Use sane default screen size if RANDR not supported

remoting/host/linux/linux_me2me_host.py

 #!/usr/bin/python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Virtual Me2Me implementation.  This script runs and manages the processes
 # required for a Virtual Me2Me desktop, which are: X server, X desktop
 # session, and Host process.
 # This script is intended to run continuously as a background daemon
 # process, running under an ordinary (non-root) user account.
@@ skipping 19 matching lines @@
 import time
 import uuid
 
 LOG_FILE_ENV_VAR = "CHROME_REMOTE_DESKTOP_LOG_FILE"
 
 # This script has a sensible default for the initial and maximum desktop size,
 # which can be overridden either on the command-line, or via a comma-separated
 # list of sizes in this environment variable.
 DEFAULT_SIZES_ENV_VAR = "CHROME_REMOTE_DESKTOP_DEFAULT_DESKTOP_SIZES"
 
-# By default, provide a relatively small size to handle the case where resize-
-# to-client is disabled, and a much larger size to support clients with large
-# or mulitple monitors. These defaults can be overridden in ~/.profile.
+# By default, provide a maximum size that is large enough to support clients
+# with large or multiple monitors. This is a comma-separated list of
+# resolutions that will be made available if the X server supports RANDR. These
+# defaults can be overridden in ~/.profile.
 DEFAULT_SIZES = "1600x1200,3840x1600"
 
+# If RANDR is not available, use a smaller default size. Only a single
+# resolution is supported in this case.
+DEFAULT_SIZE_NO_RANDR = "1600x1200"
+
 SCRIPT_PATH = sys.path[0]
 
 IS_INSTALLED = (os.path.basename(sys.argv[0]) != 'linux_me2me_host.py')
 
 if IS_INSTALLED:
   HOST_BINARY_NAME = "chrome-remote-desktop-host"
 else:
   HOST_BINARY_NAME = "remoting_me2me_host"
 
 CHROME_REMOTING_GROUP_NAME = "chrome-remote-desktop"
@@ skipping 16 matching lines @@
 
 # Thresholds for switching from fast- to slow-restart and for giving up
 # trying to restart entirely.
 SHORT_BACKOFF_THRESHOLD = 5
 MAX_LAUNCH_FAILURES = SHORT_BACKOFF_THRESHOLD + 10
 
 # Globals needed by the atexit cleanup() handler.
 g_desktops = []
 g_host_hash = hashlib.md5(socket.gethostname()).hexdigest()
 
+
 def is_supported_platform():
   # Always assume that the system is supported if the config directory or
   # session file exist.
   if (os.path.isdir(CONFIG_DIR) or os.path.isfile(SESSION_FILE_PATH) or
       os.path.isfile(SYSTEM_SESSION_FILE_PATH)):
     return True
 
   # The host has been tested only on Ubuntu.
   distribution = platform.linux_distribution()
   return (distribution[0]).lower() == 'ubuntu'
 
+
+def get_randr_supporting_x_server():
+  """Returns a path to an X server that supports the RANDR extension, if this
+  is found on the system. Otherwise returns None."""
+  try:
+    xvfb = "/usr/bin/Xvfb-randr"
+    if not os.path.exists(xvfb):
+      xvfb = locate_executable("Xvfb-randr")
+    return xvfb
+  except Exception:
+    return None
+
+
 class Config:
   def __init__(self, path):
     self.path = path
     self.data = {}
     self.changed = False
 
   def load(self):
     """Loads the config from file.
 
     Raises:
@@ skipping 218 matching lines @@
     # Run "xauth add" with |child_env| so that it modifies the same XAUTHORITY
     # file which will be used for the X session.
     ret_code = subprocess.call("xauth add :%d . `mcookie`" % display,
                                env=self.child_env, shell=True)
     if ret_code != 0:
       raise Exception("xauth failed with code %d" % ret_code)
 
     max_width = max([width for width, height in self.sizes])
     max_height = max([height for width, height in self.sizes])
 
-    try:
-      # TODO(jamiewalch): This script expects to be installed alongside
-      # Xvfb-randr, but that's no longer the case. Fix this once we have
-      # a Xvfb-randr package that installs somewhere sensible.
-      xvfb = "/usr/bin/Xvfb-randr"
-      if not os.path.exists(xvfb):
-        xvfb = locate_executable("Xvfb-randr")
+    xvfb = get_randr_supporting_x_server()
+    if xvfb:
       self.server_supports_exact_resize = True
-    except Exception:
+    else:
       xvfb = "Xvfb"
       self.server_supports_exact_resize = False
 
     # Disable the Composite extension iff the X session is the default
     # Unity-2D, since it uses Metacity which fails to generate DAMAGE
     # notifications correctly. See crbug.com/166468.
     x_session = choose_x_session()
     if (len(x_session) == 2 and
         x_session[1] == "/usr/bin/gnome-session --session=ubuntu-2d"):
       extra_x_args.extend(["-extension", "Composite"])
@@ skipping 662 matching lines @@
 
   if options.host_version:
     # TODO(sergeyu): Also check RPM package version once we add RPM package.
     return os.system(locate_executable(HOST_BINARY_NAME) + " --version") >> 8
 
   if not options.start:
     # If no modal command-line options specified, print an error and exit.
     print >> sys.stderr, EPILOG
     return 1
 
+  # If a RANDR-supporting Xvfb is not available, limit the default size to
+  # something more sensible.
+  if get_randr_supporting_x_server():

[Jamie, 2014/05/09 16:41:28]

Can you just use self.server_supports_exact_resize here?

[Lambros, 2014/05/09 19:50:01]

Not here, because this is during main() initialization. That flag is a member of
Desktop and is set in Desktop._launch_x_server().

+    default_sizes = DEFAULT_SIZES
+  else:
+    default_sizes = DEFAULT_SIZE_NO_RANDR
+
   # Collate the list of sizes that XRANDR should support.
   if not options.size:
-    default_sizes = DEFAULT_SIZES
     if os.environ.has_key(DEFAULT_SIZES_ENV_VAR):
       default_sizes = os.environ[DEFAULT_SIZES_ENV_VAR]
     options.size = default_sizes.split(",")
 
   sizes = []
   for size in options.size:
     size_components = size.split("x")
     if len(size_components) != 2:
       parser.error("Incorrect size format '%s', should be WIDTHxHEIGHT" % size)
 
@@ skipping 171 matching lines @@
         else:
           logging.info("Host exited with status %s." % os.WEXITSTATUS(status))
       elif os.WIFSIGNALED(status):
         logging.info("Host terminated by signal %s." % os.WTERMSIG(status))
 
 
 if __name__ == "__main__":
   logging.basicConfig(level=logging.DEBUG,
                       format="%(asctime)s:%(levelname)s:%(message)s")
   sys.exit(main())