macOS: set activation policy by default if app is not bundled (#3961)

src/platform_impl/apple/appkit/app_state.rs

@@ -5,7 +5,7 @@ use std::sync::atomic::Ordering as AtomicOrdering;
 use std::sync::Arc;
 use std::time::Instant;
 
-use objc2_app_kit::{NSApplication, NSApplicationActivationPolicy};
+use objc2_app_kit::{NSApplication, NSApplicationActivationPolicy, NSRunningApplication};
 use objc2_foundation::{MainThreadMarker, NSNotification};
 
 use super::super::event_handler::EventHandler;
@@ -113,10 +113,21 @@ impl AppState {
         // We need to delay setting the activation policy and activating the app
         // until `applicationDidFinishLaunching` has been called. Otherwise the
         // menu bar is initially unresponsive on macOS 10.15.
-        // If no activation policy is explicitly provided, do not set it at all
-        // to allow the package manifest to define behavior via LSUIElement.
-        if self.activation_policy.is_some() {
-            app.setActivationPolicy(self.activation_policy.unwrap());
+        if let Some(activation_policy) = self.activation_policy {
+            app.setActivationPolicy(activation_policy);
+        } else {
+            // If no activation policy is explicitly provided, and the application
+            // is bundled, do not set the activation policy at all, to allow the
+            // package manifest to define the behavior via LSUIElement.
+            //
+            // See:
+            // - https://github.com/rust-windowing/winit/issues/261
+            // - https://github.com/rust-windowing/winit/issues/3958
+            let is_bundled =
+                unsafe { NSRunningApplication::currentApplication().bundleIdentifier().is_some() };
+            if !is_bundled {
+                app.setActivationPolicy(NSApplicationActivationPolicy::Regular);
+            }
         }
 
         #[allow(deprecated)]