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Re: Cannot display through rsh


Ben,

Ben Kim wrote:

If Cygwin is not aware of java, which means the GUI
app should not be able to display on my Windows
machines, then why is it the case that number #1 in my
example works?

You got it about exactly backwards from what Igor told you.


Java for Windows does not understand the X Window System. Java for Windows displays graphics via the Win32 GDI system. Java for UNIX machines displays graphics via the X Window System.

Cygwin/XFree86 is an implementation of the X Window System. Thus, setting DISPLAY on your UNIX machine to point to your Windows machine that is running Cygwin/XFree86 will cause the X graphics to show up under Cygwin/XFree86.

However, the Win32 GDI system is nothing like the X Window System. It was not initially designed to be network transparent like the X Window System. Thus, there is not a simple way to display Windows applications running on a remote machine.

Harold

Meaning, when I'm on Unix, set the
display to Windows, and run the Java GUI, the gui
correctly displays on the Windows machine?

Ben

On Tue, 12 Aug 2003, Ben Kim wrote:


I am trying to call a script located on my Windows

box


from my Unix box through rsh. All the script does

is


run a java GUI application that outputs some
information in standard out.  When I run this script
through rsh, the java process is up and running on
Windows (I also see output, also check task manager)
but the GUI frame does not show up.  On Windows, I
installed cygwin and xfree.  I started X via
xstartwin.  I also xhost + to allow any host to
remotely display on Windows.  I know display isn't

the


problem because if I am on my Unix machine, if I set
the display to Windows, and run the java app locally
on Unix, the app correctly displays on Windows.

Only


if the I'm trying to rsh the same script on Windows
from Unix, this doesn't work.  Another interesting
point is that if I were to change the script on
Windows to run cygwin/xfree xterm instead of the

java


app,  and from Unix rsh the script, the xterm
correctly displays.  But as soon as I put in the

java


app, it does not display.

To summarize:
 1.  From Unix, run java app on Unix, display to
Windows (works)
 2.  From Unix, rsh java app on Windows, display to
Windows (does NOT work)
 3.  From Unix, rsh cygwin xapps (xterm, xclock

etc)


on Windows, display to Windows (works)

Does anyone know what this might be the case? And

is


there any way to get #2 to work?


Ben,

There is no Cygwin-aware Java JDK.  This basically
means that, unlike the
Unix one, the JDK you're using on Windows is not using
the X protocol to
display windows, but rather the Windows GDI one.  In
other words, you
cannot do what you want without a VNC-like tool that
would let you display
*any* Windows native application using X.
        Igor

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