[Qgis-developer] GEOS error Exception: IllegalArgumentException: Invalid number of points in LinearRing found 3 - must be 0 or >= 4

[A Huarte]

Hi Janneke, you are right. The simplification process is executed just when the original geometry is read from data source and it can create invalid geometries. These invalid geometries will be used in subsequent processes using geometry calculations.
You can disable the simplification of a layer from its options menu -> properties -> rendering -> uncheck the "simplify geometry" CheckBox. Or you can disable the simplification by default from -> settings -> options -> rendering -> uncheck the "Enable feature simplification by default ..." CheckBox.
This pull request moves the simplification just when the geometry is rendered, the geometry remains unchanged from the data source in order to avoid these problems. 
Kind regardsAlvaro

      De: Janneke van Dijk <janneke.qgis at gmail.com>
 Para: A Huarte <ahuarte47 at yahoo.es>; "qgis-developer at lists.osgeo.org" <qgis-developer at lists.osgeo.org> 
 Enviado: Sábado 14 de Mayo de 2016 20:30
 Asunto: Re: [Qgis-developer] GEOS error Exception: IllegalArgumentException: Invalid number of points in LinearRing found 3 - must be 0 or >= 4
   
 Hi Alvaro,
 
 How do I disable the on-the-fly simplification?
 Do I understand it correctly that the error causes problems with a virtual field with a geometry calculation in it? Would that also be solved by disabling on-the-fly simplification? Or should I avoid the issues by not making it a virtual field - if I know that the polygons won't be edited? 
 
 Thanks for your insights,
 Janneke
 
 On 13/05/2016 11:08, A Huarte wrote:
  
 
 Hi, I think this pull https://github.com/qgis/QGIS/pull/2900 fixes the error. 
  But it is pending to merge, It needs to fix some tests to be accepted finally. Meanwhile you can disable the on-the-fly simplification of the layer. 
  Kind regards Alvaro 
       De: Janneke van Dijk <janneke.qgis at gmail.com>
 Para: qgis-developer at lists.osgeo.org 
 Enviado: Viernes 13 de Mayo de 2016 9:53
 Asunto: [Qgis-developer] GEOS error Exception: IllegalArgumentException: Invalid number of points in LinearRing found 3 - must be 0 or >= 4
  
 Dear list,
 
 Using QGIS 2.14.2 on Windows 7 I get the following error message when 
 zooming out on a shapefile layer that has labels switched on:
 
 GEOS
 Exception: IllegalArgumentException: Invalid number of points in 
 LinearRing found 3 - must be 0 or >= 4
 
 It seems to be an old bug (https://hub.qgis.org/issues/9375) that was 
 fixed 2 years ago.
 
 It doesn't seem to cause any problems otherwise. Anyone else have this 
 issue? Should I file a new bug report?
 
 Regards,
 Janneke
 
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