Implement on_quit event for global watchers

Fixes #9682

docs/launch.rst

@@ -185,6 +185,14 @@ create :file:`~/.config/kitty/mywatcher.py` and use :option:`launch --watcher` =
         # managing all tabs in a single OS Window.
         ...
 
+    def on_quit(boss: Boss, window: Window, data: dict[str, Any]) -> None:
+        # called when kitty is about to quit. This is called in *global watchers*
+        # only. It is called twice: once before the quit confirmation dialog is
+        # shown (data['confirmed'] will be False) and once after the user has
+        # confirmed quitting (data['confirmed'] will be True). Setting
+        # data['aborted'] to True will abort the quit in both cases.
+        ...
+
 
 Every callback is passed a reference to the global ``Boss`` object as well as
 the ``Window`` object the action is occurring on. The ``data`` object is a dict

kitty/boss.py

@@ -173,7 +173,7 @@ from .utils import (
     timed_debug_print,
     which,
 )
-from .window import CommandOutput, CwdRequest, Window
+from .window import CommandOutput, CwdRequest, Window, global_watchers
 
 if TYPE_CHECKING:
 
@@ -2090,6 +2090,24 @@ class Boss:
 
     quit_confirmation_window_id: int = 0
 
+    def _call_on_quit_watchers(self, data: dict[str, Any]) -> bool:
+        w = self.active_window
+        if w is None:
+            for window in self.window_id_map.values():
+                w = window
+                break
+        if w is None:
+            return True
+        for watcher in global_watchers().on_quit:
+            try:
+                watcher(self, w, data)
+            except Exception:
+                import traceback
+                traceback.print_exc()
+            if data.get('aborted'):
+                return False
+        return True
+
     @ac('win', 'Quit, closing all windows')
     def quit(self, *args: Any) -> None:
         windows = []
@@ -2102,6 +2120,8 @@ class Boss:
         num = num_active_windows if x < 0 else len(windows)
         needs_confirmation = x != 0 and num >= abs(x)
         if not needs_confirmation:
+            if not self._call_on_quit_watchers({'confirmed': True}):
+                return
             set_application_quit_request(IMPERATIVE_CLOSE_REQUESTED)
             return
         if current_application_quit_request() == CLOSE_BEING_CONFIRMED:
@@ -2116,6 +2136,8 @@ class Boss:
                         tab.set_active_window(w)
                         return
             return
+        if not self._call_on_quit_watchers({'confirmed': False}):
+            return
         msg = msg or _('It has {} windows.').format(num)
         w = self.confirm(_('Are you sure you want to quit kitty?') + ' '  + msg, self.handle_quit_confirmation, window=active_window, title=_('Quit kitty?'))
         self.quit_confirmation_window_id = w.id
@@ -2123,6 +2145,10 @@ class Boss:
 
     def handle_quit_confirmation(self, confirmed: bool) -> None:
         self.quit_confirmation_window_id = 0
+        if confirmed:
+            if not self._call_on_quit_watchers({'confirmed': True}):
+                set_application_quit_request(NO_CLOSE_REQUESTED)
+                return
         set_application_quit_request(IMPERATIVE_CLOSE_REQUESTED if confirmed else NO_CLOSE_REQUESTED)
 
     def notify_on_os_window_death(self, address: str) -> None:

kitty/launch.py

@@ -548,6 +548,9 @@ def load_watch_modules(watchers: Iterable[str]) -> Watchers | None:
         w = m.get('on_tab_bar_dirty')
         if callable(w):
             ans.on_tab_bar_dirty.append(w)
+        w = m.get('on_quit')
+        if callable(w):
+            ans.on_quit.append(w)
     return ans
 
 

kitty/window.py

@@ -305,6 +305,7 @@ class Watchers:
     on_cmd_startstop: list[Watcher]
     on_color_scheme_preference_change: list[Watcher]
     on_tab_bar_dirty: list[Watcher]
+    on_quit: list[Watcher]
 
     def __init__(self) -> None:
         self.on_resize = []
@@ -315,6 +316,7 @@ class Watchers:
         self.on_cmd_startstop = []
         self.on_color_scheme_preference_change = []
         self.on_tab_bar_dirty = []
+        self.on_quit = []
 
     def add(self, others: 'Watchers') -> None:
         def merge(base: list[Watcher], other: list[Watcher]) -> None:
@@ -329,12 +331,14 @@ class Watchers:
         merge(self.on_cmd_startstop, others.on_cmd_startstop)
         merge(self.on_color_scheme_preference_change, others.on_color_scheme_preference_change)
         merge(self.on_tab_bar_dirty, others.on_tab_bar_dirty)
+        merge(self.on_quit, others.on_quit)
 
     def clear(self) -> None:
         del self.on_close[:], self.on_resize[:], self.on_focus_change[:]
         del self.on_set_user_var[:], self.on_title_change[:], self.on_cmd_startstop[:]
         del self.on_color_scheme_preference_change[:]
         del self.on_tab_bar_dirty[:]
+        del self.on_quit[:]
 
     def copy(self) -> 'Watchers':
         ans = Watchers()
@@ -346,12 +350,14 @@ class Watchers:
         ans.on_cmd_startstop = self.on_cmd_startstop[:]
         ans.on_color_scheme_preference_change = self.on_color_scheme_preference_change[:]
         ans.on_tab_bar_dirty = self.on_tab_bar_dirty[:]
+        ans.on_quit = self.on_quit[:]
         return ans
 
     @property
     def has_watchers(self) -> bool:
         return bool(self.on_close or self.on_resize or self.on_focus_change or self.on_color_scheme_preference_change
-                    or self.on_set_user_var or self.on_title_change or self.on_cmd_startstop or self.on_tab_bar_dirty)
+                    or self.on_set_user_var or self.on_title_change or self.on_cmd_startstop or self.on_tab_bar_dirty
+                    or self.on_quit)
 
 
 def call_watchers(windowref: Callable[[], Optional['Window']], which: str, data: dict[str, Any]) -> None: