Learn Cygwin / Using Cygwin X Windows

Cygwin includes optional software to run the X Windows windowing environment found on Linux. X Windows is a technology that interfaces software programs with the operating systems' graphical resources. Installing and enabling X Windows can also allow display on the local computer of programs running on remote systems.

An example of X Windows programs are Python scripts that use the Qt5 windowing packages. The Open Water Foundation GeoProcessor software is an example of such software.

• Install X Windows Software
• Starting the X Windows Server
• Running X Windows Programs

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Install X Windows Software

To use X Windows, make sure to install necessary X11 software as indicated in the Installation Section.

Starting the X Windows Server

In order to run X Windows software, the X Windows server software must be run. The server only needs to be started once. The X Windows server can be started manually via the Start / Cygwin-X / XWin Server menu. Once started, the server process will be indicated with an icon in the System Tray at the bottom of the desktop, as shown as the "X" icons in the following image. Note the server display information :0.0 in the image.

The Windows Task Manager can be run and will list the X Windows server processes as shown in the following figure (see xinit.exe, XWin.exe, and xwin-xdg-menu.exe processes).

Once the X Windows server is running, programs that use X Windows graphics can communicate with the server to display graphical output.

Running X Windows Programs

A program that uses X Windows must set the DISPLAY environment variable, which indicates to the X Windows server the window on which the application should display. Typically this is done by running a Cygwin terminal and setting the environment variable in that window, for example:

$ export DISPLAY=":0.0"

To minimize the need for software users to deal with X Windows server configuration, a shell script can be used to configure the environment and run software. For example, the following script is used to run the Open Water Foundation GeoProcessor (see the source code in GitHub):

# Set the DISPLAY variable needed for X windows
checkXWindowsDisplay() {
    if [ -z "$DISPLAY" ]; then
        # DISPLAY environment variable is not set so set it
        # - assume running X server and program on one computer
        echo "Setting DISPLAY=:0.0 to work with X Windows server"
        export DISPLAY=:0.0
    else
        # DISPLAY already set
        echo "Using DISPLAY=$DISPLAY for X Windows server."
    fi
}

# Check to make sure the X Windows Server is running
# - currently only check on Cygwin since if running on Linux X Windows is usually running
# - if the check is not performed and X Windows server is not running, will probably see:
#   "Could not connect to any X display"
checkXWindowsServer() {
    if [ ${operatingSystem} = "cygwin" ]; then
        # Check for XWin process
        xwinProcess=$(ps | grep -i XWin)
        if [ -z "${xwinProcess}" ]; then
            echo ""
            echo "It appears that the X Windows server is not running on Cygwin."
            xserverPath="/cygdrive/C/ProgramData/Microsoft/Windows/Start Menu/Programs/Cygwin-X/XWin Server.lnk"
            if [ -f "${xserverPath}" ]; then
                # Windows shortcut exists in the normal location.
                # Run it to start the X Windows server
                echo "Starting X Windows server by running:"
                echo "  cygstart ${xserverPath}"
                # See the following about running a Windows shortcut from Cygwin:
                # https://superuser.com/questions/790128/cygwin-to-execute-windows-shortcut-files-lnk
                cygstart "${xserverPath}"
                # Have to wait a bit for the X Windows server to start
                # - Loop for 10 seconds and if that is not enough continue and see what happens
                startSeconds=$(date +%s)
                while [ "1" = "1" ]; do
                    # Sleep 1 second to give X Windows server time to start
                    sleep 1
                    # See if the X Windows server process is found
                    xwinProcess=$(ps | grep -i XWin)
                    if [ ! -z "${xwinProcess}" ]; then
                        # X Windows server process is found
                        break
                    else
                        # See if 10 seconds has passed and if so break, assuming process won't start
                        nowSeconds=$(date +%s)
                        timediff=$(expr $nowSeconds - $startSeconds)
                        if [ "${timediff}" -gt "10" ]; then
                            break
                        fi
                    fi
                done
                echo "If still get errors, try starting manually with Start / Cygwin-X / XWin Server"
            else
                echo "Cannot determine how to automatically start the X Windows Server"
                echo "If get an error running GeoProcessor, try starting X Windows server manually with Start / Cygwin-X / XWin Server"
            fi
        fi
    fi
}