Re: [Gimp-print-devel] Updated spooler for Canon Selphy dye-sub printers

[Solomon P. <pi...@sh...>]

On Tue, Oct 30, 2012 at 12:00:57PM +0100, Johannes Meixner wrote:
> This means that when using CUPS to print to SELPHY ES-series printers,
> a special CUPS backend is needed that implements this
> "intelligent buffering" to send data to those printers
> and it seems the recent version of es_print/selphy_print
> can be used as such a special CUPS backend.

Yes.

> I assume that SELPHY ES-series printers are autodetected/reported
> by the generic CUPS backend "usb" which means end-users use the
> generic CUPS backend "usb" to print to SELPHY ES-series printers
> but that fails because the generic CUPS backend "usb" does not
> implement the "intelligent buffering" that is required
> to send data to those printers.

Yes. It also doesn't support readbacks, deliberately IIRC.

> A precondition for any CUPS backend that end-users can use it
> for their printers (via printer setup tools) is that the backend
> autodetects/reports the printers to which it can send data - i.e.
> the special es_print/selphy_print backend must autodetect/report
> SELPHY ES-series printers.

How is this autodetection supposed to function?  The tool only binds to 
printers it supports, but I'm assuming there's a requirement for an explicit
"probe, detect and report" command with specific behaivor/formatting.

> In this case SELPHY ES-series printers are autodetected/reported by
> two backends, the generic CUPS backend "usb" (which does not work)
> and the special es_print/selphy_print backend (which works).

Yes, or rather, the latter will do this once I know what the rest of the 
stack expects.

> Till Kamppeter already implemented special case handling
> in the generic CUPS backend "usb", for examples see
> http://www.cups.org/str.php?L4128
> and
> http://www.cups.org/str.php?L4191

Interesting; this wasn't there last time I poked around the CUPS 
sources.  I will look into this more carefully after work.

> A precondition is that it does not at all work to send data
> to SELPHY ES-series printers via the generic CUPS backend "usb".

The "usb" backend works for some (older) SELPHY CP printers, but the 
entire ES-series and the newer CP-series (we have a list) require the 
intelligent spooler.  If we know we're going to get a custom backend 
added, IMO the right thing to do is just blacklist all of them from the 
"usb" backend.

I have three of the printers that don't work (All Selphy ES-series); I'm 
lowballing on ebay for six(!) CP-series models for testing purposes;
some that supposedly work with the "usb" backend, some that don't.

 - Solomon
-- 
Solomon Peachy        		       pizza at shaftnet dot org	 
Melbourne, FL                          ^^ (mail/jabber/gtalk) ^^
Quidquid latine dictum sit, altum viditur.