Prevent winit from overriding LSUIElement in package manifests (#3920)

src/changelog/unreleased.md

@@ -44,3 +44,8 @@ changelog entry.
 
 - On macOS, add `WindowExtMacOS::set_borderless_game` and `WindowAttributesExtMacOS::with_borderless_game`
   to fully disable the menu bar and dock in Borderless Fullscreen as commonly done in games.
+
+### Fixed
+
+- On MacOS, package manifest definitions of `LSUIElement` will no longer be overridden with the
+  default activation policy, unless explicitly provided during initialization.

src/platform/macos.rs

@@ -175,14 +175,12 @@ impl WindowExtMacOS for Window {
 
     #[inline]
     fn set_borderless_game(&self, borderless_game: bool) {
-        let window = self.as_any().downcast_ref::<crate::platform_impl::Window>().unwrap();
-        window.maybe_wait_on_main(|w| w.set_borderless_game(borderless_game))
+        self.window.maybe_wait_on_main(|w| w.set_borderless_game(borderless_game))
     }
 
     #[inline]
     fn is_borderless_game(&self) -> bool {
-        let window = self.as_any().downcast_ref::<crate::platform_impl::Window>().unwrap();
-        window.maybe_wait_on_main(|w| w.is_borderless_game())
+        self.window.maybe_wait_on_main(|w| w.is_borderless_game())
     }
 }
 
@@ -313,9 +311,12 @@ impl WindowAttributesExtMacOS for WindowAttributes {
 }
 
 pub trait EventLoopBuilderExtMacOS {
-    /// Sets the activation policy for the application.
+    /// Sets the activation policy for the application. If used, this will override
+    /// any relevant settings provided in the package manifest.
+    /// For instance, `with_activation_policy(ActivationPolicy::Regular)` will prevent
+    /// the application from running as an "agent", even if LSUIElement is set to true.
     ///
-    /// It is set to [`ActivationPolicy::Regular`] by default.
+    /// If unused, the Winit will honor the package manifest.
     ///
     /// # Example
     ///
@@ -367,7 +368,7 @@ pub trait EventLoopBuilderExtMacOS {
 impl<T> EventLoopBuilderExtMacOS for EventLoopBuilder<T> {
     #[inline]
     fn with_activation_policy(&mut self, activation_policy: ActivationPolicy) -> &mut Self {
-        self.platform_specific.activation_policy = activation_policy;
+        self.platform_specific.activation_policy = Some(activation_policy);
         self
     }
 

src/platform_impl/macos/app_state.rs

@@ -18,7 +18,12 @@ use crate::window::WindowId as RootWindowId;
 
 #[derive(Debug)]
 pub(super) struct AppState {
-    activation_policy: NSApplicationActivationPolicy,
+    // <<<<<<< HEAD:src/platform_impl/macos/app_state.rs
+    //     activation_policy: NSApplicationActivationPolicy,
+    // =======
+    activation_policy: Option<NSApplicationActivationPolicy>,
+    // >>>>>>> 7e819bb2 (Prevent winit from overriding LSUIElement in package manifests
+    // (#3920)):src/platform_impl/apple/appkit/app_state.rs
     default_menu: bool,
     activate_ignoring_other_apps: bool,
     run_loop: RunLoop,
@@ -74,7 +79,7 @@ declare_class!(
 impl ApplicationDelegate {
     pub(super) fn new(
         mtm: MainThreadMarker,
-        activation_policy: NSApplicationActivationPolicy,
+        activation_policy: Option<NSApplicationActivationPolicy>,
         default_menu: bool,
         activate_ignoring_other_apps: bool,
     ) -> Retained<Self> {
@@ -111,7 +116,11 @@ impl ApplicationDelegate {
         // 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.
-        app.setActivationPolicy(self.ivars().activation_policy);
+        // If no activation policy is explicitly provided, do not set it at all
+        // to allow the package manifest to define behavior via LSUIElement.
+        if let Some(activation_policy) = self.ivars().activation_policy {
+            app.setActivationPolicy(activation_policy);
+        }
 
         window_activation_hack(&app);
         #[allow(deprecated)]

src/platform_impl/macos/event_loop.rs

@@ -202,18 +202,14 @@ pub struct EventLoop<T: 'static> {
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 pub(crate) struct PlatformSpecificEventLoopAttributes {
-    pub(crate) activation_policy: ActivationPolicy,
+    pub(crate) activation_policy: Option<ActivationPolicy>,
     pub(crate) default_menu: bool,
     pub(crate) activate_ignoring_other_apps: bool,
 }
 
 impl Default for PlatformSpecificEventLoopAttributes {
     fn default() -> Self {
-        Self {
-            activation_policy: Default::default(), // Regular
-            default_menu: true,
-            activate_ignoring_other_apps: true,
-        }
+        Self { activation_policy: None, default_menu: true, activate_ignoring_other_apps: true }
     }
 }
 
@@ -235,9 +231,10 @@ impl<T> EventLoop<T> {
         }
 
         let activation_policy = match attributes.activation_policy {
-            ActivationPolicy::Regular => NSApplicationActivationPolicy::Regular,
-            ActivationPolicy::Accessory => NSApplicationActivationPolicy::Accessory,
-            ActivationPolicy::Prohibited => NSApplicationActivationPolicy::Prohibited,
+            None => None,
+            Some(ActivationPolicy::Regular) => Some(NSApplicationActivationPolicy::Regular),
+            Some(ActivationPolicy::Accessory) => Some(NSApplicationActivationPolicy::Accessory),
+            Some(ActivationPolicy::Prohibited) => Some(NSApplicationActivationPolicy::Prohibited),
         };
         let delegate = ApplicationDelegate::new(
             mtm,