[sane-devel] option size = 0 allowed ?

[Henning Meier-Geinitz]

Hi,

On Wed, Dec 18, 2002 at 07:30:42AM +0100, Michael Herder wrote:
> from the standard:
> "Member size specifies the size of the option value (in bytes).
> ...
> SANE_TYPE_INT, SANE_TYPE_FIXED: The size must be a positive integer multiple 
> of the size of a SANE_Word. The option value is a vector of length
> size/sizeof(SANE_Word)."
> 
> The umax backend defines an option "halftone pattern" with size 0. Is this 
> allowed? 

I don't think so. While one could argue if 0 is positive (or negative,
or both or neither positive nor negative) the intention here is clear
for me: size > 0. There was a similar discussion on sane-devel years
(?) ago, but I don't remember the conclusion.

> Furthermore, the umax backend changes the option size later. IMHO, that at 
> least isn't allowed, because only the availablity or value of an option may 
> change.

It's not allowed. But at least the mustek backend does it also. And I
don't know an easy work-around if you don't want to specify options
for every combination of halftone pattern dimensions.

Changing constraints is also not allowed in SANE1, but it's done by
quite some backends.

Bye,
  Henning