LibWeb/HTML: Hook up a WorkerAgent for web workers

Author: https://github.com/shannonbooth
Commit: 041ff0c7ff
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/4453

Libraries/LibWeb/Bindings/MainThreadVM.cpp

@@ -40,6 +40,7 @@
 #include <LibWeb/HTML/Scripting/SimilarOriginWindowAgent.h>
 #include <LibWeb/HTML/Scripting/SyntheticRealmSettings.h>
 #include <LibWeb/HTML/Scripting/TemporaryExecutionContext.h>
+#include <LibWeb/HTML/Scripting/WorkerAgent.h>
 #include <LibWeb/HTML/ShadowRealmGlobalScope.h>
 #include <LibWeb/HTML/Window.h>
 #include <LibWeb/HTML/WindowProxy.h>
@@ -72,15 +73,28 @@ HTML::Script* active_script()
         });
 }
 
-void initialize_main_thread_vm(HTML::EventLoop::Type type)
+static NonnullOwnPtr<JS::Agent> create_agent(GC::Heap& heap, AgentType type)
+{
+    switch (type) {
+    case AgentType::SimilarOriginWindow:
+        return HTML::SimilarOriginWindowAgent::create(heap);
+    case AgentType::DedicatedWorker:
+    case AgentType::SharedWorker:
+        return HTML::WorkerAgent::create(heap, JS::Agent::CanBlock::Yes);
+    case AgentType::ServiceWorker:
+        return HTML::WorkerAgent::create(heap, JS::Agent::CanBlock::No);
+    default:
+        break;
+    }
+    VERIFY_NOT_REACHED();
+}
+
+void initialize_main_thread_vm(AgentType type)
 {
     VERIFY(!s_main_thread_vm);
 
     s_main_thread_vm = JS::VM::create();
-    s_main_thread_vm->set_agent(HTML::SimilarOriginWindowAgent::create());
+    s_main_thread_vm->set_agent(create_agent(s_main_thread_vm->heap(), type));
-
-    auto& agent = as<HTML::Agent>(*s_main_thread_vm->agent());
-    agent.event_loop = s_main_thread_vm->heap().allocate<HTML::EventLoop>(type);
 
     s_main_thread_vm->on_unimplemented_property_access = [](auto const& object, auto const& property_key) {
         dbgln("FIXME: Unimplemented IDL interface: '{}.{}'", object.class_name(), property_key.to_string());

Libraries/LibWeb/Bindings/MainThreadVM.h

@@ -32,7 +32,15 @@ struct WebEngineCustomJobCallbackData final : public JS::JobCallback::CustomData
 
 HTML::Script* active_script();
 
-void initialize_main_thread_vm(HTML::EventLoop::Type);
+enum class AgentType : u8 {
+    SimilarOriginWindow,
+    DedicatedWorker,
+    SharedWorker,
+    ServiceWorker,
+    Worklet,
+};
+
+void initialize_main_thread_vm(AgentType);
 JS::VM& main_thread_vm();
 
 void queue_mutation_observer_microtask(DOM::Document const&);

Libraries/LibWeb/CMakeLists.txt

@@ -508,6 +508,7 @@ set(SOURCES
     HTML/Scripting/SyntheticRealmSettings.cpp
     HTML/Scripting/TemporaryExecutionContext.cpp
     HTML/Scripting/WindowEnvironmentSettingsObject.cpp
+    HTML/Scripting/WorkerAgent.cpp
     HTML/Scripting/WorkerEnvironmentSettingsObject.cpp
     HTML/Scripting/SerializedEnvironmentSettingsObject.cpp
     HTML/SelectedFile.cpp

Libraries/LibWeb/HTML/Scripting/SimilarOriginWindowAgent.cpp

@@ -11,10 +11,12 @@
 
 namespace Web::HTML {
 
-NonnullOwnPtr<SimilarOriginWindowAgent> SimilarOriginWindowAgent::create()
+NonnullOwnPtr<SimilarOriginWindowAgent> SimilarOriginWindowAgent::create(GC::Heap& heap)
 {
     // See 'creating an agent' step in: https://html.spec.whatwg.org/multipage/webappapis.html#obtain-similar-origin-window-agent
-    return adopt_own(*new SimilarOriginWindowAgent(CanBlock::No));
+    auto agent = adopt_own(*new SimilarOriginWindowAgent(CanBlock::No));
+    agent->event_loop = heap.allocate<HTML::EventLoop>(HTML::EventLoop::Type::Window);
+    return agent;
 }
 
 // https://html.spec.whatwg.org/multipage/webappapis.html#relevant-agent

Libraries/LibWeb/HTML/Scripting/SimilarOriginWindowAgent.h

@@ -20,7 +20,7 @@ namespace Web::HTML {
 
 // https://html.spec.whatwg.org/multipage/webappapis.html#similar-origin-window-agent
 struct SimilarOriginWindowAgent : public Agent {
-    static NonnullOwnPtr<SimilarOriginWindowAgent> create();
+    static NonnullOwnPtr<SimilarOriginWindowAgent> create(GC::Heap&);
 
     // https://dom.spec.whatwg.org/#mutation-observer-compound-microtask-queued-flag
     // Each similar-origin window agent has a mutation observer microtask queued (a boolean), which is initially false. [HTML]

Libraries/LibWeb/HTML/Scripting/WorkerAgent.cpp

@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2025, Shannon Booth <shannon@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/HTML/EventLoop/EventLoop.h>
+#include <LibWeb/HTML/Scripting/WorkerAgent.h>
+
+namespace Web::HTML {
+
+NonnullOwnPtr<WorkerAgent> WorkerAgent::create(GC::Heap& heap, CanBlock can_block)
+{
+    auto agent = adopt_own(*new WorkerAgent(can_block));
+    agent->event_loop = heap.allocate<HTML::EventLoop>(HTML::EventLoop::Type::Worker);
+    return agent;
+}
+
+}

Libraries/LibWeb/HTML/Scripting/WorkerAgent.h

@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2025, Shannon Booth <shannon@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibWeb/HTML/Scripting/Agent.h>
+
+namespace Web::HTML {
+
+// https://html.spec.whatwg.org/multipage/webappapis.html#dedicated-worker-agent
+// https://html.spec.whatwg.org/multipage/webappapis.html#shared-worker-agent
+struct WorkerAgent : public Agent {
+    static NonnullOwnPtr<WorkerAgent> create(GC::Heap&, CanBlock);
+
+private:
+    using Agent::Agent;
+};
+
+}

Meta/Lagom/Fuzzers/FuzzCSSParser.cpp

@@ -17,7 +17,7 @@ struct Globals {
 Globals::Globals()
 {
     Web::Platform::EventLoopPlugin::install(*new Web::Platform::EventLoopPluginSerenity);
-    Web::Bindings::initialize_main_thread_vm(Web::HTML::EventLoop::Type::Window);
+    Web::Bindings::initialize_main_thread_vm(Web::Bindings::AgentType::SimilarOriginWindow);
 }
 
 }

Services/WebContent/main.cpp

@@ -191,7 +191,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
 
     Web::Platform::FontPlugin::install(*new WebView::FontPlugin(is_layout_test_mode, &font_provider));
 
-    Web::Bindings::initialize_main_thread_vm(Web::HTML::EventLoop::Type::Window);
+    Web::Bindings::initialize_main_thread_vm(Web::Bindings::AgentType::SimilarOriginWindow);
 
     if (collect_garbage_on_every_allocation)
         Web::Bindings::main_thread_vm().heap().set_should_collect_on_every_allocation(true);

Services/WebWorker/main.cpp

@@ -68,7 +68,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
 
     Web::Platform::FontPlugin::install(*new WebView::FontPlugin(false));
 
-    Web::Bindings::initialize_main_thread_vm(Web::HTML::EventLoop::Type::Worker);
+    Web::Bindings::initialize_main_thread_vm(Web::Bindings::AgentType::DedicatedWorker);
 
     TRY(initialize_resource_loader(Web::Bindings::main_thread_vm().heap(), request_server_socket));