Add tabbed-run control channel to open apps in new tabs

Host listens on a unix socket; tabbed-run sends a command to open it as
a new maximized casilda tab. Spawned children inherit the full
environment plus TABBED_CASILDA_CTRL so tabbed-run works from any tab.

tabbed-run

@@ -0,0 +1,24 @@
+#!/usr/bin/env python3
+import os
+import shlex
+import socket
+import sys
+
+ctrl = os.environ.get("TABBED_CASILDA_CTRL")
+if not ctrl:
+    print(
+        "tabbed-run: TABBED_CASILDA_CTRL not set (run inside a tabbed-casilda terminal)",
+        file=sys.stderr,
+    )
+    sys.exit(1)
+if len(sys.argv) < 2:
+    print("usage: tabbed-run COMMAND [ARGS...]", file=sys.stderr)
+    sys.exit(1)
+payload = (shlex.join(sys.argv[1:]) + "\n").encode()
+try:
+    with socket.socket(socket.AF_UNIX, socket.SOCK_STREAM) as s:
+        s.connect(ctrl)
+        s.sendall(payload)
+except OSError as e:
+    print(f"tabbed-run: cannot reach host: {e}", file=sys.stderr)
+    sys.exit(1)

tabbed_casilda.py

@@ -6,26 +6,17 @@
 # ]
 # ///
 import argparse
-import gi
+import atexit
+import os
 import shlex
 import shutil
 import sys
 
+import gi
+
 gi.require_version("Gtk", "4.0")
 gi.require_version("Casilda", "1.0")
-from gi.repository import GLib, Gtk, Casilda
-
-
-def make_tab(notebook, command):
-    compositor = Casilda.Compositor()
-    compositor.props.maximized = True
-    label = Gtk.Label(label=command)
-    notebook.append_page(compositor, label)
-    argv = shlex.split(command)
-    if not argv:
-        return
-    argv[0] = shutil.which(argv[0]) or argv[0]
-    compositor.spawn_async(None, argv, None, GLib.SpawnFlags.DEFAULT)
+from gi.repository import Gio, GLib, Gtk, Casilda
 
 
 class TabbedCasilda(Gtk.Application):
@@ -33,6 +24,56 @@ class TabbedCasilda(Gtk.Application):
         super().__init__(application_id="local.tabbed-casilda")
         self.win = None
         self.commands = commands
+        self.notebook = None
+        self.ctrl_path = os.path.join(
+            os.environ.get("XDG_RUNTIME_DIR", "/tmp"), "tabbed-casilda.sock"
+        )
+
+    def add_tab(self, command, ctrl_spawn=False):
+        compositor = Casilda.Compositor()
+        compositor.props.maximized = True
+        label = Gtk.Label(label=command)
+        self.notebook.append_page(compositor, label)
+        argv = shlex.split(command)
+        if not argv:
+            return
+        argv[0] = shutil.which(argv[0]) or argv[0]
+        repo_dir = os.path.dirname(os.path.abspath(__file__))
+        env = dict(os.environ)
+        env["PATH"] = f"{repo_dir}:{env.get('PATH', '')}"
+        env["TABBED_CASILDA_CTRL"] = self.ctrl_path
+        if ctrl_spawn:
+            env["G_APPLICATION_NON_UNIQUE"] = "1"
+        envp = [f"{k}={v}" for k, v in env.items()]
+        compositor.spawn_async(None, argv, envp, GLib.SpawnFlags.DEFAULT)
+
+    def start_control_channel(self):
+        try:
+            os.unlink(self.ctrl_path)
+        except FileNotFoundError:
+            pass
+        service = Gio.SocketService()
+        address = Gio.UnixSocketAddress.new(self.ctrl_path)
+        service.add_address(
+            address, Gio.SocketType.STREAM, Gio.SocketProtocol.DEFAULT, None
+        )
+        service.connect("incoming", self.on_incoming)
+        service.start()
+        self.ctrl_service = service
+        atexit.register(self.cleanup_socket)
+
+    def cleanup_socket(self):
+        try:
+            os.unlink(self.ctrl_path)
+        except FileNotFoundError:
+            pass
+
+    def on_incoming(self, service, connection, source_object):
+        stream = Gio.DataInputStream.new(connection.get_input_stream())
+        line, _ = stream.read_line()
+        if line:
+            self.add_tab(line.decode(), ctrl_spawn=True)
+        return False
 
     def do_activate(self):
         if self.win:
@@ -46,8 +87,10 @@ class TabbedCasilda(Gtk.Application):
         )
         nb = Gtk.Notebook()
         win.set_child(nb)
+        self.notebook = nb
+        self.start_control_channel()
         for command in self.commands:
-            make_tab(nb, command)
+            self.add_tab(command)
         win.present()
         self.win = win