Cygwin/X is a port of the X Window System to Cygwin. Cygwin provides a UNIX-like API on the Win32 platform.

Cygwin tools are, in the words of the Cygwin homepage, "ports of the popular GNU development tools and utilities for Windows 95, 98, and NT. They function by using the Cygwin library which provides a UNIX-like API on top of the Win32 API." Cygwin provides the compiler (gcc), libraries, headers, and other utilities which build and support the operation of Cygwin/X.

[ScheiflerGettys92]

The X Window System, or X, is a network-transparent window system. With X, multiple applications can run simultaneously in windows, generating text and graphics in monochrome or color on a bitmap display. Network transparency means that application programs can run on machines scattered through the network.

An X Server is a program that provides display and user input services to other programs. In comparison, a file server provides other programs with access to file storage devices. File servers are typically located in a remote location and you use the services of a file server from the machine that you are located at. In contrast, an X Server is typically running on the machine that you are located at; display and user input services may be requested by programs running on your machine, as well as by programs running on remote machines.

An X client is a program that utilizes the display and user input services provided by an X Server. X clients may run on the same or disparate machine as the X Server that is providing display and user input services.

The :0.0 part of the DISPLAY variable denote the display and the screen of an X server.

The display is the first number and equals to a running instance of an X server. If it is using TCP/IP for communication it listens on port 6000 + display-number for connections. With local (UNIX domain sockets) it uses the socket /tmp/.X11-unix/Xdisplay-number

The screen denotes different output devices of the X server. You could start XWin.exe with two -screen options and would end up with two X11 windows. Each of them is a different screen. Other X servers open different screens for different monitors connected to the computer.

Cygwin/X supports different formats of the DISPLAY variable

• :0.0 or unix:0.0

  This names a local X server and the communication uses the UNIX domain sockets.

• hostname:0.0

  This names a remote X server and the communication uses the TCP/IP network.

Porting X Window System to Microsoft Windows benefits many people and projects in many ways:

• Prior to Cygwin/X only commercial, closed source X Servers were available for Microsoft Windows.

• An X Server on Windows may be used to display the output of programs running on remote UNIX machines.

• Cygwin/X, in conjunction with Cygwin, provides a complete compatibility layer for compiling and running UNIX applications on Microsoft Windows.

No, Cygwin/X does not have a newsgroup; however, we do have a mailing list. See Q: 1.9.

Yes, Cygwin/X has a mailing list, namely, cygwin-xfree@cygwin.com. Visit the Cygwin Mailing Lists page to subscribe to cygwin-xfree@cygwin.com as well as to read and search an online archive of the mailing list traffic.

Cygwin/X supports Windows 95, Windows 98, Windows Me, Windows NT 4.0, Windows 2000, Windows XP, and Windows Server 2003 as of 2003-12-29.

Cygwin/X requires Cygwin to compile and run. Cygwin is not, as of 2003-12-29, available on Microsoft Windows CE, therefore Cygwin/X is not currently available on Microsoft Windows CE.

The Cygwin/X User's Guide thoroughly documents the installation process. Installation is performed through Cygwin's setup.exe program.

The configfile support was only limited. Because of this and extra dependencies it was removed again. But most of the options which were configurable in the configfile are now available as commandline options. For more information on configuring other keyboard layouts see Q: 4.1.1.

The Cygwin/X User's Guide documents the command line arguments for XWin.exe.

When running in windowed mode or GDI-based fullscreen mode, XWin.exe must run the X Server at whatever display depth Windows is currently using; in these cases the display depth passed on the command line is ignored. XWin.exe only uses the display depth parameter when running in a DirectDraw-based fullscreen mode, as DirectDraw allows applications to change the display resolution and depth when running in fullscreen mode.

Yes. Pass the -emulate3buttons timeout_in_milliseconds parameter to XWin.exe, where timeout_in_milliseconds is the, optional, maximum number of milliseconds between a button release and opposite button press that will trigger an emulated third button press.

This is a setting of the windowmanager used. The default windowmanager twm has no such feature. But with fvwm2 this can be achieved with the this configuration entry:

Focus FocusFollowsMouse

Other windowmanagers (eg. windowmaker) have similar features too.

If you are using the -multiwindow mode you can not set this behaviour in the windowmanager but you can use the TweakUI tool to enable this feature for all windows, not limited to Cygwin/X windows.

There is a keybinding to Ctrl-Alt-BackSpace which is named TerminateServer. Remove this binding and Ctrl-Alt-BackSpace will have no effect.

xmodmap -e "keycode 22 = BackSpace"

You should start XWin.exe with the -multiplemonitors options

XWin.exe uses port 6000/TCP by default. You will have to allow incoming and outgoing traffic on this port even if you are only using local clients. XWin.exe has a builtin access control so you won't have to worry about opening the port. If you are still concerned about security, you may limit the allowed hosts to 127.0.0.1 (localhost) and the local IP addresses.

If you use a different DISPLAY variable check section Q: 1.6. for details about which ports are used. For additional information about firewalls and XDMCP connections check Q: 6.4..

A1:

OpenSSH 3.8 enables untrusted X11 forwarding by default when connecting to an ssh server that supports untrusted X11Forwarding. Most ssh servers for GNU/Linux are versions of OpenSSH that do support untrusted X11Forwarding, so using OpenSSH 3.8 from Cygwin will result in a connection that uses untrusted X11Forwarding by default. You will quickly notice that this is the case if most of your X applications are now killed when you try to copy and paste or if xdpyinfo returns only a fraction of the supported extensions that it does if run locally.

It is easiest to just override untrusted X11Forwarding by passing -Y to ssh in place of -X. The -Y does the same thing as -X, but it enables trusted X11Forwarding for the current connection.

A2:

Before establishing the ssh connection the xserver must be started and the environment variable DISPLAY must be set for ssh.

$ DISPLAY=localhost:0.0 $ export DISPLAY $ ssh -Y remotehost

or

$ DISPLAY=localhost:0.0 ssh -Y remotehost

The parameter -Y enables trusted X11Forwarding. This is available since OpenSSH 3.8. If you have an older version of ssh you will have to use -X.

A3:

Make sure you're not starting ssh with the parameter -x (lowercase). This disables X11Forwarding.

A4:

Check that X11Forwarding is not disabled in the openssh client configuration.

The configfiles are by default ~/.ssh/config and /etc/ssh_config. The file in the home directory overrides settings in the global one.

The configfile is split into various sections starting with "Host wildcard". The section applies to all hosts where wildcard matches the hostname.

If this section contains an entry "ForwardX11 no" then X11Forwarding is disabled. To enable it change the entry to:

ForwardX11 yes

Starting with OpenSSH 3.8 you will need the switch "ForwardX11Trusted yes" in the client configuration to allow remote clients full access to the xserver. Without it some clients will fail with a similar error:

 X Error of failed request: BadAtom (invalid Atom parameter)
  Major opcode of failed request: 18 (X_ChangeProperty)
  Atom id in failed request: 0x114
  Serial number of failed request: 370
  Current serial number in output stream: 372

The commandline switch -Y does the same.

A5:

Check that X11Forwarding is not disabled in the ssh server configuration.

The configfile is by default /etc/ssh/sshd_config. If there is an entry "X11Forwarding no" then X11Forwarding is disabled.

If you have write access to the config file then change it to

X11Forwarding yes

Otherwise ask your you admin to change this for you.

Starting with OpenSSH 3.8 you will need to set "ForwardX11Trusted yes" in the client configuration to allow remote clients full access to the xserver. Without it some clients will fail with a similar error:

 X Error of failed request: BadAtom (invalid Atom parameter)
  Major opcode of failed request: 18 (X_ChangeProperty)
  Atom id in failed request: 0x114
  Serial number of failed request: 370
  Current serial number in output stream: 372

The commandline switch -Y does the same. See also Q: 5.1.

Cygwin/X is sometimes unable to determine which local network interface's address should be reported to the XDMCP server; in these cases you need to pass -from local_host_name_or_ip_address to XWin.exe to specify which interface address to report.

The problem is most likely a wrong DNS (Network name resolution). Make sure your windows host has a hostname which is valid from linux too and an IP address which linux can resolve to that hostname.

If you add a line

192.168.26.1 myhost

to /etc/hosts on the XDMCP server with the IP address and the hostname of your windows host the name resolution should work.

Disabled XDMCP on servers

[Mika Laitio] For security reasons, XDMCP is not enabled by default on most Linux/UNIX/*NIX/*BSD distributions (RedHat, Mandrake, SuSE, FreeBSD, NetBSD, etc.) by default. You have to manually enable remote logins to your X Display Manager (xdm, kdm, or gdm). The location of the proper config file is distribution/OS dependent, but a short list of known config file locations is given in Table 1. You must change the line:

[Xdmcp] Enable=false

to:

[Xdmcp] Enable=true

or for xdm style configuration:

DisplayManager.requestPort: 0

to:

!DisplayManager.requestPort: 0

XDMCP and firewalls

XDMCP will not work correctly if you have a personal firewall installed or the built-in firewall of Windows is activated.

The XDMCP protocol will send and receive data on port 177/UDP. But the actual connections will be made to the local port 6000/TCP. It is safe to allow connections since the xserver has an own security layer. An overview of used ports is given in Table 2.

See Q: 6.3.

Newer versions of GDM have a more complex startup mechanism than the other display manager have. This interferes with the way the clipboard client is started.

See also Q: 6.7. and Q: 6.8.

[David Dawson] For whatever reason, certain versions of Solaris need fonts that are not provided by Cygwin/X; the result is that you may see the Solaris background tile and the hourglass cursor, but the XDM login prompt will never appear. The simplest solution is to point Cygwin/X at the font server that is usually running on the Solaris machine. You'll need a command line similar to the following to start your XDMCP session and to connect to the Solaris font server:

XWin.exe -query solaris_hostname_or_ip_address -fp tcp/solaris_hostname_or_ip_address:7100

The standard port number for a font server is 7100, however, you may need to ask your system administrator what the font server port number is if you cannot connect to a font server on port 7100. It is also possible that your Solaris machine is not running a font server, in which case you will need to consult your Solaris documentation for instructions on how to run a font server.

See also Q: 6.6. and Q: 6.8.

Solaris appears to not support certain display bit depths, such as 24 bits per pixel. Change your Windows display bit depth to 8, 16, or 32 and try logging in again. File a complaint with Sun if this issue is important to you, or change your Solaris machines to use XFree86 instead of the Solaris X Window System.

See also Q: 6.6. and Q: 6.7.

Install the recommended set of patches for your version of Solaris.

See the Linux XDMCP HOWTO for more information about XDMCP.

The Fatal Error is a general error message. More specific information what caused this is available in /tmp/XWin.log. Please check the common error messages in the Section called Error and Warning Messages. If your error is not mentioned proceed with Q: 7.4.

Yes. The Cygwin/X log file is located at /tmp/XWin.log. You will find solutions to the most common error messages in the Section called Error and Warning Messages.

See the Error and Warning Messages section for help with specific error messages. Return to this section if you do not find a specific answer for the error message that you have.

Search the Cygwin/X mailing list archives to see if the error message has already been reported and/or addressed. Report the error message to the Cygwin/X mailing list, how the error message was caused, and the behavior of the X Server after the error message was generated (exit, freeze, etc.), only if the error message has not been reported, if the circumstances that produced the error message are significantly different from other reports, or if you have additional information regarding the error message to contribute. Please include /tmp/XWin.log in your mail. This may help us identify the cause of your problem quicker.

Some bug reports are deliberately ignored by project members if the bug in question was recently dealt with; did you search the mailing list archives for a solution to your problem before submitting your bug report? Some bug reports are ignored if they do not contain sufficient information to understand the situation that produces the bug; did your bug report have enough information? Some bug reports are missed or forgotten, thus some valid bug reports do not receive a reply; simply resubmit such bug reports that have not received a response within 7 days of submission.

Zone Alarm 5 is known to break Cygwin/X. As a result you'll see this line (or a similar) as last output in /tmp/XWin.log

Rules = "xorg" Model = "pc101" Layout = "us" Variant = "(null)" Options = "(null)"

Disabling Zone Alarm will not solve this problem. You can only uninstall Zone Alarm 5 and switch to an earlier version (4.5 is known to work) or use a different personal firewall.

Another reason is /tmp mounted in textmode. This does only happen with the -multiwindow and -clipboard switches because of the extra threads within Cygwin/X.

You can remount /tmp to binmode with these commands:

mount -b "$(cygpath -m /tmp)" /tmp

If this fails with an errormessage stating unsufficient rights, try

mount -b -u "$(cygpath -m /tmp)" /tmp

Most likely you have installed some kind of personal firewall, VPN software or any other software that modifies the TCP/IP stack of Windows. Especially Webwasher and some other filtering software are known to slow down the network traffic.

Some online virus scanners like Symantec Antivirus do slowdown Cygwin/X a lot. They scan every file access and network traffic which causes serious processing overhead beyond that from the X11 protocol and the unix emulation layer.

So far there is no know solution but to disable the virus scanner completely.

[Dr. Edward Wornar] Certain programs that are installed by various drivers and software packages can consume an incredible amount of system resources and processing time. One known example of such a program is ATI2evxx.exe, a utility installed with some ATI Technologies graphics card drivers. Answers That Work has information on ATI2evxx.exe on their Task List Programs - A page. You may want to try disabling, one-by-one, ATI2evxx.exe and other such programs until you find the program that is causing the slowdown.

Microsoft Services for Unix set some environment variables which points Cygwin/X to outdated or not existing files. These variables are

XAPPLRESDIR XCMSDB XKEYSYMDB XNLSPATH

To have Cygwin/X work correctly you have to unset at least XKEYSYMDB.

Reported by Juan Medina, Pavel Rozenboim

see Q: 7.7..

[Gerald S. Williams] The TrackPoint driver tries to send scroll up/down messages to the default scrollbar in a window. Cygwin/X does not use Windows scrollbars for X Client windows, so we must configure the TrackPoint driver to send standard WM_MOUSEWHEEL messages to the Cygwin/X window. This can be done by editing the TrackPoint configuration file that can be found either in %SYSTEM_ROOT%\System32\tp4table.dat or %SYSTEM_ROOT%\System32\tp4scrol.dat. Add the following to the "Pass 0 rules"section:

; X Windows *,*,XWin.exe,*,*,Cygwin/X,WheelStd,0,9

This is a small problem with run.exe. If you start XWin.exe with -nodecoration, -multiwindow or -fullscreen the window will come up normally.

To workaround this add the command

run xsetroot -cursor_name left_ptr -fg white -bg black

to startxwin.bat

Try starting resize.

The problem are programs which treat Num-Lock as modifier similar to Control. The programs expect a plain click but received some strange Num-Lock-Click combination and can't associate this with the action "open menu".

This warning message can be ignored; it does not cause any known problems.

This error is harmless.

Most likely you have started XWin.exe twice with startxwin.bat or startx or a similar script.

if you start multiple instances of XWin.exe you have to start to number them

XWin.exe -query foo XWin.exe :1 -query bar XWin.exe :2 -query blubb

Specifying no number is the same as using :0

If you want another terminal window (which in fact is just a convenient side effect of running startxwin.bat) you should do this by starting xterm from the cygwin shell or from the startmenu entries.

This error occurs for one of two reasons:

1. You do not have the xorg-x11-fnts package installed. This is rarely the problem; but in the event that it is the problem, just rerun Cygwin's setup.exe, select the xorg-x11-fnts package and install it.

2. The mount point for /usr/X11R6/lib/X11/fonts was invalid at the time that Cygwin's setup.exe installed the xorg-x11-fnts package. You can confirm that this is the problem by running mount from a Cygwin shell and checking the disk path returned for the /usr/X11R6/lib/X11/fonts mount point. You have this problem if the mount point is not pointing to a valid folder on your system, or if there are not about 400 files in the misc/ subdirectory of that folder on your system.

   Note: You cannot reliably fix this problem by deleting your Cygwin installation and reinstalling it. The mount points that Cygwin was using will be left in your system settings and the invalid mount point for /usr/X11R6/lib/X11/fonts will be used again when you perform the reinstallation. You SHOULD follow the instructions below to fix the problem.

   To fix the problem, perform the following steps:

   1. Open a Cygwin shell and run umount /usr/X11R6/lib/X11/fonts.

   2. Close the Cygwin shell.

   3. Run Cygwin's setup.exe.

   4. For each of the following packages, if they are marked Keep, then select Reinstall, otherwise leave them as they are:

      • xorg-x11-f100

      • xorg-x11-fcyr

      • xorg-x11-fenc

      • xorg-x11-fnts

      • xorg-x11-fscl

   5. Allow Cygwin's setup.exe to download and reinstall the fonts packages. The key to fixing this problem is that the files were previously untarred into an invalid location; removing the mount point for the fonts directory should result in the files being untarred to a valid location.

These warnings are generally harmless since they indicate that default search paths for fonts do not actually contain fonts; this is only a problem if the misc path does not contain fonts and/or all of the paths do not contain fonts. For example, this message is generally useless if it only notifies you that /usr/X11R6/lib/X11/fonts/100dpi (optional 100 dpi fonts) is being removed.

If you are getting these message and the X Server is also failing to start, then see Q: 8.4. for information on how to fix your fonts.

Programs that you are attempting to use were compiled against a newer version of Cygwin than is currently on your system. Run Cygwin's setup program to update your installation to the latest version.

Reinstall the xorg-x11-bin-dlls package. Make sure not to reinstall any XFree-* packages.

Check if /usr/X11R6/bin/cygX11-6.dll does exist.

Check if $PATH contains /usr/X11R6/bin.

cygwin1.dll uses a shared memory section amongst all loaded copies of cygwin1.dll; unfortunately, the layout and usage of the shared memory section changes between versions of cygwin1.dll. Loading two different versions of cygwin1.dll will cause the shared memory section to become corrupted, which almost always results in an Exception: STATUS_ACCESS_VIOLATION. You must search your filesystem(s) and remove all copies of cygwin1.dll except the copy in /bin. You must remove the different versions of cygwin1.dll even if they are not in your path, as programs that depend on cygwin1.dll attempt to load the file from the local directory before searching other paths; thus, it is rather easy, and common, for multiple versions of cygwin1.dll to become loaded at the same time if they exist on a particular system.

Cygwin/X queries getdtablesize () for the maximum number of client connections allowed; by default Cygwin returns 32 from getdtablesize (). Cygwin/X Server Test Series release Test44, released on 2001-08-15, changes the maximum number of clients from 32 to 1024 by passing the square of getdtablesize () to setdtablesize ().

See Q: 8.9.

Certain classes of software, such as that used for Virtual Private Networking and fire-walling may cause the IP address 127.0.0.1, or other local adapter addresses, to be redirected, to become inoperable in some way, or to be operated in a manner that violates the defined operation of IP address.

As a potential remedy, try removing all instances of such software; this may not always fix the problem though, as some software may leave artifacts even after uninstallation is completed. The only way to be sure that you have not found a Cygwin/X bug is to install Windows on a freshly formatted hard drive, followed by Cygwin and Cygwin/X, and finally add your other software one application at a time until Cygwin/X stops working.

Some products that have been reported to cause problems:

• Aventail Connect

• Zonealarm PC Firewall from Zonelab

Increase your Windows environment space by following the instructions provided by Microsoft.

See Q: 8.12.

Yes, see the Cygwin/X - Ported Software page.

Cygwin/X provides a software interface that is very similar to the software interface provided by GNU/Linux and other UNIX systems. Most software packages will compile on Cygwin/X without any changes at all. To begin with, try to compile a given software package following that package's compilation instructions for GNU/Linux.

One common problem encountered when porting software to Cygwin/X is due to Cygwin's inability to distinguish between files with the same name but different capitalization (e.g. XvMC.h and xvmc.h), which is due to a Windows' limitation.

#include "XvMC.h"

#include "../../../include/extensions/XvMC.h"

Yes. The Cygwin/X Contributor's Guide has step-by-step instructions for obtaining the source, building the source, building debug versions of the source, and even cross-compiling under Linux.

Yes. Emacs and XEmacs are available for Windows; they both understand and preserve UNIX end of line characters.

Only submit patches that have UNIX end of line characters. See Q: 10.2. for information on editors for Windows that are aware of UNIX end of line characters.

Generally it is better for us if you generate your patches against the X.org CVS tree. For example, run cvs -z4 diff -U3 hw/xwin/ from xc/programs/Xserver/ to generate a diff file for all the modified files in hw/xwin/. CVS is smart enough to only generate diffs for files that are in the CVS repository; for example, CVS diff will not create diffs for Emacs temporary files.

In the case that you have modified a single file, create the diff with cvs -z4 diff -U3 file_name.

Submit patches for Cygwin/X to the cygwin-xfree@cygwin.com mailing list.

See Q: 10.3. for more information on generating patches.

The X Window System does not use autoconf because autoconf was not available when the X Window System was started in 1984.

Cygwin/X uses the gcc compiler from the Free Software Foundation. Cygwin/X source code is mostly ANSI C compliant, but we cannot guarantee that Cygwin/X will compile with any other compiler, nor can we afford the time to support compilers other than gcc.

See the GCC Home Page for more information on gcc.

Cross-compiling from a non-Cygwin platform is described in the Cygwin/X Contributor's Guide

See SGML for Windows NT: Setting up a free SGML editing and publishing system on Windows NT/Cygwin by Markus Hoenicka.

Cygwin/X proper isn't covered by a single license, as Cygwin/X is made up of two parts that are covered by distinct licenses: Cygwin and the X Window System.

See Q: 11.2. and Q: 11.3. for more information regarding the licenses that apply to Cygwin/X.

X Window System source code is generally licensed under an X11 style license, which is certified by the Free Software Foundation as compatible with the GNU GPL.

Cygwin source code is licensed under a modified version of the GNU GPL. Cygwin's license modification specifically allows third-party software under an open source license to be linked with Cygwin without requiring that the source code for the third-party software be distributed under the terms of the GNU GPL. Cygwin's developers went to great trouble to obtain this modification and should be thanked for doing so, as without it the modification, Cygwin/X linking to Cygwin would be the subject of endless discussion.

Cygwin/X proper doesn't have a single copyright holder, as Cygwin/X is made up of two parts, namely Cygwin and the X Window System; each part follows a different scheme in regards to who will hold the copyright on source code.

See Q: 11.5. and Q: 11.6. for more information regarding who holds the copyright on Cygwin/X source code.

Each source code file in the X Window System typically has its own license and copyright statement. Therefore, there is not a general rule for determining who holds the copyright on a particular X Window System source file, as each author is free to assign the copyright to someone else, to some group, or to keep the copyright themselves. You must inspect the source code file in question to determine who holds the copyright for that file.

RedHat owns the copyright on the Cygwin source code. RedHat requires that copyright be assigned to RedHat for non-trivial changes to Cygwin. You must fill out a copyright transfer form if you are going to contribute substantial changes to Cygwin.

Motif is a closed source product produced by The Open Group. However, The Open Group released Open Motif on 2000-05-15 under a public license, The Open Group Public License, that allows Open Motif to be distributed with and used on Open Source platforms. As of 2001-07-10, Cygwin/X does not qualify as a platform that Open Motif can be distributed with and used on. However, the Open Motif FAQ states, "[...] we hope to be able to make a distribution under a license complying with the Open Source guidelines sometime in the future. For now this is as close as to Open Source as we could get."

No. A quick search at the United States Patent and Trademark Office for "XWin" turns up one dead record and one live record. The live record is for a logo belonging to a rock crusher manufacturer based out of Belgium. Neither trademark affects Cygwin/X, as the dead record is no longer enforceable, while the live record is in an unrelated and distinct industry; there cannot be confusion between rock crushers and computer programs.