From 3480c99b3ed7f06b88b3493134f5bc6303ff4e04 Mon Sep 17 00:00:00 2001
From: Marco Arnulfo <marcoarnulfo1@gmail.com>
Date: Mon, 12 Oct 2026 23:58:13 +0200
Subject: [PATCH] macOS: closing the window ends the process in on_exit, as
 menu Quit does (fixes #1331)

The close button let eframe drop the window while AppKit's run loop was
still running; AccessKit restored the content view's class and AppKit's
Touch Bar KVO observer threw on the next display cycle. on_exit now ends
the process on macOS once settings and library are saved and background
work has stopped, as #444 does for Quit from the menu bar. Same fix as
storytold/gridcraft#117.
---
 apps/lightcraft/src/main.rs | 39 +++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/apps/lightcraft/src/main.rs b/apps/lightcraft/src/main.rs
index c9b9696e1..b206c58f1 100644
--- a/apps/lightcraft/src/main.rs
+++ b/apps/lightcraft/src/main.rs
@@ -87,6 +87,16 @@ impl eframe::App for App {
         if !self.0.shutdown(EXIT_WAIT) {
             log::warn!("quit: background work was still running after {EXIT_WAIT:?}");
         }
+        // macOS (#1331): end the process here, before eframe tears the window down, as Quit from
+        // the menu bar already does (PR #444). AccessKit's macOS adapter subclasses the window's
+        // content view and restores its class on teardown; AppKit's Touch Bar support observes
+        // that view (KVO), so in the next display cycle `-[_NSTouchBarFinderObservation
+        // invalidate]` throws "not registered" and closing the window ends in a crash report.
+        // Nothing after this is needed: settings and library are saved, background work has
+        // stopped and the log file is unbuffered. `on_exit` only runs once the app exists, so a
+        // renderer that fails to start still relaunches on the next one (`window_gpu`).
+        #[cfg(target_os = "macos")]
+        std::process::exit(0);
     }
 }
 
@@ -1207,6 +1217,35 @@ mod tests {
         assert!(loaded.is_some() && warning.is_none());
         let _ = std::fs::remove_dir_all(&d);
     }
+
+    /// #1331: on macOS the process ends inside `on_exit`, before eframe would tear the window down.
+    /// The check runs in a child (this test binary again), since on macOS it ends the process.
+    #[test]
+    fn on_exit_ends_the_process_on_macos() {
+        if std::env::var_os("LIGHTCRAFT_TEST_ON_EXIT").is_some() {
+            let app = LightcraftApp::new(lightcraft_engine::Session::new(), Services::default());
+            let mut app = App(
+                app,
+                PrefsWriter::default(),
+                #[cfg(target_os = "macos")]
+                None,
+            );
+            println!("calling on_exit");
+            eframe::App::on_exit(&mut app, None);
+            println!("on_exit returned");
+            return;
+        }
+        let out = std::process::Command::new(std::env::current_exe().unwrap())
+            .args(["--exact", "tests::on_exit_ends_the_process_on_macos", "--nocapture"])
+            .env("LIGHTCRAFT_TEST_ON_EXIT", "1")
+            .env("LIGHTCRAFT_NO_PREFS", "1")
+            .output()
+            .unwrap();
+        let stdout = String::from_utf8_lossy(&out.stdout);
+        assert!(out.status.success(), "{stdout}");
+        assert!(stdout.contains("calling on_exit"), "the child didn't run the test: {stdout}");
+        assert_eq!(stdout.contains("on_exit returned"), !cfg!(target_os = "macos"), "{stdout}");
+    }
 }
 
 #[cfg(test)]