From 3393a7477103cb2dc2fe970e3559abb34b3a0ce8 Mon Sep 17 00:00:00 2001
From: Timothy Flynn <trflynn89@pm.me>
Date: Tue, 1 Oct 2024 11:49:07 -0400
Subject: [PATCH] UI/Qt: Do not create signal notifiers until after an event
 loop exists

We are currently creating a signal socket and socket notifier before the
Qt event loop itself has been created. Thus, when we receive a signal,
we are not actually notified when we write that signal number to the
signal socket.

This was also the source of the following error message being displayed
on every launch of the browser:

    QSocketNotifier: Can only be used with threads started with QThread
---
 Ladybird/Qt/EventLoopImplementationQt.cpp | 12 ++++++++++++
 Ladybird/Qt/EventLoopImplementationQt.h   |  5 ++++-
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/Ladybird/Qt/EventLoopImplementationQt.cpp b/Ladybird/Qt/EventLoopImplementationQt.cpp
index 7c5276863f9..0dd08a22969 100644
--- a/Ladybird/Qt/EventLoopImplementationQt.cpp
+++ b/Ladybird/Qt/EventLoopImplementationQt.cpp
@@ -209,6 +209,14 @@ void EventLoopImplementationQt::post_event(Core::EventReceiver& receiver, Nonnul
         wake();
 }
 
+void EventLoopImplementationQt::set_main_loop()
+{
+    m_main_loop = true;
+
+    auto& event_loop_manager = static_cast<EventLoopManagerQt&>(Core::EventLoopManager::the());
+    event_loop_manager.set_main_loop_signal_notifiers({});
+}
+
 static void qt_timer_fired(Core::TimerShouldFireWhenNotVisible should_fire_when_not_visible, Core::EventReceiver& object)
 {
     if (should_fire_when_not_visible == Core::TimerShouldFireWhenNotVisible::No) {
@@ -330,6 +338,10 @@ bool EventLoopManagerQt::event_target_received_event(Badge<EventLoopImplementati
 
 EventLoopManagerQt::EventLoopManagerQt()
     : m_main_thread_event_target(make<EventLoopImplementationQtEventTarget>())
+{
+}
+
+void EventLoopManagerQt::set_main_loop_signal_notifiers(Badge<EventLoopImplementationQt>)
 {
     MUST(Core::System::socketpair(AF_LOCAL, SOCK_STREAM, 0, m_signal_socket_fds));
     m_signal_socket_notifier = new QSocketNotifier(m_signal_socket_fds[0], QSocketNotifier::Read);
diff --git a/Ladybird/Qt/EventLoopImplementationQt.h b/Ladybird/Qt/EventLoopImplementationQt.h
index f3cf16e8a49..89fd7fa20b3 100644
--- a/Ladybird/Qt/EventLoopImplementationQt.h
+++ b/Ladybird/Qt/EventLoopImplementationQt.h
@@ -18,6 +18,7 @@
 
 namespace Ladybird {
 
+class EventLoopImplementationQt;
 class EventLoopImplementationQtEventTarget;
 
 class EventLoopManagerQt final : public Core::EventLoopManager {
@@ -38,6 +39,8 @@ public:
     virtual int register_signal(int, Function<void(int)>) override;
     virtual void unregister_signal(int) override;
 
+    void set_main_loop_signal_notifiers(Badge<EventLoopImplementationQt>);
+
 private:
     static void handle_signal(int);
 
@@ -77,7 +80,7 @@ public:
     virtual bool was_exit_requested() const override { return false; }
     virtual void notify_forked_and_in_child() override { }
 
-    void set_main_loop() { m_main_loop = true; }
+    void set_main_loop();
 
 private:
     friend class EventLoopManagerQt;