Add RFC107 text: Add OGRLayer::IGetExtent() and OGRLayer::ISetSpatial…

…Filter()

doc/source/development/rfc/index.rst

@@ -113,3 +113,4 @@ RFC list
     rfc104_gdal_cli
     rfc105_safe_path_manipulation_functions
     rfc106_update_metadata
+    rfc107_igetextent_isetspatialfilter

doc/source/development/rfc/rfc107_igetextent_isetspatialfilter.rst

@@ -0,0 +1,105 @@
+.. _rfc-107:
+
+=====================================================================
+RFC 107: Add OGRLayer::IGetExtent() and OGRLayer::ISetSpatialFilter()
+=====================================================================
+
+============== =============================================
+Author:        Even Rouault
+Contact:       even.rouault @ spatialys.com
+Started:       2025-02-06
+Status:        Drat
+Target:        GDAL 3.11
+============== =============================================
+
+Summary
+-------
+
+This RFC changes the prototype of the OGRLayer::GetExtent(), GetExtent3D(),
+SetSpatialFilter() and SetSpatialFilterRect() methods.
+
+Motivation
+----------
+
+Originally GetExtent(), SetSpatialFilter() and SetSpatialFilterRect() were
+designed for a single geometry field. When support for multiple geometry fields
+was added per :ref:`rfc-41`, alternate virtual methods were added to accept a
+``int iGeomField`` argument, but this causes slighly repeating code patterns
+in most drivers, and omissions of the boilerplate can cause bugs.
+This RFC proceeds to minor changes to improve the code and reduce slightly its
+amount by 900 lines.
+
+Technical solution
+------------------
+
+The ``OGRErr GetExtent(OGREnvelope*, int bForce = TRUE)`` and
+``OGRErr GetExtent(int iGeomField, OGREnvelope*, int bForce = TRUE)``
+methods are changed to no longer be virtual. Furthermore they are modified to
+accept a ``bool`` type for the ``bForce`` argument. Those non-virtual methods
+validate the value of ``iGeomField`` and delegate the work to a
+``OGRErr IGetExtent(int iGeomField, OGREnvelope*, bool bForce)`` virtual method
+(note the leading ``I`` for interface, consistently with practice for similar
+situations), which has a default implementation in OGRLayer and is
+overriden in drivers that support a more efficient implementation. Overriden
+implementations must take care to call the base IGetExtent() method, and not
+GetExtent() (otherwise infinite recursion would occur).
+
+The same change is done for ``GetExtent3D``, made non-virtual, and with the addition
+of a virtual ``IGetExtent3D`` method.
+
+Similarly, the ``void SetSpatialFilter(OGRGeometry*)``, ``void SetSpatialFilter(int iGeomField, OGRGeometry*)``,
+``void SetSpatialFilterRect(double, double, double, double)`` and
+``void SetSpatialFilterRect(int iGeomField, double, double, double, double)``
+methods which used to be virtual, are changed to no longer be virtual, and their
+return type is changed to be ``OGRErr``. They
+validate the value of ``iGeomField`` and delegate the work to a new
+``OGRErr ISetSpatialFilter(int iGeomField, const OGRGeometry*)`` virtual method,
+which has a default implementation in OGRLayer and is
+overriden in drivers that support a more efficient implementation
+Note that this method returns a ``OGRErr`` to allow drivers to report errors
+(currently they can only emit a CPLError(CE_Failure, ...) message), the leading ``I``
+in the method name, and the ``OGRGeometry*`` argment being made const.
+Overriden implementations must take care to call the base ISetSpatialFilter()
+method, and not SetSpatialFilter() (otherwise infinite recursion would occur).
+
+Impact on drivers
+-----------------
+
+All drivers that implement those methods must be updated.
+
+Backward compatibility
+----------------------
+
+- No impact for the C API
+- Little impact for the user-facing C++ API, which should cause little to no
+  changes in external C++ code. The bForce argument of GetExtent/GetExtent3D
+  is now a ``bool`` instead of a ``int``. SetSpatialFilter/SetSpatialFilterRect
+  now return ``OGRErr`` instead of ``void``.
+- Out-of-tree drivers (in particular the GDAL-GRASS plugin) must adapt for the
+  above changes, also mentionned in MIGRATION_GUIDE.TXT.
+
+Testing
+-------
+
+No specific new tests. Minor adaptions to existing ones.
+
+Documentation
+-------------
+
+- The 2 new virtual methods receive Doxygen documentation.
+- New paragraphs are added in MIGRATION_GUIDE.TXT
+
+Related issues and PRs
+----------------------
+
+* Candidate implementation: https://github.com/OSGeo/gdal/pull/11813
+
+Funding
+-------
+
+Funded by GDAL Sponsorship Program (GSP)
+
+Voting history
+--------------
+
+TBD