Hi,
On 2022-08-06 10:35, Thierry Huchard wrote:
Le 6 août 2022 18:17:12 GMT+02:00, Ralph Little <[email protected]> a écrit :
Hi,
I'm having a go at writing my first SANE backend for a learning exercise.
I notice that a few backends that use the functions:
sanei_usb_attach_matching_devices() and sanei_usb_find_devices() require some
context information in the callback function to complete the find function.
This is typically because the backend is looping through a list of known device
configurations and calling the sanei_* function on each one: the callback needs
to know the element in that loop to complete the attach function in the
callback.
This is typically achieved with setting some global variables to be picked up
by the callback function, or searching again through the original loop using
information gleaned from the devicename (such as vendor and product), both of
which are messy and ugly hacks.
I propose that we change the function signature of the functions and the
callback to include a (void *) context pointer:
SANE_Status
sanei_usb_find_devices (SANE_Int vendor, SANE_Int product, void *context,
SANE_Status (*attach) (SANE_String_Const dev, void *context));
void
sanei_usb_attach_matching_devices (const char *name, void *context,
SANE_Status (*attach) (const char *dev, void *context));
Hi Ralph,
Your change may impact proprietary backends (Brother, Canon, ...).
Thierry
That is a good point.
We could introduce additional functions with the above signatures (e.g.
sanei_usb_find_devices2()) but I feel that to be an unsatisfactory solution.
Any other suggestions/comments welcome.
Cheers,
Ralph
