[Qgis-developer] new dependency on GEOS C++ library

Sandro Mani manisandro at gmail.com
Thu Oct 1 05:01:53 PDT 2015

On 01.10.2015 13:55, Sandro Santilli wrote:
> On Thu, Oct 01, 2015 at 01:39:37PM +0200, Sandro Mani wrote:
>> As resulted from the discussion in the geos ticket: the goal is
>> having the operations run in reduced precision, not just merely snap
>> to grid. The discussion revealed however that snap to grid is
>> basically what ends up being done with the current implementation,
>> due to a mis-understanding of mine of the geos internals. As
>> suggested in the geos ticket, I'd like to fix this to work as
>> initially intended, and keep geosextra in QGIS until a new release
>> of GEOS comes out which implements needed changes in the C-API.
> That's fine by me.
> I'm wondering if the easiest way to do it would be something like this:
>   GEOSGeometry* GEOSGeometry_setFactory( GEOSGeometryFactory* factory, int roundCoordinates );
> But note that for such a call, the "factory" parameter would need
> to be alive for the whole lifetime of the returned GEOSGeometry
> _and_ for any further product from it (operation involving it as an input).
> These GeometryFactory links are sticky, that's what makes it hard to
> deal with them.

If one sets the reduced precision factories on the geometries, does one 
still need to explicitly reduce those geometries prior to performing the 
analysis operation, or are they reduced implicitly while performing the 

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