[sane-devel] scanner buttons

[Rene Rebe]

Hi,

On: Fri, 9 Jul 2004 09:12:19 -0400 (EDT),
    "m. allan noah" <anoah@pfeiffer.edu> wrote:

> > The user should not be able to toggle the option in the interface .=
..
> =

> do any other backends currently use hard_select? if not, perhaps that=
 =

> description should be updated slightly?

A quick grep only reviels the test.c test backend.

But I think it might be usful as it is now: I think it was intent for
the case you click the ADF button and the user needs to change
s.th. on the scanenr hardware, e.g. connecting the ADF adapter or so
...

Shouldn't be SANE_CAP_SOFT_DETECT enought?:

The option value can be detected by software.  ... If this capability
is set but neither SANE_CAP_SOFT_SELECT nor SANE_CAP_HARD_SELECT are,
then there is no way to control the option.  That is, the option
provides read-out of the current value only.

> > Since there is yet no way to mark it as "auto-pull" / "auto-refresh=
"
> > or whatever I must rely, on the tiny example "buttond" program to
> > reload options with the name "button" periodically. So I have no
> > thread or singalling in the backend.
> =

> i dont understand. is there a separate program that runs, and talks t=
o the =

> backend, and just polls the status of the buttons every few seconds? =
does =

> this program close the scanner and execv() over to a front end when t=
hat =

> happens?

Yes - this is what I guess most users expect: A background "daemon
like" program that closes the sane interface when a button is pressed
and starts the user configured scan, copy, fax, ... application.

I think most backends won't or shouldn't use this options directly -
maybe only the scan button to trigger the scan. But most scanners have
more buttons ...

Ah - btw: The HP 74xx have buttons to change the mode from s/w to
color, to select whether to email as foto or document and last but not
least you can step a number up/down to indicate the copy or scan
count. Any idea how we could add those ;-)?

> > Of course the interface details can be easily changed - and I'm ope=
n
> > for suggestions or interfaace additions to mark to-be-polled option=
s.
> > =

> =

> i think we need a polling capability, though that would mean changes =
to =

> front-ends....

Yes, we should add some polling cap. But since it is just another bit
unused currently. I think adding it should not be a problem: Existing
frontends just do not pull the info then - they have yet no use for
the info anyway.

Sincerely yours,
  Ren=E9 Rebe
    - ROCK Linux stable release maintainer

--  =

Ren=E9 Rebe - Europe/Germany/Berlin
  rene@rocklinux.org rene@rocklinux-consulting.de
http://www.rocklinux.org http://www.rocklinux-consulting.de