[QGIS-Developer] get all the features of a specific layer which are visible in the viewport

[Jo]

Wonderful, I'm going to try that. Muchas gracias!

Jo

On Sun, Jan 19, 2020, 16:36 Jorge Gustavo Rocha <jgr at di.uminho.pt> wrote:

> Hi Jo,
>
> You can use setFilterRect (see
> https://docs.qgis.org/3.4/en/docs/pyqgis_developer_cookbook/vector.html).
>
> request = QgsFeatureRequest().setFilterRect(iface.mapCanvas().extent())
> for feature in layer.getFeatures(request):
>         print(feature.id)
>
> This way, you only iterate over the visible features.
>
> Regards,
>
> Jorge Gustavo
>
> On 18/01/20 20:39, Jo wrote:
> > Hi,
> >
> > I created the following code:
> >
> > class FBSegmentPoiComboBox(FBComboBox):
> >     def __init__(self, name, identifier=None, update_method=None,
> iface=None):
> >         super().__init__(name=name, identifier=identifier,
> update_method=update_method)
> >         self.iface = iface
> >         self.items_list = []
> >         self.find_segments()
> >         self.rubber_band = QgsRubberBand(self.iface.mapCanvas(), False)
> >         self.rubber_band.setWidth(12)
> >         self.rubber_band.setStrokeColor(QColor.fromRgb(90, 0, 20))
> >         self.highlighted.connect(self.highlight_segment)
> >         self.currentIndexChanged.connect(self.clear_rubberband)
> >
> >     def find_segments(self):
> >         self.clear()
> >         self.add_item(REFRESH_SEGMENTS_LIST, None)
> >         # put a dummy at position 0
> > self.items_list = ['dummy']
> >         segment_layer_list =
> QgsProject.instance().mapLayersByName('segment')
> >         if segment_layer_list:
> >             segment_layer = segment_layer_list[0]
> >             layer =
> QgsProject.instance().layerTreeRoot().findLayer(segment_layer)
> >             if layer:
> >                 layer.setItemVisibilityChecked(True)
> >             if self.iface:
> >                 segments = QgsSpatialIndex()
> >                 for segment in segment_layer.getFeatures():
> >                     segments.insertFeature(segment)
> >                 nearby =
> segments.nearestNeighbor(self.iface.mapCanvas().center(), neighbors=10) # ,
> maxDistance=1000)
> > for featureId in nearby:
> >                     fit2 =
> segment_layer.getFeatures(QgsFeatureRequest().setFilterFid(featureId))
> >                     ftr = QgsFeature()
> >                     fit2.nextFeature(ftr)
> >                     self.add_item(ftr.attribute(0), ftr.attribute(0))
> >                     self.items_list.append(ftr)
> >         self.changed = False
> >
> > def highlight_segment(self, index):
> >         self.rubber_band.reset()
> >         if index == 0:
> >             self.find_segments()
> >         elif index < len(self.items_list):
> >
>  self.rubber_band.setToGeometry(self.items_list[index].geometry())
> >
> >     def clear_rubberband(self, index):
> >         self.rubber_band.reset()
> >
> >
> > It populates a drop down with all the LineStrings near to the center of
> the screen.
> >
> > It's not very efficient though, as I need to first pass all the
> LineStrings on that particular layer to it.
> >
> > Is there a way to replace this code:
> >
> >                 for segment in segment_layer.getFeatures():
> >                     segments.insertFeature(segment)
> >
> > So it only works on a smaller subset of features that are actually
> visible to on the user's screen?
> >
> > Jo
> >
> >
> > _______________________________________________
> > QGIS-Developer mailing list
> > QGIS-Developer at lists.osgeo.org
> > List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer
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> >
>
> J. Gustavo
> --
> Jorge Gustavo Rocha
> Departamento de Informática
> Universidade do Minho
> 4710-057 Braga
> Gabinete 3.29 (Piso 3)
> Tel: +351 253604480
> Fax: +351 253604471
> Móvel: +351 910333888
> skype: nabocudnosor
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