Filter selected feature to the related feature parent

src/gui/attributetable/qgsvectorlayerselectionmanager.cpp

@@ -21,7 +21,7 @@ QgsVectorLayerSelectionManager::QgsVectorLayerSelectionManager( QgsVectorLayer *
   : QgsIFeatureSelectionManager( parent )
   , mLayer( layer )
 {
-  connect( mLayer, &QgsVectorLayer::selectionChanged, this, &QgsVectorLayerSelectionManager::selectionChanged );
+  connect( mLayer, &QgsVectorLayer::selectionChanged, this, &QgsVectorLayerSelectionManager::onSelectionChanged );
 }
 
 int QgsVectorLayerSelectionManager::selectedFeatureCount()
@@ -48,3 +48,13 @@ const QgsFeatureIds &QgsVectorLayerSelectionManager::selectedFeatureIds() const
 {
   return mLayer->selectedFeatureIds();
 }
+
+QgsVectorLayer *QgsVectorLayerSelectionManager::layer() const
+{
+  return mLayer;
+}
+
+void QgsVectorLayerSelectionManager::onSelectionChanged( const QgsFeatureIds &selected, const QgsFeatureIds &deselected, bool clearAndSelect )
+{
+  emit selectionChanged( selected, deselected, clearAndSelect );
+}

src/gui/attributetable/qgsvectorlayerselectionmanager.h

@@ -41,6 +41,10 @@ class GUI_EXPORT QgsVectorLayerSelectionManager : public QgsIFeatureSelectionMan
     void deselect( const QgsFeatureIds &ids ) override;
     void setSelectedFeatures( const QgsFeatureIds &ids ) override;
     const QgsFeatureIds &selectedFeatureIds() const override;
+    QgsVectorLayer *layer() const;
+
+  protected slots:
+    virtual void onSelectionChanged( const QgsFeatureIds &selected, const QgsFeatureIds &deselected, bool clearAndSelect );
 
   private:
     QgsVectorLayer *mLayer = nullptr;

src/gui/qgsrelationeditorwidget.cpp

@@ -36,6 +36,64 @@
 #include <QLabel>
 #include <QMessageBox>
 
+class QgsFilteredSelectionManager : public QgsVectorLayerSelectionManager
+{
+  public:
+    QgsFilteredSelectionManager( QgsVectorLayer *layer, const QgsFeatureRequest &request, QObject *parent = nullptr )
+      : QgsVectorLayerSelectionManager( layer, parent )
+      , mRequest( request )
+    {
+      QgsFeature feature;
+      QgsFeatureIterator it = layer->getSelectedFeatures( mRequest );
+      while ( it.nextFeature( feature ) )
+      {
+        mSelectedFeatureIds << feature.id();
+      }
+
+      connect( layer, &QgsVectorLayer::selectionChanged, this, &QgsFilteredSelectionManager::onSelectionChanged );
+    }
+
+    const QgsFeatureIds &selectedFeatureIds() const override
+    {
+      return mSelectedFeatureIds;
+    }
+
+
+    int selectedFeatureCount() override
+    {
+      return mSelectedFeatureIds.count();
+    }
+
+  public slots:
+
+    void onSelectionChanged( const QgsFeatureIds &selected, const QgsFeatureIds &deselected, bool clearAndSelect ) override
+    {
+      QgsFeatureIds lselected = selected;
+      if ( clearAndSelect )
+      {
+        mSelectedFeatureIds.clear();
+      }
+      else
+      {
+        for ( auto fid : deselected )
+          mSelectedFeatureIds.remove( fid );
+      }
+
+      for ( auto fid : selected )
+        if ( mRequest.acceptFeature( layer()->getFeature( fid ) ) )
+          mSelectedFeatureIds << fid;
+        else
+          lselected.remove( fid );
+
+      emit selectionChanged( lselected, deselected, clearAndSelect );
+    }
+
+  private:
+
+    QgsFeatureRequest mRequest;
+    QgsFeatureIds mSelectedFeatureIds;
+};
+
 QgsRelationEditorWidget::QgsRelationEditorWidget( QWidget *parent )
   : QgsCollapsibleGroupBox( parent )
 {
@@ -203,7 +261,7 @@ void QgsRelationEditorWidget::setRelationFeature( const QgsRelation &relation, c
 void QgsRelationEditorWidget::initDualView( QgsVectorLayer *layer, const QgsFeatureRequest &request )
 {
   mDualView->init( layer, nullptr, request, mEditorContext );
-  mFeatureSelectionMgr = new QgsVectorLayerSelectionManager( layer, mDualView );
+  mFeatureSelectionMgr = new QgsFilteredSelectionManager( layer, request, mDualView );
   mDualView->setFeatureSelectionManager( mFeatureSelectionMgr );
   connect( mFeatureSelectionMgr, &QgsIFeatureSelectionManager::selectionChanged, this, &QgsRelationEditorWidget::updateButtons );
 }

tests/src/python/test_qgsrelationeditwidget.py

@@ -255,6 +255,37 @@ class TestQgsRelationEditWidget(unittest.TestCase):
         self.assertEqual([2, 3], relation.referencingFields())
         self.assertEqual([0, 1], relation.referencedFields())
 
+    def test_selection(self):
+
+        fbook = QgsFeature(self.vl_books.fields())
+        fbook.setAttributes([self.vl_books.dataProvider().defaultValueClause(0), 'The Hitchhiker\'s Guide to the Galaxy', 'Sputnik Editions', 1961])
+        self.vl_books.addFeature(fbook)
+
+        flink = QgsFeature(self.vl_link_books_authors.fields())
+        flink.setAttributes([fbook.id(), 5])
+        self.vl_link_books_authors.addFeature(flink)
+
+        self.createWrapper(self.vl_authors, '"name"=\'Douglas Adams\'')
+
+        self.zoomToButton = self.widget.findChild(QToolButton, "mDeleteFeatureButton")
+        self.assertTrue(self.zoomToButton)
+        self.assertTrue(not self.zoomToButton.isEnabled())
+
+        selectionMgr = self.widget.featureSelectionManager()
+        self.assertTrue(selectionMgr)
+
+        self.vl_books.select(fbook.id())
+        self.assertEqual([fbook.id()], selectionMgr.selectedFeatureIds())
+        self.assertTrue(self.zoomToButton.isEnabled())
+
+        selectionMgr.deselect([fbook.id()])
+        self.assertEqual([], selectionMgr.selectedFeatureIds())
+        self.assertTrue(not self.zoomToButton.isEnabled())
+
+        self.vl_books.select([1, fbook.id()])
+        self.assertEqual([fbook.id()], selectionMgr.selectedFeatureIds())
+        self.assertTrue(self.zoomToButton.isEnabled())
+
     def startTransaction(self):
         """
         Start a new transaction and set all layers into transaction mode.