Curve support in GEOS C API

[Daniel Baston]

Correct, just for 3.15 and up.

Dan

On Wed, Jan 7, 2026 at 10:18 AM Regina Obe <lr at pcorp.us> wrote:

> So this would just be for GEOS 3.15 and above right?  So projects would
> still need to change if GEOS >= 3.15 to know if curve support is available.
>
>
>
> That’s fine.  But backporting would not be fine.
>
>
>
> *From:* Daniel Baston <dbaston at gmail.com>
> *Sent:* Wednesday, January 7, 2026 10:07 AM
> *To:* GEOS Development List <geos-devel at lists.osgeo.org>
> *Subject:* Curve support in GEOS C API
>
>
>
> Hi,
>
> I have been incrementally adding curve support in GEOS, for example in
> https://github.com/libgeos/geos/pull/1347.  I've been thinking about the
> best way for applications such as QGIS/PostGIS/GDAL to integrate this
> functionality.
>
>
>
> Currently, these applications linearize all geometries before sending them
> to GEOS. That will not be necessary for GEOSNode and a list of functions
> that will likely increase over multiple GEOS releases. It seems cumbersome
> for applications to rely on GEOS version checks to know if linearization is
> needed, so I think GEOS should offer an ability to automatically linearize
> inputs and curvify outputs where needed. The parameters for this conversion
> (and whether to perform it all) could be held by the context handle, and
> controlled with functions like GEOSContext_setCurveToLine([ DISABLED /
> STEP_DEGREES / MAX_DEVIATION ]) and GEOSContext_setLineToCurve([ DISABLED /
> SOME_OTHER_TOLERANCE]). I would also expose a
> GEOSCurveToLine(GEOSGeometry*, params) and GEOSLineToCurve(GEOSGeometry*,
> params).
>
>
>
> If needed, we could also provide a capabilities function that would take a
> function name (or pointer?) and report whether the function supports curves
> in the current GEOS version.
>
>
>
> Does this seem like a reasonable approach?
>
>
>
> Dan
>
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