAKE_COMMAND}" -E copy_if_different "$<TARGET_FILE:WebDriver>" "${app_dir}"
             COMMAND "${CMAKE_COMMAND}" -E copy_if_different "$<TARGET_FILE:WebSocketServer>" "${app_dir}"
+            COMMAND "${CMAKE_COMMAND}" -E copy_if_different "$<TARGET_FILE:WebWorker>" "${app_dir}"
             COMMAND "${CMAKE_COMMAND}" -E copy_if_different "$<TARGET_FILE:headless-browser>" "${app_dir}"
             COMMAND "mkdir" -p "${bundle_dir}/Contents/Resources"
             COMMAND "iconutil" --convert icns "${SERENITY_SOURCE_DIR}/Ladybird/Icons/macos/app_icon.iconset" --output "${bundle_dir}/Contents/Resources/app_icon.icns"

Ladybird/WebDriver/CMakeLists.txt

@@ -14,5 +14,5 @@ target_include_directories(WebDriver PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/..)
 target_include_directories(WebDriver PRIVATE ${CMAKE_CURRENT_BINARY_DIR}/..)
 target_include_directories(WebDriver PRIVATE ${SERENITY_SOURCE_DIR}/Userland)
 target_include_directories(WebDriver PRIVATE ${SERENITY_SOURCE_DIR}/Userland/Services)
-target_link_libraries(WebDriver PRIVATE LibCore LibFileSystem LibGfx LibIPC LibJS LibMain LibWeb LibWebSocket)
+target_link_libraries(WebDriver PRIVATE LibCore LibFileSystem LibGfx LibIPC LibJS LibMain LibWeb LibWebSocket LibWebView)
 add_dependencies(WebDriver headless-browser)

Ladybird/WebWorker/CMakeLists.txt

@@ -0,0 +1,24 @@
+set(WEBWORKER_SOURCE_DIR ${SERENITY_SOURCE_DIR}/Userland/Services/WebWorker)
+
+set(CMAKE_AUTOMOC OFF)
+set(CMAKE_AUTORCC OFF)
+set(CMAKE_AUTOUIC OFF)
+
+set(WEBWORKER_SOURCES
+    "${WEBWORKER_SOURCE_DIR}/ConnectionFromClient.cpp"
+    "${WEBWORKER_SOURCE_DIR}/DedicatedWorkerHost.cpp"
+    "${WEBWORKER_SOURCE_DIR}/PageHost.cpp"
+    ../HelperProcess.cpp
+    ../Utilities.cpp
+)
+
+# FIXME: Add Android service
+
+add_library(webworker STATIC ${WEBWORKER_SOURCES})
+
+target_include_directories(webworker PRIVATE ${SERENITY_SOURCE_DIR}/Userland/Services/)
+target_include_directories(webworker PRIVATE ${CMAKE_CURRENT_BINARY_DIR}/..)
+target_link_libraries(webworker PUBLIC LibCore LibFileSystem LibGfx LibIPC LibJS LibProtocol LibWeb LibWebView LibLocale LibImageDecoderClient LibMain)
+
+add_executable(WebWorker main.cpp)
+target_link_libraries(WebWorker PRIVATE webworker)

Ladybird/WebWorker/main.cpp

@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2023, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <Ladybird/FontPlugin.h>
+#include <Ladybird/HelperProcess.h>
+#include <Ladybird/Utilities.h>
+#include <LibCore/ArgsParser.h>
+#include <LibCore/EventLoop.h>
+#include <LibCore/LocalServer.h>
+#include <LibCore/StandardPaths.h>
+#include <LibCore/System.h>
+#include <LibFileSystem/FileSystem.h>
+#include <LibIPC/SingleServer.h>
+#include <LibMain/Main.h>
+#include <LibWeb/Bindings/MainThreadVM.h>
+#include <LibWeb/Loader/GeneratedPagesLoader.h>
+#include <LibWeb/Loader/ResourceLoader.h>
+#include <LibWeb/Platform/EventLoopPlugin.h>
+#include <LibWeb/Platform/EventLoopPluginSerenity.h>
+#include <LibWeb/Platform/FontPluginSerenity.h>
+#include <LibWeb/WebSockets/WebSocket.h>
+#include <LibWebView/RequestServerAdapter.h>
+#include <LibWebView/WebSocketClientAdapter.h>
+#include <WebWorker/ConnectionFromClient.h>
+
+static ErrorOr<void> initialize_lagom_networking();
+
+ErrorOr<int> serenity_main(Main::Arguments arguments)
+{
+    int fd_passing_socket { -1 };
+
+    Core::ArgsParser args_parser;
+    args_parser.add_option(fd_passing_socket, "File descriptor of the fd passing socket", "fd-passing-socket", 'c', "fd-passing-socket");
+    args_parser.parse(arguments);
+
+    platform_init();
+
+    Web::Platform::EventLoopPlugin::install(*new Web::Platform::EventLoopPluginSerenity);
+    Core::EventLoop event_loop;
+
+    Web::Platform::FontPlugin::install(*new Web::Platform::FontPluginSerenity);
+
+    TRY(initialize_lagom_networking());
+
+    VERIFY(fd_passing_socket >= 0);
+
+    Web::set_resource_directory_url(TRY(String::formatted("file://{}/res", s_serenity_resource_root)));
+    Web::set_error_page_url(TRY(String::formatted("file://{}/res/html/error.html", s_serenity_resource_root)));
+    Web::set_directory_page_url(TRY(String::formatted("file://{}/res/html/directory.html", s_serenity_resource_root)));
+
+    TRY(Web::Bindings::initialize_main_thread_vm());
+
+    auto client = TRY(IPC::take_over_accepted_client_from_system_server<WebWorker::ConnectionFromClient>());
+    client->set_fd_passing_socket(TRY(Core::LocalSocket::adopt_fd(fd_passing_socket)));
+
+    return event_loop.exec();
+}
+
+static ErrorOr<void> initialize_lagom_networking()
+{
+    auto candidate_request_server_paths = TRY(get_paths_for_helper_process("RequestServer"sv));
+    auto request_server_client = TRY(launch_request_server_process(candidate_request_server_paths, s_serenity_resource_root));
+    Web::ResourceLoader::initialize(TRY(WebView::RequestServerAdapter::try_create(move(request_server_client))));
+
+    auto candidate_web_socket_paths = TRY(get_paths_for_helper_process("WebSocket"sv));
+    auto web_socket_client = TRY(launch_web_socket_process(candidate_web_socket_paths, s_serenity_resource_root));
+    Web::WebSockets::WebSocketClientManager::initialize(TRY(WebView::WebSocketClientManagerAdapter::try_create(move(web_socket_client))));
+
+    return {};
+}

Ladybird/cmake/InstallRules.cmake

@@ -4,7 +4,7 @@ include(GNUInstallDirs)
 
 set(package ladybird)
 
-set(ladybird_applications ladybird SQLServer WebContent WebDriver WebSocketServer RequestServer ImageDecoder headless-browser)
+set(ladybird_applications ladybird SQLServer WebContent WebDriver WebSocketServer RequestServer ImageDecoder WebWorker headless-browser)
 
 set(app_install_targets ${ladybird_applications})
 
@@ -45,7 +45,7 @@ macro(install_service_lib service)
       endif()
     endif()
 endmacro()
-foreach(service IN LISTS webcontent requestserver websocket)
+foreach(service IN LISTS webcontent requestserver websocket webworker)
     install_service_lib(${service})
 endforeach()
 

Userland/Libraries/LibWeb/CMakeLists.txt

@@ -382,6 +382,7 @@ set(SOURCES
     HTML/Scripting/Script.cpp
     HTML/Scripting/TemporaryExecutionContext.cpp
     HTML/Scripting/WindowEnvironmentSettingsObject.cpp
+    HTML/Scripting/WorkerEnvironmentSettingsObject.cpp
     HTML/SessionHistoryEntry.cpp
     HTML/SharedImageRequest.cpp
     HTML/SourceSet.cpp
@@ -403,6 +404,7 @@ set(SOURCES
     HTML/WindowOrWorkerGlobalScope.cpp
     HTML/WindowProxy.cpp
     HTML/Worker.cpp
+    HTML/WorkerAgent.cpp
     HTML/WorkerDebugConsoleClient.cpp
     HTML/WorkerGlobalScope.cpp
     HTML/WorkerLocation.cpp
@@ -632,8 +634,12 @@ set(SOURCES
     XHR/XMLHttpRequestUpload.cpp
     XML/XMLDocumentBuilder.cpp
     XLink/AttributeNames.cpp
+    Worker/WebWorkerClient.cpp
 )
 
+compile_ipc(Worker/WebWorkerClient.ipc Worker/WebWorkerClientEndpoint.h)
+compile_ipc(Worker/WebWorkerServer.ipc Worker/WebWorkerServerEndpoint.h)
+
 invoke_generator(
         "AriaRoles.cpp"
         Lagom::GenerateAriaRoles
@@ -659,6 +665,8 @@ set(GENERATED_SOURCES
     CSS/ValueID.cpp
     MathML/MathMLStyleSheetSource.cpp
     SVG/SVGStyleSheetSource.cpp
+    Worker/WebWorkerClientEndpoint.h
+    Worker/WebWorkerServerEndpoint.h
 )
 
 serenity_lib(LibWeb web)

Userland/Libraries/LibWeb/HTML/Scripting/WorkerEnvironmentSettingsObject.cpp

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2023, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/HTML/Scripting/WorkerEnvironmentSettingsObject.h>
+#include <LibWeb/HTML/WorkerGlobalScope.h>
+
+namespace Web::HTML {
+
+JS::NonnullGCPtr<WorkerEnvironmentSettingsObject> WorkerEnvironmentSettingsObject::setup(NonnullOwnPtr<JS::ExecutionContext> execution_context /* FIXME: null or an environment reservedEnvironment, a URL topLevelCreationURL, and an origin topLevelOrigin */)
+{
+    auto realm = execution_context->realm;
+    VERIFY(realm);
+
+    auto& worker = verify_cast<HTML::WorkerGlobalScope>(realm->global_object());
+
+    auto settings_object = realm->heap().allocate<WorkerEnvironmentSettingsObject>(*realm, move(execution_context), worker);
+    settings_object->target_browsing_context = nullptr;
+
+    auto intrinsics = realm->heap().allocate<Bindings::Intrinsics>(*realm, *realm);
+    auto host_defined = make<Bindings::HostDefined>(settings_object, intrinsics);
+    realm->set_host_defined(move(host_defined));
+
+    // Non-Standard: We cannot fully initialize worker object until *after* the we set up
+    //    the realm's [[HostDefined]] internal slot as the internal slot contains the web platform intrinsics
+    worker.initialize_web_interfaces({});
+
+    return settings_object;
+}
+
+void WorkerEnvironmentSettingsObject::visit_edges(JS::Cell::Visitor& visitor)
+{
+    Base::visit_edges(visitor);
+    visitor.visit(m_global_scope);
+}
+
+}

Userland/Libraries/LibWeb/HTML/Scripting/WorkerEnvironmentSettingsObject.h

@@ -7,7 +7,6 @@
 #pragma once
 
 #include <AK/URL.h>
-#include <LibWeb/Bindings/DedicatedWorkerExposedInterfaces.h>
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/Forward.h>
 
@@ -18,27 +17,13 @@ class WorkerEnvironmentSettingsObject final
     JS_CELL(WindowEnvironmentSettingsObject, EnvironmentSettingsObject);
 
 public:
-    WorkerEnvironmentSettingsObject(NonnullOwnPtr<JS::ExecutionContext> execution_context)
+    WorkerEnvironmentSettingsObject(NonnullOwnPtr<JS::ExecutionContext> execution_context, JS::NonnullGCPtr<WorkerGlobalScope> global_scope)
         : EnvironmentSettingsObject(move(execution_context))
+        , m_global_scope(global_scope)
     {
     }
 
-    static JS::NonnullGCPtr<WorkerEnvironmentSettingsObject> setup(NonnullOwnPtr<JS::ExecutionContext> execution_context /* FIXME: null or an environment reservedEnvironment, a URL topLevelCreationURL, and an origin topLevelOrigin */)
-    {
-        auto realm = execution_context->realm;
-        VERIFY(realm);
-        auto settings_object = realm->heap().allocate<WorkerEnvironmentSettingsObject>(*realm, move(execution_context));
-        settings_object->target_browsing_context = nullptr;
-
-        auto intrinsics = realm->heap().allocate<Bindings::Intrinsics>(*realm, *realm);
-        auto host_defined = make<Bindings::HostDefined>(settings_object, intrinsics);
-        realm->set_host_defined(move(host_defined));
-
-        // FIXME: Shared workers should use the shared worker method
-        Bindings::add_dedicated_worker_exposed_interfaces(realm->global_object());
-
-        return settings_object;
-    }
+    static JS::NonnullGCPtr<WorkerEnvironmentSettingsObject> setup(NonnullOwnPtr<JS::ExecutionContext> execution_context /* FIXME: null or an environment reservedEnvironment, a URL topLevelCreationURL, and an origin topLevelOrigin */);
 
     virtual ~WorkerEnvironmentSettingsObject() override = default;
 
@@ -47,13 +32,17 @@ public:
     AK::URL api_base_url() override { return m_url; }
     Origin origin() override { return m_origin; }
     PolicyContainer policy_container() override { return m_policy_container; }
-    CanUseCrossOriginIsolatedAPIs cross_origin_isolated_capability() override { TODO(); }
+    CanUseCrossOriginIsolatedAPIs cross_origin_isolated_capability() override { return CanUseCrossOriginIsolatedAPIs::No; }
 
 private:
+    virtual void visit_edges(JS::Cell::Visitor&) override;
+
     DeprecatedString m_api_url_character_encoding;
     AK::URL m_url;
     HTML::Origin m_origin;
     HTML::PolicyContainer m_policy_container;
+
+    JS::NonnullGCPtr<WorkerGlobalScope> m_global_scope;
 };
 
 }

Userland/Libraries/LibWeb/HTML/Worker.cpp

@@ -21,9 +21,6 @@ Worker::Worker(String const& script_url, WorkerOptions const options, DOM::Docum
     , m_script_url(script_url)
     , m_options(options)
     , m_document(&document)
-    , m_custom_data()
-    , m_worker_vm(JS::VM::create(adopt_own(m_custom_data)).release_value_but_fixme_should_propagate_errors())
-    , m_implicit_port(MessagePort::create(document.realm()))
 {
 }
 
@@ -37,22 +34,12 @@ void Worker::visit_edges(Cell::Visitor& visitor)
 {
     Base::visit_edges(visitor);
     visitor.visit(m_document);
-    visitor.visit(m_inner_settings);
-    visitor.visit(m_implicit_port);
     visitor.visit(m_outside_port);
-
-    // These are in a separate VM and shouldn't be visited
-    visitor.ignore(m_worker_realm);
-    visitor.ignore(m_worker_scope);
 }
 
 // https://html.spec.whatwg.org/multipage/workers.html#dom-worker
 WebIDL::ExceptionOr<JS::NonnullGCPtr<Worker>> Worker::create(String const& script_url, WorkerOptions const options, DOM::Document& document)
 {
-    // NOTE: We don't start a worker because they're not properly implemented yet and would likely crash.
-    dbgln("FIXME: Implement web workers");
-    return WebIDL::NotSupportedError::create(document.realm(), "Web workers not supported yet"_fly_string);
-
     dbgln_if(WEB_WORKER_DEBUG, "WebWorker: Creating worker with script_url = {}", script_url);
 
     // Returns a new Worker object. scriptURL will be fetched and executed in the background,
@@ -98,12 +85,10 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<Worker>> Worker::create(String const& scrip
 }
 
 // https://html.spec.whatwg.org/multipage/workers.html#run-a-worker
-void Worker::run_a_worker(AK::URL& url, EnvironmentSettingsObject& outside_settings, MessagePort& outside_port, WorkerOptions const& options)
+void Worker::run_a_worker(AK::URL& url, EnvironmentSettingsObject& outside_settings, MessagePort&, WorkerOptions const& options)
 {
     // 1. Let is shared be true if worker is a SharedWorker object, and false otherwise.
     // FIXME: SharedWorker support
-    auto is_shared = false;
-    auto is_top_level = false;
 
     // 2. Let owner be the relevant owner to add given outside settings.
     // FIXME: Support WorkerGlobalScope options
@@ -119,204 +104,9 @@ void Worker::run_a_worker(AK::URL& url, EnvironmentSettingsObject& outside_setti
 
     // 6. Let agent be the result of obtaining a dedicated/shared worker agent given outside settings
     // and is shared. Run the rest of these steps in that agent.
-    // NOTE: This is effectively the worker's vm
 
-    // 7. Let realm execution context be the result of creating a new JavaScript realm given agent and the following customizations:
-    auto realm_execution_context = Bindings::create_a_new_javascript_realm(
-        *m_worker_vm,
-        [&](JS::Realm& realm) -> JS::Object* {
-            //      7a. For the global object, if is shared is true, create a new SharedWorkerGlobalScope object.
-            //      7b. Otherwise, create a new DedicatedWorkerGlobalScope object.
-            // FIXME: Proper support for both SharedWorkerGlobalScope and DedicatedWorkerGlobalScope
-            if (is_shared)
-                TODO();
-            // FIXME: Make and use subclasses of WorkerGlobalScope, however this requires JS::GlobalObject to
-            //        play nicely with the IDL interpreter, to make spec-compliant extensions, which it currently does not.
-            m_worker_scope = m_worker_vm->heap().allocate_without_realm<JS::GlobalObject>(realm);
-            return m_worker_scope.ptr();
-        },
-        nullptr);
-
-    auto& console_object = *realm_execution_context->realm->intrinsics().console_object();
-    m_worker_realm = realm_execution_context->realm;
-
-    m_console = adopt_ref(*new WorkerDebugConsoleClient(console_object.console()));
-    console_object.console().set_client(*m_console);
-
-    // FIXME: This should be done with IDL
-    u8 attr = JS::Attribute::Writable | JS::Attribute::Enumerable | JS::Attribute::Configurable;
-    m_worker_scope->define_native_function(
-        m_worker_scope->shape().realm(),
-        "postMessage",
-        [this](auto& vm) {
-            // This is the implementation of the function that the spawned worked calls
-
-            // https://html.spec.whatwg.org/multipage/workers.html#dom-dedicatedworkerglobalscope-postmessage
-            // The postMessage(message, transfer) and postMessage(message, options) methods on DedicatedWorkerGlobalScope
-            // objects act as if, when invoked, it immediately invoked the respective postMessage(message, transfer) and
-            // postMessage(message, options) on the port, with the same arguments, and returned the same return value
-
-            auto message = vm.argument(0);
-            // FIXME: `transfer` not support by post_message yet
-
-            dbgln_if(WEB_WORKER_DEBUG, "WebWorker: Inner post_message");
-
-            // FIXME: This is a bit of a hack, in reality, we should m_outside_port->post_message and the onmessage event
-            //        should bubble up to the Worker itself from there.
-
-            auto& event_loop = get_vm_event_loop(m_document->realm().vm());
-
-            event_loop.task_queue().add(HTML::Task::create(HTML::Task::Source::PostedMessage, nullptr, [this, message] {
-                MessageEventInit event_init {};
-                event_init.data = message;
-                event_init.origin = "<origin>"_string;
-                dispatch_event(MessageEvent::create(*m_worker_realm, HTML::EventNames::message, event_init));
-            }));
-
-            return JS::js_undefined();
-        },
-        2, attr);
-
-    // 8. Let worker global scope be the global object of realm execution context's Realm component.
-    // NOTE: This is the DedicatedWorkerGlobalScope or SharedWorkerGlobalScope object created in the previous step.
-
-    // 9. Set up a worker environment settings object with realm execution context,
-    //    outside settings, and unsafeWorkerCreationTime, and let inside settings be the result.
-    m_inner_settings = WorkerEnvironmentSettingsObject::setup(move(realm_execution_context));
-
-    // 10. Set worker global scope's name to the value of options's name member.
-    // FIXME: name property requires the SharedWorkerGlobalScope or DedicatedWorkerGlobalScope child class to be used
-
-    // 11. Append owner to worker global scope's owner set.
-    // FIXME: support for 'owner' set on WorkerGlobalScope
-
-    // 12. If is shared is true, then:
-    if (is_shared) {
-        // FIXME: Shared worker support
-        // 1. Set worker global scope's constructor origin to outside settings's origin.
-        // 2. Set worker global scope's constructor url to url.
-        // 3. Set worker global scope's type to the value of options's type member.
-        // 4. Set worker global scope's credentials to the value of options's credentials member.
-    }
-
-    // 13. Let destination be "sharedworker" if is shared is true, and "worker" otherwise.
-
-    // 14. Obtain script by switching on the value of options's type member:
-    // classic: Fetch a classic worker script given url, outside settings, destination, and inside settings.
-    // module:  Fetch a module worker script graph given url, outside settings, destination, the value of the
-    //          credentials member of options, and inside settings.
-    if (options.type != "classic") {
-        dbgln_if(WEB_WORKER_DEBUG, "Unsupported script type {} for LibWeb/Worker", options.type);
-        TODO();
-    }
-
-    ResourceLoader::the().load(
-        url,
-        [this, is_shared, is_top_level, url, &outside_port](auto data, auto&, auto) {
-            // In both cases, to perform the fetch given request, perform the following steps if the is top-level flag is set:
-            if (is_top_level) {
-                // 1. Set request's reserved client to inside settings.
-
-                // 2. Fetch request, and asynchronously wait to run the remaining steps
-                //    as part of fetch's process response for the response response.
-                // Implied
-
-                // 3. Set worker global scope's url to response's url.
-
-                // 4. Initialize worker global scope's policy container given worker global scope, response, and inside settings.
-                // FIXME: implement policy container
-
-                // 5. If the Run CSP initialization for a global object algorithm returns "Blocked" when executed upon worker
-                //    global scope, set response to a network error. [CSP]
-                // FIXME: CSP support
-
-                // 6. If worker global scope's embedder policy's value is compatible with cross-origin isolation and is shared is true,
-                //    then set agent's agent cluster's cross-origin isolation mode to "logical" or "concrete".
-                //    The one chosen is implementation-defined.
-                // FIXME: CORS policy support
-
-                // 7. If the result of checking a global object's embedder policy with worker global scope, outside settings,
-                //    and response is false, then set response to a network error.
-                // FIXME: Embed policy support
-
-                // 8. Set worker global scope's cross-origin isolated capability to true if agent's agent cluster's cross-origin
-                //    isolation mode is "concrete".
-                // FIXME: CORS policy support
-
-                if (!is_shared) {
-                    // 9.  If is shared is false and owner's cross-origin isolated capability is false, then set worker
-                    //     global scope's cross-origin isolated capability to false.
-                    // 10. If is shared is false and response's url's scheme is "data", then set worker global scope's
-                    //     cross-origin isolated capability to false.
-                }
-            }
-
-            if (data.is_null()) {
-                dbgln_if(WEB_WORKER_DEBUG, "WebWorker: Failed to load {}", url);
-                return;
-            }
-
-            // Asynchronously complete the perform the fetch steps with response.
-            dbgln_if(WEB_WORKER_DEBUG, "WebWorker: Script ready!");
-            auto script = ClassicScript::create(url.to_deprecated_string(), data, *m_inner_settings, AK::URL());
-
-            // NOTE: Steps 15-31 below pick up after step 14 in the main context, steps 1-10 above
-            //       are only for validation when used in a top-level case (ie: from a Window)
-
-            // 15. Associate worker with worker global scope.
-            // FIXME: Global scope association
-
-            // 16. Let inside port be a new MessagePort object in inside settings's Realm.
-            auto inside_port = MessagePort::create(m_inner_settings->realm());
-
-            // 17. Associate inside port with worker global scope.
-            // FIXME: Global scope association
-
-            // 18. Entangle outside port and inside port.
-            outside_port.entangle_with(*inside_port);
-
-            // 19. Create a new WorkerLocation object and associate it with worker global scope.
-
-            // 20. Closing orphan workers: Start monitoring the worker such that no sooner than it
-            //     stops being a protected worker, and no later than it stops being a permissible worker,
-            //     worker global scope's closing flag is set to true.
-            // FIXME: Worker monitoring and cleanup
-
-            // 21. Suspending workers: Start monitoring the worker, such that whenever worker global scope's
-            //     closing flag is false and the worker is a suspendable worker, the user agent suspends
-            //     execution of script in that worker until such time as either the closing flag switches to
-            //     true or the worker stops being a suspendable worker
-            // FIXME: Worker suspending
-
-            // 22. Set inside settings's execution ready flag.
-            // FIXME: Implement worker settings object
-
-            // 23. If script is a classic script, then run the classic script script.
-            //     Otherwise, it is a module script; run the module script script.
-            auto result = script->run();
-
-            // 24. Enable outside port's port message queue.
-            outside_port.start();
-
-            // 25. If is shared is false, enable the port message queue of the worker's implicit port.
-            if (!is_shared)
-                m_implicit_port->start();
-
-            // 26. If is shared is true, then queue a global task on DOM manipulation task source given worker
-            //     global scope to fire an event named connect at worker global scope, using MessageEvent,
-            //     with the data attribute initialized to the empty string, the ports attribute initialized
-            //     to a new frozen array containing inside port, and the source attribute initialized to inside port.
-            // FIXME: Shared worker support
-
-            // 27. Enable the client message queue of the ServiceWorkerContainer object whose associated service
-            //     worker client is worker global scope's relevant settings object.
-            // FIXME: Understand....and support worker global settings
-
-            // 28. Event loop: Run the responsible event loop specified by inside settings until it is destroyed.
-        },
-        [](auto&, auto, auto, auto&) {
-            dbgln_if(WEB_WORKER_DEBUG, "WebWorker: HONK! Failed to load script.");
-        });
+    // Note: This spawns a new process to act as the 'agent' for the worker.
+    m_agent = heap().allocate_without_realm<WorkerAgent>(url, options);
 }
 
 // https://html.spec.whatwg.org/multipage/workers.html#dom-worker-terminate

Userland/Libraries/LibWeb/HTML/Worker.h

@@ -16,6 +16,7 @@
 #include <LibWeb/HTML/Scripting/WindowEnvironmentSettingsObject.h>
 #include <LibWeb/HTML/Scripting/WorkerEnvironmentSettingsObject.h>
 #include <LibWeb/HTML/Window.h>
+#include <LibWeb/HTML/WorkerAgent.h>
 #include <LibWeb/HTML/WorkerDebugConsoleClient.h>
 #include <LibWeb/Loader/ResourceLoader.h>
 
@@ -25,12 +26,6 @@
 
 namespace Web::HTML {
 
-struct WorkerOptions {
-    String type { "classic"_string };
-    String credentials { "same-origin"_string };
-    String name { String {} };
-};
-
 // https://html.spec.whatwg.org/multipage/workers.html#dedicated-workers-and-the-worker-interface
 class Worker : public DOM::EventTarget {
     WEB_PLATFORM_OBJECT(Worker, DOM::EventTarget);
@@ -49,7 +44,6 @@ public:
 
     virtual ~Worker() = default;
 
-    MessagePort* implicit_message_port() { return m_implicit_port.ptr(); }
     JS::GCPtr<MessagePort> outside_message_port() { return m_outside_port; }
 
 #undef __ENUMERATE
@@ -63,11 +57,6 @@ protected:
     Worker(String const&, const WorkerOptions, DOM::Document&);
 
 private:
-    static HTML::EventLoop& get_vm_event_loop(JS::VM& target_vm)
-    {
-        return static_cast<Bindings::WebEngineCustomData*>(target_vm.custom_data())->event_loop;
-    }
-
     virtual void initialize(JS::Realm&) override;
     virtual void visit_edges(Cell::Visitor&) override;
 
@@ -75,19 +64,9 @@ private:
     WorkerOptions m_options;
 
     JS::GCPtr<DOM::Document> m_document;
-
-    Bindings::WebEngineCustomData m_custom_data;
-
-    NonnullRefPtr<JS::VM> m_worker_vm;
-    JS::GCPtr<WorkerEnvironmentSettingsObject> m_inner_settings;
-    RefPtr<WorkerDebugConsoleClient> m_console;
-
-    JS::NonnullGCPtr<MessagePort> m_implicit_port;
     JS::GCPtr<MessagePort> m_outside_port;
 
-    // NOTE: These are inside the worker VM.
-    JS::GCPtr<JS::Realm> m_worker_realm;
-    JS::GCPtr<JS::Object> m_worker_scope;
+    JS::GCPtr<WorkerAgent> m_agent;
 
     void run_a_worker(AK::URL& url, EnvironmentSettingsObject& outside_settings, MessagePort& outside_port, WorkerOptions const& options);
 };

Userland/Libraries/LibWeb/HTML/WorkerAgent.cpp

@@ -0,0 +1,115 @@
+/*
+ * Copyright (c) 2023, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/LexicalPath.h>
+#include <LibCore/Socket.h>
+#include <LibCore/System.h>
+#include <LibWeb/HTML/WorkerAgent.h>
+#include <LibWeb/Worker/WebWorkerClient.h>
+
+// FIXME: Deduplicate this code with ladybird!!
+
+#ifndef AK_OS_SERENITY
+namespace {
+
+ErrorOr<String> application_directory()
+{
+    auto current_executable_path = TRY(Core::System::current_executable_path());
+    auto dirname = LexicalPath::dirname(current_executable_path.to_deprecated_string());
+    return String::from_deprecated_string(dirname);
+}
+
+ErrorOr<Vector<String>> get_paths_for_helper_process(StringView process_name)
+{
+    auto application_path = TRY(application_directory());
+    Vector<String> paths;
+
+    TRY(paths.try_append(TRY(String::formatted("{}/{}", application_path, process_name))));
+    TRY(paths.try_append(TRY(String::formatted("./{}", process_name))));
+    // NOTE: Add platform-specific paths here
+    return paths;
+}
+
+ErrorOr<NonnullRefPtr<Web::HTML::WebWorkerClient>> launch_web_worker_process(ReadonlySpan<String> candidate_web_content_paths)
+{
+    int socket_fds[2] {};
+    TRY(Core::System::socketpair(AF_LOCAL, SOCK_STREAM, 0, socket_fds));
+
+    int ui_fd = socket_fds[0];
+    int wc_fd = socket_fds[1];
+
+    int fd_passing_socket_fds[2] {};
+    TRY(Core::System::socketpair(AF_LOCAL, SOCK_STREAM, 0, fd_passing_socket_fds));
+
+    int ui_fd_passing_fd = fd_passing_socket_fds[0];
+    int wc_fd_passing_fd = fd_passing_socket_fds[1];
+
+    if (auto child_pid = TRY(Core::System::fork()); child_pid == 0) {
+        TRY(Core::System::close(ui_fd_passing_fd));
+        TRY(Core::System::close(ui_fd));
+
+        auto takeover_string = TRY(String::formatted("WebWorker:{}", wc_fd));
+        TRY(Core::System::setenv("SOCKET_TAKEOVER"sv, takeover_string, true));
+
+        auto webcontent_fd_passing_socket_string = TRY(String::number(wc_fd_passing_fd));
+
+        ErrorOr<void> result;
+        for (auto const& path : candidate_web_content_paths) {
+            if (Core::System::access(path, X_OK).is_error())
+                continue;
+
+            auto arguments = Vector {
+                path.bytes_as_string_view(),
+                "--fd-passing-socket"sv,
+                webcontent_fd_passing_socket_string
+            };
+
+            result = Core::System::exec(arguments[0], arguments.span(), Core::System::SearchInPath::Yes);
+            if (!result.is_error())
+                break;
+        }
+
+        if (result.is_error())
+            warnln("Could not launch any of {}: {}", candidate_web_content_paths, result.error());
+        VERIFY_NOT_REACHED();
+    }
+
+    TRY(Core::System::close(wc_fd_passing_fd));
+    TRY(Core::System::close(wc_fd));
+
+    auto socket = TRY(Core::LocalSocket::adopt_fd(ui_fd));
+    TRY(socket->set_blocking(true));
+
+    auto new_client = TRY(adopt_nonnull_ref_or_enomem(new (nothrow) Web::HTML::WebWorkerClient(move(socket))));
+    new_client->set_fd_passing_socket(TRY(Core::LocalSocket::adopt_fd(ui_fd_passing_fd)));
+
+    return new_client;
+}
+}
+#endif
+
+namespace Web::HTML {
+
+WorkerAgent::WorkerAgent(AK::URL url, WorkerOptions const& options)
+    : m_worker_options(options)
+    , m_url(move(url))
+{
+#ifndef AK_OS_SERENITY
+    // FIXME: Add factory function
+    auto paths = MUST(get_paths_for_helper_process("WebWorker"sv));
+    m_worker_ipc = MUST(launch_web_worker_process(paths));
+#else
+    m_worker_ipc = MUST(Web::HTML::WebWorkerClient::try_create());
+#endif
+
+    int fds[2] = {};
+    MUST(Core::System::socketpair(AF_LOCAL, SOCK_STREAM, 0, fds));
+    m_message_port_fd = fds[0];
+
+    m_worker_ipc->async_start_dedicated_worker(m_url, options.type, options.credentials, options.name, fds[1]);
+}
+
+}

Userland/Libraries/LibWeb/HTML/WorkerAgent.h

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2023, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/RefCounted.h>
+#include <LibWeb/Forward.h>
+#include <LibWeb/HTML/MessageEvent.h>
+#include <LibWeb/HTML/MessagePort.h>
+#include <LibWeb/HTML/Scripting/ClassicScript.h>
+#include <LibWeb/HTML/Scripting/WorkerEnvironmentSettingsObject.h>
+#include <LibWeb/HTML/Window.h>
+#include <LibWeb/Worker/WebWorkerClient.h>
+
+namespace Web::HTML {
+
+struct WorkerOptions {
+    String type { "classic"_string };
+    String credentials { "same-origin"_string };
+    String name { String {} };
+};
+
+struct WorkerAgent : JS::Cell {
+    JS_CELL(Agent, JS::Cell);
+
+    WorkerAgent(AK::URL url, WorkerOptions const& options);
+
+    RefPtr<Web::HTML::WebWorkerClient> m_worker_ipc;
+
+private:
+    WorkerOptions m_worker_options;
+    AK::URL m_url;
+
+    // TODO: associate with MessagePorts?
+    int m_message_port_fd;
+};
+
+}

Userland/Libraries/LibWeb/HTML/WorkerGlobalScope.cpp

@@ -5,7 +5,9 @@
  */
 
 #include <AK/Vector.h>
+#include <LibWeb/Bindings/DedicatedWorkerExposedInterfaces.h>
 #include <LibWeb/Bindings/ExceptionOrUtils.h>
+#include <LibWeb/Bindings/Intrinsics.h>
 #include <LibWeb/Bindings/WorkerGlobalScopePrototype.h>
 #include <LibWeb/Forward.h>
 #include <LibWeb/HTML/EventHandler.h>
@@ -16,17 +18,26 @@
 
 namespace Web::HTML {
 
-WorkerGlobalScope::WorkerGlobalScope(JS::Realm& realm)
+WorkerGlobalScope::WorkerGlobalScope(JS::Realm& realm, Web::Page& page)
     : DOM::EventTarget(realm)
-
+    , m_page(page)
 {
 }
 
 WorkerGlobalScope::~WorkerGlobalScope() = default;
 
-void WorkerGlobalScope::initialize(JS::Realm& realm)
+void WorkerGlobalScope::initialize_web_interfaces(Badge<WorkerEnvironmentSettingsObject>)
 {
+    auto& realm = this->realm();
     Base::initialize(realm);
+
+    // FIXME: Handle shared worker
+    add_dedicated_worker_exposed_interfaces(*this);
+
+    Object::set_prototype(&Bindings::ensure_web_prototype<Bindings::WorkerGlobalScopePrototype>(realm, "WorkerGlobalScope"));
+
+    WindowOrWorkerGlobalScopeMixin::initialize(realm);
+
     m_navigator = WorkerNavigator::create(*this);
 }
 

Userland/Libraries/LibWeb/HTML/WorkerGlobalScope.h

@@ -41,6 +41,16 @@ public:
     virtual Bindings::PlatformObject& this_impl() override { return *this; }
     virtual Bindings::PlatformObject const& this_impl() const override { return *this; }
 
+    using WindowOrWorkerGlobalScopeMixin::atob;
+    using WindowOrWorkerGlobalScopeMixin::btoa;
+    using WindowOrWorkerGlobalScopeMixin::clear_interval;
+    using WindowOrWorkerGlobalScopeMixin::clear_timeout;
+    using WindowOrWorkerGlobalScopeMixin::fetch;
+    using WindowOrWorkerGlobalScopeMixin::queue_microtask;
+    using WindowOrWorkerGlobalScopeMixin::set_interval;
+    using WindowOrWorkerGlobalScopeMixin::set_timeout;
+    using WindowOrWorkerGlobalScopeMixin::structured_clone;
+
     // Following methods are from the WorkerGlobalScope IDL definition
     // https://html.spec.whatwg.org/multipage/workers.html#the-workerglobalscope-common-interface
 
@@ -67,16 +77,17 @@ public:
     //            this is not problematic as it cannot be observed from script.
     void set_location(JS::NonnullGCPtr<WorkerLocation> loc) { m_location = move(loc); }
 
+    void initialize_web_interfaces(Badge<WorkerEnvironmentSettingsObject>);
+
+    Web::Page* page() { return &m_page; }
+
 protected:
-    explicit WorkerGlobalScope(JS::Realm&);
+    explicit WorkerGlobalScope(JS::Realm&, Web::Page&);
 
 private:
-    virtual void initialize(JS::Realm&) override;
-
     virtual void visit_edges(Cell::Visitor&) override;
 
     JS::GCPtr<WorkerLocation> m_location;
-
     JS::GCPtr<WorkerNavigator> m_navigator;
 
     // FIXME: Add all these internal slots
@@ -110,6 +121,8 @@ private:
 
     // https://html.spec.whatwg.org/multipage/workers.html#concept-workerglobalscope-cross-origin-isolated-capability
     bool m_cross_origin_isolated_capability { false };
+
+    Web::Page& m_page;
 };
 
 }

Userland/Libraries/LibWeb/Worker/WebWorkerClient.cpp

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2023, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/Worker/WebWorkerClient.h>
+
+namespace Web::HTML {
+
+void WebWorkerClient::die()
+{
+    // FIXME: Notify WorkerAgent that the worker is ded
+}
+
+WebWorkerClient::WebWorkerClient(NonnullOwnPtr<Core::LocalSocket> socket)
+    : IPC::ConnectionToServer<WebWorkerClientEndpoint, WebWorkerServerEndpoint>(*this, move(socket))
+{
+}
+
+}

Userland/Libraries/LibWeb/Worker/WebWorkerClient.h

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2023, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/HashMap.h>
+#include <LibIPC/ConnectionToServer.h>
+#include <LibWeb/Worker/WebWorkerClientEndpoint.h>
+#include <LibWeb/Worker/WebWorkerServerEndpoint.h>
+
+namespace Web::HTML {
+
+class WebWorkerClient final
+    : public IPC::ConnectionToServer<WebWorkerClientEndpoint, WebWorkerServerEndpoint>
+    , public WebWorkerClientEndpoint {
+    IPC_CLIENT_CONNECTION(WebWorkerClient, "/tmp/session/%sid/portal/webworker"sv);
+
+public:
+    explicit WebWorkerClient(NonnullOwnPtr<Core::LocalSocket>);
+
+private:
+    virtual void die() override;
+};
+
+}

Userland/Libraries/LibWeb/Worker/WebWorkerClient.ipc

@@ -0,0 +1,2 @@
+endpoint WebWorkerClient {
+}

Userland/Libraries/LibWeb/Worker/WebWorkerServer.ipc

@@ -0,0 +1,9 @@
+#include <AK/URL.h>
+#include <LibIPC/File.h>
+
+endpoint WebWorkerServer {
+
+    start_dedicated_worker(URL url, String type, String credentials, String name, IPC::File message_port) =|
+
+    handle_file_return(i32 error, Optional<IPC::File> file, i32 request_id) =|
+}

Userland/Services/CMakeLists.txt

@@ -27,5 +27,6 @@ if (SERENITYOS)
     add_subdirectory(WebContent)
     add_subdirectory(WebDriver)
     add_subdirectory(WebSocket)
+    add_subdirectory(WebWorker)
     add_subdirectory(WindowServer)
 endif()

Userland/Services/WebContent/main.cpp

@@ -41,6 +41,7 @@ ErrorOr<int> serenity_main(Main::Arguments)
     TRY(Core::System::unveil("/tmp/session/%sid/portal/request", "rw"));
     TRY(Core::System::unveil("/tmp/session/%sid/portal/image", "rw"));
     TRY(Core::System::unveil("/tmp/session/%sid/portal/websocket", "rw"));
+    TRY(Core::System::unveil("/tmp/session/%sid/portal/webworker", "rw"));
     TRY(Core::System::unveil(nullptr, nullptr));
 
     Web::Platform::EventLoopPlugin::install(*new Web::Platform::EventLoopPluginSerenity);

Userland/Services/WebDriver/CMakeLists.txt

@@ -17,4 +17,4 @@ set(GENERATED_SOURCES
 )
 
 serenity_bin(WebDriver)
-target_link_libraries(WebDriver PRIVATE LibCore LibHTTP LibMain LibIPC LibWeb LibGfx)
+target_link_libraries(WebDriver PRIVATE LibCore LibHTTP LibMain LibIPC LibWeb LibGfx LibWebView)

Userland/Services/WebWorker/CMakeLists.txt

@@ -0,0 +1,21 @@
+serenity_component(
+    WebWorker
+    TARGETS WebWorker
+    DEPENDS WebContent
+)
+
+set(SOURCES
+    ConnectionFromClient.cpp
+    DedicatedWorkerHost.cpp
+    PageHost.cpp
+    main.cpp
+)
+
+set(GENERATED_SOURCES
+    ../Libraries/LibWeb/Worker/WebWorkerClientEndpoint.h
+    ../Libraries/LibWeb/Worker/WebWorkerServerEndpoint.h
+)
+
+serenity_bin(WebWorker)
+target_link_libraries(WebWorker PRIVATE LibCore LibFileSystem LibGfx LibIPC LibJS LibWeb LibWebView LibLocale LibMain)
+link_with_locale_data(WebWorker)

Userland/Services/WebWorker/ConnectionFromClient.cpp

@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2023, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <WebWorker/ConnectionFromClient.h>
+#include <WebWorker/DedicatedWorkerHost.h>
+#include <WebWorker/PageHost.h>
+
+namespace WebWorker {
+
+void ConnectionFromClient::die()
+{
+    // FIXME: Do something here (shutdown process/script gracefully?)
+}
+
+void ConnectionFromClient::request_file(Web::FileRequest request)
+{
+    // FIXME: Route this to FSAS or Brower chrome as appropriate instead of allowing
+    //        the WebWorker process filesystem access
+    auto path = request.path();
+    auto request_id = ++last_id;
+
+    m_requested_files.set(request_id, move(request));
+
+    auto file = Core::File::open(path, Core::File::OpenMode::Read);
+
+    if (file.is_error())
+        handle_file_return(file.error().code(), {}, request_id);
+    else
+        handle_file_return(0, IPC::File(*file.value()), request_id);
+}
+
+ConnectionFromClient::ConnectionFromClient(NonnullOwnPtr<Core::LocalSocket> socket)
+    : IPC::ConnectionFromClient<WebWorkerClientEndpoint, WebWorkerServerEndpoint>(*this, move(socket), 1)
+    , m_page_host(PageHost::create(*this))
+{
+}
+
+ConnectionFromClient::~ConnectionFromClient() = default;
+
+Web::Page& ConnectionFromClient::page()
+{
+    return m_page_host->page();
+}
+
+Web::Page const& ConnectionFromClient::page() const
+{
+    return m_page_host->page();
+}
+
+void ConnectionFromClient::start_dedicated_worker(AK::URL const& url, String const& type, String const&, String const&, IPC::File const&)
+{
+    m_worker_host = make_ref_counted<DedicatedWorkerHost>(page(), url, type);
+
+    m_worker_host->run();
+}
+
+void ConnectionFromClient::handle_file_return(i32 error, Optional<IPC::File> const& file, i32 request_id)
+{
+    auto file_request = m_requested_files.take(request_id);
+
+    VERIFY(file_request.has_value());
+    VERIFY(file_request.value().on_file_request_finish);
+
+    file_request.value().on_file_request_finish(error != 0 ? Error::from_errno(error) : ErrorOr<i32> { file->take_fd() });
+}
+
+}

Userland/Services/WebWorker/ConnectionFromClient.h

@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2023, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/HashMap.h>
+#include <LibIPC/ConnectionFromClient.h>
+#include <LibJS/Forward.h>
+#include <LibWeb/Forward.h>
+#include <LibWeb/Loader/FileRequest.h>
+#include <LibWeb/Worker/WebWorkerClientEndpoint.h>
+#include <LibWeb/Worker/WebWorkerServerEndpoint.h>
+#include <WebWorker/Forward.h>
+
+namespace WebWorker {
+
+class ConnectionFromClient final
+    : public IPC::ConnectionFromClient<WebWorkerClientEndpoint, WebWorkerServerEndpoint> {
+    C_OBJECT(ConnectionFromClient);
+
+public:
+    virtual ~ConnectionFromClient() override;
+
+    virtual void die() override;
+
+    void request_file(Web::FileRequest);
+
+    PageHost& page_host() { return *m_page_host; }
+    PageHost const& page_host() const { return *m_page_host; }
+
+private:
+    explicit ConnectionFromClient(NonnullOwnPtr<Core::LocalSocket>);
+
+    Web::Page& page();
+    Web::Page const& page() const;
+
+    virtual void start_dedicated_worker(AK::URL const& url, String const&, String const&, String const&, IPC::File const&) override;
+    virtual void handle_file_return(i32 error, Optional<IPC::File> const& file, i32 request_id) override;
+
+    NonnullOwnPtr<PageHost> m_page_host;
+
+    // FIXME: Route console messages to the Browser UI using a ConsoleClient
+
+    HashMap<int, Web::FileRequest> m_requested_files {};
+    int last_id { 0 };
+
+    RefPtr<DedicatedWorkerHost> m_worker_host;
+};
+
+}

Userland/Services/WebWorker/DedicatedWorkerHost.cpp

@@ -0,0 +1,217 @@
+/*
+ * Copyright (c) 2023, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibJS/Runtime/ConsoleObject.h>
+#include <LibWeb/Fetch/Fetching/Fetching.h>
+#include <LibWeb/Fetch/Infrastructure/FetchAlgorithms.h>
+#include <LibWeb/HTML/Scripting/ClassicScript.h>
+#include <LibWeb/HTML/Scripting/Fetching.h>
+#include <LibWeb/HTML/Scripting/WorkerEnvironmentSettingsObject.h>
+#include <LibWeb/HTML/WorkerDebugConsoleClient.h>
+#include <LibWeb/HTML/WorkerGlobalScope.h>
+#include <LibWeb/Loader/ResourceLoader.h>
+#include <WebWorker/DedicatedWorkerHost.h>
+
+namespace WebWorker {
+
+DedicatedWorkerHost::DedicatedWorkerHost(Web::Page& page, AK::URL url, String type)
+    : m_worker_vm(JS::VM::create(make<Web::Bindings::WebEngineCustomData>()).release_value_but_fixme_should_propagate_errors())
+    , m_page(page)
+    , m_url(move(url))
+    , m_type(move(type))
+{
+    // FIXME: We need to attach all the HostDefined hooks from MainThreadVM onto this VM in order to load
+    //        module scripts in Workers.
+}
+
+DedicatedWorkerHost::~DedicatedWorkerHost() = default;
+
+// https://html.spec.whatwg.org/multipage/workers.html#run-a-worker
+// FIXME: Extract out into a helper for both shared and dedicated workers
+void DedicatedWorkerHost::run()
+{
+    bool const is_shared = false;
+
+    // 7. Let realm execution context be the result of creating a new JavaScript realm given agent and the following customizations:
+    auto realm_execution_context = Web::Bindings::create_a_new_javascript_realm(
+        *m_worker_vm,
+        [this](JS::Realm& realm) -> JS::Object* {
+            //      7a. For the global object, if is shared is true, create a new SharedWorkerGlobalScope object.
+            //      7b. Otherwise, create a new DedicatedWorkerGlobalScope object.
+            // FIXME: Proper support for both SharedWorkerGlobalScope and DedicatedWorkerGlobalScope
+            if (is_shared)
+                TODO();
+            return m_worker_vm->heap().allocate_without_realm<Web::HTML::WorkerGlobalScope>(realm, m_page);
+        },
+        nullptr);
+
+    // 8. Let worker global scope be the global object of realm execution context's Realm component.
+    // NOTE: This is the DedicatedWorkerGlobalScope or SharedWorkerGlobalScope object created in the previous step.
+    JS::NonnullGCPtr<Web::HTML::WorkerGlobalScope> worker_global_scope = verify_cast<Web::HTML::WorkerGlobalScope>(realm_execution_context->realm->global_object());
+
+    // 9. Set up a worker environment settings object with realm execution context,
+    //    outside settings, and unsafeWorkerCreationTime, and let inside settings be the result.
+    auto inner_settings = Web::HTML::WorkerEnvironmentSettingsObject::setup(move(realm_execution_context));
+    inner_settings->responsible_event_loop().set_vm(*m_worker_vm);
+
+    auto& console_object = *inner_settings->realm().intrinsics().console_object();
+    m_console = adopt_ref(*new Web::HTML::WorkerDebugConsoleClient(console_object.console()));
+    VERIFY(m_console);
+    console_object.console().set_client(*m_console);
+
+    // 10. Set worker global scope's name to the value of options's name member.
+    // FIXME: name property requires the SharedWorkerGlobalScope or DedicatedWorkerGlobalScope child class to be used
+
+    // 11. Append owner to worker global scope's owner set.
+    // FIXME: support for 'owner' set on WorkerGlobalScope
+
+    // 12. If is shared is true, then:
+    if (is_shared) {
+        // FIXME: Shared worker support
+        // 1. Set worker global scope's constructor origin to outside settings's origin.
+        // 2. Set worker global scope's constructor url to url.
+        // 3. Set worker global scope's type to the value of options's type member.
+        // 4. Set worker global scope's credentials to the value of options's credentials member.
+    }
+
+    // 13. Let destination be "sharedworker" if is shared is true, and "worker" otherwise.
+    auto destination = is_shared ? Web::Fetch::Infrastructure::Request::Destination::SharedWorker
+                                 : Web::Fetch::Infrastructure::Request::Destination::Worker;
+
+    // In both cases, let performFetch be the following perform the fetch hook given request, isTopLevel and processCustomFetchResponse:
+    auto perform_fetch_function = [inner_settings, worker_global_scope](JS::NonnullGCPtr<Web::Fetch::Infrastructure::Request> request, Web::HTML::IsTopLevel is_top_level, Web::Fetch::Infrastructure::FetchAlgorithms::ProcessResponseConsumeBodyFunction process_custom_fetch_response) -> Web::WebIDL::ExceptionOr<void> {
+        auto& realm = inner_settings->realm();
+        auto& vm = realm.vm();
+
+        Web::Fetch::Infrastructure::FetchAlgorithms::Input fetch_algorithms_input {};
+
+        // 1. If isTopLevel is false, fetch request with processResponseConsumeBody set to processCustomFetchResponse, and abort these steps.
+        if (is_top_level == Web::HTML::IsTopLevel::No) {
+            fetch_algorithms_input.process_response_consume_body = move(process_custom_fetch_response);
+            TRY(Web::Fetch::Fetching::fetch(realm, request, Web::Fetch::Infrastructure::FetchAlgorithms::create(vm, move(fetch_algorithms_input))));
+            return {};
+        }
+
+        // 2. Set request's reserved client to inside settings.
+        request->set_reserved_client(JS::GCPtr<Web::HTML::EnvironmentSettingsObject>(inner_settings));
+
+        // We need to store the process custom fetch response function on the heap here, because we're storing it in another heap function
+        auto process_custom_fetch_response_function = JS::create_heap_function(vm.heap(), move(process_custom_fetch_response));
+
+        // 3. Fetch request with processResponseConsumeBody set to the following steps given response response and null, failure, or a byte sequence bodyBytes:
+        fetch_algorithms_input.process_response_consume_body = [worker_global_scope, process_custom_fetch_response_function](auto response, auto body_bytes) {
+            // 1. Set worker global scope's url to response's url.
+            worker_global_scope->set_url(response->url().value_or({}));
+
+            // FIXME: 2. Initialize worker global scope's policy container given worker global scope, response, and inside settings.
+            // FIXME: 3. If the Run CSP initialization for a global object algorithm returns "Blocked" when executed upon worker
+            //    global scope, set response to a network error. [CSP]
+            // FIXME: 4. If worker global scope's embedder policy's value is compatible with cross-origin isolation and is shared is true,
+            //    then set agent's agent cluster's cross-origin isolation mode to "logical" or "concrete".
+            //    The one chosen is implementation-defined.
+            // FIXME: 5. If the result of checking a global object's embedder policy with worker global scope, outside settings,
+            //    and response is false, then set response to a network error.
+            // FIXME: 6. Set worker global scope's cross-origin isolated capability to true if agent's agent cluster's cross-origin
+            //    isolation mode is "concrete".
+
+            if (!is_shared) {
+                // 7.  If is shared is false and owner's cross-origin isolated capability is false, then set worker
+                //     global scope's cross-origin isolated capability to false.
+                // 8. If is shared is false and response's url's scheme is "data", then set worker global scope's
+                //     cross-origin isolated capability to false.
+            }
+
+            // 9. Run processCustomFetchResponse with response and bodyBytes.
+            process_custom_fetch_response_function->function()(response, body_bytes);
+        };
+        TRY(Web::Fetch::Fetching::fetch(realm, request, Web::Fetch::Infrastructure::FetchAlgorithms::create(vm, move(fetch_algorithms_input))));
+        return {};
+    };
+    auto perform_fetch = Web::HTML::create_perform_the_fetch_hook(inner_settings->heap(), move(perform_fetch_function));
+
+    auto on_complete_function = [inner_settings, worker_global_scope](JS::GCPtr<Web::HTML::Script> script) {
+        auto& realm = inner_settings->realm();
+        // 1. If script is null or if script's error to rethrow is non-null, then:
+        if (!script || !script->error_to_rethrow().is_null()) {
+            // FIXME: 1. Queue a global task on the DOM manipulation task source given worker's relevant global object to fire an event named error at worker.
+            // FIXME: Notify Worker parent through IPC to fire an error event at Worker
+            // FIXME 2. Run the environment discarding steps for inside settings.
+
+            // 3. Abort these steps.
+            dbgln("Didn't get my script :(");
+            return;
+        }
+
+        // FIXME: 2. Associate worker with worker global scope.
+        // What does this even mean?
+
+        // FIXME: 3. Let inside port be a new MessagePort object in inside settings's Realm.
+        // FIXME: 4. Associate inside port with worker global scope.
+        // FIXME: 5. Entangle outside port and inside port.
+
+        // 6. Create a new WorkerLocation object and associate it with worker global scope.
+        worker_global_scope->set_location(realm.heap().allocate<Web::HTML::WorkerLocation>(realm, *worker_global_scope));
+
+        // FIXME: 7. Closing orphan workers: Start monitoring the worker such that no sooner than it
+        //     stops being a protected worker, and no later than it stops being a permissible worker,
+        //     worker global scope's closing flag is set to true.
+
+        // FIXME: 8. Suspending workers: Start monitoring the worker, such that whenever worker global scope's
+        //     closing flag is false and the worker is a suspendable worker, the user agent suspends
+        //     execution of script in that worker until such time as either the closing flag switches to
+        //     true or the worker stops being a suspendable worker
+
+        // 9. Set inside settings's execution ready flag.
+        inner_settings->execution_ready = true;
+
+        // 10. If script is a classic script, then run the classic script script.
+        //     Otherwise, it is a module script; run the module script script.
+        if (is<Web::HTML::ClassicScript>(*script))
+            (void)static_cast<Web::HTML::ClassicScript&>(*script).run();
+        else
+            (void)verify_cast<Web::HTML::JavaScriptModuleScript>(*script).run();
+
+        // FIXME: 11. Enable outside port's port message queue.
+
+        // FIXME: 12. If is shared is false, enable the port message queue of the worker's implicit port.
+
+        // FIXME: 13. If is shared is true, then queue a global task on DOM manipulation task source given worker
+        //     global scope to fire an event named connect at worker global scope, using MessageEvent,
+        //     with the data attribute initialized to the empty string, the ports attribute initialized
+        //     to a new frozen array containing inside port, and the source attribute initialized to inside port.
+
+        // FIXME: 14. Enable the client message queue of the ServiceWorkerContainer object whose associated service
+        //     worker client is worker global scope's relevant settings object.
+
+        // 15. Event loop: Run the responsible event loop specified by inside settings until it is destroyed.
+        inner_settings->responsible_event_loop().schedule();
+
+        // FIXME: We need to react to the closing flag being set on the responsible event loop
+        //        And use that to shutdown the WorkerHost
+        // FIXME: 16. Clear the worker global scope's map of active timers.
+        // FIXME: 17. Disentangle all the ports in the list of the worker's ports.
+        // FIXME: 18. Empty worker global scope's owner set.
+    };
+    auto on_complete = Web::HTML::create_on_fetch_script_complete(inner_settings->vm().heap(), move(on_complete_function));
+
+    // 14. Obtain script by switching on the value of options's type member:
+    // classic:  Fetch a classic worker script given url, outside settings, destination, inside settings,
+    //               and with onComplete and performFetch as defined below.
+    // module:   Fetch a module worker script graph given url, outside settings, destination, the value of the credentials member of options, inside settings,
+    //               and with onComplete and performFetch as defined below.
+    if (m_type != "classic"sv) {
+        dbgln("Unsupported script type {} for LibWeb/Worker", m_type);
+        TODO();
+    }
+    // FIXME: We don't have outside settings anymore, they live in the owner. https://github.com/whatwg/html/issues/9920
+    if (auto err = Web::HTML::fetch_classic_worker_script(m_url, inner_settings, destination, inner_settings, perform_fetch, on_complete); err.is_error()) {
+        dbgln("Failed to run worker script");
+        // FIXME: Abort the worker properly
+        TODO();
+    }
+}
+
+}

Userland/Services/WebWorker/DedicatedWorkerHost.h

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2023, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/RefCounted.h>
+#include <AK/URL.h>
+#include <LibJS/Runtime/VM.h>
+#include <LibWeb/Bindings/MainThreadVM.h>
+#include <LibWeb/Forward.h>
+
+namespace WebWorker {
+
+class DedicatedWorkerHost : public RefCounted<DedicatedWorkerHost> {
+public:
+    explicit DedicatedWorkerHost(Web::Page&, AK::URL url, String type);
+    ~DedicatedWorkerHost();
+
+    void run();
+
+private:
+    NonnullRefPtr<JS::VM> m_worker_vm;
+    RefPtr<Web::HTML::WorkerDebugConsoleClient> m_console;
+    Web::Page& m_page;
+
+    AK::URL m_url;
+    String m_type;
+};
+
+}

Userland/Services/WebWorker/Forward.h

@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2023, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+namespace WebWorker {
+
+class ConnectionFromClient;
+class DedicatedWorkerHost;
+class PageHost;
+
+}

Userland/Services/WebWorker/PageHost.cpp

@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2023, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <WebWorker/ConnectionFromClient.h>
+#include <WebWorker/PageHost.h>
+
+namespace WebWorker {
+
+PageHost::~PageHost() = default;
+
+Web::Page& PageHost::page()
+{
+    return *m_page;
+}
+
+Web::Page const& PageHost::page() const
+{
+    return *m_page;
+}
+
+Gfx::Palette PageHost::palette() const
+{
+    return Gfx::Palette(*m_palette_impl);
+}
+
+void PageHost::setup_palette()
+{
+    // FIXME: We don't actually need a palette :thonk:
+    auto buffer_or_error = Core::AnonymousBuffer::create_with_size(sizeof(Gfx::SystemTheme));
+    VERIFY(!buffer_or_error.is_error());
+    auto buffer = buffer_or_error.release_value();
+    auto* theme = buffer.data<Gfx::SystemTheme>();
+    theme->color[to_underlying(Gfx::ColorRole::Window)] = Color::Magenta;
+    theme->color[to_underlying(Gfx::ColorRole::WindowText)] = Color::Cyan;
+    m_palette_impl = Gfx::PaletteImpl::create_with_anonymous_buffer(buffer);
+}
+
+bool PageHost::is_connection_open() const
+{
+    return m_client.is_open();
+}
+
+Web::DevicePixelRect PageHost::screen_rect() const
+{
+    return {};
+}
+
+double PageHost::device_pixels_per_css_pixel() const
+{
+    return 1.0;
+}
+
+Web::CSS::PreferredColorScheme PageHost::preferred_color_scheme() const
+{
+    return Web::CSS::PreferredColorScheme::Auto;
+}
+
+void PageHost::paint(Web::DevicePixelRect const&, Gfx::Bitmap&)
+{
+}
+
+void PageHost::request_file(Web::FileRequest request)
+{
+    m_client.request_file(move(request));
+}
+
+PageHost::PageHost(ConnectionFromClient& client)
+    : m_client(client)
+    , m_page(make<Web::Page>(*this))
+{
+    setup_palette();
+}
+
+}

Userland/Services/WebWorker/PageHost.h

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2023, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibGfx/Rect.h>
+#include <LibWeb/Page/Page.h>
+#include <LibWeb/PixelUnits.h>
+#include <WebWorker/Forward.h>
+
+namespace WebWorker {
+
+class PageHost final : public Web::PageClient {
+    AK_MAKE_NONCOPYABLE(PageHost);
+    AK_MAKE_NONMOVABLE(PageHost);
+
+public:
+    static NonnullOwnPtr<PageHost> create(ConnectionFromClient& client) { return adopt_own(*new PageHost(client)); }
+    virtual ~PageHost();
+
+    virtual Web::Page& page() override;
+    virtual Web::Page const& page() const override;
+    virtual bool is_connection_open() const override;
+    virtual Gfx::Palette palette() const override;
+    virtual Web::DevicePixelRect screen_rect() const override;
+    virtual double device_pixels_per_css_pixel() const override;
+    virtual Web::CSS::PreferredColorScheme preferred_color_scheme() const override;
+    virtual void paint(Web::DevicePixelRect const&, Gfx::Bitmap&) override;
+    virtual void request_file(Web::FileRequest) override;
+
+private:
+    explicit PageHost(ConnectionFromClient&);
+
+    void setup_palette();
+
+    ConnectionFromClient& m_client;
+    NonnullOwnPtr<Web::Page> m_page;
+    RefPtr<Gfx::PaletteImpl> m_palette_impl;
+};
+
+}

Userland/Services/WebWorker/main.cpp

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2023, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibCore/EventLoop.h>
+#include <LibCore/LocalServer.h>
+#include <LibCore/StandardPaths.h>
+#include <LibCore/System.h>
+#include <LibFileSystem/FileSystem.h>
+#include <LibIPC/SingleServer.h>
+#include <LibMain/Main.h>
+#include <LibWeb/Bindings/MainThreadVM.h>
+#include <LibWeb/Loader/ResourceLoader.h>
+#include <LibWeb/Platform/EventLoopPlugin.h>
+#include <LibWeb/Platform/EventLoopPluginSerenity.h>
+#include <LibWeb/Platform/FontPluginSerenity.h>
+#include <LibWeb/WebSockets/WebSocket.h>
+#include <LibWebView/RequestServerAdapter.h>
+#include <LibWebView/WebSocketClientAdapter.h>
+#include <WebWorker/ConnectionFromClient.h>
+
+ErrorOr<int> serenity_main(Main::Arguments)
+{
+    TRY(Core::System::pledge("stdio recvfd sendfd accept unix rpath thread proc"));
+
+    Core::EventLoop event_loop;
+    TRY(Core::System::unveil("/res", "r"));
+    TRY(Core::System::unveil("/etc/timezone", "r"));
+    TRY(Core::System::unveil("/tmp/session/%sid/portal/request", "rw"));
+    TRY(Core::System::unveil("/tmp/session/%sid/portal/image", "rw"));
+    TRY(Core::System::unveil("/tmp/session/%sid/portal/websocket", "rw"));
+    TRY(Core::System::unveil(nullptr, nullptr));
+
+    Web::Platform::EventLoopPlugin::install(*new Web::Platform::EventLoopPluginSerenity);
+    Web::Platform::FontPlugin::install(*new Web::Platform::FontPluginSerenity);
+
+    Web::WebSockets::WebSocketClientManager::initialize(TRY(WebView::WebSocketClientManagerAdapter::try_create()));
+    Web::ResourceLoader::initialize(TRY(WebView::RequestServerAdapter::try_create()));
+    TRY(Web::Bindings::initialize_main_thread_vm());
+
+    auto client = TRY(IPC::take_over_accepted_client_from_system_server<WebWorker::ConnectionFromClient>());
+
+    return event_loop.exec();
+}