LibCore: Allow listening for multiple conditions using a single Notifier

While on it, implement currently unused Notifier::set_type correctly
(but not efficiently) by re-registering Notifier in the EventLoop.

Ladybird/AppKit/Application/EventLoopImplementation.mm

@@ -106,7 +106,7 @@ static void socket_notifier(CFSocketRef socket, CFSocketCallBackType notificatio
     // before dispatching the event, which allows it to be triggered again.
     CFSocketEnableCallBacks(socket, notification_type);
 
-    Core::NotifierActivationEvent event(notifier.fd());
+    Core::NotifierActivationEvent event(notifier.fd(), notifier.type());
     notifier.dispatch_event(event);
 
     // This manual process of enabling the callbacks also seems to require waking the event loop,

Ladybird/Qt/EventLoopImplementationQt.cpp

@@ -118,7 +118,7 @@ bool EventLoopManagerQt::unregister_timer(int timer_id)
 
 static void qt_notifier_activated(Core::Notifier& notifier)
 {
-    Core::NotifierActivationEvent event(notifier.fd());
+    Core::NotifierActivationEvent event(notifier.fd(), notifier.type());
     notifier.dispatch_event(event);
 }
 

Userland/Libraries/LibCore/Event.h

@@ -7,6 +7,7 @@
 
 #pragma once
 
+#include <AK/EnumBits.h>
 #include <AK/Function.h>
 #include <AK/Types.h>
 #include <AK/WeakPtr.h>
@@ -78,19 +79,30 @@ private:
     int m_timer_id;
 };
 
+enum class NotificationType {
+    None = 0,
+    Read = 1,
+    Write = 2,
+};
+
+AK_ENUM_BITWISE_OPERATORS(NotificationType);
+
 class NotifierActivationEvent final : public Event {
 public:
-    explicit NotifierActivationEvent(int fd)
+    explicit NotifierActivationEvent(int fd, NotificationType type)
         : Event(Event::NotifierActivation)
         , m_fd(fd)
+        , m_type(type)
     {
     }
     ~NotifierActivationEvent() = default;
 
     int fd() const { return m_fd; }
+    NotificationType type() const { return m_type; }
 
 private:
     int m_fd;
+    NotificationType m_type;
 };
 
 class ChildEvent final : public Event {

Userland/Libraries/LibCore/EventLoopImplementationUnix.cpp

@@ -157,12 +157,10 @@ retry:
     add_fd_to_set(thread_data.wake_pipe_fds[0], read_fds);
 
     for (auto& notifier : thread_data.notifiers) {
-        if (notifier->type() == Notifier::Type::Read)
+        if (has_flag(notifier->type(), Notifier::Type::Read))
             add_fd_to_set(notifier->fd(), read_fds);
-        if (notifier->type() == Notifier::Type::Write)
+        if (has_flag(notifier->type(), Notifier::Type::Write))
             add_fd_to_set(notifier->fd(), write_fds);
-        if (notifier->type() == Notifier::Type::Exceptional)
-            TODO();
     }
 
     bool has_pending_events = ThreadEventQueue::current().has_pending_events();
@@ -257,12 +255,14 @@ try_select_again:
 
     // Handle file system notifiers by making them normal events.
     for (auto& notifier : thread_data.notifiers) {
-        if (notifier->type() == Notifier::Type::Read && FD_ISSET(notifier->fd(), &read_fds)) {
-            ThreadEventQueue::current().post_event(*notifier, make<NotifierActivationEvent>(notifier->fd()));
-        }
-        if (notifier->type() == Notifier::Type::Write && FD_ISSET(notifier->fd(), &write_fds)) {
-            ThreadEventQueue::current().post_event(*notifier, make<NotifierActivationEvent>(notifier->fd()));
-        }
+        auto type = NotificationType::None;
+        if (FD_ISSET(notifier->fd(), &read_fds))
+            type |= NotificationType::Read;
+        if (FD_ISSET(notifier->fd(), &write_fds))
+            type |= NotificationType::Write;
+        type &= notifier->type();
+        if (type != NotificationType::None)
+            ThreadEventQueue::current().post_event(*notifier, make<NotifierActivationEvent>(notifier->fd(), type));
     }
 }
 

Userland/Libraries/LibCore/Notifier.cpp

@@ -27,6 +27,9 @@ void Notifier::set_enabled(bool enabled)
 {
     if (m_fd < 0)
         return;
+    if (enabled == m_is_enabled)
+        return;
+    m_is_enabled = enabled;
     if (enabled)
         Core::EventLoop::register_notifier({}, *this);
     else
@@ -41,6 +44,18 @@ void Notifier::close()
     m_fd = -1;
 }
 
+void Notifier::set_type(Type type)
+{
+    if (m_is_enabled) {
+        // FIXME: Directly communicate intent to the EventLoop.
+        set_enabled(false);
+        m_type = type;
+        set_enabled(true);
+    } else {
+        m_type = type;
+    }
+}
+
 void Notifier::event(Core::Event& event)
 {
     if (event.type() == Core::Event::NotifierActivation) {

Userland/Libraries/LibCore/Notifier.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <AK/Function.h>
+#include <LibCore/Event.h>
 #include <LibCore/EventReceiver.h>
 
 namespace Core {
@@ -15,12 +16,7 @@ class Notifier final : public EventReceiver {
     C_OBJECT(Notifier);
 
 public:
-    enum class Type {
-        None,
-        Read,
-        Write,
-        Exceptional,
-    };
+    using Type = NotificationType;
 
     virtual ~Notifier() override;
 
@@ -32,7 +28,7 @@ public:
 
     int fd() const { return m_fd; }
     Type type() const { return m_type; }
-    void set_type(Type type) { m_type = type; }
+    void set_type(Type type);
 
     void event(Core::Event&) override;
 
@@ -40,6 +36,7 @@ private:
     Notifier(int fd, Type type, EventReceiver* parent = nullptr);
 
     int m_fd { -1 };
+    bool m_is_enabled { false };
     Type m_type { Type::None };
 };