Le portail francophone de la géomatique

# -*- coding: utf-8 -*-
from qgis.gui import QgsMapTool
from qgis.core import QgsMapLayer, QgsMapToPixel, QgsFeature, QgsFeatureRequest, QgsGeometry
from PyQt4.QtGui import QCursor, QPixmap
from PyQt4.QtCore import Qt

class NearestFeatureMapTool(QgsMapTool):
    
    def __init__(self, canvas):
        super(QgsMapTool, self).__init__(canvas)
        self.canvas = canvas
        self.cursor = QCursor(Qt.CrossCursor)
        
    def activate(self):
        self.canvas.setCursor(self.cursor)
    
    def canvasReleaseEvent(self, mouseEvent): # méthode surchargée de QgsMapTool
        layerData = []
        
        for layer in self.canvas.layers():
            if layer.type() != QgsMapLayer.VectorLayer:
                # Ignore this layer as it's not a vector
                continue
            
            if layer.featureCount() == 0:
                # There are no features - skip
                continue
            
            layer.removeSelection()
            
            # Determine the location of the click in real-world coords
            layerPoint = self.toLayerCoordinates(layer, mouseEvent.pos() )
            
            print "point = " + str(layerPoint)
            
            shortestDistance = float("inf") #infini : + grande valeur possible de float
            closestFeatureId = -1
            
            # Loop through all features in the layer
            for f in layer.getFeatures():
                dist = f.geometry().distance(QgsGeometry.fromPoint(layerPoint))
                if dist < shortestDistance:
                    shortestDistance = dist
                    print dist
                    closestFeatureId = f.id()
            
            info = (layer, closestFeatureId, shortestDistance)
            layerData.append(info)
                
        if not len(layerData) > 0:
            # Looks like no vector layers were found - do nothing
            return
        
        # Sort the layer information by shortest distance
        layerData.sort(key=lambda element: element[2] ) #tri d'une liste de tuples
        
        # Select the closest feature
        layerWithClosestFeature, closestFeatureId, shortestDistance = layerData[0]
        layerWithClosestFeature.select( closestFeatureId )