Hello everyone, I found ! Looking around a solution to my problem, I understand that python would be the solution .
Thanks to the QGis documentation and to those 3 resources : - http://nathanw.net/2012/11/10/user-defined-expression-functions-for-qgis/ - http://www.3liz.com/blog/rldhont/index.php?post/2012/11/06/Op%C3%A9rateurs-spatiaux-dans-les-expressions-de-QGIS - http://gis.stackexchange.com/questions/28625/how-to-create-a-polygon-based-on-view-extent-in-qgis-1-8 So I created a python script ( userfunctions.py ), which contains a function called current_canvas_extent , which returns a Polygon representing the current influence of the window. [code] from qgis.utils import qgsfunction from qgis.utils import iface from qgis.core import QGis @qgsfunction(0, "Python") def current_canvas_extent(values, feature, parent): """ retourne l etendue courante de la carte """ ##extend = QgsGeometry.fromRect( iface.mapCanvas().extent() ) ##extend = iface.mapCanvas().extent().toString() extend = iface.mapCanvas().extent().asWktPolygon() return extend [/code] QGis call the script on start (add the option " - code path \ to \ userfunctions.py " ) So I now have access to this "variable" inside the expression editor. And I can ask QGis restrict the list to the objects intersecting the current canvas. [code] intersects ($ geometry , geomFromWKT ($ current_canvas_extent ) ) [/code] Thanks a lot for this great software you give us! Mathieu BOSSAERT -- Responsable du système d'information Membre de la Fédération des Conservatoires d'espaces naturels www.reseau-cen.org ----- Mail original ----- De: "Mathieu Bossaert (CEN L-R)" <mathieu.bossa...@cenlr.org> À: qgis-user@lists.osgeo.org Envoyé: Mardi 1 Octobre 2013 11:26:55 Objet: How to make use of python variables in Qgis filter expression Good morning, thanks to the new Qgis, I can make a really pratical interface to my postgis database. I want to make use of relationnal value in the editing form. The table I use to populate the list is a spatial table. I would like to restrict the list of available values in the form to the objects within the current extent of my map. I found an example wich is ok but I would like to make use of a variable instead of a fixed extend (GeomFromWKT()). The example I tried is here : http://www.3liz.com/blog/rldhont/index.php?post/2012/11/06/Spatial-operators-in-QGIS-expression Thanks a lot, Mathieu -- Mathieu BOSSAERT Responsable du système d'information Membre de la Fédération des Conservatoires d'espaces naturels www.reseau-cen.org
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