[sane-devel] Are options consistent across all backends?

[m. allan noah]

On Thu, May 21, 2009 at 1:24 PM, Mark Pemburn <mark at pemburn.com> wrote:
> Hi All,
>
>   The marvels of the SANE standard are starting to become clearer to me and
> I'm making good progress in getting and setting the various device options
> in my OS X interface project.  However, since I have only the one Canon
> N670U scanner to play with (at the moment, anyhow -- I'm borrowing a Fujitsu
> fi5110c from a client), I have no way to compare how options are treated
> from one device to another.  Should I be able to assume that say, the
> "resolution" option will _always_ have a constraint type of
> SANE_CONSTRAINT_RANGE with a "min", "max" and a "quant" showing the steps
> between or that "mode" will consistently provide a string list of supported
> modes?  If not, are there any guidelines that would help the interface
> programmer work around such things?

The only 'standard' options are the 'well-known' options listed in the
sane spec, and that is sometimes just the names. But, a backend is
free to exclude those options, or implement them in a different way.

For instance, the fujitsu backend shows the resolution as
SANE_CONSTRAINT_RANGE when your machine supports it, but for older
machines, you will get a SANE_CONSTRAINT_WORD_LIST, since they only
support a few fixed resolutions. So, dont assume anything :)

The reason that the options are so descriptive is exactly so that you
WONT have to code things specific to that option. That said- there is
still some room for improvement/consistency.

allan
-- 
"The truth is an offense, but not a sin"