Add validation of changed geometries

Whenever geometries are modified, validation will be run while node tool
is active and validation errors are displayed in status bar and with markers on canvas

src/app/nodetool/qgsnodetool2.cpp

@@ -19,12 +19,14 @@
 #include "qgscurve.h"
 #include "qgscurvepolygon.h"
 #include "qgsgeometryutils.h"
+#include "qgsgeometryvalidator.h"
 #include "qgslogger.h"
 #include "qgsmapcanvas.h"
 #include "qgsmulticurve.h"
 #include "qgspointlocator.h"
 #include "qgsproject.h"
 #include "qgsrubberband.h"
+#include "qgssettings.h"
 #include "qgssnappingutils.h"
 #include "qgsvectorlayer.h"
 #include "qgsvertexmarker.h"
@@ -845,6 +847,9 @@ void QgsNodeTool2::onCachedGeometryChanged( QgsFeatureId fid, const QgsGeometry
 
   // refresh highlighted nodes - their position may have changed
   setHighlightedNodes( mSelectedNodes );
+
+  // re-run validation for the feature
+  validateGeometry( layer, fid );
 }
 
 void QgsNodeTool2::onCachedGeometryDeleted( QgsFeatureId fid )
@@ -1521,7 +1526,6 @@ void QgsNodeTool2::deleteVertex()
       setHighlightedNodes( nodes_new );
     }
   }
-
 }
 
 void QgsNodeTool2::setHighlightedNodes( QList<Vertex> listNodes )
@@ -1635,3 +1639,106 @@ void QgsNodeTool2::CircularBand::updateRubberBand( const QgsPoint &mapPoint )
   Q_FOREACH ( const QgsPointV2 &p, points )
     band->addPoint( p );
 }
+
+
+void QgsNodeTool2::validationErrorFound( QgsGeometry::Error e )
+{
+  QgsGeometryValidator *validator = qobject_cast<QgsGeometryValidator *>( sender() );
+  if ( !validator )
+    return;
+
+  QHash< QPair<QgsVectorLayer *, QgsFeatureId>, GeometryValidation>::iterator it = mValidations.begin();
+  for ( ; it != mValidations.end(); ++it )
+  {
+    GeometryValidation &validation = *it;
+    if ( validation.validator == validator )
+    {
+      validation.addError( e );
+      break;
+    }
+  }
+}
+
+void QgsNodeTool2::validationFinished()
+{
+  QgsGeometryValidator *validator = qobject_cast<QgsGeometryValidator *>( sender() );
+  if ( !validator )
+    return;
+
+  QHash< QPair<QgsVectorLayer *, QgsFeatureId>, GeometryValidation>::iterator it = mValidations.begin();
+  for ( ; it != mValidations.end(); ++it )
+  {
+    GeometryValidation &validation = *it;
+    if ( validation.validator == validator )
+    {
+      QStatusBar *sb = QgisApp::instance()->statusBar();
+      sb->showMessage( tr( "Validation finished (%n error(s) found).", "number of geometry errors", validation.errorMarkers.size() ) );
+    }
+  }
+}
+
+void QgsNodeTool2::GeometryValidation::start( QgsGeometry &geom, QgsNodeTool2 *t, QgsVectorLayer *l )
+{
+  tool = t;
+  layer = l;
+  validator = new QgsGeometryValidator( &geom );
+  connect( validator, &QgsGeometryValidator::errorFound, tool, &QgsNodeTool2::validationErrorFound );
+  connect( validator, &QThread::finished, tool, &QgsNodeTool2::validationFinished );
+  validator->start();
+}
+
+void QgsNodeTool2::GeometryValidation::addError( QgsGeometry::Error e )
+{
+  if ( !errors.isEmpty() )
+    errors += '\n';
+  errors += e.what();
+
+  if ( e.hasWhere() )
+  {
+    QgsVertexMarker *marker = new QgsVertexMarker( tool->canvas() );
+    marker->setCenter( tool->canvas()->mapSettings().layerToMapCoordinates( layer, e.where() ) );
+    marker->setIconType( QgsVertexMarker::ICON_X );
+    marker->setColor( Qt::green );
+    marker->setZValue( marker->zValue() + 1 );
+    marker->setPenWidth( 2 );
+    marker->setToolTip( e.what() );
+    errorMarkers << marker;
+  }
+
+  QStatusBar *sb = QgisApp::instance()->statusBar();
+  sb->showMessage( e.what() );
+  sb->setToolTip( errors );
+}
+
+void QgsNodeTool2::GeometryValidation::cleanup()
+{
+  if ( validator )
+  {
+    validator->stop();
+    validator->wait();
+    validator->deleteLater();
+    validator = nullptr;
+  }
+
+  qDeleteAll( errorMarkers );
+  errorMarkers.clear();
+}
+
+void QgsNodeTool2::validateGeometry( QgsVectorLayer *layer, QgsFeatureId featureId )
+{
+  QgsSettings settings;
+  if ( settings.value( QStringLiteral( "qgis/digitizing/validate_geometries" ), 1 ).toInt() == 0 )
+    return;
+
+  QPair<QgsVectorLayer *, QgsFeatureId> id( layer, featureId );
+  if ( mValidations.contains( id ) )
+  {
+    mValidations[id].cleanup();
+    mValidations.remove( id );
+  }
+
+  GeometryValidation validation;
+  QgsGeometry geom = cachedGeometry( layer, featureId );
+  validation.start( geom, this, layer );
+  mValidations.insert( id, validation );
+}

src/app/nodetool/qgsnodetool2.h

@@ -20,9 +20,11 @@
 
 #include "qgis_app.h"
 #include "qgsmaptooladvanceddigitizing.h"
+#include "qgsgeometry.h"
 
 class QRubberBand;
 
+class QgsGeometryValidator;
 class QgsNodeEditor;
 class QgsSelectedFeature;
 class QgsVertexMarker;
@@ -88,6 +90,10 @@ class APP_EXPORT QgsNodeTool2 : public QgsMapToolAdvancedDigitizing
 
     void deleteNodeEditorSelection();
 
+    void validationErrorFound( QgsGeometry::Error e );
+
+    void validationFinished();
+
   private:
 
     void buildDragBandsForVertices( const QSet<Vertex> &movingVertices, const QgsPoint &dragVertexMapPoint );
@@ -178,6 +184,9 @@ class APP_EXPORT QgsNodeTool2 : public QgsMapToolAdvancedDigitizing
 
     void cleanupNodeEditor();
 
+    //! Run validation on a geometry (in a background thread)
+    void validateGeometry( QgsVectorLayer *layer, QgsFeatureId featureId );
+
   private:
 
     // members used for temporary highlight of stuff
@@ -305,6 +314,26 @@ class APP_EXPORT QgsNodeTool2 : public QgsMapToolAdvancedDigitizing
     std::unique_ptr<QgsSelectedFeature> mSelectedFeature;
     //! Dock widget which allows editing vertices
     std::unique_ptr<QgsNodeEditor> mNodeEditor;
+
+    // suport for validation of geometries
+
+    //! data structure for validation of one geometry of a vector layer
+    struct GeometryValidation
+    {
+      QgsNodeTool2 *tool = nullptr;               //!< Pointer to the parent node tool (for connections / canvas)
+      QgsVectorLayer *layer = nullptr;            //!< Pointer to the layer of the validated geometry (for reporojection)
+      QgsGeometryValidator *validator = nullptr;  //!< Object that does validation. Non-null if active
+      QList<QgsVertexMarker *> errorMarkers;      //!< Markers created by validation
+      QString errors;                             //!< Full error text from validation
+
+      void start( QgsGeometry &geom, QgsNodeTool2 *tool, QgsVectorLayer *l );  //!< Start validation
+      void addError( QgsGeometry::Error e );  //!< Add another error to the validation
+      void cleanup(); //!< Delete everything
+    };
+
+    //! data structure to keep validation details
+    QHash< QPair<QgsVectorLayer *, QgsFeatureId>, GeometryValidation> mValidations;
+
 };