How to do a spatial search without select() using PyQGIS?

Question

Using QGIS 1.9.0-master, I want to do a spatial search for features in a vector layer without selecting them, i.e., without using QgsVectorLayer.select(), QgsVectorLayer.selectedFeatures() et al.

More specifically:

I want to get the feature IDs inside a rectangle. That could be accomplished with something similar to QgsSpatialIndex.intersects() if I could gain access to the spatial index of the layer's dataprovider.

Unfortunately, I didn't find a way to do it. I was only able to find how to create the index using QgsVectorDataProvider::createSpatialIndex()

Does anyone know if this is possible?

Answer 1

For now, as a workaround, I created a function that iterates over the layer features:

def spatial_select_features(layer, rect):

  layer.dataProvider().rewind()

  feature = QgsFeature()
  features = []
  while layer.dataProvider().nextFeature(feature):
    if feature.geometry().intersects(rect):
       features += [QgsFeature(feature)]

  return features

Answer 2

Pending changes in the API ...

Another solution that combines geographic selection and loop on features.

Canvas freeze and restore the previous selection.

            self.canvas.freeze(True)
            oldSelection = layer.selectedFeaturesIds()
            try:
                layer.select(MyRect, False)

                # refining interesection
                feature = QgsFeature()
                for feature in layer.selectedFeatures():
                    if feature.geometry().intersects(rectGeom):
                        # DO SOMETHING
            finally:
                layer.setSelectedFeatures(oldSelection)
                self.plugin.canvas.freeze(False)