Make all Transform methods of OGRCoordinateTransformation and GDALTransformerFunc return FALSE as soon as one point fails to transform

[rouault]

Fixes #11817

Kind of a breaking change, but the current behavior was highly inconsistent and hard to reason about.

New paragraph in MIGRATION_GUIDE.TXT:

• The following methods OGRCoordinateTransformation::Transform(size_t nCount, double *x, double *y, double *z, double *t, int *pabSuccess) and OGRCoordinateTransformation::TransformWithErrorCodes(size_t nCount, double *x, double *y, double *z, double *t, int *panErrorCodes) are modified to return FALSE as soon as at least one point fails to transform (to be consistent with the other form of Transform() that doesn't take a "t" argument), whereas previously they would return FALSE only if no transformation was found. When FALSE is returned the pabSuccess[] or panErrorCodes[] arrays indicate which point succeeded or failed to transform.

  The GDALTransformerFunc callback and its implementations (GenImgProjTransformer, RPCTransformer, etc.) are also modified to return FALSE as soon as at least one point fails to transform.

[ctoney]

This seems a little awkward. If FALSE is returned, does it mean modification in-place still may have happened but we need to check pabSuccess to find out?

[rouault]

If FALSE is returned, does it mean modification in-place still may have happened but we need to check pabSuccess to find out?

yes. I can't really think of a better alternative

[coveralls]

coverage: 70.063% (+0.003%) from 70.06%
when pulling 063e2a8 on rouault:fix_11817
into e5044c3 on OSGeo:master.

[rouault]

yes. I can't really think of a better alternative

well, there's an alternative, which would be to return the number of points that have succeeded in being transformed, which would allow quickly to discriminate all-failed, all-succeeded, mixed success, but that wouldn't be any longer a boolean return value.

[ctoney]

That sounds good, but trade-offs for breaking change I would leave up to you.

It's not too bad the way it is. I ended with something like

    int res = poCT->Transform(pts_in.nrow(), xbuf.data(), ybuf.data(),
                              nullptr, nullptr, success.data());

    if (!res &&
        std::find(success.begin(), success.end(), TRUE) == success.end()) {

        // all failed
    } else if (!res) {
        // some failed
    } else {
        // all succeeded
    }