HACKING

Copyright notices
=================

If you make a contribution substantial enough to add or update a copyright
notice on a file, such notice must be mirrored in the AUTHORS file. This is
to make it easy for people to comply to section 6 of the LGPL, which states
that a "work that uses the Library" must include copyright notices from
this library. By providing them all in one place, hopefully we save such
users some time.


USB
===

At the time of development, there are no known consumer fingerprint readers
which do not operate over the USB bus. Therefore the library is designed around
the fact that each driver drivers USB devices, and each device is a USB device.
If we were to ever support a non-USB device, some rearchitecting would be
needed, but this would not be a substantial task.


GLib
====

Although the library uses GLib internally, libfprint is designed to provide
a completely neutral interface to it's application users. So, the public
APIs should never return GLib data types or anything like that.


Two-faced-ness
==============

Like any decent library, this one is designed to provide a stable and
documented API to it's users: applications. Clear distinction is made between
data available internally in the library, and data/functions available to
the applications.

This library is confused a little by the fact that there is another 'interface'
at hand: the internal interface provided to drivers. So, we effectively end
up with 2 APIs:

 1. The external-facing API for applications
 2. The internal API for fingerprint drivers

Non-static functions which are intended for internal use only are prepended
with the "fpi_" prefix.


API stability
=============

No API stability has been promised to anyone: go wild, there's no issue with
breaking APIs at this point in time.


Portability
===========

libfprint is primarily written for Linux. However, I'm interested in
supporting efforts to port this to other operating systems too.

You should ensure code is portable wherever possible. Try and use GLib rather
than OS-specific features.

Endianness must be considered in all code. libfprint must support both big-
and little-endian systems.


Coding Style
============

This project follows Linux kernel coding style but with a tab width of 4.


Documentation
=============

All additions of public API functions must be accompanied with doxygen
comments.

All changes which potentially change the behaviour of the public API must
be reflected by updating the appropriate doxygen comments.


Contributing
============

Patches should be sent to the fprint bugzilla:
https://bugs.freedesktop.org/enter_bug.cgi?product=libfprint

Information about libfprint development repositories can be found here:
http://www.freedesktop.org/wiki/Software/fprint/libfprint

If you're looking for ideas for things to work on, look at the TODO file or
grep the source code for FIXMEs.