[cups.general] How does CUPS work?

[Space Ship Traveller]

Thanks for your detailed reply. You have clarified a lot of things for  
me. I have a few more questions.

On 21/05/2009, at 4:32 AM, Michael Sweet wrote:

> On May 20, 2009, at 5:58 AM, Space Ship Traveller wrote:
>> ....
>> I then have a client such as OS X with a local CUPS server which I  
>> can
>> load the printer into. This printer is loaded as IPP with the above
>> URL. I also select the same PPD for use on the client.
>
> Normally you actually want to use no PPD - "-m raw" when adding via  
> the lpadmin command - so that the client grabs the PPD from the  
> server and does no local filtering.

What exactly is filtering? What does the process entail? Does the PPD  
make adjustments to the post script data stream somehow?

> Mac OS X clients currently use a half-way approach for Bonjour  
> shared printers - they copy the PPD to the local system and update  
> it to basically say "I can print all of the standard formats  
> directly" so that there is a local PPD (so you can still show  
> options and queue jobs when you aren't on the server's network) but  
> still get the benefits of server-side option processing.

Does this happen for any other printer type and on other platforms? Or  
is this behaviour unique to Bonjour shared printers?

And we expect in this case that the client will pick up the PPD from  
the server? Is this a reliable behaviour across different platforms?

Is it possible to pull down the PPD from the server given the printer  
URL?

i.e.
http://printserver:631/printers/myprinter/ppd

How is it different between the following cases:
	1) Manually setting the PPD to be the same as what is on the server
	2) Having the client automatically set the PPD to what the server  
supplies

For case (2) Is there some option in the configuration stored  
somewhere to indicate that the server is actually going to do  
"filtering"?

Also, in that case, does the client supply the options from the print  
dialogue form to the server, so it can then process it via the PPD?  
How does this work?

>
>
>> If I have a PPD on a print queue on a server, does the client somehow
>> automatically pick that up?
>
> Normally yes.  If you manually configure an IPP queue, then it  
> doesn't.

If you manually configure an IPP queue as raw, does this not pick up  
the PPD on the server?

Is there documentation about what kinds of queues normally pick up the  
PPD from the server, and what kinds of queues don't?

Is there a way to tell on the client if a PPD is being supplied by the  
server?


Thanks for your time and answers,
Samuel

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