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

[Olaf Meeuwissen]

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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?
 - How would one use libsane to do that for that matter?
 - 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?
 - How does this relate to button handling for non-button sensors such
as, for example, a paper tray empty sensor?

> 	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.

Hope this helps,
- -- 
Olaf Meeuwissen, LPIC-2           FLOSS Engineer -- AVASYS CORPORATION
FSF Associate Member #1962               Help support software freedom
                 http://www.fsf.org/jf?referrer=1962
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