[sane-devel] Behavior when sane_read() returns SANE_STATUS_EOF?

[Henning Meier-Geinitz]

Hi,

On Tue, Feb 25, 2003 at 11:36:51AM -0500, Matto Marjanovic wrote:
> Suppose a scan is set-up and initiated, and sane_parameters() returns
>  a definite value for 'lines' (i.e., not -1).  What should a backend
>  do if, before that number of lines is delivered, sand_read() returns
>  with SANE_STATUS_EOF?  Will/should the frontend abort the scan, or
>  gracefully truncate the output?  (Or fill the remaining output with
>  black/white?)

Print a warning and ask the user what to do. Or let the user decide by
preferences.

> I guess another version of my question is:  If the backend cannot be
>  *certain* that it will deliver 'lines' lines of data, is it required
>  to set 'lines' to -1?  (Or, can/should it provide the optimistic
>  intended image size, which assumes that the paper is long enough?)

You're speaking about a sheet-fed scanner? I'd use lines = -1 in this
case by default. Maybe add an option "image size" (A4, Legal,
automatic) and use lines = -1 for automatic and a fixed size for the
other settings.

Bye,
  Henning