[sane-standard] More device properties

[abel deuring]

Étienne Bersac wrote:
> Hi,
> 
>> Think about the scanners, where the feeder moves a document onto the
>> glass pane, and where the scanner make an "ordinary" flatbed scan.
>> Here it makes indeed sense to know, from which side a document is
>> moved onto the glass pane: If a frontend has a selection list for
>> document sizes, and if the the scanner's firmware has "no idea"
>> about paper sizes, the frontend must calculate the scan window
>> coordinates for the flatbed area.
> 
> I prefer the backends normalize hardwares : some hardware automatically
> handle paper-size, others don't; this is to the backend to emulate this
> behaviour then, not the frontend.
> 
> I really join allan in this : we should keep only the two simple options
> paper-width and paper-height and let the backend determine if he add to
> modify internally {tl,br}-{x,y} or not.

Not every ADF scanner "knows" about a page width/length, so this
adds some burden on backend developers -- let's hope that they will
accept it ;)

Abel