Remove symlinking between winit-appkit and winit-uikit (#4530)

winit-common/Cargo.toml

@@ -20,6 +20,9 @@ xkb = ["dep:xkbcommon-dl", "dep:smol_str"]
 # CoreFoundation
 core-foundation = ["dep:block2", "dep:objc2", "dep:objc2-core-foundation"]
 
+# Foundation
+foundation = ["dep:block2", "dep:objc2", "dep:objc2-foundation"]
+
 [dependencies]
 smol_str = { workspace = true, optional = true }
 tracing.workspace = true
@@ -30,7 +33,7 @@ memmap2 = { workspace = true, optional = true }
 x11-dl = { workspace = true, optional = true }
 xkbcommon-dl = { workspace = true, optional = true }
 
-# CoreFoundation
+# Foundation / CoreFoundation
 block2 = { workspace = true, optional = true }
 objc2 = { workspace = true, optional = true }
 objc2-core-foundation = { workspace = true, optional = true, features = [
@@ -40,6 +43,13 @@ objc2-core-foundation = { workspace = true, optional = true, features = [
     "CFRunLoop",
     "CFString",
 ] }
+objc2-foundation = { workspace = true, optional = true, features = [
+    "std",
+    "block2",
+    "NSNotification",
+    "NSString",
+    "NSOperation",
+] }
 
 [package.metadata.docs.rs]
 all-features = true

winit-common/src/foundation/mod.rs

@@ -0,0 +1,3 @@
+mod notification_center;
+
+pub use self::notification_center::*;

winit-common/src/foundation/notification_center.rs

@@ -0,0 +1,30 @@
+use std::ptr::NonNull;
+
+use block2::RcBlock;
+use objc2::rc::Retained;
+use objc2::runtime::ProtocolObject;
+use objc2_foundation::{
+    NSNotification, NSNotificationCenter, NSNotificationName, NSObjectProtocol,
+};
+
+/// Observe the given notification.
+///
+/// This is used in Winit as an alternative to declaring an application delegate, as we want to
+/// give the user full control over those.
+pub fn create_observer(
+    center: &NSNotificationCenter,
+    name: &NSNotificationName,
+    handler: impl Fn(&NSNotification) + 'static,
+) -> Retained<ProtocolObject<dyn NSObjectProtocol>> {
+    let block = RcBlock::new(move |notification: NonNull<NSNotification>| {
+        handler(unsafe { notification.as_ref() });
+    });
+    unsafe {
+        center.addObserverForName_object_queue_usingBlock(
+            Some(name),
+            None, // No sender filter
+            None, // No queue, run on posting thread (i.e. main thread)
+            &block,
+        )
+    }
+}

winit-common/src/lib.rs

@@ -4,5 +4,7 @@
 pub mod core_foundation;
 #[cfg(feature = "event-handler")]
 pub mod event_handler;
+#[cfg(feature = "foundation")]
+pub mod foundation;
 #[cfg(feature = "xkb")]
 pub mod xkb;