Add a load event for watchers

docs/launch.rst

@@ -128,6 +128,12 @@ create :file:`~/.config/kitty/mywatcher.py` and use :option:`launch --watcher` =
     from kitty.window import Window
 
 
+    def on_load(boss: Boss) -> None:
+        # This is a special function that is called just once when this watcher
+        # module is first loaded, can be used to perform any initializztion/one
+        # time setup.
+        ...
+
     def on_resize(boss: Boss, window: Window, data: Dict[str, Any]) -> None:
         # Here data will contain old_geometry and new_geometry
         # Note that resize is also called the first time a window is created

kitty/launch.py

@@ -423,6 +423,7 @@ def load_watch_modules(watchers: Iterable[str]) -> Optional[Watchers]:
         return None
     import runpy
     ans = Watchers()
+    boss = get_boss()
     for path in watchers:
         path = resolve_custom_file(path)
         m = watcher_modules.get(path, None)
@@ -436,6 +437,9 @@ def load_watch_modules(watchers: Iterable[str]) -> Optional[Watchers]:
                 watcher_modules[path] = False
                 continue
             watcher_modules[path] = m
+            w = m.get('on_load')
+            if callable(w):
+                w(boss)
         if m is False:
             continue
         w = m.get('on_close')