Created
March 29, 2024 16:14
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QGIS - Set layers substring filter with WHERE clause depending on map canvas extent and intersected polygons
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| class filterLayersFromExtent: | |
| polygon_layer = { | |
| 'name': 'polygons', | |
| 'field': 'code', | |
| 'layer': None | |
| } | |
| target_layers = [ | |
| { | |
| 'name': 'observation', | |
| 'field': 'departement', | |
| 'layer': None | |
| } | |
| ] | |
| def __init__(self): | |
| # Set layers | |
| p = QgsProject.instance() | |
| # QGIS polygon layer | |
| self.polygon_layer['layer'] = p.mapLayersByName( | |
| self.polygon_layer['name'] | |
| )[0] | |
| # QGIS target layers | |
| for layer in self.target_layers: | |
| layer['layer'] = p.mapLayersByName( | |
| layer['name'] | |
| )[0] | |
| self.canvas = iface.mapCanvas() | |
| self.canvas.extentsChanged.connect(self.onCanvasExtentsChanged) | |
| def getSubsetString(self, extent, layer): | |
| # Request polygon layer data in the map extent | |
| request = QgsFeatureRequest(extent) | |
| request.setFlags(QgsFeatureRequest.ExactIntersect) | |
| features = self.polygon_layer['layer'].getFeatures(request) | |
| # Get ids of the found features | |
| ids = [] | |
| field = self.polygon_layer['field'] | |
| for feature in features: | |
| ids.append(feature[field]) | |
| # Compute subset string filter | |
| target_field = layer['field'] | |
| ids_string = "'" + ("', '").join(ids) + "'" | |
| return f'"{target_field}" IN ( {ids_string} )' | |
| def onCanvasExtentsChanged(self): | |
| # Get polygons in canvas | |
| extent = self.canvas.extent() | |
| # For each target layer | |
| for target_layer in self.target_layers: | |
| # Get the subset string | |
| subset_string = self.getSubsetString(extent, target_layer) | |
| print(subset_string) | |
| # Apply the subset string to the layer | |
| layer = target_layer['layer'] | |
| if layer and layer.subsetString() != subset_string: | |
| print(f"{target_layer['name']}: subset string modified !") | |
| layer.setSubsetString(subset_string) | |
| test = filterLayersFromExtent() |
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