macOS: add option to explicitly hide menu/dock in Borderless (#3882)

src/changelog/unreleased.md

@@ -39,3 +39,8 @@ The migration guide could reference other migration examples in the current
 changelog entry.
 
 ## Unreleased
+
+### Added
+
+- 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.

src/platform/macos.rs

@@ -94,6 +94,12 @@ pub trait WindowExtMacOS {
 
     /// Getter for the [`WindowExtMacOS::set_option_as_alt`].
     fn option_as_alt(&self) -> OptionAsAlt;
+
+    /// Disable the Menu Bar and Dock in Borderless Fullscreen mode. Useful for games.
+    fn set_borderless_game(&self, borderless_game: bool);
+
+    /// Getter for the [`WindowExtMacOS::set_borderless_game`].
+    fn is_borderless_game(&self) -> bool;
 }
 
 impl WindowExtMacOS for Window {
@@ -166,6 +172,18 @@ impl WindowExtMacOS for Window {
     fn option_as_alt(&self) -> OptionAsAlt {
         self.window.maybe_wait_on_main(|w| w.option_as_alt())
     }
+
+    #[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))
+    }
+
+    #[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())
+    }
 }
 
 /// Corresponds to `NSApplicationActivationPolicy`.
@@ -216,6 +234,8 @@ pub trait WindowAttributesExtMacOS {
     ///
     /// See [`WindowExtMacOS::set_option_as_alt`] for details on what this means if set.
     fn with_option_as_alt(self, option_as_alt: OptionAsAlt) -> Self;
+    /// See [`WindowExtMacOS::set_borderless_game`] for details on what this means if set.
+    fn with_borderless_game(self, borderless_game: bool) -> Self;
 }
 
 impl WindowAttributesExtMacOS for WindowAttributes {
@@ -284,6 +304,12 @@ impl WindowAttributesExtMacOS for WindowAttributes {
         self.platform_specific.option_as_alt = option_as_alt;
         self
     }
+
+    #[inline]
+    fn with_borderless_game(mut self, borderless_game: bool) -> Self {
+        self.platform_specific.borderless_game = borderless_game;
+        self
+    }
 }
 
 pub trait EventLoopBuilderExtMacOS {

src/platform_impl/macos/window_delegate.rs

@@ -55,6 +55,7 @@ pub struct PlatformSpecificWindowAttributes {
     pub accepts_first_mouse: bool,
     pub tabbing_identifier: Option<String>,
     pub option_as_alt: OptionAsAlt,
+    pub borderless_game: bool,
 }
 
 impl Default for PlatformSpecificWindowAttributes {
@@ -72,6 +73,7 @@ impl Default for PlatformSpecificWindowAttributes {
             accepts_first_mouse: true,
             tabbing_identifier: None,
             option_as_alt: Default::default(),
+            borderless_game: false,
         }
     }
 }
@@ -120,6 +122,7 @@ pub(crate) struct State {
     standard_frame: Cell<Option<NSRect>>,
     is_simple_fullscreen: Cell<bool>,
     saved_style: Cell<Option<NSWindowStyleMask>>,
+    is_borderless_game: Cell<bool>,
 }
 
 declare_class!(
@@ -725,6 +728,7 @@ impl WindowDelegate {
             standard_frame: Cell::new(None),
             is_simple_fullscreen: Cell::new(false),
             saved_style: Cell::new(None),
+            is_borderless_game: Cell::new(attrs.platform_specific.borderless_game),
         });
         let delegate: Retained<WindowDelegate> = unsafe { msg_send_id![super(delegate), init] };
 
@@ -1409,7 +1413,7 @@ impl WindowDelegate {
         }
 
         match (old_fullscreen, fullscreen) {
-            (None, Some(_)) => {
+            (None, Some(fullscreen)) => {
                 // `toggleFullScreen` doesn't work if the `StyleMask` is none, so we
                 // set a normal style temporarily. The previous state will be
                 // restored in `WindowDelegate::window_did_exit_fullscreen`.
@@ -1419,6 +1423,17 @@ impl WindowDelegate {
                     self.set_style_mask(required);
                     self.ivars().saved_style.set(Some(curr_mask));
                 }
+
+                // In borderless games, we want to disable the dock and menu bar
+                // by setting the presentation options. We do this here rather than in
+                // `window:willUseFullScreenPresentationOptions` because for some reason
+                // the menu bar remains interactable despite being hidden.
+                if self.is_borderless_game() && matches!(fullscreen, Fullscreen::Borderless(_)) {
+                    let presentation_options = NSApplicationPresentationOptions::NSApplicationPresentationHideDock
+                            | NSApplicationPresentationOptions::NSApplicationPresentationHideMenuBar;
+                    app.setPresentationOptions(presentation_options);
+                }
+
                 toggle_fullscreen(self.window());
             },
             (Some(Fullscreen::Borderless(_)), None) => {
@@ -1829,6 +1844,14 @@ impl WindowExtMacOS for WindowDelegate {
     fn option_as_alt(&self) -> OptionAsAlt {
         self.view().option_as_alt()
     }
+
+    fn set_borderless_game(&self, borderless_game: bool) {
+        self.ivars().is_borderless_game.set(borderless_game);
+    }
+
+    fn is_borderless_game(&self) -> bool {
+        self.ivars().is_borderless_game.get()
+    }
 }
 
 const DEFAULT_STANDARD_FRAME: NSRect =