[sane-devel] Setting backend capabilities

[Ralph Little]

Hi,

On 2020-03-07 6:06 p.m., Olaf Meeuwissen wrote:
>
>> Thanks that makes sense to me.
>> Perhaps the SANE spec could be updated to add some clarity in this regard.
> Issue and/or MR welcome at https://gitlab.com/sane-project/standard :-)
>
> That said, I also think SANE_CAP_SOFT_SELECT is the better choice from
> the user point of view.  However, you might consider adding a check for
> the current hardware side setting to sane_control_option() so it can
> signal the frontend in case changes were made hardware side.
>
> # I considered adding a polling loop but that doesn't make much sense.
> # You can only signal the frontend via sane_control_option() that it
> # needs to SANE_INFO_RELOAD_OPTIONS, so checking there is good enough.
>

Ah, I have implemented and checked in the change to make those sensors 
work but as you say, xsane currently does not take account of changes 
made on the hardware which is a shame.
I will look into the SANE_INFO_RELOAD_OPTIONS aspect.

I think most proprietary scan software implementations that I have 
observed use a polling loop of some sort, some utilizing USB INTERRUPT, 
some not.

When I have looked into that, perhaps you would be kind enough to review 
the changes? :D

Cheers,
Ralph