[processing] add cancellation support where possible

Author: alexbruy

python/plugins/processing/algs/qgis/ShortestPathLayerToPoint.py

@@ -237,6 +237,9 @@ def processAlgorithm(self, parameters, context, feedback):
 
         total = 100.0 / source.featureCount() if source.featureCount() else 1
         for i in range(1, count + 1):
+            if feedback.isCanceled():
+                break
+
             idxStart = graph.findVertex(snappedPoints[i])
             tree, cost = QgsGraphAnalyzer.dijkstra(graph, idxStart, 0)
 

python/plugins/processing/algs/qgis/ShortestPathPointToLayer.py

@@ -238,6 +238,9 @@ def processAlgorithm(self, parameters, context, feedback):
 
         total = 100.0 / source.featureCount() if source.featureCount() else 1
         for i in range(1, count + 1):
+            if feedback.isCanceled():
+                break
+
             idxEnd = graph.findVertex(snappedPoints[i])
 
             if tree[idxEnd] == -1: