[sane-devel] SANE2 standard revisited: message callback

[Henning Meier-Geinitz]

Hi,

On Tue, Dec 10, 2002 at 07:47:08PM +0100, Oliver Rauch wrote:
> On Tuesday 10 December 2002 01:35, Henning Meier-Geinitz wrote:
> > I don't even know how to implement the "simple" callback over the
> > network. For a double callback, oh well. I don't want to think about
> 
> I do not understand where you see the problem with a callback over the 
> network.
> 
> 
> frontend----sane-net=======saned----backend
> 
> backend calls callback of saned. saned sends info about callback to sane-net
> and transmits the text that shall be displayed. sane-net calls callback of 
> frontend. When we do not use any selections then the backend does not
> need a feedback when/if the text is displayed.

After Matto's and mine discussion about the auth_callback I think you
are right. But adding the message callback means that we need to add
at least one parameter to every reply of a SANE_NET RPC that should be
able to display messages. Two, if we add a window (or other reference)
parameter.

Speaking of which functions should be able to call the callback:

At least sane_start, because of the calibration/warm up message

Other options that may make sense?

Which function to use to supply the callback pointer? I propose
sane_open, because then the backend knows, which device calls the
callback.

Bye,
  Henning