[sane-devel] [sane-commit] [SCM] SANE backends - scanner drivers branch, master, updated. RELEASE_1_0_21-248-gaaa34de

[m. allan noah]

On Mon, Nov 1, 2010 at 8:53 PM, Olaf Meeuwissen
<olaf.meeuwissen at avasys.jp> wrote:
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> On 2010年11月01日 23:45, stef wrote:
>> Le Monday 01 November 2010 14:51:59 m. allan noah, vous avez écrit :
>>> We need a way for authors of button handling programs to figure out
>>> what sensors a scanner exposes. Yes, they can use libsane to query the
>>> options, but then a third user would have to install the button
>>> daemon, just to find out if there are any sensors. I'd rather that
>>> scanimage could tell us.
>
> Not sure I understand the scenario you have in mind.  Care to explain?
> Within that scenario:
>
>  - How would one use scanimage to figure out what sensors a scanner exposes?

In this case- scanimage --all-options

>  - How would one use libsane to do that for that matter?

get options and check the CAP bits.

>  - Why would a button handling program need a button daemon to find out
> if there are any sensors when using libsane if scanimage can do the same
> thing using libsane without that button daemon?

It does not- but as I said above- the third party end user might like
to know if his scanner exposes sensors BEFORE he installs the button
daemon. We have no other program installed as part of sane-backends
which can do this.

>  - How does this relate to button handling for non-button sensors such
> as, for example, a paper tray empty sensor?

A sensor is a sensor, regardless of type- look at the fujitsu,
canon_dr, genesys backends.

>
>>       I think there are different points to answer. First there is a bug to
>> fix: the --help argument (which is geared to scanimage command line usage)
>> shouldn't print command line options that cannot be used.
>
> Agreed.  Read-only SANE options aren't command line options.
>
>>       Second listing all the options a backend provides including buttons is
>> useful. It will better served with a specific argument (--list-options / --
>> list-buttons / --show-options ?). I'll submit a patch that brings such an
>> argument for everyone to review.
>
> Read-only SANE options are just a somewhat odd way for a backend to
> inform the user about some aspect of the device it controls and the
> information may even change over time.  Having a means to show this
> information is definitely required but I doubt this should be made
> scanimage's responsibility.

It is a perfectly logical place, given that it is the only thing
installed as a part of sane-backends...

allan

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