Current locale considered when converting a geometry to WKT

[luizvital]

This was noticed when using geodjango ctypes wraper in python. A more detailed description here  http://code.djangoproject.com/ticket/8563

[jbronn]

More specifically, GeoDjango's GEOSGeometry object is essentially just returning the output of the GEOS C API method GEOSGeomToWKT (link).

[sgillies]

From the Django ticket:

I'm getting a OGRGeometry Exception intermittently, when saving a form.

After debuging the code I noticed that the WKT string generated from geometries were taking the current locale into account, thus raising the Exceptions due to a bad WKT string representation. Here goes an example:

>>> import locale
>>> from django.contrib.gis.geos import Point
>>> p = Point(-45.23, -23.15)
>>> p.wkt
'POINT (-45.2299999999999969 -23.1499999999999986)'
>>> locale.getlocale()
(None, None)
>>> locale.setlocale(locale.LC_ALL, ('pt_BR','UTF-8'))
'pt_BR.UTF8'
>>> p.wkt
'POINT (-45,2299999999999969 -23,1499999999999986)'

Notice de comma "," for decimal separator in the last output.

It must be something in the GEOS C library and in this case should be fixed there, but maybe it should be avoided reseting de locale before calling the C routine and restoring the locale to what it was just after.

I think the reason this problem was not always happening is related to the some setlocale thread safety issue.

I was using the wkt from the geometry in a custom form PointField?? to get the coordinate transformed to the desired srid.

[mloskot]

AFAIU, the problem is that GEOS does not ignore current locale in numeric/string operations and casting. Obviously, WKT processing should be locale-indenepdent.

Please, to complete the report, what version of GEOS you use?

[jbronn]

This is with version 3.0.0.

[sgillies]

So, we imbue the stream at

 http://trac.osgeo.org/geos/browser/trunk/source/geom/Coordinate.cpp?rev=2144#L36

with a null locale?

[sgillies]

I meant "C" locale.

[mloskot]

Sean, yes forcing C or POSIX locale should fix the problem. This schema should be sufficient:

#include <iostream>
#include <sstream>
#include <locale>
int main()
{
    double a = 1.234;

    std::ostringstream s;
    std::locale loc("C");
    s.imbue(loc);
    s<<a;
    std::cout << s.str() << std::endl;

    return 0;
}

However, I'm not very happy with (re)setting locale in every call of toString(), as potentially decreasing performance. Better would be to do it from WKT reader and writer. I can look at it but after Wednesday next week.

[sgillies]

I looked into the WKTWriter code for a while today and found it rather confusing. There is code in there that doesn't seem to be called by anything, mixtures of C and C++ patterns ... ugh. Geometry::toString() doesn't appear to be used by the writer after all. Seems like sprintf() in WKTWriter::writeNumber might be the problem.

[sgillies]

Fix for the C API (read and write, old function and new) is in r2172.

[sgillies]

Better solution in r2174 after consultation with Frank and Mateusz.

[sgillies]

Snapshot with the fix at  http://gispython.org/downloads/geos/geos-r2174.tar.gz.

[CrAsH0v3r]

The trunk is currently broken because of theses changes.

I'm building on Windows using msvc8 and I'm getting the following "unresolved external" at the linker step.

 Creating library geos_i.
lib and object geos_i.exp
geos_c.obj : error LNK2019: unresolved external symbol "public: __thiscall geos::io::CLocalizer::~CLocalizer(void)" (??1CLocalizer@io@geos@@QAE@XZ) referenced in function _GEOSGeom
FromWKT
geos_c.obj : error LNK2019: unresolved external symbol "public: __thiscall geos::io::CLocalizer::CLocalizer(void)" (??0CLocalizer@io@geos@@QAE@XZ) referenced in function _GEOSGeomF
romWKT
geos.dll : fatal error LNK1120: 2 unresolved externals

I'm looking into it, i'll will come back with the solution if I find it.

Thanks for help.

Philippe

[CrAsH0v3r]

Update of the situation : CLocalizer.cpp is never compiled. I added it to the project file under "Build/msvc80..." and it does not compile, due to following :

1>c:\geos\geos-lag\source\io\clocalizer.cpp(12) : error C2039: 'setlocale' : is not a member of 'std'
1>c:\geos\geos-lag\source\io\clocalizer.cpp(17) : error C2039: 'setlocale' : is not a member of 'std'
1>c:\geos\geos-lag\source\io\clocalizer.cpp(22) : error C2039: 'setlocale' : is not a member of 'std'

I'll work on that tomorrow.

Thanks

Phil

Replying to CrAsH0v3r:

The trunk is currently broken because of theses changes. I'm building on Windows using msvc8 and I'm getting the following "unresolved external" at the linker step. {{{ Creating library geos_i. lib and object geos_i.exp geos_c.obj : error LNK2019: unresolved external symbol "public: thiscall geos::io::CLocalizer::~CLocalizer(void)" (??1CLocalizer@io@geos@@QAE@XZ) referenced in function _GEOSGeom FromWKT geos_c.obj : error LNK2019: unresolved external symbol "public: thiscall geos::io::CLocalizer::CLocalizer(void)" (??0CLocalizer@io@geos@@QAE@XZ) referenced in function _GEOSGeomF romWKT geos.dll : fatal error LNK1120: 2 unresolved externals }}} I'm looking into it, i'll will come back with the solution if I find it. Thanks for help. Philippe

[mloskot]

Philippe,

Thanks for reporting this issue. I've applied patch, so should be fixed in trunk (r2183)

[mloskot]

I've also updated Visual C++ 2005/2008 project - geos_lib.vcproj (r2185)

I would consider this issue as fixed, so closing. Please, verify if it works and reopen if something is wrong still.

[CrAsH0v3r]

Hi,

Thanks a lot. It works both ways, command line and via the project file.

Philippe