[gdal-dev] argument default value in the C API to GDALAlgorithmArg

[Chris Toney]

Even,
Got it, thanks.

I'm thinking of the case analogous to GDALDataset, OGRGeometry and
others that have a fromHandle() method. That is occasionally helpful,
when we use primarily the C APIs but there is some public C++ method
not exposed in C that we want to use (i.e., "public" via gdal_priv.h
in the case of dataset). But yeah a workaround there too, not needed
often.

WIth GDALAlgorithmArg there is a "hidden" flag that can be accessed
with GDALAlgorithmArg::IsHidden(). It seems to to mean the arg is
hidden in both CLI and non-CLI "application" contexts, i.e., should
not be given as a user option in either context? In the C API there is
GDALAlgorithmArgIsHiddenForCLI() and GDALAlgorithmArgIsOnlyForCLI(),
but with those I can't tell for sure if the arg should be hidden
either way (e.g., "help-doc" but potentially others it looks like).

Chris

On Thu, Aug 7, 2025 at 2:56 AM Even Rouault <even.rouault at spatialys.com> wrote:
>
> Chris,
>
> why would you need it to be exposed ? If it is to workaround missing C
> API entry points, we should add them
>
> Regarding struct GDALAlgorithmHS being exposed in gdalalgorithm.h, this
> is because another GDAL .cpp file needed it, but I think I should create
> instead a gdalalgorithm_priv.h header to move those struct definitions.
> Please don't rely on the internals of struct GDALAlgorithmHS
>
> Even
>
> Le 07/08/2025 à 06:44, Chris Toney a écrit :
> > Hi Even,
> >> If you need this in 3.11, you can define the following implementation
> >> detail in your code
> >>
> >> struct GDALAlgorithmArgHS
> > Could GDALAlgorithmArgHS be defined in gdalalgorithm.h (as struct
> > GDALAlgorithmHS is)?
> >
> > Chris
> >
> >
> > On Mon, Aug 4, 2025 at 2:42 AM Even Rouault <even.rouault at spatialys.com> wrote:
> >> Hi Chris,
> >>
> >> This was indeed missing in the C API. Queued for 3.12 in
> >> https://github.com/OSGeo/gdal/pull/12853
> >>
> >> If you need this in 3.11, you can define the following implementation
> >> detail in your code
> >>
> >> struct GDALAlgorithmArgHS
> >> {
> >>       GDALAlgorithmArg *ptr = nullptr;
> >>
> >>       explicit GDALAlgorithmArgHS(GDALAlgorithmArg *arg) : ptr(arg)
> >>       {
> >>       }
> >> };
> >>
> >> but better conditionalize it to 3.11 only, so that to avoid issues in
> >> later version if we would change the definition of struct GDALAlgorithmArgHS
> >>
> >> and then do things like
> >>
> >> GDALAlgorithmArgH hArg;
> >>
> >> hArg->ptr->GetDefault<std::string>();
> >>
> >> Even
> >>
> >>
> >> Le 04/08/2025 à 03:46, Chris Toney via gdal-dev a écrit :
> >>> Hi,
> >>> In the C API there is GDALAlgorithmArgHasDefaultValue(), but no
> >>> interface to the GetDefault() class method to access the value itself
> >>> when there is one (nor in the Python bindings, AFAICS).
> >>>
> >>> I don't believe there is a fromHandle() method on GDALAlgorithmArg to
> >>> get to the C++ object.
> >>>
> >>> Is there possibly a workaround for that when working through the C API?
> >>>
> >>> Chris
> >>> _______________________________________________
> >>> gdal-dev mailing list
> >>> gdal-dev at lists.osgeo.org
> >>> https://lists.osgeo.org/mailman/listinfo/gdal-dev
> >> --
> >> http://www.spatialys.com
> >> My software is free, but my time generally not.
> >>
> --
> http://www.spatialys.com
> My software is free, but my time generally not.
>