Merge pull request #4684 from nyalldawson/processing_pt3

Add sourceExtent method to QgsFeatureSource

Author: nyalldawson

python/core/qgsfeaturesource.sip

@@ -78,6 +78,14 @@ class QgsFeatureSource
  :rtype: set of QVariant
 %End
 
+    virtual QgsRectangle sourceExtent() const;
+%Docstring
+ Returns the extent of all geometries from the source.
+ The base class implementation uses a non-optimised approach of looping through
+ all features in the source.
+ :rtype: QgsRectangle
+%End
+
 };
 
 

python/core/qgsvectordataprovider.sip

@@ -126,6 +126,8 @@ Bitmask of all provider's editing capabilities
 
     virtual QgsCoordinateReferenceSystem sourceCrs() const;
 
+    virtual QgsRectangle sourceExtent() const;
+
 
     virtual QString dataComment() const;
 %Docstring

python/core/qgsvectorlayer.sip

@@ -1103,10 +1103,8 @@ Synchronises with changes in the datasource
 
     virtual QgsRectangle extent() const;
 
-%Docstring
-Return the extent of the layer
- :rtype: QgsRectangle
-%End
+    virtual QgsRectangle sourceExtent() const;
+
 
     virtual QgsFields fields() const;
 %Docstring

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

@@ -36,6 +36,11 @@
                        QgsFeature,
                        QgsWkbTypes,
                        QgsProcessingUtils,
+                       QgsProcessingParameterFeatureSource,
+                       QgsProcessingParameterFeatureSink,
+                       QgsProcessingOutputVectorLayer,
+                       QgsProcessingParameterBoolean,
+                       QgsProcessingParameterDefinition,
                        QgsFields)
 
 from processing.algs.qgis.QgisAlgorithm import QgisAlgorithm
@@ -65,12 +70,13 @@ def group(self):
 
     def __init__(self):
         super().__init__()
-        self.addParameter(ParameterVector(self.INPUT_LAYER,
-                                          self.tr('Input layer')))
-        self.addParameter(ParameterBoolean(self.BY_FEATURE,
-                                           self.tr('Calculate extent for each feature separately'), False))
 
-        self.addOutput(OutputVector(self.OUTPUT, self.tr('Extent'), datatype=[dataobjects.TYPE_VECTOR_POLYGON]))
+        self.addParameter(QgsProcessingParameterFeatureSource(self.INPUT_LAYER, self.tr('Input layer')))
+        self.addParameter(QgsProcessingParameterBoolean(self.BY_FEATURE,
+                                                        self.tr('Calculate extent for each feature separately'), False))
+
+        self.addParameter(QgsProcessingParameterFeatureSink(self.OUTPUT, self.tr('Extent')))
+        self.addOutput(QgsProcessingOutputVectorLayer(self.OUTPUT, self.tr("Extent"), QgsProcessingParameterDefinition.TypeVectorPolygon))
 
     def name(self):
         return 'polygonfromlayerextent'
@@ -79,8 +85,8 @@ def displayName(self):
         return self.tr('Polygon from layer extent')
 
     def processAlgorithm(self, parameters, context, feedback):
-        layer = QgsProcessingUtils.mapLayerFromString(self.getParameterValue(self.INPUT_LAYER), context)
-        byFeature = self.getParameterValue(self.BY_FEATURE)
+        source = self.parameterAsSource(parameters, self.INPUT_LAYER, context)
+        byFeature = self.parameterAsBool(parameters, self.BY_FEATURE, context)
 
         fields = QgsFields()
         fields.append(QgsField('MINX', QVariant.Double))
@@ -94,17 +100,19 @@ def processAlgorithm(self, parameters, context, feedback):
         fields.append(QgsField('HEIGHT', QVariant.Double))
         fields.append(QgsField('WIDTH', QVariant.Double))
 
-        writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(fields, QgsWkbTypes.Polygon, layer.crs(), context)
+        (sink, dest_id) = self.parameterAsSink(parameters, self.OUTPUT, context,
+                                               fields, QgsWkbTypes.Polygon, source.sourceCrs())
 
         if byFeature:
-            self.featureExtent(layer, context, writer, feedback)
+            self.featureExtent(source, context, sink, feedback)
         else:
-            self.layerExtent(layer, writer, feedback)
+            self.layerExtent(source, sink, feedback)
 
-        del writer
+        return {self.OUTPUT: dest_id}
 
-    def layerExtent(self, layer, writer, feedback):
-        rect = layer.extent()
+    def layerExtent(self, source, sink, feedback):
+        rect = source.sourceExtent()
+        geometry = QgsGeometry.fromRect(rect)
         minx = rect.xMinimum()
         miny = rect.yMinimum()
         maxx = rect.xMaximum()
@@ -116,9 +124,6 @@ def layerExtent(self, layer, writer, feedback):
         area = width * height
         perim = 2 * width + 2 * height
 
-        rect = [QgsPointXY(minx, miny), QgsPointXY(minx, maxy), QgsPointXY(maxx,
-                                                                           maxy), QgsPointXY(maxx, miny), QgsPointXY(minx, miny)]
-        geometry = QgsGeometry().fromPolygon([rect])
         feat = QgsFeature()
         feat.setGeometry(geometry)
         attrs = [
@@ -134,13 +139,16 @@ def layerExtent(self, layer, writer, feedback):
             width,
         ]
         feat.setAttributes(attrs)
-        writer.addFeature(feat)
+        sink.addFeature(feat)
 
-    def featureExtent(self, layer, context, writer, feedback):
-        features = QgsProcessingUtils.getFeatures(layer, context)
-        total = 100.0 / QgsProcessingUtils.featureCount(layer, context)
+    def featureExtent(self, source, context, sink, feedback):
+        features = source.getFeatures()
+        total = 100.0 / source.featureCount()
         feat = QgsFeature()
         for current, f in enumerate(features):
+            if feedback.isCanceled():
+                break
+
             rect = f.geometry().boundingBox()
             minx = rect.xMinimum()
             miny = rect.yMinimum()
@@ -171,5 +179,5 @@ def featureExtent(self, layer, context, writer, feedback):
             ]
             feat.setAttributes(attrs)
 
-            writer.addFeature(feat)
+            sink.addFeature(feat)
             feedback.setProgress(int(current * total))

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

@@ -79,7 +79,7 @@
 # from .Difference import Difference
 # from .Dissolve import Dissolve
 # from .Intersection import Intersection
-# from .ExtentFromLayer import ExtentFromLayer
+from .ExtentFromLayer import ExtentFromLayer
 # from .RandomSelection import RandomSelection
 # from .RandomSelectionWithinSubsets import RandomSelectionWithinSubsets
 # from .SelectByLocation import SelectByLocation
@@ -210,7 +210,7 @@ def getAlgs(self):
         #         PolygonsToLines(), LinesToPolygons(), ExtractNodes(),
         #         ConvexHull(), FixedDistanceBuffer(),
         #         VariableDistanceBuffer(), Dissolve(), Difference(),
-        #         Intersection(), Union(), ExtentFromLayer(),
+        #         Intersection(), Union(),
         #         RandomSelection(), RandomSelectionWithinSubsets(),
         #         SelectByLocation(), RandomExtract(), DeleteHoles(),
         #         RandomExtractWithinSubsets(), ExtractByLocation(),
@@ -265,7 +265,8 @@ def getAlgs(self):
                 Boundary(),
                 BoundingBox(),
                 Clip(),
-                DeleteColumn()
+                DeleteColumn(),
+                ExtentFromLayer()
                 ]
 
         if hasPlotly:

python/plugins/processing/tests/testdata/expected/polygon_from_extent.gml

@@ -13,7 +13,7 @@
 
   <gml:featureMember>
     <ogr:polygon_from_extent fid="polygon_from_extent.0">
-      <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>-1,-3 -1,6 10,6 10,-3 -1,-3</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
+      <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>-1,-3 10,-3 10,6 -1,6 -1,-3</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
       <ogr:MINX>-1</ogr:MINX>
       <ogr:MINY>-3</ogr:MINY>
       <ogr:MAXX>10</ogr:MAXX>

python/plugins/processing/tests/testdata/qgis_algorithm_tests.yaml

@@ -2342,18 +2342,18 @@ tests:
 #        name: expected/find_projection.html
 #        type: file
 #
-#  - algorithm: qgis:polygonfromlayerextent
-#    name: Standard polygon from layer extent
-#    params:
-#      BY_FEATURE: false
-#      INPUT_LAYER:
-#        name: polys.gml
-#        type: vector
-#    results:
-#      OUTPUT:
-#        name: expected/polygon_from_extent.gml
-#        type: vector
-#
+  - algorithm: qgis:polygonfromlayerextent
+    name: Standard polygon from layer extent
+    params:
+      BY_FEATURE: false
+      INPUT_LAYER:
+        name: polys.gml
+        type: vector
+    results:
+      OUTPUT:
+        name: expected/polygon_from_extent.gml
+        type: vector
+
 #  - algorithm: qgis:topologicalcoloring
 #    name: Topological coloring
 #    params:

src/core/qgsfeaturesource.cpp

@@ -40,3 +40,20 @@ QSet<QVariant> QgsFeatureSource::uniqueValues( int fieldIndex, int limit ) const
   return values;
 }
 
+QgsRectangle QgsFeatureSource::sourceExtent() const
+{
+  QgsRectangle r;
+
+  QgsFeatureRequest req;
+  req.setSubsetOfAttributes( QgsAttributeList() );
+
+  QgsFeatureIterator it = getFeatures( req );
+  QgsFeature f;
+  while ( it.nextFeature( f ) )
+  {
+    if ( f.hasGeometry() )
+      r.combineExtentWith( f.geometry().boundingBox() );
+  }
+  return r;
+}
+

src/core/qgsfeaturesource.h

@@ -87,6 +87,13 @@ class CORE_EXPORT QgsFeatureSource
      */
     virtual QSet<QVariant> uniqueValues( int fieldIndex, int limit = -1 ) const;
 
+    /**
+     * Returns the extent of all geometries from the source.
+     * The base class implementation uses a non-optimised approach of looping through
+     * all features in the source.
+     */
+    virtual QgsRectangle sourceExtent() const;
+
 };
 
 Q_DECLARE_METATYPE( QgsFeatureSource * )

src/core/qgsvectordataprovider.cpp

@@ -52,6 +52,11 @@ QgsCoordinateReferenceSystem QgsVectorDataProvider::sourceCrs() const
   return crs();
 }
 
+QgsRectangle QgsVectorDataProvider::sourceExtent() const
+{
+  return extent();
+}
+
 QString QgsVectorDataProvider::dataComment() const
 {
   return QString();