From 478b36c37b887d6d33915738111e9063778ceab2 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Sun, 3 Oct 2021 18:23:25 +0200
Subject: [PATCH] LibWeb: Only auto-reschedule HTML::EventLoop when there are
 runnables

HTML::EventLoop tries to reschedule itself when there are more tasks in
any of its queues, but let's not do it if none of them are runnable.
---
 Userland/Libraries/LibWeb/HTML/EventLoop/EventLoop.cpp | 2 +-
 Userland/Libraries/LibWeb/HTML/EventLoop/TaskQueue.cpp | 9 +++++++++
 Userland/Libraries/LibWeb/HTML/EventLoop/TaskQueue.h   | 2 ++
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/Userland/Libraries/LibWeb/HTML/EventLoop/EventLoop.cpp b/Userland/Libraries/LibWeb/HTML/EventLoop/EventLoop.cpp
index 41a52e5a53..129ff9174c 100644
--- a/Userland/Libraries/LibWeb/HTML/EventLoop/EventLoop.cpp
+++ b/Userland/Libraries/LibWeb/HTML/EventLoop/EventLoop.cpp
@@ -200,7 +200,7 @@ void EventLoop::process()
     // FIXME:     2. If there are no tasks in the event loop's task queues and the WorkerGlobalScope object's closing flag is true, then destroy the event loop, aborting these steps, resuming the run a worker steps described in the Web workers section below.
 
     // If there are tasks in the queue, schedule a new round of processing. :^)
-    if (!m_task_queue.is_empty() || !m_microtask_queue.is_empty())
+    if (m_task_queue.has_runnable_tasks() || !m_microtask_queue.is_empty())
         schedule();
 }
 
diff --git a/Userland/Libraries/LibWeb/HTML/EventLoop/TaskQueue.cpp b/Userland/Libraries/LibWeb/HTML/EventLoop/TaskQueue.cpp
index 51fb07df29..8a773faa89 100644
--- a/Userland/Libraries/LibWeb/HTML/EventLoop/TaskQueue.cpp
+++ b/Userland/Libraries/LibWeb/HTML/EventLoop/TaskQueue.cpp
@@ -33,4 +33,13 @@ OwnPtr<Task> TaskQueue::take_first_runnable()
     return nullptr;
 }
 
+bool TaskQueue::has_runnable_tasks() const
+{
+    for (auto& task : m_tasks) {
+        if (task->is_runnable())
+            return true;
+    }
+    return false;
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/HTML/EventLoop/TaskQueue.h b/Userland/Libraries/LibWeb/HTML/EventLoop/TaskQueue.h
index e7638b07bb..cfc2a15254 100644
--- a/Userland/Libraries/LibWeb/HTML/EventLoop/TaskQueue.h
+++ b/Userland/Libraries/LibWeb/HTML/EventLoop/TaskQueue.h
@@ -18,6 +18,8 @@ public:
 
     bool is_empty() const { return m_tasks.is_empty(); }
 
+    bool has_runnable_tasks() const;
+
     void add(NonnullOwnPtr<HTML::Task>);
     OwnPtr<HTML::Task> take_first_runnable();