Implement ability to make non-activating window on macOS (#4035)

Fixes #3894

Cargo.toml

@@ -128,6 +128,7 @@ objc2-app-kit = { version = "0.2.2", features = [
     "NSMenu",
     "NSMenuItem",
     "NSOpenGLView",
+    "NSPanel",
     "NSPasteboard",
     "NSResponder",
     "NSRunningApplication",

src/changelog/unreleased.md

@@ -76,6 +76,7 @@ changelog entry.
 - Added `Window::surface_position`, which is the position of the surface inside the window.
 - Added `Window::safe_area`, which describes the area of the surface that is unobstructed.
 - On X11, Wayland, Windows and macOS, improved scancode conversions for more obscure key codes.
+- Add ability to make non-activating window on macOS using `NSPanel` with `NSWindowStyleMask::NonactivatingPanel`.
 
 ### Changed
 

src/platform/macos.rs

@@ -332,6 +332,13 @@ pub trait WindowAttributesExtMacOS {
     fn with_borderless_game(self, borderless_game: bool) -> Self;
     /// See [`WindowExtMacOS::set_unified_titlebar`] for details on what this means if set.
     fn with_unified_titlebar(self, unified_titlebar: bool) -> Self;
+    /// Use [`NSPanel`] window with [`NonactivatingPanel`] window style mask instead of
+    /// [`NSWindow`].
+    ///
+    /// [`NSWindow`]: https://developer.apple.com/documentation/appkit/NSWindow?language=objc
+    /// [`NSPanel`]: https://developer.apple.com/documentation/appkit/NSPanel?language=objc
+    /// [`NonactivatingPanel`]: https://developer.apple.com/documentation/appkit/nswindow/stylemask-swift.struct/nonactivatingpanel?language=objc
+    fn with_panel(self, panel: bool) -> Self;
 }
 
 impl WindowAttributesExtMacOS for WindowAttributes {
@@ -412,6 +419,12 @@ impl WindowAttributesExtMacOS for WindowAttributes {
         self.platform_specific.unified_titlebar = unified_titlebar;
         self
     }
+
+    #[inline]
+    fn with_panel(mut self, panel: bool) -> Self {
+        self.platform_specific.panel = panel;
+        self
+    }
 }
 
 pub trait EventLoopBuilderExtMacOS {

src/platform_impl/apple/appkit/view.rs

@@ -9,7 +9,7 @@ use objc2::runtime::{AnyObject, Sel};
 use objc2::{declare_class, msg_send_id, mutability, ClassType, DeclaredClass};
 use objc2_app_kit::{
     NSApplication, NSCursor, NSEvent, NSEventPhase, NSResponder, NSTextInputClient,
-    NSTrackingRectTag, NSView,
+    NSTrackingRectTag, NSView, NSWindow,
 };
 use objc2_foundation::{
     MainThreadMarker, NSArray, NSAttributedString, NSAttributedStringKey, NSCopying,
@@ -23,7 +23,7 @@ use super::event::{
     code_to_key, code_to_location, create_key_event, event_mods, lalt_pressed, ralt_pressed,
     scancode_to_physicalkey, KeyEventExtra,
 };
-use super::window::WinitWindow;
+use super::window::window_id;
 use crate::dpi::{LogicalPosition, LogicalSize};
 use crate::event::{
     DeviceEvent, ElementState, Ime, KeyEvent, Modifiers, MouseButton, MouseScrollDelta,
@@ -201,7 +201,7 @@ declare_class!(
         fn draw_rect(&self, _rect: NSRect) {
             trace_scope!("drawRect:");
 
-            self.ivars().app_state.handle_redraw(self.window().id());
+            self.ivars().app_state.handle_redraw(window_id(&self.window()));
 
             // This is a direct subclass of NSView, no need to call superclass' drawRect:
         }
@@ -426,7 +426,7 @@ declare_class!(
             }
 
             // Send command action to user if they requested it.
-            let window_id = self.window().id();
+            let window_id = window_id(&self.window());
             self.ivars().app_state.maybe_queue_with_handler(move |app, event_loop| {
                 if let Some(handler) = app.macos_handler() {
                     handler.standard_key_binding(event_loop, window_id, command.name());
@@ -828,19 +828,12 @@ impl WinitView {
         this
     }
 
-    fn window(&self) -> Retained<WinitWindow> {
-        let window = (**self).window().expect("view must be installed in a window");
-
-        if !window.isKindOfClass(WinitWindow::class()) {
-            unreachable!("view installed in non-WinitWindow");
-        }
-
-        // SAFETY: Just checked that the window is `WinitWindow`
-        unsafe { Retained::cast(window) }
+    fn window(&self) -> Retained<NSWindow> {
+        (**self).window().expect("view must be installed in a window")
     }
 
     fn queue_event(&self, event: WindowEvent) {
-        let window_id = self.window().id();
+        let window_id = window_id(&self.window());
         self.ivars().app_state.maybe_queue_with_handler(move |app, event_loop| {
             app.window_event(event_loop, window_id, event);
         });

src/platform_impl/apple/appkit/window.rs

@@ -3,7 +3,7 @@
 use dpi::{Position, Size};
 use objc2::rc::{autoreleasepool, Retained};
 use objc2::{declare_class, mutability, ClassType, DeclaredClass};
-use objc2_app_kit::{NSResponder, NSWindow};
+use objc2_app_kit::{NSPanel, NSResponder, NSWindow};
 use objc2_foundation::{MainThreadBound, MainThreadMarker, NSObject};
 
 use super::event_loop::ActiveEventLoop;
@@ -16,7 +16,7 @@ use crate::window::{
 };
 
 pub(crate) struct Window {
-    window: MainThreadBound<Retained<WinitWindow>>,
+    window: MainThreadBound<Retained<NSWindow>>,
     /// The window only keeps a weak reference to this, so we must keep it around here.
     delegate: MainThreadBound<Retained<WindowDelegate>>,
 }
@@ -360,8 +360,30 @@ declare_class!(
     }
 );
 
-impl WinitWindow {
-    pub(super) fn id(&self) -> WindowId {
-        WindowId::from_raw(self as *const Self as usize)
+declare_class!(
+    #[derive(Debug)]
+    pub struct WinitPanel;
+
+    unsafe impl ClassType for WinitPanel {
+        #[inherits(NSWindow, NSResponder, NSObject)]
+        type Super = NSPanel;
+        type Mutability = mutability::MainThreadOnly;
+        const NAME: &'static str = "WinitPanel";
     }
+
+    impl DeclaredClass for WinitPanel {}
+
+    unsafe impl WinitPanel {
+        // although NSPanel can become key window
+        // it doesn't if window doesn't have NSWindowStyleMask::Titled
+        #[method(canBecomeKeyWindow)]
+        fn can_become_key_window(&self) -> bool {
+            trace_scope!("canBecomeKeyWindow");
+            true
+        }
+    }
+);
+
+pub(super) fn window_id(window: &NSWindow) -> WindowId {
+    WindowId::from_raw(window as *const _ as usize)
 }

src/platform_impl/apple/appkit/window_delegate.rs

@@ -16,7 +16,7 @@ use objc2_app_kit::{
     NSAppearanceNameAqua, NSApplication, NSApplicationPresentationOptions, NSBackingStoreType,
     NSColor, NSDraggingDestination, NSFilenamesPboardType, NSPasteboard,
     NSRequestUserAttentionType, NSScreen, NSToolbar, NSView, NSViewFrameDidChangeNotification,
-    NSWindowButton, NSWindowDelegate, NSWindowFullScreenButton, NSWindowLevel,
+    NSWindow, NSWindowButton, NSWindowDelegate, NSWindowFullScreenButton, NSWindowLevel,
     NSWindowOcclusionState, NSWindowOrderingMode, NSWindowSharingType, NSWindowStyleMask,
     NSWindowTabbingMode, NSWindowTitleVisibility, NSWindowToolbarStyle,
 };
@@ -33,7 +33,7 @@ use super::cursor::cursor_from_icon;
 use super::monitor::{self, flip_window_screen_coordinates, get_display_id};
 use super::observer::RunLoop;
 use super::view::WinitView;
-use super::window::WinitWindow;
+use super::window::{window_id, WinitPanel, WinitWindow};
 use super::{ffi, Fullscreen, MonitorHandle};
 use crate::dpi::{
     LogicalInsets, LogicalPosition, LogicalSize, PhysicalInsets, PhysicalPosition, PhysicalSize,
@@ -62,6 +62,7 @@ pub struct PlatformSpecificWindowAttributes {
     pub option_as_alt: OptionAsAlt,
     pub borderless_game: bool,
     pub unified_titlebar: bool,
+    pub panel: bool,
 }
 
 impl Default for PlatformSpecificWindowAttributes {
@@ -81,6 +82,7 @@ impl Default for PlatformSpecificWindowAttributes {
             option_as_alt: Default::default(),
             borderless_game: false,
             unified_titlebar: false,
+            panel: false,
         }
     }
 }
@@ -90,7 +92,7 @@ pub(crate) struct State {
     /// Strong reference to the global application state.
     app_state: Rc<AppState>,
 
-    window: Retained<WinitWindow>,
+    window: Retained<NSWindow>,
 
     // During `windowDidResize`, we use this to only send Moved if the position changed.
     //
@@ -501,7 +503,7 @@ fn new_window(
     app_state: &Rc<AppState>,
     attrs: &WindowAttributes,
     mtm: MainThreadMarker,
-) -> Option<Retained<WinitWindow>> {
+) -> Option<Retained<NSWindow>> {
     autoreleasepool(|_| {
         let screen = match attrs.fullscreen.clone().map(Into::into) {
             Some(Fullscreen::Borderless(Some(monitor)))
@@ -584,16 +586,33 @@ fn new_window(
         // confusing issues with the window not being properly activated.
         //
         // Winit ensures this by not allowing access to `ActiveEventLoop` before handling events.
-        let window: Option<Retained<WinitWindow>> = unsafe {
-            msg_send_id![
-                super(mtm.alloc().set_ivars(())),
-                initWithContentRect: frame,
-                styleMask: masks,
-                backing: NSBackingStoreType::NSBackingStoreBuffered,
-                defer: false,
-            ]
+        let window: Retained<NSWindow> = if attrs.platform_specific.panel {
+            masks |= NSWindowStyleMask::NonactivatingPanel;
+
+            let window: Option<Retained<WinitPanel>> = unsafe {
+                msg_send_id![
+                    super(mtm.alloc().set_ivars(())),
+                    initWithContentRect: frame,
+                    styleMask: masks,
+                    backing: NSBackingStoreType::NSBackingStoreBuffered,
+                    defer: false,
+                ]
+            };
+
+            window?.as_super().as_super().retain()
+        } else {
+            let window: Option<Retained<WinitWindow>> = unsafe {
+                msg_send_id![
+                    super(mtm.alloc().set_ivars(())),
+                    initWithContentRect: frame,
+                    styleMask: masks,
+                    backing: NSBackingStoreType::NSBackingStoreBuffered,
+                    defer: false,
+                ]
+            };
+
+            window?.as_super().retain()
         };
-        let window = window?;
 
         // It is very important for correct memory management that we
         // disable the extra release that would otherwise happen when
@@ -841,17 +860,17 @@ impl WindowDelegate {
     }
 
     #[track_caller]
-    pub(super) fn window(&self) -> &WinitWindow {
+    pub(super) fn window(&self) -> &NSWindow {
         &self.ivars().window
     }
 
     #[track_caller]
     pub(crate) fn id(&self) -> WindowId {
-        self.window().id()
+        window_id(self.window())
     }
 
     pub(crate) fn queue_event(&self, event: WindowEvent) {
-        let window_id = self.window().id();
+        let window_id = window_id(self.window());
         self.ivars().app_state.maybe_queue_with_handler(move |app, event_loop| {
             app.window_event(event_loop, window_id, event);
         });
@@ -950,7 +969,7 @@ impl WindowDelegate {
     }
 
     pub fn request_redraw(&self) {
-        self.ivars().app_state.queue_redraw(self.window().id());
+        self.ivars().app_state.queue_redraw(window_id(self.window()));
     }
 
     #[inline]
@@ -1488,7 +1507,7 @@ impl WindowDelegate {
 
         self.ivars().fullscreen.replace(fullscreen.clone());
 
-        fn toggle_fullscreen(window: &WinitWindow) {
+        fn toggle_fullscreen(window: &NSWindow) {
             // Window level must be restored from `CGShieldingWindowLevel()
             // + 1` back to normal in order for `toggleFullScreen` to do
             // anything