Oops, sorry for the typo in my first paragraph. Here's my previous post with a corrected first paragraph:
The initial version of my application (written in scheme) does not use the sane api directly, but utilizes scanimage and scanadf to perform scanning. In a future release, I would like to use the sane api directly for better control. Although I have a number of years of experience programming C/C++/Java, I now prefer to use scheme for most of my programming. After briefly looking at the sane api, I noticed that callbacks are sometimes used. I am aware of a number of ways and various ffi libraries to handle callbacks from non-C to C, but it sure would be nice if the sane API was a little more non-C friendly. Specifically, when a callback pointer is required, why not also require a "user data" void pointer (or perhaps an integer id) that would be returned untouched to the callback as a parameter? This would allow non-C languages to interface more easily to the sane api. A thin C interface layer could then use one callback dispatcher to handle all C callbacks. The callback dispatcher could use stdarg.h to process the other args or perhaps they could be passed to the callback using a count and array. In the future, I would be happy to contribute a scheme->sane interface library to the sane project, but it sure would be nice if the sane api was more non-C friendly. Peter
