[Printing-architecture] Concept for PPD-less CUPS-spooled printing on Bonjour-discovered network printers

Michael Sweet msweet at apple.com
Mon Jul 29 14:25:13 UTC 2013


On 2013-07-25, at 10:46 AM, Till Kamppeter <till.kamppeter at gmail.com> wrote:
> ...
> 1. The client sends only pages with sizes valid for the printer, so that
> the server does not need to check. This does not allow simply sending an
> arbitrary PDF file at CUPS. A PDF viewer has to prepare the print jobs
> appropriately.

Generally speaking, this is the approach we take in Apple OS's, with arbitrary PDF files getting scaled/centered/rotated to the default media if any rasterization occurs.

> 2. The client has to send a full list of the supported/available paper
> sizes (name, size, tray, ...) to the server along with the job, so that
> the server can use this list instead of a PPD file. In this case, what
> is the syntax of the key=value pairs which I have to send as IPP
> attributes together with the job?

I don't see the client sending any printer capability information to the server with a job; it *might* provide a list of supported sizes (media-supported) or collections (media-col-database) when configuring a local queue, but in general I think it is better for the server to grab its own copy (as needed).

For current CUPS the way you pass this configuration information is with a PPD file. Future versions of CUPS might adopt a different format, e.g. IPP attributes in a file.

> 3. The pdftoippprinter filter requests the printer's capabilities from
> the printer by itselfaccessing the printer via IPP. Should a filter do
> that should it do it somehow through the IPP backend of CUPS? Is it
> possible to do this through the IPP backend of CUPS?


> WDYT? How should one proceed here?

If you are printing through cupsd, you need a PPD.  If you are implementing some other kind of spooler, have the client pass the printer URI and default media size/color mode/type/resolution info.

Michael Sweet, Senior Printing System Engineer, PWG Chair

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