[sane-devel] sane_get_devices() is very slow

[Henning Meier-Geinitz]

Hi,

[CC to the list, I guess that was intended :-)]

On Thu, Feb 13, 2003 at 11:18:46AM -0800, Derry Bryson wrote:
[I wrote:]
> > No, sorry. That's not how it works. It only works for TWAIN because
> > the user is forced to manually install a driver for every single
> > scanner and Windows users usally have only one scanner at a single
> > computer. Think about what would happen if all the scanner drivers had
> > been provided by Microsoft together with the operating system and
> > installed by default. If the drivers didn't check for the existance of
> > the devices, the TWAIN list would be endless.
> > 
> 
> I see your point.  I was only looking at the number of backends and not
> really considering how many scanners really are supported.
> 
> I will have to give this more thought.  It doesn't seem like a good idea
> to go through the detection process every time an app requests the device
> list.

Usually it happens only once during the runtime of the application
even if the standard allows that the list changes during runtime.

But keeping a fixed list doesn't work, as devices (especially USB) can
be plugged in and out everytime. In an ideal world, you would plug-in
any (supported) scanner and run the scan application without any other
setup action. That works for most USB scanners nowerdays.
And keep in mind that the device file/address of the device may change
after replugging, so even if you have a list of device files, the
scanner may have changed meanwhile.

Bye,
  Henning