#include <spiroentrypoints.h> and then compile and link with -lspiro
Spiro library for curve design which simplifies drawing of beautiful curves.
libspiro takes an array of spiro control points which can be easier for an artist to create and modify, and then converts these into a series of bezier splines which can then be used in the myriad of ways the world has come to use beziers.
spiroentrypoints.h has technical information on how to connect with libspiro and further information and example code can be found at http://github.com/fontforge/libspiro
Before reporting a problem, please check the libspiro web site to verify that you have the latest version of libspiro
Great care was taken to maintain backwards compatibility so it is recommended to upgrade if you experience problems with earlier libspiro versions.
libspiro originated from spiro code (in 2007) found in ppedit which is a pattern plate editor for Spiro splines. ppedit was/is Copyright (C) 2007 Raph Levien. GNU GPL version 2 or higher. ppedit was later relicensed also as Apache-2 MIT code in May of 2019. This relicensing is fine since all ppedit was written by Raph Levien in 2007. Copyright allows for this. Unfortunately, this re-licensing of ppedit has caused some confusion in assuming that this relicensing also applies to libspiro which is not valid and does not apply.
libspiro was later picked up in 2013 and continued with further development and improvements at http://github.com/fontforge/libspiro
libspiro is now Copyright (C) 2013... as GNU GPL version 3 or higher.
Please see AUTHORS file for everyone involved in creating and improving this libspiro
Further details (on why and what) can also be seen in git history as well as the Changelog and README files.