From 9567e211e7c0ae27a65c1f23c4fd9071e8c35e29 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Wed, 7 Sep 2022 20:30:31 +0200
Subject: LibWeb+WebContent: Add abstraction layer for event loop and timers

Instead of using Core::EventLoop and Core::Timer directly, LibWeb now
goes through a Web::Platform abstraction layer instead.

This will allow us to plug in Qt's event loop (and QTimer) over in
Ladybird, to avoid having to deal with multiple event loops.
---
 Userland/Libraries/LibWeb/CMakeLists.txt           |  2 ++
 Userland/Libraries/LibWeb/DOM/Document.cpp         |  6 ++--
 Userland/Libraries/LibWeb/DOM/Document.h           |  4 +--
 Userland/Libraries/LibWeb/Forward.h                |  4 +++
 .../LibWeb/HTML/AnimationFrameCallbackDriver.h     |  6 ++--
 Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp |  2 +-
 Userland/Libraries/LibWeb/HTML/BrowsingContext.h   |  4 +--
 .../Libraries/LibWeb/HTML/EventLoop/EventLoop.cpp  | 14 +++-----
 .../Libraries/LibWeb/HTML/EventLoop/EventLoop.h    |  2 +-
 .../Libraries/LibWeb/HTML/HTMLBlinkElement.cpp     |  4 +--
 Userland/Libraries/LibWeb/HTML/HTMLBlinkElement.h  |  2 +-
 Userland/Libraries/LibWeb/HTML/Timer.cpp           |  4 +--
 Userland/Libraries/LibWeb/HTML/Timer.h             |  2 +-
 Userland/Libraries/LibWeb/HTML/Window.h            |  2 ++
 Userland/Libraries/LibWeb/Loader/ImageLoader.cpp   |  4 +--
 Userland/Libraries/LibWeb/Loader/ImageLoader.h     |  4 +--
 Userland/Libraries/LibWeb/Loader/Resource.cpp      |  4 +--
 .../Libraries/LibWeb/Loader/ResourceLoader.cpp     | 12 +++----
 .../Libraries/LibWeb/Platform/EventLoopPlugin.cpp  | 28 +++++++++++++++
 .../Libraries/LibWeb/Platform/EventLoopPlugin.h    | 26 ++++++++++++++
 Userland/Libraries/LibWeb/Platform/Timer.cpp       | 38 ++++++++++++++++++++
 Userland/Libraries/LibWeb/Platform/Timer.h         | 40 ++++++++++++++++++++++
 22 files changed, 174 insertions(+), 40 deletions(-)
 create mode 100644 Userland/Libraries/LibWeb/Platform/EventLoopPlugin.cpp
 create mode 100644 Userland/Libraries/LibWeb/Platform/EventLoopPlugin.h
 create mode 100644 Userland/Libraries/LibWeb/Platform/Timer.cpp
 create mode 100644 Userland/Libraries/LibWeb/Platform/Timer.h

(limited to 'Userland/Libraries/LibWeb')

diff --git a/Userland/Libraries/LibWeb/CMakeLists.txt b/Userland/Libraries/LibWeb/CMakeLists.txt
index 0e7dfaa0f0..079311fe98 100644
--- a/Userland/Libraries/LibWeb/CMakeLists.txt
+++ b/Userland/Libraries/LibWeb/CMakeLists.txt
@@ -351,6 +351,8 @@ set(SOURCES
     Painting/ShadowPainting.cpp
     Painting/StackingContext.cpp
     Painting/TextPaintable.cpp
+    Platform/EventLoopPlugin.cpp
+    Platform/Timer.cpp
     RequestIdleCallback/IdleDeadline.cpp
     ResizeObserver/ResizeObserver.cpp
     SVG/AttributeNames.cpp
diff --git a/Userland/Libraries/LibWeb/DOM/Document.cpp b/Userland/Libraries/LibWeb/DOM/Document.cpp
index 43a88e19ed..5de2904b39 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Document.cpp
@@ -10,7 +10,6 @@
 #include <AK/CharacterTypes.h>
 #include <AK/StringBuilder.h>
 #include <AK/Utf8View.h>
-#include <LibCore/Timer.h>
 #include <LibJS/Interpreter.h>
 #include <LibJS/Parser.h>
 #include <LibJS/Runtime/FunctionObject.h>
@@ -67,6 +66,7 @@
 #include <LibWeb/Layout/TreeBuilder.h>
 #include <LibWeb/Namespace.h>
 #include <LibWeb/Page/Page.h>
+#include <LibWeb/Platform/Timer.h>
 #include <LibWeb/SVG/TagNames.h>
 #include <LibWeb/UIEvents/EventNames.h>
 #include <LibWeb/UIEvents/FocusEvent.h>
@@ -286,11 +286,11 @@ Document::Document(HTML::Window& window, const AK::URL& url)
 
     HTML::main_thread_event_loop().register_document({}, *this);
 
-    m_style_update_timer = Core::Timer::create_single_shot(0, [this] {
+    m_style_update_timer = Platform::Timer::create_single_shot(0, [this] {
         update_style();
     });
 
-    m_layout_update_timer = Core::Timer::create_single_shot(0, [this] {
+    m_layout_update_timer = Platform::Timer::create_single_shot(0, [this] {
         force_layout();
     });
 }
diff --git a/Userland/Libraries/LibWeb/DOM/Document.h b/Userland/Libraries/LibWeb/DOM/Document.h
index 894e9011d9..6eda355046 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.h
+++ b/Userland/Libraries/LibWeb/DOM/Document.h
@@ -386,8 +386,8 @@ private:
     Optional<Color> m_active_link_color;
     Optional<Color> m_visited_link_color;
 
-    RefPtr<Core::Timer> m_style_update_timer;
-    RefPtr<Core::Timer> m_layout_update_timer;
+    RefPtr<Platform::Timer> m_style_update_timer;
+    RefPtr<Platform::Timer> m_layout_update_timer;
 
     RefPtr<HTML::HTMLParser> m_parser;
     bool m_active_parser_was_aborted { false };
diff --git a/Userland/Libraries/LibWeb/Forward.h b/Userland/Libraries/LibWeb/Forward.h
index 1c7718b722..8b4ec2d74c 100644
--- a/Userland/Libraries/LibWeb/Forward.h
+++ b/Userland/Libraries/LibWeb/Forward.h
@@ -351,6 +351,10 @@ struct BorderRadiiData;
 struct LinearGradientData;
 }
 
+namespace Web::Platform {
+class Timer;
+}
+
 namespace Web::RequestIdleCallback {
 class IdleDeadline;
 }
diff --git a/Userland/Libraries/LibWeb/HTML/AnimationFrameCallbackDriver.h b/Userland/Libraries/LibWeb/HTML/AnimationFrameCallbackDriver.h
index 397ab1f3e6..510b2c449c 100644
--- a/Userland/Libraries/LibWeb/HTML/AnimationFrameCallbackDriver.h
+++ b/Userland/Libraries/LibWeb/HTML/AnimationFrameCallbackDriver.h
@@ -8,8 +8,8 @@
 
 #include <AK/Function.h>
 #include <AK/IDAllocator.h>
-#include <LibCore/Timer.h>
 #include <LibWeb/HTML/EventLoop/EventLoop.h>
+#include <LibWeb/Platform/Timer.h>
 
 namespace Web::HTML {
 
@@ -18,7 +18,7 @@ struct AnimationFrameCallbackDriver {
 
     AnimationFrameCallbackDriver()
     {
-        m_timer = Core::Timer::create_single_shot(16, [] {
+        m_timer = Platform::Timer::create_single_shot(16, [] {
             HTML::main_thread_event_loop().schedule();
         });
     }
@@ -57,7 +57,7 @@ struct AnimationFrameCallbackDriver {
 private:
     HashMap<i32, Callback> m_callbacks;
     IDAllocator m_id_allocator;
-    RefPtr<Core::Timer> m_timer;
+    RefPtr<Platform::Timer> m_timer;
 };
 
 }
diff --git a/Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp b/Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp
index d92e1532e3..28fdb48a01 100644
--- a/Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp
+++ b/Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp
@@ -229,7 +229,7 @@ BrowsingContext::BrowsingContext(Page& page, HTML::BrowsingContextContainer* con
     , m_event_handler({}, *this)
     , m_container(container)
 {
-    m_cursor_blink_timer = Core::Timer::construct(500, [this] {
+    m_cursor_blink_timer = Platform::Timer::create_repeating(500, [this] {
         if (!is_focused_context())
             return;
         if (m_cursor_position.node() && m_cursor_position.node()->layout_node()) {
diff --git a/Userland/Libraries/LibWeb/HTML/BrowsingContext.h b/Userland/Libraries/LibWeb/HTML/BrowsingContext.h
index ddcd870ea1..1185caf3a9 100644
--- a/Userland/Libraries/LibWeb/HTML/BrowsingContext.h
+++ b/Userland/Libraries/LibWeb/HTML/BrowsingContext.h
@@ -10,7 +10,6 @@
 #include <AK/Noncopyable.h>
 #include <AK/RefPtr.h>
 #include <AK/WeakPtr.h>
-#include <LibCore/Timer.h>
 #include <LibGfx/Bitmap.h>
 #include <LibGfx/Rect.h>
 #include <LibGfx/Size.h>
@@ -20,6 +19,7 @@
 #include <LibWeb/HTML/SessionHistoryEntry.h>
 #include <LibWeb/Loader/FrameLoader.h>
 #include <LibWeb/Page/EventHandler.h>
+#include <LibWeb/Platform/Timer.h>
 #include <LibWeb/TreeNode.h>
 
 namespace Web::HTML {
@@ -148,7 +148,7 @@ private:
     Gfx::IntPoint m_viewport_scroll_offset;
 
     DOM::Position m_cursor_position;
-    RefPtr<Core::Timer> m_cursor_blink_timer;
+    RefPtr<Platform::Timer> m_cursor_blink_timer;
     bool m_cursor_blink_state { false };
 
     HashTable<ViewportClient*> m_viewport_clients;
diff --git a/Userland/Libraries/LibWeb/HTML/EventLoop/EventLoop.cpp b/Userland/Libraries/LibWeb/HTML/EventLoop/EventLoop.cpp
index 34978bc6c3..5602e5545d 100644
--- a/Userland/Libraries/LibWeb/HTML/EventLoop/EventLoop.cpp
+++ b/Userland/Libraries/LibWeb/HTML/EventLoop/EventLoop.cpp
@@ -5,8 +5,6 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
-#include <LibCore/EventLoop.h>
-#include <LibCore/Timer.h>
 #include <LibJS/Runtime/VM.h>
 #include <LibWeb/Bindings/MainThreadVM.h>
 #include <LibWeb/DOM/Document.h>
@@ -15,6 +13,8 @@
 #include <LibWeb/HTML/Scripting/Environments.h>
 #include <LibWeb/HTML/Window.h>
 #include <LibWeb/HighResolutionTime/Performance.h>
+#include <LibWeb/Platform/EventLoopPlugin.h>
+#include <LibWeb/Platform/Timer.h>
 
 namespace Web::HTML {
 
@@ -29,7 +29,7 @@ EventLoop::~EventLoop() = default;
 void EventLoop::schedule()
 {
     if (!m_system_event_loop_timer) {
-        m_system_event_loop_timer = Core::Timer::create_single_shot(0, [this] {
+        m_system_event_loop_timer = Platform::Timer::create_single_shot(0, [this] {
             process();
         });
     }
@@ -74,13 +74,7 @@ void EventLoop::spin_until(Function<bool()> goal_condition)
     //       NOTE: This is achieved by returning from the function.
 
     //    1. Wait until the condition goal is met.
-    Core::EventLoop loop;
-    loop.spin_until([&]() -> bool {
-        if (goal_condition())
-            return true;
-
-        return goal_condition();
-    });
+    Platform::EventLoopPlugin::the().spin_until(move(goal_condition));
 
     // 7. Stop task, allowing whatever algorithm that invoked it to resume.
     // NOTE: This is achieved by returning from the function.
diff --git a/Userland/Libraries/LibWeb/HTML/EventLoop/EventLoop.h b/Userland/Libraries/LibWeb/HTML/EventLoop/EventLoop.h
index 61685ae6d6..024666b992 100644
--- a/Userland/Libraries/LibWeb/HTML/EventLoop/EventLoop.h
+++ b/Userland/Libraries/LibWeb/HTML/EventLoop/EventLoop.h
@@ -84,7 +84,7 @@ private:
 
     JS::VM* m_vm { nullptr };
 
-    RefPtr<Core::Timer> m_system_event_loop_timer;
+    RefPtr<Platform::Timer> m_system_event_loop_timer;
 
     // https://html.spec.whatwg.org/#performing-a-microtask-checkpoint
     bool m_performing_a_microtask_checkpoint { false };
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLBlinkElement.cpp b/Userland/Libraries/LibWeb/HTML/HTMLBlinkElement.cpp
index c28d574fad..6bfa7806fd 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLBlinkElement.cpp
+++ b/Userland/Libraries/LibWeb/HTML/HTMLBlinkElement.cpp
@@ -4,14 +4,14 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
-#include <LibCore/Timer.h>
 #include <LibWeb/HTML/HTMLBlinkElement.h>
+#include <LibWeb/Platform/Timer.h>
 
 namespace Web::HTML {
 
 HTMLBlinkElement::HTMLBlinkElement(DOM::Document& document, DOM::QualifiedName qualified_name)
     : HTMLElement(document, move(qualified_name))
-    , m_timer(Core::Timer::construct())
+    , m_timer(Platform::Timer::create())
 {
     m_timer->set_interval(500);
     m_timer->on_timeout = [this] { blink(); };
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLBlinkElement.h b/Userland/Libraries/LibWeb/HTML/HTMLBlinkElement.h
index 39bb55d611..43097c9cad 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLBlinkElement.h
+++ b/Userland/Libraries/LibWeb/HTML/HTMLBlinkElement.h
@@ -22,7 +22,7 @@ private:
 
     void blink();
 
-    NonnullRefPtr<Core::Timer> m_timer;
+    NonnullRefPtr<Platform::Timer> m_timer;
 };
 
 }
diff --git a/Userland/Libraries/LibWeb/HTML/Timer.cpp b/Userland/Libraries/LibWeb/HTML/Timer.cpp
index b2e75fbdbc..228b514481 100644
--- a/Userland/Libraries/LibWeb/HTML/Timer.cpp
+++ b/Userland/Libraries/LibWeb/HTML/Timer.cpp
@@ -4,9 +4,9 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
-#include <LibCore/Timer.h>
 #include <LibWeb/HTML/Timer.h>
 #include <LibWeb/HTML/Window.h>
+#include <LibWeb/Platform/Timer.h>
 
 namespace Web::HTML {
 
@@ -20,7 +20,7 @@ Timer::Timer(Window& window, i32 milliseconds, Function<void()> callback, i32 id
     , m_callback(move(callback))
     , m_id(id)
 {
-    m_timer = Core::Timer::create_single_shot(milliseconds, [this] {
+    m_timer = Platform::Timer::create_single_shot(milliseconds, [this] {
         m_callback();
     });
 }
diff --git a/Userland/Libraries/LibWeb/HTML/Timer.h b/Userland/Libraries/LibWeb/HTML/Timer.h
index aa2edfb3f5..2f1aab762e 100644
--- a/Userland/Libraries/LibWeb/HTML/Timer.h
+++ b/Userland/Libraries/LibWeb/HTML/Timer.h
@@ -30,7 +30,7 @@ private:
 
     virtual void visit_edges(Cell::Visitor&) override;
 
-    RefPtr<Core::Timer> m_timer;
+    RefPtr<Platform::Timer> m_timer;
     JS::NonnullGCPtr<Window> m_window;
     Function<void()> m_callback;
     i32 m_id { 0 };
diff --git a/Userland/Libraries/LibWeb/HTML/Window.h b/Userland/Libraries/LibWeb/HTML/Window.h
index e1ce9e953b..587cc8616f 100644
--- a/Userland/Libraries/LibWeb/HTML/Window.h
+++ b/Userland/Libraries/LibWeb/HTML/Window.h
@@ -8,7 +8,9 @@
 
 #include <AK/Badge.h>
 #include <AK/IDAllocator.h>
+#include <AK/NonnullRefPtrVector.h>
 #include <AK/RefPtr.h>
+#include <AK/TypeCasts.h>
 #include <AK/URL.h>
 #include <LibJS/Heap/Heap.h>
 #include <LibWeb/Bindings/CrossOriginAbstractOperations.h>
diff --git a/Userland/Libraries/LibWeb/Loader/ImageLoader.cpp b/Userland/Libraries/LibWeb/Loader/ImageLoader.cpp
index dc4e3f3544..ecbe258b40 100644
--- a/Userland/Libraries/LibWeb/Loader/ImageLoader.cpp
+++ b/Userland/Libraries/LibWeb/Loader/ImageLoader.cpp
@@ -5,18 +5,18 @@
  */
 
 #include <AK/Debug.h>
-#include <LibCore/Timer.h>
 #include <LibGfx/Bitmap.h>
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/DOM/Element.h>
 #include <LibWeb/Loader/ImageLoader.h>
 #include <LibWeb/Loader/ResourceLoader.h>
+#include <LibWeb/Platform/Timer.h>
 
 namespace Web {
 
 ImageLoader::ImageLoader(DOM::Element& owner_element)
     : m_owner_element(owner_element)
-    , m_timer(Core::Timer::construct())
+    , m_timer(Platform::Timer::create())
 {
 }
 
diff --git a/Userland/Libraries/LibWeb/Loader/ImageLoader.h b/Userland/Libraries/LibWeb/Loader/ImageLoader.h
index 23c5344b1f..03a00cd682 100644
--- a/Userland/Libraries/LibWeb/Loader/ImageLoader.h
+++ b/Userland/Libraries/LibWeb/Loader/ImageLoader.h
@@ -7,8 +7,8 @@
 #pragma once
 
 #include <AK/Function.h>
-#include <LibCore/Timer.h>
 #include <LibWeb/Loader/ImageResource.h>
+#include <LibWeb/Platform/Timer.h>
 
 namespace Web {
 
@@ -60,7 +60,7 @@ private:
     size_t m_current_frame_index { 0 };
     size_t m_loops_completed { 0 };
     LoadingState m_loading_state { LoadingState::Loading };
-    NonnullRefPtr<Core::Timer> m_timer;
+    NonnullRefPtr<Platform::Timer> m_timer;
     size_t m_redirects_count { 0 };
 };
 
diff --git a/Userland/Libraries/LibWeb/Loader/Resource.cpp b/Userland/Libraries/LibWeb/Loader/Resource.cpp
index e5ac447050..79c54edcfa 100644
--- a/Userland/Libraries/LibWeb/Loader/Resource.cpp
+++ b/Userland/Libraries/LibWeb/Loader/Resource.cpp
@@ -6,12 +6,12 @@
 
 #include <AK/Debug.h>
 #include <AK/Function.h>
-#include <LibCore/EventLoop.h>
 #include <LibCore/MimeData.h>
 #include <LibTextCodec/Decoder.h>
 #include <LibWeb/HTML/HTMLImageElement.h>
 #include <LibWeb/Loader/Resource.h>
 #include <LibWeb/Loader/ResourceLoader.h>
+#include <LibWeb/Platform/EventLoopPlugin.h>
 
 namespace Web {
 
@@ -168,7 +168,7 @@ void ResourceClient::set_resource(Resource* resource)
         // This ensures that these callbacks always happen in a consistent way, instead of being invoked
         // synchronously in some cases, and asynchronously in others.
         if (resource->is_loaded() || resource->is_failed()) {
-            Core::deferred_invoke([this, strong_resource = NonnullRefPtr { *m_resource }] {
+            Platform::EventLoopPlugin::the().deferred_invoke([this, strong_resource = NonnullRefPtr { *m_resource }] {
                 if (m_resource != strong_resource.ptr())
                     return;
 
diff --git a/Userland/Libraries/LibWeb/Loader/ResourceLoader.cpp b/Userland/Libraries/LibWeb/Loader/ResourceLoader.cpp
index 98101888d8..d562506ac6 100644
--- a/Userland/Libraries/LibWeb/Loader/ResourceLoader.cpp
+++ b/Userland/Libraries/LibWeb/Loader/ResourceLoader.cpp
@@ -9,14 +9,14 @@
 #include <AK/Debug.h>
 #include <AK/JsonObject.h>
 #include <LibCore/ElapsedTimer.h>
-#include <LibCore/EventLoop.h>
 #include <LibCore/File.h>
-#include <LibCore/Timer.h>
 #include <LibWeb/Loader/ContentFilter.h>
 #include <LibWeb/Loader/LoadRequest.h>
 #include <LibWeb/Loader/ProxyMappings.h>
 #include <LibWeb/Loader/Resource.h>
 #include <LibWeb/Loader/ResourceLoader.h>
+#include <LibWeb/Platform/EventLoopPlugin.h>
+#include <LibWeb/Platform/Timer.h>
 
 #ifdef __serenity__
 #    include <serenity.h>
@@ -179,7 +179,7 @@ void ResourceLoader::load(LoadRequest& request, Function<void(ReadonlyBytes, Has
         HashMap<String, String, CaseInsensitiveStringTraits> response_headers;
         response_headers.set("Content-Type", "text/html; charset=UTF-8");
 
-        deferred_invoke([success_callback = move(success_callback), response_headers = move(response_headers)] {
+        Platform::EventLoopPlugin::the().deferred_invoke([success_callback = move(success_callback), response_headers = move(response_headers)] {
             success_callback(String::empty().to_byte_buffer(), response_headers, {});
         });
         return;
@@ -206,7 +206,7 @@ void ResourceLoader::load(LoadRequest& request, Function<void(ReadonlyBytes, Has
         }
 
         log_success(request);
-        deferred_invoke([data = move(data), success_callback = move(success_callback)] {
+        Platform::EventLoopPlugin::the().deferred_invoke([data = move(data), success_callback = move(success_callback)] {
             success_callback(data, {}, {});
         });
         return;
@@ -284,7 +284,7 @@ void ResourceLoader::load(LoadRequest& request, Function<void(ReadonlyBytes, Has
         }
 
         if (timeout.has_value() && timeout.value() > 0) {
-            auto timer = Core::Timer::create_single_shot(timeout.value(), nullptr);
+            auto timer = Platform::Timer::create_single_shot(timeout.value(), nullptr);
             timer->on_timeout = [timer, protocol_request, timeout_callback = move(timeout_callback)]() mutable {
                 protocol_request->stop();
                 if (timeout_callback)
@@ -312,7 +312,7 @@ void ResourceLoader::load(LoadRequest& request, Function<void(ReadonlyBytes, Has
             }
             log_success(request);
             success_callback(payload, response_headers, status_code);
-            deferred_invoke([this, &protocol_request] {
+            Platform::EventLoopPlugin::the().deferred_invoke([this, &protocol_request] {
                 m_active_requests.remove(protocol_request);
             });
         };
diff --git a/Userland/Libraries/LibWeb/Platform/EventLoopPlugin.cpp b/Userland/Libraries/LibWeb/Platform/EventLoopPlugin.cpp
new file mode 100644
index 0000000000..dcd9b01b26
--- /dev/null
+++ b/Userland/Libraries/LibWeb/Platform/EventLoopPlugin.cpp
@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Function.h>
+#include <LibWeb/Platform/EventLoopPlugin.h>
+
+namespace Web::Platform {
+
+EventLoopPlugin* s_the;
+
+EventLoopPlugin& EventLoopPlugin::the()
+{
+    VERIFY(s_the);
+    return *s_the;
+}
+
+void EventLoopPlugin::install(EventLoopPlugin& plugin)
+{
+    VERIFY(!s_the);
+    s_the = &plugin;
+}
+
+EventLoopPlugin::~EventLoopPlugin() = default;
+
+}
diff --git a/Userland/Libraries/LibWeb/Platform/EventLoopPlugin.h b/Userland/Libraries/LibWeb/Platform/EventLoopPlugin.h
new file mode 100644
index 0000000000..de08e14fb9
--- /dev/null
+++ b/Userland/Libraries/LibWeb/Platform/EventLoopPlugin.h
@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Forward.h>
+#include <LibWeb/Forward.h>
+
+namespace Web::Platform {
+
+class EventLoopPlugin {
+public:
+    static EventLoopPlugin& the();
+    static void install(EventLoopPlugin&);
+
+    virtual ~EventLoopPlugin();
+
+    virtual void spin_until(Function<bool()> goal_condition) = 0;
+    virtual void deferred_invoke(Function<void()>) = 0;
+    virtual NonnullRefPtr<Timer> create_timer() = 0;
+};
+
+}
diff --git a/Userland/Libraries/LibWeb/Platform/Timer.cpp b/Userland/Libraries/LibWeb/Platform/Timer.cpp
new file mode 100644
index 0000000000..d3de49a958
--- /dev/null
+++ b/Userland/Libraries/LibWeb/Platform/Timer.cpp
@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/NonnullRefPtr.h>
+#include <LibWeb/Platform/EventLoopPlugin.h>
+#include <LibWeb/Platform/Timer.h>
+
+namespace Web::Platform {
+
+Timer::~Timer() = default;
+
+NonnullRefPtr<Timer> Timer::create()
+{
+    return EventLoopPlugin::the().create_timer();
+}
+
+NonnullRefPtr<Timer> Timer::create_repeating(int interval_ms, Function<void()>&& timeout_handler)
+{
+    auto timer = EventLoopPlugin::the().create_timer();
+    timer->set_single_shot(false);
+    timer->set_interval(interval_ms);
+    timer->on_timeout = move(timeout_handler);
+    return timer;
+}
+
+NonnullRefPtr<Timer> Timer::create_single_shot(int interval_ms, Function<void()>&& timeout_handler)
+{
+    auto timer = EventLoopPlugin::the().create_timer();
+    timer->set_single_shot(true);
+    timer->set_interval(interval_ms);
+    timer->on_timeout = move(timeout_handler);
+    return timer;
+}
+
+}
diff --git a/Userland/Libraries/LibWeb/Platform/Timer.h b/Userland/Libraries/LibWeb/Platform/Timer.h
new file mode 100644
index 0000000000..bde3ca3f3a
--- /dev/null
+++ b/Userland/Libraries/LibWeb/Platform/Timer.h
@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Function.h>
+#include <AK/RefCounted.h>
+
+namespace Web::Platform {
+
+class Timer : public RefCounted<Timer> {
+public:
+    static NonnullRefPtr<Timer> create();
+    static NonnullRefPtr<Timer> create_repeating(int interval_ms, Function<void()>&& timeout_handler);
+    static NonnullRefPtr<Timer> create_single_shot(int interval_ms, Function<void()>&& timeout_handler);
+
+    virtual ~Timer();
+
+    virtual void start() = 0;
+    virtual void start(int interval_ms) = 0;
+    virtual void restart() = 0;
+    virtual void restart(int interval_ms) = 0;
+    virtual void stop() = 0;
+
+    virtual void set_active(bool) = 0;
+
+    virtual bool is_active() const = 0;
+    virtual int interval() const = 0;
+    virtual void set_interval(int interval_ms) = 0;
+
+    virtual bool is_single_shot() const = 0;
+    virtual void set_single_shot(bool) = 0;
+
+    Function<void()> on_timeout;
+};
+
+}
-- 
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