RE: [hpoj-devel] Scan To

[PASCHAL,DAVID (HP-Roseville,ex1) <dav...@hp...>]

Hi, Allen.

Allen Barnett wrote:
> Of course, I'd like to press the 'Scan To' button and see 'The GIMP'
> appear on the LCD panel and then press 'START SCAN' and have The GIMP
> start up (via ptal-mlcd?) and read the scanned image. Same for
> 'StarOffice'.
Actually, when you push "start scan", the peripheral only sends a small
notification (a PML trap) to the PC indicating that a scan has been
requested; it doesn't actually start the scan at this point.  Software on
the PC has to register and listen for and handle this notification, which
would consist of starting the desired application and starting the scan.
The problem with this scheme is that there are typically various scan
options that need to be adjusted (color vs grayscale, resolution,
contrast/brightness) before starting the scan, possibly on a trial&error
basis.  An "automatic" scan doesn't give you this opportunity.

> I think I understand, though, why this might be
> problematic on a multiuser machine.
The solution could consist of a daemon started by a user (possibly in a
login or X-startup script) that would handle the notification and start the
application, but I don't think it will be easy to tell the started
application (i.e. GIMP or xsane) to also start a scan.  And if multiple
users are logged in, then there could be problems if all users' scan-to
daemons started the application, or if only a "primary" user could use it
but a "secondary" user wanted to.

> Does ptal-mlcd implement 
> any kind of
> security on it's socket?
No.  ptal-mlcd only provides connections to various services on the
peripheral (PML, print, scan, etc.).  AFAIK there isn't a portable way to
implement secure authentication and access controls using Unix-domain
sockets.  Even if there were, I'm sure it would be trivial to work around it
by starting another daemon, or by connecting the peripheral to a JetDirect
print server, which usually lacks security as well.

> You might limit this functionality 
> to whomever
> is logged on to X, though there might be cases where you'd 
> like to scan
> to a batch job, too. Perhaps this is a job for a PAM module, 
> treat it as
> though the scanner was logging in?
Since scan-to was designed for a single-user Windows box, I think that makes
it about as useful under Linux as the "Windows" keys on today's keyboards.
Personally I think it would be much easier to just start the application
first and then start the scan.  That has the added advantage of working on
peripherals that don't have a "scan" button.  :-)

Of course, just because the button says "scan" doesn't mean that it can't do
something else instead in a Windows-free environment.  I suppose there are
lots of possibilities here (remote shutdown/reboot or paging different users
on a system come to mind, not that those are necessarily good ideas, of
course).  The key would be to keep the solution as generic as possible.

David