Hi Jürgen,
On 10/20/20 7:40 PM, Jürgen Mellinger wrote:
I would like to add "mssing option to poll ADF state" to what is missing from
the current API.
With the current API, it is not possible to prompt the user with meaningful messages such as
"please put a document into the ADF" vs "there is a paper jam in the ADF" and
similar.
From my experience with eSCL/WSD scanners
1) Polling current ADF state BEFORE scan attempt is not reliable
2) Reporting of ADF-related errors AFTER failed scan attempt is reliable
—Juergen
Am 20.10.2020 um 10:12 schrieb Alexander Pevzner <[email protected]>:
Hi Thierry,
On 10/20/20 9:50 AM, Thierry HUCHARD wrote:
I went to quickly look at sane-2.0: - I agree with @paddy-hack,
making new with old is not necessarily a good thing! - I found that
the difference was in the options. The operations are identical. It
will be easy for a developer to create a gateway from sane-1.0 to
sane-2.0. - The options are hardware dependent and there, some
options are emulatable, others are not. - If sane-2.0 is just the
formatting of the options, why not do it in sane-1.0?
Current API misses some essential things, that cannot be implemented in terms
of options:
- PnP notifications (scanner was connected/disconnected some time after
driver was initialized). This limitation can be worked around by
continuous poll, but this poll drains a battery a generates network/USB
traffic, so it is better to avoid.
- If some scanner is identified by multiple backends, it would be nice
to let user app to automatically choose one of the list. For this
purpose, it would be nice to expose some information regarding scanner
location, before scanner is opened (say, "USB bus X device Y, or NET
addr aaa.bbb.ccc.ddd). It requires adding extra fields to the
SANE_Device structure, which makes it incompatible with SANE 1.0
For the following things we just don't have appropriate SANE_Value_Type:
- Scanner resolution if a form of X*Y pair. This is important, to
support "asymmetrical" resolutions (300*600, for example)
For the following options we don't have enough discipline:
- SANE_NAME_SCAN_SOURCE. There is no common names for ADF simplex/ADF duplex,
ADF front/ADF back
sane_airscan_get_parameters() must be accurate immediately after return from
sane_start(). It is not always possible, unless sane_start() has to wait until
image is available (compare sane-escl and sane-airscan approach).
sane_airscan_get_select_fd() defined with serious mistake: it requires backend
to close select_fd immediately after completion or cancellation of the scan
job. In multi-threaded program closed file descriptor could be immediately
reused for some different purpose by another thread.
There is no possibility to request image in the device-specific "raw" format. I.e.,
if I want PDF and device can return PDF, image still will be repacked PDF->sane
format->PDF.
My list is most likely very incomplete.
--
Wishes, Alexander Pevzner ([email protected])
--
Wishes, Alexander Pevzner ([email protected])
