using VNC display(s) to generate images on a webserver

[James Weatherall]

Ehud,

Out of interest, why do you need a -viewonly argument, if you're never going
to use the actual VNC functionality of the server?  Why not just disable
incoming VNC connections instead?

Regards,

Wez @ RealVNC Ltd.
 

> -----Original Message-----
> From: vnc-list-admin "at" realvnc.com 
> [mailto:vnc-list-admin "at" realvnc.com] On Behalf Of Ehud Karni
> Sent: 02 August 2006 15:16
> To: throopw "at" sheol.org
> Cc: paul.robins "at" st.com; throopw "at" sheol.org; 
> larry.brigman "at" gmail.com; vnc-list "at" realvnc.com
> Subject: Re: using VNC display(s) to generate images on a webserver
> 
> On Mon, 31 Jul 2006 11:21:41 Wayne Throop wrote:
> >
> > : Paul ROBINS <paul.robins "at" st.com>
> > : I'm a bit surprised that there have been no other 
> responses :( Xvnc
> > : initally seems very nice to use as a virtual display for 
> running in
> > : batch or cgi X11 apps that need a display.  It's a real 
> shame that you
> > : can't control it a bit more :(
> >
> > But more importantly, I'd suggest using Xvfb instead.  This task is
> > pretty much what it's specialized for, and it won't do any 
> extra work
> > at all besides the X rendering on a bitmap.  It should be 
> lightweight
> > enough you can just start it for each client request, or so 
> I suspect.
> > If not, you'd still have collision and timeout issues just 
> like Xvnc,
> > but they should be addressable the same ways.  And it's part of the
> > standard X.org release (and Xfree86 before it).
> >
> > http://en.wikipedia.org/wiki/Xvfb
> >
> > Note that, if you need to take a peek at the screen, or even use
> > mouse and keyboard at it for debugging, you can use x11vnc 
> or x0vncserver
> > to treat it as a vnc server for debugging, without  having 
> any vnc access
> > overhead during normal operation.
> 
> Pardon me for getting to this thread in the middle. I have to 
> disagree.
> I use VNC for display purpose for over 5 years, also on a web page.
> 
> Here is what I do:
>  1. Create a virtual X by using a modified vncserver script with
>     3 important arguments: -alwaysshared -dontdisconnect -viewonly
>     (for the -viewonly argument which uses my view-only patch, see:
>      http://realvnc.com/pipermail/vnc-list/2000-July/015830.html,
>      http://www.tightvnc.com/whatsnew.html [under 1.2.5] ).
> 
>  2. Run the needed applications (xload, xterm+top, xclock, etc.)
>     with display set to the virtual X created in {1}.
> 
>  3. I use import (from the ImageMagick package) to convert the
>     virtual X to png like this:
>         import -display vncs:3 -silent -window root vnc-3.png
> 
>  4. Since my web server is across the Atlantic, I use ftp to copy
>     this png to the remote server.
> 
> You can see the result (updated every 5 minutes) at:
>     http://t-e-k.biz/VNC/vnc_load.html .
> 
> Hint. You can use xsri (available on GNU/Linux and Cygwin) to set
>       the background of the virtual X created by VNC.
>       I use:  xsri --tile=bg.png --set
> 
> Ehud.
> 
> 
> --
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