[cups] some IPP attributes don't work for some printers

[Jacob Marble]

Michael, just curious, what non-standard keywords does CUPS check for? I
found one possible reference in cups/ppd-cache.c
"com.apple.print.preset.output-mode"; are there others?

Jacob

On Wed, Sep 9, 2015 at 1:38 PM, Jacob Marble <jacobmarble at google.com> wrote:

> Thanks
>
> Jacob
>
> On Wed, Sep 9, 2015 at 12:44 PM, Michael Sweet <msweet at apple.com> wrote:
>
>> Jacob,
>>
>> > On Sep 8, 2015, at 7:39 PM, Jacob Marble <jacobmarble at google.com>
>> wrote:
>> >
>> > A PPD for a particular color printer lacks a ColorModel entry, but CUPS
>> > indicates that color printing is possible with:
>> >
>> > color-supported=true
>> > print-color-mode-default=color
>> > print-color-mode-supported=color,monochrome
>> >
>> > So, instead of printing with the ColorModel attribute, I use
>> > print-color-mode=monochrome. But. Color comes out of the printer.
>> >
>> > Digging into other PPD entries, I found this attribute, which *does*
>> > control color vs monochrome in print tests:
>> > *OpenUI *CMAndResolution/Print Color as Gray: PickOne
>> >
>> > Looks like this occurs in a dozen or so HP printers, out of my
>> collection
>> > of about 7000 PPDs from multiple manufacturers.
>> >
>> > How does CUPS decide that this printer should have the print-color-mode
>> > attribute? Is this a bug in CUPS or in the PPD?
>>
>> The PPD.
>>
>> CUPS looks for the ColorDevice keyword in the PPD, and uses that to
>> determine what values of the print-color-mode attribute  are supported.
>> CUPS supports the standard ColorModel plus a handful of non-standard
>> keywords that directly map to it for applying the print-color-mode value,
>> but *not* CMAndResolution (which by its name is likely a non-standard
>> combination of ColorModel and Resolution...)
>>
>> _________________________________________________________
>> Michael Sweet, Senior Printing System Engineer, PWG Chair
>>
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>
>