From 2bfed2e417ce80f3595dbcf7081d342c5476f95c Mon Sep 17 00:00:00 2001
From: stasoid <stasoid@yahoo.com>
Date: Wed, 8 Jan 2025 12:27:40 +0500
Subject: [PATCH] LibCore: Check for all events in
 EventLoopImplementationWindows::pump

This fixes the problem when none of the timers or notifiers get
executed if wake() is called frequently.

Note that calling WaitForMultipleObjects repeatedly until it fails
will not work because rapidly firing timer can get all the attention.
That's why I check every event individually with WaitForSingleObject.

This behavior matches EventLoopImplementationUnix.
---
 .../EventLoopImplementationWindows.cpp        | 40 ++++++++++++-------
 1 file changed, 25 insertions(+), 15 deletions(-)

diff --git a/Libraries/LibCore/EventLoopImplementationWindows.cpp b/Libraries/LibCore/EventLoopImplementationWindows.cpp
index c6274e01ea8..21e5235e304 100644
--- a/Libraries/LibCore/EventLoopImplementationWindows.cpp
+++ b/Libraries/LibCore/EventLoopImplementationWindows.cpp
@@ -94,7 +94,8 @@ int EventLoopImplementationWindows::exec()
 
 size_t EventLoopImplementationWindows::pump(PumpMode)
 {
-    auto thread_data = ThreadData::the();
+    auto& event_queue = ThreadEventQueue::current();
+    auto* thread_data = ThreadData::the();
     auto& notifiers = thread_data->notifiers;
     auto& timers = thread_data->timers;
 
@@ -112,25 +113,34 @@ size_t EventLoopImplementationWindows::pump(PumpMode)
     for (auto& entry : timers)
         event_handles.append(entry.key.handle);
 
-    bool has_pending_events = ThreadEventQueue::current().has_pending_events();
+    bool has_pending_events = event_queue.has_pending_events();
     int timeout = has_pending_events ? 0 : INFINITE;
     DWORD result = WaitForMultipleObjects(event_count, event_handles.data(), FALSE, timeout);
-    size_t index = result - WAIT_OBJECT_0;
-    VERIFY(index < event_count);
-
-    if (index != 0) {
-        if (index <= notifiers.size()) {
-            Notifier* notifier = *notifiers.get(event_handles[index]);
-            ThreadEventQueue::current().post_event(*notifier, make<NotifierActivationEvent>(notifier->fd(), notifier->type()));
-        } else {
-            auto& timer = *timers.get(event_handles[index]);
-            if (auto strong_owner = timer.owner.strong_ref())
-                if (timer.fire_when_not_visible == TimerShouldFireWhenNotVisible::Yes || strong_owner->is_visible_for_timer_purposes())
-                    ThreadEventQueue::current().post_event(*strong_owner, make<TimerEvent>());
+    if (result == WAIT_TIMEOUT) {
+        // FIXME: This verification sometimes fails with ERROR_INVALID_HANDLE, but when I check
+        //        the handles they all seem to be valid.
+        // VERIFY(GetLastError() == ERROR_SUCCESS || GetLastError() == ERROR_IO_PENDING);
+    } else {
+        size_t const index = result - WAIT_OBJECT_0;
+        VERIFY(index < event_count);
+        // : 1 - skip wake event
+        for (size_t i = index ? index : 1; i < event_count; i++) {
+            // i == index already checked by WaitForMultipleObjects
+            if (i == index || WaitForSingleObject(event_handles[i], 0) == WAIT_OBJECT_0) {
+                if (i <= notifiers.size()) {
+                    Notifier* notifier = *notifiers.get(event_handles[i]);
+                    event_queue.post_event(*notifier, make<NotifierActivationEvent>(notifier->fd(), notifier->type()));
+                } else {
+                    auto& timer = *timers.get(event_handles[i]);
+                    if (auto strong_owner = timer.owner.strong_ref())
+                        if (timer.fire_when_not_visible == TimerShouldFireWhenNotVisible::Yes || strong_owner->is_visible_for_timer_purposes())
+                            event_queue.post_event(*strong_owner, make<TimerEvent>());
+                }
+            }
         }
     }
 
-    return ThreadEventQueue::current().process();
+    return event_queue.process();
 }
 
 void EventLoopImplementationWindows::quit(int code)