fix(tray): build tray on main thread (#11583)

Author: amrbashir

.changes/tray-async-command.md

@@ -0,0 +1,5 @@
+---
+"tauri": "patch:bug"
+---
+
+Fix tray events not fired for tray icons created inside an async command.

crates/tauri/src/lib.rs

@@ -1011,6 +1011,15 @@ pub(crate) mod sealed {
   }
 }
 
+struct UnsafeSend<T>(T);
+unsafe impl<T> Send for UnsafeSend<T> {}
+
+impl<T> UnsafeSend<T> {
+  fn take(self) -> T {
+    self.0
+  }
+}
+
 #[allow(unused)]
 macro_rules! run_main_thread {
   ($handle:ident, $ex:expr) => {{

crates/tauri/src/menu/mod.rs

@@ -75,7 +75,6 @@ macro_rules! gen_wrappers {
         app_handle: $crate::AppHandle<R>,
       }
 
-
       /// # Safety
       ///
       /// We make sure it always runs on the main thread.
@@ -96,11 +95,9 @@ macro_rules! gen_wrappers {
 
       impl<R: Runtime> Drop for $inner<R> {
         fn drop(&mut self) {
-          struct SafeSend<T>(T);
-          unsafe impl<T> Send for SafeSend<T> {}
-
           let inner = self.inner.take();
-          let inner = SafeSend(inner);
+          // SAFETY: inner was created on main thread and is being dropped on main thread
+          let inner = $crate::UnsafeSend(inner);
           let _ = self.app_handle.run_on_main_thread(move || {
             drop(inner);
           });

crates/tauri/src/tray/mod.rs

@@ -10,6 +10,7 @@ use crate::app::{GlobalMenuEventListener, GlobalTrayIconEventListener};
 use crate::menu::ContextMenu;
 use crate::menu::MenuEvent;
 use crate::resources::Resource;
+use crate::UnsafeSend;
 use crate::{
   image::Image, menu::run_item_main_thread, AppHandle, Manager, PhysicalPosition, Rect, Runtime,
 };
@@ -342,10 +343,24 @@ impl<R: Runtime> TrayIconBuilder<R> {
   /// Builds and adds a new [`TrayIcon`] to the system tray.
   pub fn build<M: Manager<R>>(self, manager: &M) -> crate::Result<TrayIcon<R>> {
     let id = self.id().clone();
-    let inner = self.inner.build()?;
+
+    // SAFETY:
+    // the menu within this builder was created on main thread
+    // and will be accessed on the main thread
+    let unsafe_builder = UnsafeSend(self.inner);
+
+    let (tx, rx) = std::sync::mpsc::channel();
+    let unsafe_tray = manager
+      .app_handle()
+      .run_on_main_thread(move || {
+        // SAFETY: will only be accessed on main thread
+        let _ = tx.send(unsafe_builder.take().build().map(UnsafeSend));
+      })
+      .and_then(|_| rx.recv().map_err(|_| crate::Error::FailedToReceiveMessage))??;
+
     let icon = TrayIcon {
       id,
-      inner,
+      inner: unsafe_tray.take(),
       app_handle: manager.app_handle().clone(),
     };