Fixes #5016 - Fix deadlock in EventIPCTransport.DispatchWailsEvent holding RLock during InvokeSync

v3/UNRELEASED_CHANGELOG.md

@@ -48,6 +48,7 @@ After processing, the content will be moved to the main changelog and this file
 **Fixed:**
 - Fix memory leak in event system during window close operations (#5678)
 - Fix crash when using context menus on Linux with Wayland
+- Fix deadlock EventIPCTransport.DispatchWailsEvent holding RLock during InvokeSync (#5106)
 
 **Security:**
 - Update dependencies to address CVE-2024-12345 in third-party library

v3/pkg/application/transport_event_ipc.go

@@ -5,10 +5,21 @@ type EventIPCTransport struct {
 }
 
 func (t *EventIPCTransport) DispatchWailsEvent(event *CustomEvent) {
-	// Snapshot windows under RLock
+	// Snapshot the window list under the lock, then release before dispatching.
+	// DispatchWailsEvent calls ExecJS → InvokeSync which blocks until the main
+	// thread executes the JS. Holding windowsLock.RLock during InvokeSync causes
+	// a deadlock when the main thread (or any other goroutine) needs windowsLock
+	// for write operations (NewWithOptions, Remove) — the pending writer blocks
+	// new readers, and the existing readers can't complete because InvokeSync
+	// needs the main thread which is waiting for the write lock.
 	t.app.windowsLock.RLock()
-	defer t.app.windowsLock.RUnlock()
-	for _, window := range t.app.windows {
+	windows := make([]Window, 0, len(t.app.windows))
+	for _, w := range t.app.windows {
+		windows = append(windows, w)
+	}
+	t.app.windowsLock.RUnlock()
+
+	for _, window := range windows {
 		if event.IsCancelled() {
 			return
 		}