Fix macOS system window tabs sync after merging windows

crates/gpui/src/app.rs

@@ -504,6 +504,38 @@ impl SystemWindowTabController {
         }
     }
 
+    /// Replace the tab group containing the given window with the platform-provided tabs.
+    pub fn sync_tab_group(cx: &mut App, id: WindowId, tabs: Vec<SystemWindowTab>) {
+        if tabs.is_empty() || !tabs.iter().any(|tab| tab.id == id) {
+            return;
+        }
+
+        let synced_tab_ids: FxHashSet<_> = tabs.iter().map(|tab| tab.id).collect();
+        let mut controller = cx.global_mut::<SystemWindowTabController>();
+
+        let existing_group_id = controller
+            .tab_groups
+            .iter()
+            .find_map(|(group_id, group_tabs)| {
+                group_tabs
+                    .iter()
+                    .any(|tab| tab.id == id)
+                    .then_some(*group_id)
+            })
+            .unwrap_or_else(|| controller.tab_groups.keys().max().map_or(0, |id| id + 1));
+
+        controller.tab_groups.retain(|group_id, group_tabs| {
+            if *group_id == existing_group_id {
+                return true;
+            }
+
+            group_tabs.retain(|tab| !synced_tab_ids.contains(&tab.id));
+            !group_tabs.is_empty()
+        });
+
+        controller.tab_groups.insert(existing_group_id, tabs);
+    }
+
     /// Remove a tab from a tab group.
     pub fn remove_tab(cx: &mut App, id: WindowId) -> Option<SystemWindowTab> {
         let mut controller = cx.global_mut::<SystemWindowTabController>();

crates/gpui/src/window.rs

@@ -1640,8 +1640,12 @@ impl Window {
             let mut cx = cx.to_async();
             Box::new(move || {
                 handle
-                    .update(&mut cx, |_, _window, cx| {
-                        SystemWindowTabController::merge_all_windows(cx, handle.window_id());
+                    .update(&mut cx, |_, window, cx| {
+                        if let Some(tabs) = window.platform_window.tabbed_windows() {
+                            SystemWindowTabController::sync_tab_group(cx, handle.window_id(), tabs);
+                        } else {
+                            SystemWindowTabController::merge_all_windows(cx, handle.window_id());
+                        }
                     })
                     .log_err();
             })

crates/gpui_macos/src/window.rs

@@ -735,6 +735,15 @@ unsafe impl Send for MacWindowState {}
 
 pub(crate) struct MacWindow(Arc<Mutex<MacWindowState>>);
 
+fn notify_windows_merged(window_state: Arc<Mutex<MacWindowState>>) {
+    let mut lock = window_state.as_ref().lock();
+    if let Some(mut callback) = lock.merge_all_windows_callback.take() {
+        drop(lock);
+        callback();
+        window_state.lock().merge_all_windows_callback = Some(callback);
+    }
+}
+
 impl MacWindow {
     pub fn open(
         handle: AnyWindowHandle,
@@ -3101,12 +3110,7 @@ extern "C" fn merge_all_windows(this: &Object, _: Sel, _: id) {
         let _: () = msg_send![super(this, class!(NSWindow)), mergeAllWindows:nil];
 
         let window_state = get_window_state(this);
-        let mut lock = window_state.as_ref().lock();
-        if let Some(mut callback) = lock.merge_all_windows_callback.take() {
-            drop(lock);
-            callback();
-            window_state.lock().merge_all_windows_callback = Some(callback);
-        }
+        notify_windows_merged(window_state);
     }
 }