Add Xorg+dummy as alternative for Xvfb

remoting/host/curtain_mode_linux.cc

 // 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.
 
 #include "remoting/host/curtain_mode.h"
 
 #include <X11/extensions/XInput.h>
 
 #include "base/callback.h"
 #include "base/macros.h"
@@ skipping 27 matching lines @@
   // attached to the physical console (i.e. impossible to curtain).
   bool activated = IsXvfbSession();
   if (!activated) {
     LOG(ERROR) << "Curtain-mode is not supported when running on non-Xvfb "
                   "X server";
   }
 
   return activated;
 }
 
 bool CurtainModeLinux::IsXvfbSession() {

[Lambros, 2016/05/09 23:24:24]

Rename this to avoid mentioning Xvfb, maybe IsVirtualSession() ?

   // Try to identify an Xvfb session. There's no way to query what X server we
   // are running under, so we check for the Xvfb input devices.
   // TODO(rmsousa): Find a similar way to determine that the *output* is secure.
   Display* display = XOpenDisplay(nullptr);
   int opcode, event, error;
   if (!XQueryExtension(display, "XInputExtension", &opcode, &event, &error)) {
     // If XInput is not available, assume it is not an Xvfb session.
     LOG(ERROR) << "X Input extension not available: " << error;
     XCloseDisplay(display);
     return false;
   }
   int num_devices;
   XDeviceInfo* devices;
   bool found_xvfb_mouse = false;
   bool found_xvfb_keyboard = false;
+  bool found_crd_void_input = false;
   bool found_other_devices = false;
   devices = XListInputDevices(display, &num_devices);
   for (int i = 0; i < num_devices; i++) {
     XDeviceInfo* device_info = &devices[i];
     if (device_info->use == IsXExtensionPointer) {
       if (strcmp(device_info->name, "Xvfb mouse") == 0) {
         found_xvfb_mouse = true;
+      } else if (strcmp(device_info->name,
+                        "Chrome Remote Desktop Input") == 0) {
+        found_crd_void_input = true;
       } else if (strcmp(device_info->name, "Virtual core XTEST pointer") != 0) {
         found_other_devices = true;
         HOST_LOG << "Non Xvfb mouse found: " << device_info->name;
       }
     } else if (device_info->use == IsXExtensionKeyboard) {
       if (strcmp(device_info->name, "Xvfb keyboard") == 0) {
         found_xvfb_keyboard = true;
       } else if (strcmp(device_info->name,
                         "Virtual core XTEST keyboard") != 0) {
         found_other_devices = true;
         HOST_LOG << "Non Xvfb keyboard found: " << device_info->name;
       }
     } else if (device_info->use == IsXPointer) {
       if (strcmp(device_info->name, "Virtual core pointer") != 0) {
         found_other_devices = true;
         HOST_LOG << "Non Xvfb mouse found: " << device_info->name;
       }
     } else if (device_info->use == IsXKeyboard) {
       if (strcmp(device_info->name, "Virtual core keyboard") != 0) {
         found_other_devices = true;
         HOST_LOG << "Non Xvfb keyboard found: " << device_info->name;
       }
     } else {
       found_other_devices = true;
       HOST_LOG << "Non Xvfb device found: " << device_info->name;
     }
   }
   XFreeDeviceList(devices);
   XCloseDisplay(display);
-  return found_xvfb_mouse && found_xvfb_keyboard && !found_other_devices;
+  return (found_xvfb_mouse && found_xvfb_keyboard) != found_crd_void_input

[Jamie, 2016/05/07 00:05:47]

Why are you using != here instead of ||? It makes the code harder to read, and I
don't think we care if we find both.

[rkjnsn, 2016/05/09 16:58:33]

My initial thought was that it should be xor since we'll either be running on
one or the other, but I agree it shouldn't be a problem to use ||, so I'll
switch if you think it's more readable that way.

[Jamie, 2016/05/09 17:08:43]

Xor is unusual enough that it's not immediately clear that "!=" is the
non-bitwise form of "^", which is mostly what makes this hard to read.  I think
"^" would work, and would be clearer, but I think "||" is better.

+      && !found_other_devices;
 }
 
 // static
 std::unique_ptr<CurtainMode> CurtainMode::Create(
     scoped_refptr<base::SingleThreadTaskRunner> caller_task_runner,
     scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner,
     base::WeakPtr<ClientSessionControl> client_session_control) {
   return base::WrapUnique(new CurtainModeLinux());
 }
 
 }  // namespace remoting