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

[Paul ROBINS]

Thanks for the various posts on this topic but unfortunately none of the 
suggestions cover  my original problem and seem to have missed the point 
a bit ;) which was to find a way to quietly close down an instance of 
Xvnc after a perdiod of inactivity.

Regarding the suggestions; Xvfb. I used this for several years on other 
systems but I don't have it easily available on the platform I have here 
(Solaris 8) and I don't have root access to the system, which is pretty 
much needed if you want to make a sane installation of Xvfb on this 
platform.  I also need to export my image generation code to other 
hosts, where I don't have root access either. Thats one reason why VNC 
is attractive - it's easier to install and configure. Another is that an 
Xvnc server is nice and simple to use/monitor during the testing phase.

Regarding the decription of how to run a kind of batch screen capture 
system using a single Xvnc display, plus ImageMagick, etc. That's not at 
all what I'm doing. In my case the images are generated on the fly based 
on what the users select in the browser. At any time 'n' different users 
may generate any one of many thousands of possible images from data 
files that are updated constantly - I can't do batch processing and I 
dont need any kind of capture software, my own program does this just 
fine. I do need multiple displays (Xvnc servers) to cope with all the 
requests, and a way to close them down.

As I've still not found a solution then I guess I'm going to have to do 
it with a nasty hack - some kind of log of which servers are running and 
which haven't been used for a certain time, then kill them off and hope 
that someone wasn't using it. I was hoping to find a more elegant, 
automatic solution.

Thanks

Paul

Wayne Throop wrote:
> : "Ehud Karni" <ehud "at" unix.mvs.co.il>
> : I have to disagree.
> 
> I'm not sure I understand what you are disagreeing with.  My suggestion
> was that Xvfb would suffice.  Is that what you are disagreeing with, or
> some other point?  Because I don't see anything vnc-specific in your
> list of steps (below).  They would all work with Xvfb.  What am I missing? 
> That is, who's connecting to it via the rfb protocol; none of the steps
> show that, near as I can tell.
> 
> Mind you, there's nothing particularly *wrong* about doing it that way. 
> Xvnc is a perfectly wonderful tool.  I'm just saying I don't see anything
> vnc specific below. 
> 
> : 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
> 
> 
> Wayne Throop   throopw "at" sheol.org
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