Add an option :opt:command_on_bell to run an arbitrary command when a bell occurs

Fixes #1660

docs/changelog.rst

@@ -7,6 +7,9 @@ To update |kitty|, :doc:`follow the instructions <binary>`.
 0.14.1 [future]
 ---------------------
 
+- Add an option :opt:`command_on_bell` to run an arbitrary command when
+  a bell occurs (:iss:`1660`)
+
 - Add support for the underscore key found in some keyboard layouts
   (:iss:`1639`)
 

kitty/child.py

@@ -57,6 +57,13 @@ else:
         return ans
 
 
+def checked_terminfo_dir():
+    ans = getattr(checked_terminfo_dir, 'ans', None)
+    if ans is None:
+        ans = checked_terminfo_dir.ans = terminfo_dir if os.path.isdir(terminfo_dir) else None
+    return ans
+
+
 def processes_in_group(grp):
     gmap = getattr(process_group_map, 'cached_map', None)
     if gmap is None:
@@ -149,6 +156,23 @@ class Child:
         self.stdin = stdin
         self.env = env or {}
 
+    @property
+    def final_env(self):
+        env = getattr(self, '_final_env', None)
+        if env is None:
+            env = self._final_env = default_env().copy()
+            env.update(self.env)
+            env['TERM'] = self.opts.term
+            env['COLORTERM'] = 'truecolor'
+            if self.cwd:
+                # needed incase cwd is a symlink, in which case shells
+                # can use it to display the current directory name rather
+                # than the resolved path
+                env['PWD'] = self.cwd
+            if checked_terminfo_dir():
+                env['TERMINFO'] = checked_terminfo_dir()
+        return env
+
     def fork(self):
         if self.forked:
             return
@@ -164,17 +188,7 @@ class Child:
             remove_cloexec(stdin_read_fd)
         else:
             stdin_read_fd = stdin_write_fd = -1
-        env = default_env().copy()
-        env.update(self.env)
-        env['TERM'] = self.opts.term
-        env['COLORTERM'] = 'truecolor'
-        if self.cwd:
-            # needed incase cwd is a symlink, in which case shells
-            # can use it to display the current directory name rather
-            # than the resolved path
-            env['PWD'] = self.cwd
-        if os.path.isdir(terminfo_dir):
-            env['TERMINFO'] = terminfo_dir
+        env = self.final_env
         env = tuple('{}={}'.format(k, v) for k, v in env.items())
         argv = list(self.argv)
         exe = argv[0]

kitty/config_data.py

@@ -513,6 +513,9 @@ o('bell_on_tab', True, long_text=_('''
 Show a bell symbol on the tab if a bell occurs in one of the windows in the
 tab and the window is not the currently focused window'''))
 
+o('command_on_bell', 'none', option_type=to_cmdline, long_text=_('''
+Program to run when a bell occurs.
+'''))
 # }}}
 
 g('window')  # {{{

kitty/window.py

@@ -306,6 +306,12 @@ class Window:
         return get_boss().active_window is self
 
     def on_bell(self):
+        if self.opts.command_on_bell and self.opts.command_on_bell != ['none']:
+            import subprocess
+            import shlex
+            env = self.child.final_env
+            env['KITTY_CHILD_CMDLINE'] = ' '.join(map(shlex.quote, self.child.cmdline))
+            subprocess.Popen(self.opts.command_on_bell, env=env, cwd=self.child.foreground_cwd)
         if not self.is_active:
             self.needs_attention = True
             tab = self.tabref()