Add methods for getting vector iterators to QgsProcessingUtils

nyalldawson · nyalldawson · commit b32b39501ea6 · 2017-04-26T12:53:35.000+10:00
diff --git a/python/core/processing/qgsprocessingutils.sip b/python/core/processing/qgsprocessingutils.sip
@@ -97,6 +97,24 @@ class QgsProcessingUtils
  :rtype: str
 %End
 
+    static QgsFeatureIterator getFeatures( QgsVectorLayer *layer, const QgsProcessingContext &context, const QgsFeatureRequest &request = QgsFeatureRequest() );
+%Docstring
+ Returns an iterator for the features in a ``layer``, respecting
+ the settings from the supplied ``context``.
+ An optional base ``request`` can be used to optimise the returned
+ iterator, eg by restricting the returned attributes or geometry.
+ :rtype: QgsFeatureIterator
+%End
+
+    static long featureCount( QgsVectorLayer *layer, const QgsProcessingContext &context );
+%Docstring
+ Returns an approximate feature count for a ``layer``, when
+ the settings from the supplied ``context`` are respected. E.g. if the
+ context is set to only use selected features, then calling this will
+ return the count of selected features in the layer.
+ :rtype: long
+%End
+
 };
 
 
diff --git a/src/core/processing/qgsprocessingutils.cpp b/src/core/processing/qgsprocessingutils.cpp
@@ -18,6 +18,7 @@
 #include "qgsprocessingutils.h"
 #include "qgsproject.h"
 #include "qgssettings.h"
+#include "qgsprocessingcontext.h"
 
 QList<QgsRasterLayer *> QgsProcessingUtils::compatibleRasterLayers( QgsProject *project, bool sort )
 {
@@ -172,3 +173,28 @@ QString QgsProcessingUtils::normalizeLayerSource( const QString &source )
   return normalized.trimmed();
 }
 
+QgsFeatureIterator QgsProcessingUtils::getFeatures( QgsVectorLayer *layer, const QgsProcessingContext &context, const QgsFeatureRequest &request )
+{
+  bool useSelection = context.flags() & QgsProcessingContext::UseSelection && layer->selectedFeatureCount() > 0;
+
+  QgsFeatureRequest req( request );
+  req.setInvalidGeometryCheck( context.invalidGeometryCheck() );
+  if ( useSelection )
+  {
+    return layer->selectedFeaturesIterator( req );
+  }
+  else
+  {
+    return layer->getFeatures( req );
+  }
+}
+
+long QgsProcessingUtils::featureCount( QgsVectorLayer *layer, const QgsProcessingContext &context )
+{
+  bool useSelection = context.flags() & QgsProcessingContext::UseSelection && layer->selectedFeatureCount() > 0;
+  if ( useSelection )
+    return layer->selectedFeatureCount();
+  else
+    return layer->featureCount();
+}
+
diff --git a/src/core/processing/qgsprocessingutils.h b/src/core/processing/qgsprocessingutils.h
@@ -24,6 +24,7 @@
 #include "qgsvectorlayer.h"
 
 class QgsProject;
+class QgsProcessingContext;
 
 #include <QString>
 
@@ -105,6 +106,22 @@ class CORE_EXPORT QgsProcessingUtils
      */
     static QString normalizeLayerSource( const QString &source );
 
+    /**
+     * Returns an iterator for the features in a \a layer, respecting
+     * the settings from the supplied \a context.
+     * An optional base \a request can be used to optimise the returned
+     * iterator, eg by restricting the returned attributes or geometry.
+     */
+    static QgsFeatureIterator getFeatures( QgsVectorLayer *layer, const QgsProcessingContext &context, const QgsFeatureRequest &request = QgsFeatureRequest() );
+
+    /**
+     * Returns an approximate feature count for a \a layer, when
+     * the settings from the supplied \a context are respected. E.g. if the
+     * context is set to only use selected features, then calling this will
+     * return the count of selected features in the layer.
+     */
+    static long featureCount( QgsVectorLayer *layer, const QgsProcessingContext &context );
+
   private:
 
     static bool canUseLayer( const QgsRasterLayer *layer );
diff --git a/tests/src/core/testqgsprocessing.cpp b/tests/src/core/testqgsprocessing.cpp
@@ -19,11 +19,14 @@
 #include "qgsprocessingprovider.h"
 #include "qgsprocessingutils.h"
 #include "qgsprocessingalgorithm.h"
+#include "qgsprocessingcontext.h"
 #include <QObject>
 #include <QtTest/QSignalSpy>
 #include "qgstest.h"
 #include "qgsrasterlayer.h"
 #include "qgsproject.h"
+#include "qgspointv2.h"
+#include "qgsgeometry.h"
 
 class DummyAlgorithm : public QgsProcessingAlgorithm
 {
@@ -102,6 +105,7 @@ class TestQgsProcessing: public QObject
     void normalizeLayerSource();
     void mapLayerFromString();
     void algorithm();
+    void features();
 
   private:
 
@@ -430,5 +434,80 @@ void TestQgsProcessing::algorithm()
   QCOMPARE( p3->algorithms().size(), 2 );
 }
 
+void TestQgsProcessing::features()
+{
+  QgsVectorLayer *layer = new QgsVectorLayer( "Point", "v1", "memory" );
+  for ( int i = 1; i < 6; ++i )
+  {
+    QgsFeature f( i );
+    f.setGeometry( QgsGeometry( new QgsPointV2( 1, 2 ) ) );
+    layer->dataProvider()->addFeatures( QgsFeatureList() << f );
+  }
+
+  QgsProcessingContext context;
+  // disable check for geometry validity
+  context.setFlags( QgsProcessingContext::Flags( 0 ) );
+
+  std::function< QgsFeatureIds( QgsFeatureIterator it ) > getIds = []( QgsFeatureIterator it )
+  {
+    QgsFeature f;
+    QgsFeatureIds ids;
+    while ( it.nextFeature( f ) )
+    {
+      ids << f.id();
+    }
+    return ids;
+  };
+
+  // test with all features
+  QgsFeatureIds ids = getIds( QgsProcessingUtils::getFeatures( layer, context ) );
+  QCOMPARE( ids, QgsFeatureIds() << 1 << 2 << 3 << 4 << 5 );
+  QCOMPARE( QgsProcessingUtils::featureCount( layer, context ), 5L );
+
+  // test with selected features
+  context.setFlags( QgsProcessingContext::UseSelection );
+  layer->selectByIds( QgsFeatureIds() << 2 << 4 );
+  ids = getIds( QgsProcessingUtils::getFeatures( layer, context ) );
+  QCOMPARE( ids, QgsFeatureIds() << 2 << 4 );
+  QCOMPARE( QgsProcessingUtils::featureCount( layer, context ), 2L );
+
+  // selection, but not using selected features
+  context.setFlags( QgsProcessingContext::Flags( 0 ) );
+  layer->selectByIds( QgsFeatureIds() << 2 << 4 );
+  ids = getIds( QgsProcessingUtils::getFeatures( layer, context ) );
+  QCOMPARE( ids, QgsFeatureIds() << 1 << 2 << 3 << 4 << 5 );
+  QCOMPARE( QgsProcessingUtils::featureCount( layer, context ), 5L );
+
+  // using selected features, but no selection
+  context.setFlags( QgsProcessingContext::UseSelection );
+  layer->removeSelection();
+  ids = getIds( QgsProcessingUtils::getFeatures( layer, context ) );
+  QCOMPARE( ids, QgsFeatureIds() << 1 << 2 << 3 << 4 << 5 );
+  QCOMPARE( QgsProcessingUtils::featureCount( layer, context ), 5L );
+
+
+  // test that feature request is honored
+  context.setFlags( QgsProcessingContext::Flags( 0 ) );
+  ids = getIds( QgsProcessingUtils::getFeatures( layer, context, QgsFeatureRequest().setFilterFids( QgsFeatureIds() << 1 << 3 << 5 ) ) );
+  QCOMPARE( ids, QgsFeatureIds() << 1 << 3 << 5 );
+
+  // count is only rough - but we expect (for now) to see full layer count
+  QCOMPARE( QgsProcessingUtils::featureCount( layer, context ), 5L );
+
+
+  //test that feature request is honored when using selections
+  context.setFlags( QgsProcessingContext::UseSelection );
+  layer->selectByIds( QgsFeatureIds() << 2 << 4 );
+  ids = getIds( QgsProcessingUtils::getFeatures( layer, context, QgsFeatureRequest().setFlags( QgsFeatureRequest::NoGeometry ) ) );
+  QCOMPARE( ids, QgsFeatureIds() << 2 << 4 );
+
+#if 0
+  // test exception is raised when filtering invalid geoms
+  context.setInvalidGeometryCheck( QgsFeatureRequest.GeometryAbortOnInvalid )
+#endif
+
+  delete layer;
+}
+
 QGSTEST_MAIN( TestQgsProcessing )
 #include "testqgsprocessing.moc"
