Allow freeing NSView based on parent window closing notifications.

src/macos/view.rs

@@ -137,6 +137,10 @@ unsafe fn create_view_class() -> &'static Class {
         sel!(viewWillMoveToWindow:),
         view_will_move_to_window as extern "C" fn(&Object, Sel, id),
     );
+    class.add_method(
+        sel!(parentWindowClosing:),
+        parent_window_closing as extern "C" fn(&mut Object, Sel, id),
+    );
     class.add_method(
         sel!(updateTrackingAreas:),
         update_tracking_areas as extern "C" fn(&Object, Sel, id),
@@ -217,6 +221,16 @@ extern "C" fn release(this: &mut Object, _sel: Sel) {
     }
 }
 
+extern "C" fn parent_window_closing(this: &mut Object, _sel: Sel, _: id) {
+    unsafe {
+        let state_ptr: *mut c_void = *this.get_ivar(BASEVIEW_STATE_IVAR);
+
+        if !state_ptr.is_null() {
+            WindowState::stop_and_free(this);
+        }
+    }
+}
+
 extern "C" fn dealloc(this: &mut Object, _sel: Sel) {
     unsafe {
         let class = msg_send![this, class];

src/macos/window.rs

@@ -15,7 +15,7 @@ use core_foundation::runloop::{
 };
 use keyboard_types::KeyboardEvent;
 
-use objc::{msg_send, runtime::Object, sel, sel_impl};
+use objc::{class, msg_send, runtime::Object, sel, sel_impl};
 
 use raw_window_handle::{AppKitHandle, HasRawWindowHandle, RawWindowHandle};
 
@@ -130,8 +130,30 @@ impl Window {
             panic!("Not a macOS window");
         };
 
+        let ns_window = if handle.ns_window.is_null() {
+            unsafe { msg_send![handle.ns_view as *mut Object, window] }
+        } else {
+            handle.ns_window
+        };
+
         let ns_view = unsafe { create_view(&options) };
 
+        if !ns_window.is_null() {
+            unsafe {
+                let notification_center: &Object =
+                    msg_send![class!(NSNotificationCenter), defaultCenter];
+                let notification_name =
+                    NSString::alloc(nil).init_str("NSWindowWillCloseNotification").autorelease();
+                let _: () = msg_send![
+                    notification_center,
+                    addObserver: ns_view
+                    selector: sel!(parentWindowClosing:)
+                    name: notification_name
+                    object: ns_window
+                ];
+            }
+        }
+
         let window = Window {
             ns_app: None,
             ns_window: None,