diff --git a/vncviewer/DesktopWindow.cxx b/vncviewer/DesktopWindow.cxx

index 47fe8f8..8f387dc 100644

--- a/vncviewer/DesktopWindow.cxx

+++ b/vncviewer/DesktopWindow.cxx

@@ -1,16 +1,16 @@

 /* Copyright (C) 2002-2005 RealVNC Ltd.  All Rights Reserved.

  * Copyright 2011 Pierre Ossman <ossman@cendio.se> for Cendio AB

- * 

+ *

  * This is free software; you can redistribute it and/or modify

  * it under the terms of the GNU General Public License as published by

  * the Free Software Foundation; either version 2 of the License, or

  * (at your option) any later version.

- * 

+ *

  * This software is distributed in the hope that it will be useful,

  * but WITHOUT ANY WARRANTY; without even the implied warranty of

  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

  * GNU General Public License for more details.

- * 

+ *

  * You should have received a copy of the GNU General Public License

  * along with this software; if not, write to the Free Software

  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,

@@ -662,20 +662,16 @@ int DesktopWindow::fltkHandle(int event, Fl_Window *win)

   if (dw && fullscreenSystemKeys) {

     switch (event) {

+    // Focus might not stay with us just because we have grabbed the

+    // keyboard. E.g. we might have sub windows, or we're not using

+    // all monitors and the user clicked on another application.

+    // Make sure we update our grabs with the focus changes.

     case FL_FOCUS:

-      // FIXME: We reassert the keyboard grabbing on focus as FLTK there are

-      //        some issues we need to work around:

-      //        a) Fl::grab(0) on X11 will release the keyboard grab for us.

-      //        b) Gaining focus on the system level causes FLTK to switch

-      //           window level on OS X.

       if (dw->fullscreen_active())

         dw->grabKeyboard();

       break;

     case FL_UNFOCUS:

-      // FIXME: We need to relinquish control when the entire window loses

-      //        focus as it is very tied to this specific window on some

-      //        platforms and we want to be able to open subwindows.

       dw->ungrabKeyboard();

       break;

     }

@@ -729,6 +725,23 @@ void DesktopWindow::fullscreen_on()

   fullscreen();

 }

+#if !defined(WIN32) && !defined(__APPLE__)

+Bool eventIsFocusWithSerial(Display *display, XEvent *event, XPointer arg)

+{

+  unsigned long serial;

+

+  serial = *(unsigned long*)arg;

+

+  if (event->xany.serial != serial)

+    return False;

+

+  if ((event->type != FocusIn) && (event->type != FocusOut))

+   return False;

+

+  return True;

+}

+#endif

+

 void DesktopWindow::grabKeyboard()

 {

   // Grabbing the keyboard is fairly safe as FLTK reroutes events to the

@@ -739,19 +752,24 @@ void DesktopWindow::grabKeyboard()

 #if defined(WIN32)

   int ret;

-  

+

   ret = win32_enable_lowlevel_keyboard(fl_xid(this));

   if (ret != 0)

     vlog.error(_("Failure grabbing keyboard"));

 #elif defined(__APPLE__)

   int ret;

-  

+

   ret = cocoa_capture_display(this, fullScreenAllMonitors);

   if (ret != 0)

     vlog.error(_("Failure grabbing keyboard"));

 #else

   int ret;

+  XEvent xev;

+  unsigned long serial;

+

+  serial = XNextRequest(fl_display);

+

   ret = XGrabKeyboard(fl_display, fl_xid(this), True,

                       GrabModeAsync, GrabModeAsync, CurrentTime);

   if (ret) {

@@ -774,6 +792,16 @@ void DesktopWindow::grabKeyboard()

                      None, None, CurrentTime);

   if (ret)

     vlog.error(_("Failure grabbing mouse"));

+

+  // Xorg 1.20+ generates FocusIn/FocusOut even when there is no actual

+  // change of focus. This causes us to get stuck in an endless loop

+  // grabbing and ungrabbing the keyboard. Avoid this by filtering out

+  // any focus events generated by XGrabKeyboard().

+  XSync(fl_display, False);

+  while (XCheckIfEvent(fl_display, &xev, &eventIsFocusWithSerial,

+                       (XPointer)&serial) == True) {

+    vlog.debug("Ignored synthetic focus event cause by grab change");

+  }

 #endif

 }

@@ -791,8 +819,20 @@ void DesktopWindow::ungrabKeyboard()

   if (Fl::grab())

     return;

+  XEvent xev;

+  unsigned long serial;

+

+  serial = XNextRequest(fl_display);

+

   XUngrabPointer(fl_display, fl_event_time);

   XUngrabKeyboard(fl_display, fl_event_time);

+

+  // See grabKeyboard()

+  XSync(fl_display, False);

+  while (XCheckIfEvent(fl_display, &xev, &eventIsFocusWithSerial,

+                       (XPointer)&serial) == True) {

+    vlog.debug("Ignored synthetic focus event cause by grab change");

+  }

 #endif

 }