Use existing Xorg session for chrome-remote-desktop

use_existing_session.patch

Add an option to use the existing Xorg session with
chrome-remote-desktop.

The original idea of the patch: https://superuser.com/a/850359
--- a/chrome-remote-desktop	2024-03-27 16:03:20.518579015 +0000
+++ b/chrome-remote-desktop	2024-03-27 16:17:58.241912847 +0000
@@ -110,6 +110,8 @@
 
 X_LOCK_FILE_TEMPLATE = "/tmp/.X%d-lock"
 FIRST_X_DISPLAY_NUMBER = 20
+EXISTING_X_DISPLAY_FILE_PATH = os.path.join(CONFIG_DIR, "Xsession")
+X_SESSION_FILE_TEMPLATE = "/tmp/.X11-unix/X%d"
 
 # Amount of time to wait between relaunching processes.
 SHORT_BACKOFF_TIME = 5
@@ -738,16 +740,33 @@
       return True
     return False
 
+  def _use_existing_session(self):
+    with open(EXISTING_X_DISPLAY_FILE_PATH) as fh:
+      try:
+        display_raw = fh.readline().rstrip()
+        display = int(display_raw)
+      except ValueError:
+        logging.error("Display must be a number; got: '%s'" % display_raw)
+        sys.exit(1)
+    if not os.path.exists(X_SESSION_FILE_TEMPLATE % display):
+      logging.error("Xorg session file doesn't exist")
+      sys.exit(1)
+    logging.info("Using existing Xorg session: %d" % display)
+    self.child_env["DISPLAY"] = ":%d" % display
+
   def launch_session(self, server_args, backoff_time):
     """Launches process required for session and records the backoff time
     for inhibitors so that process restarts are not attempted again until
     that time has passed."""
     logging.info("Setting up and launching session")
     self._setup_gnubby()
-    self._launch_server(server_args)
-    if not self._launch_pre_session():
-      # If there was no pre-session script, launch the session immediately.
-      self.launch_desktop_session()
+    if os.path.exists(EXISTING_X_DISPLAY_FILE_PATH):
+      self._use_existing_session()
+    else:
+      self._launch_server(server_args)
+      if not self._launch_pre_session():
+        # If there was no pre-session script, launch the session immediately.
+        self.launch_desktop_session()
     self.server_inhibitor.record_started(MINIMUM_PROCESS_LIFETIME,
                                       backoff_time)
     self.session_inhibitor.record_started(MINIMUM_PROCESS_LIFETIME,

Updated the patch. Works for me on Ubuntu 22.04 in a virtual machine. The sound didn’t work, probably because the pipewire version is too old (there’s a check in the code). It’s not clear whether the setup_audio is being called at the moment, but it looks like it should.