[QGIS-Developer] Feedback on introducing a new (abstract) class: QgsSimpleCurve

[Loïc BARTOLETTI]

+1 from me for the QgsSimpleCurve class like gdal one.

Loïc,

On 27/05/2026 11:27, Germán Carrillo via QGIS-Developer wrote:
>Hi All,
>
>
>In the context of the crowdfunded project to improve Circular Arcs support in
>GEOS/QGIS, between Opengis.ch and Dan Baston from iSciences, we'd like to ask
>you for technical feedback at an early stage of the QGIS implementation.
>
>
>We've come to the conclusion that in order to avoid code duplication in the
>QgsGeos class, when importing/exporting LineString or CircularString geometries
>from/to GEOS (used, e.g., in QgsGeos::fromGeos() and QgsGeos::asGeos()
>methods), we would need to introduce a new abstract class called
>QgsSimpleCurve.
>
>This new class would inherit from QgsCurve and would be the base class for
>QgsLineString and QgsCircularString. Namely, importing/exporting
>QgsCircularString geometries would largely benefit from the existing import/
>export code for QgsLineString, so we'd be reusing as much code as possible.
>
>Moreover, other projects like GDAL/OGR [1] and GEOS itself [2], already have
>SimpleCurve classes to ease implementation, even if a SimpleCurve class is not
>part of the SQL/MM standard.
>
>
>An alternative would be to keep using QgsCurve as the base class, and add some
>methods to it that would be ONLY used by QgsLineString/QgsCircularString,
>ensuring that QgsCompoundCurve returns exceptions when those methods are
>called.
>Other alternatives are also welcome for the discussion, just let us know.
>
>
>Since this decision is one of the building blocks for improving Circular Arcs
>support in QGIS (e.g., for integrating a brand new Geometry Splitter from GEOS,
>expected for the 3.15 release), we'd like to kindly ask for your feedback
>before proceeding with a PR, so that we can assess early whether the community
>estimates this move as risky or as a natural step for the QGIS project.
>
>Also, let us know if a QEP would be needed here, or if we could go on with this
>discussion and then with a well isolated PR.
>Thank you in advance.
>
>
>Regards,
>
>Germán
>-----------
>[1] [1]https://gdal.org/en/stable/doxygen/classOGRSimpleCurve.html
>[2] [2]https://github.com/libgeos/geos/blob/main/include/geos/geom/
>SimpleCurve.h
>
>References:
>
>[1] https://gdal.org/en/stable/doxygen/classOGRSimpleCurve.html
>[2] https://github.com/libgeos/geos/blob/main/include/geos/geom/SimpleCurve.h

>_______________________________________________
>QGIS-Developer mailing list
>QGIS-Developer at lists.osgeo.org
>List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer
>Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer