diff --git a/vncviewer/CMakeLists.txt b/vncviewer/CMakeLists.txt
index 5988640..54c9344 100644
--- a/vncviewer/CMakeLists.txt
+++ b/vncviewer/CMakeLists.txt
@@ -13,6 +13,14 @@
   keysym2ucs.c
   vncviewer.cxx)
 
+if(WIN32)
+  set(VNCVIEWER_SOURCES ${VNCVIEWER_SOURCES} win32.c)
+endif()
+
+if(APPLE)
+  set(VNCVIEWER_SOURCES ${VNCVIEWER_SOURCES} cocoa.mm)
+endif()
+
 add_executable(vncviewer ${VNCVIEWER_SOURCES})
 
 target_link_libraries(vncviewer rfb network rdr os Xregion ${FLTK_LIBRARIES} ${GETTEXT_LIBRARIES})
diff --git a/vncviewer/DesktopWindow.cxx b/vncviewer/DesktopWindow.cxx
index 5628142..ce9e9ab 100644
--- a/vncviewer/DesktopWindow.cxx
+++ b/vncviewer/DesktopWindow.cxx
@@ -22,11 +22,22 @@
 #include <string.h>
 
 #include <FL/Fl_Scroll.H>
+#include <FL/x.H>
 
 #include <rfb/LogWriter.h>
 
 #include "DesktopWindow.h"
+#include "OptionsDialog.h"
 #include "i18n.h"
+#include "parameters.h"
+
+#ifdef WIN32
+#include "win32.h"
+#endif
+
+#ifdef __APPLE__
+#include "cocoa.h"
+#endif
 
 using namespace rfb;
 
@@ -56,6 +67,8 @@
 
   setName(name);
 
+  OptionsDialog::addCallback(handleOptions, this);
+
   show();
 
   // The window manager might give us an initial window size that is different
@@ -68,6 +81,12 @@
 
 DesktopWindow::~DesktopWindow()
 {
+  // Unregister all timeouts in case they get a change tro trigger
+  // again later when this object is already gone.
+  Fl::remove_timeout(handleGrab, this);
+
+  OptionsDialog::removeCallback(handleOptions);
+
   // FLTK automatically deletes all child widgets, so we shouldn't touch
   // them ourselves here
 }
@@ -152,7 +171,132 @@
 }
 
 
+int DesktopWindow::handle(int event)
+{
+  switch (event) {
+#ifdef HAVE_FLTK_FULLSCREEN
+  case FL_FOCUS:
+    // FIXME: We reassert the keyboard grabbing on focus/unfocus as FLTK
+    //        releases the grab when someone calls Fl::grab(0)
+  case FL_FULLSCREEN:
+    if (!fullscreenSystemKeys)
+      break;
+
+    if (fullscreen_active())
+      grabKeyboard();
+    else
+      ungrabKeyboard();
+
+    break;
+  case FL_UNFOCUS:
+    // FIXME: We need to relinquish control when the entire window loses
+    //        focus as it seems to interfere with the WM:s ability to handle
+    //        interactions with popups' window decorations.
+    ungrabKeyboard();
+    break;
+#endif
+  case FL_SHORTCUT:
+    // Sometimes the focus gets out of whack and we fall through to the
+    // shortcut dispatching. Try to make things sane again...
+    if (Fl::focus() == NULL) {
+      take_focus();
+      Fl::handle(FL_KEYDOWN, this);
+    }
+    return 1;
+  }
+
+  return Fl_Window::handle(event);
+}
+
+
+void DesktopWindow::grabKeyboard()
+{
+  // Grabbing the keyboard is fairly safe as FLTK reroutes events to the
+  // correct widget regardless of which low level window got the system
+  // event.
+
+  // FIXME: Push this stuff into FLTK.
+
+#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);
+  if (ret != 0)
+    vlog.error(_("Failure grabbing keyboard"));
+#else
+  int ret;
+
+  ret = XGrabKeyboard(fl_display, fl_xid(this), True,
+                      GrabModeAsync, GrabModeAsync, fl_event_time);
+  if (ret) {
+    if (ret == AlreadyGrabbed) {
+      // It seems like we can race with the WM in some cases.
+      // Try again in a bit.
+      if (!Fl::has_timeout(handleGrab, this))
+        Fl::add_timeout(0.500, handleGrab, this);
+    } else {
+      vlog.error(_("Failure grabbing keyboard"));
+    }
+  }
+#endif
+}
+
+
+void DesktopWindow::ungrabKeyboard()
+{
+  Fl::remove_timeout(handleGrab, this);
+
+#if defined(WIN32)
+  win32_disable_lowlevel_keyboard(fl_xid(this));
+#elif defined(__APPLE__)
+  cocoa_release_display(this);
+#else
+  // FLTK has a grab so lets not mess with it
+  if (Fl::grab())
+    return;
+
+  XUngrabKeyboard(fl_display, fl_event_time);
+#endif
+}
+
+
+void DesktopWindow::handleGrab(void *data)
+{
+  DesktopWindow *self = (DesktopWindow*)data;
+
+  assert(self);
+
+#ifdef HAVE_FLTK_FULLSCREEN
+  if (!fullscreenSystemKeys)
+    return;
+  if (!self->fullscreen_active())
+    return;
+
+  self->grabKeyboard();
+#endif
+}
+
+
 void DesktopWindow::handleClose(Fl_Widget *wnd, void *data)
 {
   exit_vncviewer();
 }
+
+
+void DesktopWindow::handleOptions(void *data)
+{
+  DesktopWindow *self = (DesktopWindow*)data;
+
+#ifdef HAVE_FLTK_FULLSCREEN
+  if (self->fullscreen_active() && fullscreenSystemKeys)
+    self->grabKeyboard();
+  else
+    self->ungrabKeyboard();
+#endif
+}
diff --git a/vncviewer/DesktopWindow.h b/vncviewer/DesktopWindow.h
index e616b05..9378d7b 100644
--- a/vncviewer/DesktopWindow.h
+++ b/vncviewer/DesktopWindow.h
@@ -68,9 +68,18 @@
   // Fl_Window callback methods
   void resize(int x, int y, int w, int h);
 
+  int handle(int event);
+
 private:
+  void grabKeyboard();
+  void ungrabKeyboard();
+
+  static void handleGrab(void *data);
+
   static void handleClose(Fl_Widget *wnd, void *data);
 
+  static void handleOptions(void *data);
+
 private:
   Viewport *viewport;
 };
diff --git a/vncviewer/OptionsDialog.cxx b/vncviewer/OptionsDialog.cxx
index 7a2cf2e..31064ba 100644
--- a/vncviewer/OptionsDialog.cxx
+++ b/vncviewer/OptionsDialog.cxx
@@ -259,6 +259,7 @@
   acceptClipboardCheckbox->value(acceptClipboard);
   sendClipboardCheckbox->value(sendClipboard);
   sendPrimaryCheckbox->value(sendPrimary);
+  systemKeysCheckbox->value(fullscreenSystemKeys);
 
   menuKeyChoice->value(0);
 
@@ -352,6 +353,7 @@
   acceptClipboard.setParam(acceptClipboardCheckbox->value());
   sendClipboard.setParam(sendClipboardCheckbox->value());
   sendPrimary.setParam(sendPrimaryCheckbox->value());
+  fullscreenSystemKeys.setParam(systemKeysCheckbox->value());
 
   if (menuKeyChoice->value() == 0)
     menuKey.setParam("");
@@ -683,6 +685,12 @@
                                                      _("Send primary selection and cut buffer as clipboard")));
   ty += CHECK_HEIGHT + TIGHT_MARGIN;
 
+  systemKeysCheckbox = new Fl_Check_Button(LBLRIGHT(tx, ty,
+                                                    CHECK_MIN_WIDTH,
+                                                    CHECK_HEIGHT,
+                                                    _("Pass system keys directly to server (full screen)")));
+  ty += CHECK_HEIGHT + TIGHT_MARGIN;
+
   menuKeyChoice = new Fl_Choice(LBLLEFT(tx, ty, 150, CHOICE_HEIGHT, _("Menu key")));
 
   menuKeyChoice->add(_("None"), 0, NULL, (void*)0, FL_MENU_DIVIDER);
diff --git a/vncviewer/OptionsDialog.h b/vncviewer/OptionsDialog.h
index d499469..9968331 100644
--- a/vncviewer/OptionsDialog.h
+++ b/vncviewer/OptionsDialog.h
@@ -105,6 +105,7 @@
   Fl_Check_Button *acceptClipboardCheckbox;
   Fl_Check_Button *sendClipboardCheckbox;
   Fl_Check_Button *sendPrimaryCheckbox;
+  Fl_Check_Button *systemKeysCheckbox;
   Fl_Choice *menuKeyChoice;
 
   /* Misc. */
diff --git a/vncviewer/Viewport.cxx b/vncviewer/Viewport.cxx
index beee8ba..f522ca0 100644
--- a/vncviewer/Viewport.cxx
+++ b/vncviewer/Viewport.cxx
@@ -605,6 +605,13 @@
   const Fl_Menu_Item *m;
   char buffer[1024];
 
+  // FIXME: Hacky workaround for the fact that menus grab and ungrab the
+  //        keyboard. Releasing focus here triggers some events on ungrab
+  //        that DesktopWindow can catch and trigger some voodoo.
+  //        See DesktopWindow::handle().
+  if (window()->contains(Fl::focus()))
+    Fl::focus(NULL);
+
   contextMenu->position(Fl::event_x(), Fl::event_y());
 
   m = contextMenu->popup();
diff --git a/vncviewer/cocoa.h b/vncviewer/cocoa.h
new file mode 100644
index 0000000..3bbe6fa
--- /dev/null
+++ b/vncviewer/cocoa.h
@@ -0,0 +1,25 @@
+/* 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,
+ * USA.
+ */
+
+#ifndef __VNCVIEWER_COCOA_H__
+#define __VNCVIEWER_COCOA_H__
+
+int cocoa_capture_display(Fl_Window *win);
+void cocoa_release_display(Fl_Window *win);
+
+#endif
diff --git a/vncviewer/cocoa.mm b/vncviewer/cocoa.mm
new file mode 100644
index 0000000..589da2d
--- /dev/null
+++ b/vncviewer/cocoa.mm
@@ -0,0 +1,69 @@
+/* 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,
+ * USA.
+ */
+
+#include <FL/Fl.H>
+#include <FL/Fl_Window.H>
+#include <FL/x.H>
+
+#import <Cocoa/Cocoa.h>
+
+int cocoa_capture_display(Fl_Window *win)
+{
+  NSWindow *nsw;
+
+  nsw = (NSWindow*)fl_xid(win);
+
+  // Already captured?
+  if ([nsw level] == CGShieldingWindowLevel())
+    return 0;
+
+  if (CGDisplayCapture(kCGDirectMainDisplay) != kCGErrorSuccess)
+    return 1;
+
+  [nsw setLevel:CGShieldingWindowLevel()];
+
+  return 0;
+}
+
+void cocoa_release_display(Fl_Window *win)
+{
+  NSWindow *nsw;
+  int newlevel;
+
+  CGDisplayRelease(kCGDirectMainDisplay);
+
+  nsw = (NSWindow*)fl_xid(win);
+
+  // Someone else has already changed the level of this window
+  if ([nsw level] != CGShieldingWindowLevel())
+    return;
+
+  // FIXME: Store the previous level somewhere so we don't have to hard
+  //        code a level here.
+#ifdef HAVE_FLTK_FULLSCREEN
+  if (win->fullscreen_active() && win->contains(Fl::focus()))
+    newlevel = NSStatusWindowLevel;
+  else
+#endif
+    newlevel = NSNormalWindowLevel;
+
+  // Only change if different as the level change also moves the window
+  // to the top of that level.
+  if ([nsw level] != newlevel)
+    [nsw setLevel:newlevel];
+}
diff --git a/vncviewer/parameters.cxx b/vncviewer/parameters.cxx
index ff0e49c..3fa2433 100644
--- a/vncviewer/parameters.cxx
+++ b/vncviewer/parameters.cxx
@@ -88,3 +88,8 @@
 StringParameter menuKey("MenuKey", "The key which brings up the popup menu",
                         "F8");
 
+BoolParameter fullscreenSystemKeys("FullscreenSystemKeys",
+                                   "Pass special keys (like Alt+Tab) directly "
+                                   "to the server when in full screen mode.",
+                                   true);
+
diff --git a/vncviewer/parameters.h b/vncviewer/parameters.h
index df4b080..77c5ae9 100644
--- a/vncviewer/parameters.h
+++ b/vncviewer/parameters.h
@@ -50,4 +50,6 @@
 
 extern rfb::StringParameter menuKey;
 
+extern rfb::BoolParameter fullscreenSystemKeys;
+
 #endif
diff --git a/vncviewer/win32.c b/vncviewer/win32.c
new file mode 100644
index 0000000..d75cc57
--- /dev/null
+++ b/vncviewer/win32.c
@@ -0,0 +1,115 @@
+/* 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,
+ * USA.
+ */
+
+#include <windows.h>
+
+static HANDLE thread;
+static DWORD thread_id;
+
+static HHOOK hook = 0;
+static HWND target_wnd = 0;
+
+static int is_system_hotkey(int vkCode) {
+  switch (vkCode) {
+  case VK_LWIN:
+  case VK_RWIN:
+  case VK_SNAPSHOT:
+    return 1;
+  case VK_TAB:
+    if (GetAsyncKeyState(VK_MENU) & 0x8000)
+      return 1;
+  case VK_ESCAPE:
+    if (GetAsyncKeyState(VK_MENU) & 0x8000)
+      return 1;
+    if (GetAsyncKeyState(VK_CONTROL) & 0x8000)
+      return 1;
+  }
+  return 0;
+}
+
+static LRESULT CALLBACK keyboard_hook(int nCode, WPARAM wParam, LPARAM lParam)
+{
+  if (nCode >= 0) {
+    KBDLLHOOKSTRUCT* msgInfo = (KBDLLHOOKSTRUCT*)lParam;
+
+    // Grabbing everything seems to mess up some keyboard state that
+    // FLTK relies on, so just grab the keys that we normally cannot.
+    if (is_system_hotkey(msgInfo->vkCode)) {
+      PostMessage(target_wnd, wParam, msgInfo->vkCode,
+                  (msgInfo->scanCode & 0xff) << 16 |
+                  (msgInfo->flags & 0xff) << 24);
+      return 1;
+    }
+  }
+
+  return CallNextHookEx(hook, nCode, wParam, lParam);
+}
+
+static DWORD WINAPI keyboard_thread(LPVOID data)
+{
+  MSG msg;
+
+  target_wnd = (HWND)data;
+
+  // Make sure a message queue is created
+  PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE | PM_NOYIELD);
+
+  hook = SetWindowsHookEx(WH_KEYBOARD_LL, keyboard_hook, GetModuleHandle(0), 0);
+  // If something goes wrong then there is not much we can do.
+  // Just sit around and wait for WM_QUIT...
+
+  while (GetMessage(&msg, NULL, 0, 0));
+
+  if (hook)
+    UnhookWindowsHookEx(hook);
+
+  target_wnd = 0;
+
+  return 0;
+}
+
+int win32_enable_lowlevel_keyboard(HWND hwnd)
+{
+  // Only one target at a time for now
+  if (thread != NULL) {
+    if (hwnd == target_wnd)
+      return 0;
+
+    return 1;
+  }
+
+  // We create a separate thread as it is crucial that hooks are processed
+  // in a timely manner.
+  thread = CreateThread(NULL, 0, keyboard_thread, hwnd, 0, &thread_id);
+  if (thread == NULL)
+    return 1;
+
+  return 0;
+}
+
+void win32_disable_lowlevel_keyboard(HWND hwnd)
+{
+  if (hwnd != target_wnd)
+    return;
+
+  PostThreadMessage(thread_id, WM_QUIT, 0, 0);
+
+  CloseHandle(thread);
+  thread = NULL;
+}
diff --git a/vncviewer/win32.h b/vncviewer/win32.h
new file mode 100644
index 0000000..0cc1c11
--- /dev/null
+++ b/vncviewer/win32.h
@@ -0,0 +1,30 @@
+/* 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,
+ * USA.
+ */
+
+#ifndef __VNCVIEWER_WIN32_H__
+#define __VNCVIEWER_WIN32_H__
+
+extern "C" {
+
+int win32_enable_lowlevel_keyboard(HWND hwnd);
+void win32_disable_lowlevel_keyboard(HWND hwnd);
+
+};
+
+#endif