add support for AsGML() and AsKML() for the Spatialite backend

[Stefano Costa]

Spatialite supports AsGML() and AsKML() since version 2.4.0-RC4, that is largely used in production environments.

This trivial patch adds support for these two output formats to the Spatialite backend in GeoDjango.

I've also made the small changes one would expect to both the test suite and to the documentation.

Tests seem to pass, but this is my first Django patch ever and I'm not very familiar with running the test suite.

[Stefano Costa]

git diff style patch

[Aymeric Augustin]

Overall the patch looks good, but I think it needs actual tests.

[John Paulett]

Fix test

[John Paulett]

I attached a tweak to the patch, spatialite-kml-gml.2.diff (assertRaises was still called for sqlite due to a bug in the if statement).

I am new to the GeoDjango, so this may be irrelevant, but it appears that the version of Spatialite that supports AsGML and AsKML is not considered "stable" (2.4.0-RC4). The GeoDjango docs still include instructions on installing the stable version of Spatialite, 2.3.1. Ubuntu 11.04 & 11.10 (not yet released) appear to only have 2.4.0-RC2--so even on the bleading edge versions of Ubuntu these functions will not be available.

[John Paulett]

Only add AsGML and AsKML if SpatialLite >= 2.4.0

[John Paulett]

The latest patch, spatialite-kml-gml.3.diff, checks the Spatialite version before adding AsKML and AsGML. It works for Spatialite 2.4.0-RC4+, but fails for the default Ubuntu libspatialite2 package (2.4.0-RC2). Not sure how to detect RC2 vs RC4 given that spatialite_version() returns for 2.4.0 regardless of RC2 or RC4.

[John Paulett]

Feature detection of AsGML to detect 2.4.0 RC2 vs RC4

[John Paulett]

Rebase patch after big changes in [16749]

[jbronn]

In [16800]:

Fixed #16231 -- Added support for GML and KML on the SpatiaLite backend. Thanks, steko for the bug report and jpaulett for the patch.