I know this is a two year ago reply. But I have some information which
should help understand what's going on with the spiro.
On Fri, 2020-02-07 at 21:03 +0000, Fred Brennan wrote:
I write from the FontForge project. Of particular interest to me is
spline feature, which was originated around ten years ago by
One thing I'd like to add, (which would benefit both our
is the ability of FontForge to understand the Inkscape Spiro
However, there are several things about the format which to me as an
outsider appear to be defects serious enough that I have no idea how to
even *import* these splines correctly, much less export our Spiro
splines to this format. I would very much like to support the _de
facto_ standard Inkscape has originated of supporting Spiro in SVG, but
I am lost.
... snip ...
I can probably overcome this, although George Williams was right to
be skeptical of this format. There is no way I can see to define a G2
curve in this strange "original-d" format.
So, anywhere you see `original-d` this means that there is a Live Path
Effect (LPE) happening. These are transformational processes which live
in their own element in defs and you can see the id contained within
the `inkscape:path-effect` attribute.
Following this id you come to an inkscape:path-effect element in <defs>
which usually contains all the extra data required for the effect. This
does not just control spiros, but also any of the other many many live
If you were to make a path with just the original-d, you would not have
a spiro in inkscape. At least not an editable one. And you only need
original-d if you want the spiro to continue to be editable.
This format was created to allow inkscape to render SVG 1.1 paths,
while containing much more feature rich path editing. But not intended
for importing from other programs. I'm already aware that Blender has
co-opted the inkscape:groupmode attribute for their svg files (and
never said anything to us) so it's not unheard of to have
Best Regards, Martin Owens