[needs-docs] Attribute table "show selected features" shows no features

when none are selected

This change is being driven by performance - the "show selected" mode
can be used to speed up the attribute table loading for large layers.
The current behaviour (showing ALL features when none are selected)
breaks this performance benefit, because if users accidently open
the table with no selection then they are forced to wait for the
entire table to load (sometimes takes hours on large tables/slow
connections).

src/app/qgsattributetabledialog.cpp

@@ -144,8 +144,7 @@ QgsAttributeTableDialog::QgsAttributeTableDialog( QgsVectorLayer *layer, QWidget
   }
   else if ( initialMode == QgsAttributeTableFilterModel::ShowSelected )
   {
-    if ( layer->selectedFeatureCount() > 0 )
-      r.setFilterFids( layer->selectedFeatureIds() );
+    r.setFilterFids( layer->selectedFeatureIds() );
   }
   if ( !needsGeom )
     r.setFlags( QgsFeatureRequest::NoGeometry );

src/gui/attributetable/qgsattributetablefiltermodel.cpp

@@ -311,7 +311,7 @@ bool QgsAttributeTableFilterModel::filterAcceptsRow( int sourceRow, const QModel
       return mFilteredFeatures.contains( masterModel()->rowToId( sourceRow ) );
 
     case ShowSelected:
-      return layer()->selectedFeatureIds().isEmpty() || layer()->selectedFeatureIds().contains( masterModel()->rowToId( sourceRow ) );
+      return layer()->selectedFeatureIds().contains( masterModel()->rowToId( sourceRow ) );
 
     case ShowVisible:
       return mFilteredFeatures.contains( masterModel()->rowToId( sourceRow ) );

src/gui/attributetable/qgsdualview.cpp

@@ -245,8 +245,7 @@ void QgsDualView::setFilterMode( QgsAttributeTableFilterModel::FilterMode filter
 
     case QgsAttributeTableFilterModel::ShowSelected:
       connect( masterModel()->layer(), &QgsVectorLayer::selectionChanged, this, &QgsDualView::updateSelectedFeatures );
-      if ( masterModel()->layer()->selectedFeatureCount() > 0 )
-        r.setFilterFids( masterModel()->layer()->selectedFeatureIds() );
+      r.setFilterFids( masterModel()->layer()->selectedFeatureIds() );
       break;
   }
 
@@ -718,10 +717,7 @@ void QgsDualView::updateSelectedFeatures()
   if ( r.filterType() == QgsFeatureRequest::FilterNone && r.filterRect().isNull() )
     return; // already requested all features
 
-  if ( masterModel()->layer()->selectedFeatureCount() > 0 )
-    r.setFilterFids( masterModel()->layer()->selectedFeatureIds() );
-  else
-    r.disableFilter();
+  r.setFilterFids( masterModel()->layer()->selectedFeatureIds() );
   mMasterModel->setRequest( r );
   mMasterModel->loadLayer();
   emit filterChanged();

tests/src/app/testqgsattributetable.cpp

@@ -45,6 +45,7 @@ class TestQgsAttributeTable : public QObject
     void testFieldCalculation();
     void testFieldCalculationArea();
     void testNoGeom();
+    void testSelected();
 
   private:
     QgisApp *mQgisApp = nullptr;
@@ -209,6 +210,43 @@ void TestQgsAttributeTable::testNoGeom()
 
 }
 
+void TestQgsAttributeTable::testSelected()
+{
+  // test attribute table opening in show selected mode
+  QgsSettings s;
+
+  std::unique_ptr< QgsVectorLayer> tempLayer( new QgsVectorLayer( QStringLiteral( "LineString?crs=epsg:3111&field=pk:int&field=col1:double" ), QStringLiteral( "vl" ), QStringLiteral( "memory" ) ) );
+  QVERIFY( tempLayer->isValid() );
+
+  QgsFeature f1( tempLayer->dataProvider()->fields(), 1 );
+  QgsFeature f2( tempLayer->dataProvider()->fields(), 2 );
+  QgsFeature f3( tempLayer->dataProvider()->fields(), 3 );
+  QVERIFY( tempLayer->dataProvider()->addFeatures( QgsFeatureList() << f1 << f2 << f3 ) );
+
+  s.setValue( QStringLiteral( "/qgis/attributeTableBehavior" ), QgsAttributeTableFilterModel::ShowSelected );
+  std::unique_ptr< QgsAttributeTableDialog > dlg( new QgsAttributeTableDialog( tempLayer.get() ) );
+
+  QVERIFY( !dlg->mMainView->masterModel()->layerCache()->cacheGeometry() );
+  //should be nothing - because no selection!
+  QCOMPARE( dlg->mMainView->masterModel()->request().filterType(), QgsFeatureRequest::FilterFids );
+  QVERIFY( dlg->mMainView->masterModel()->request().filterFids().isEmpty() );
+
+  // make a selection
+  tempLayer->selectByIds( QgsFeatureIds() << 1 << 3 );
+  QCOMPARE( dlg->mMainView->masterModel()->request().filterType(), QgsFeatureRequest::FilterFids );
+  QCOMPARE( dlg->mMainView->masterModel()->request().filterFids(), QgsFeatureIds() << 1 << 3 );
+
+  // another test - start with selection when dialog created
+  dlg.reset( new QgsAttributeTableDialog( tempLayer.get() ) );
+  QVERIFY( !dlg->mMainView->masterModel()->layerCache()->cacheGeometry() );
+  QCOMPARE( dlg->mMainView->masterModel()->request().filterType(), QgsFeatureRequest::FilterFids );
+  QCOMPARE( dlg->mMainView->masterModel()->request().filterFids(), QgsFeatureIds() << 1 << 3 );
+  // remove selection
+  tempLayer->removeSelection();
+  QCOMPARE( dlg->mMainView->masterModel()->request().filterType(), QgsFeatureRequest::FilterFids );
+  QVERIFY( dlg->mMainView->masterModel()->request().filterFids().isEmpty() );
+}
+
 
 QGSTEST_MAIN( TestQgsAttributeTable )
 #include "testqgsattributetable.moc"

tests/src/gui/testqgsdualview.cpp

@@ -50,6 +50,7 @@ class TestQgsDualView : public QObject
     void testColumnHeaders();
 
     void testData();
+    void testFilterSelected();
 
     void testSelectAll();
 
@@ -134,6 +135,36 @@ void TestQgsDualView::testData()
   }
 }
 
+void TestQgsDualView::testFilterSelected()
+{
+  QgsFeature feature;
+  QList< QgsFeatureId > ids;
+  QgsFeatureIterator it = mPointsLayer->getFeatures( QgsFeatureRequest().setOrderBy( QgsFeatureRequest::OrderBy() << QgsFeatureRequest::OrderByClause( "Heading" ) ) );
+  while ( it.nextFeature( feature ) )
+    ids << feature.id();
+
+  // select some features
+  QList< QgsFeatureId > selected;
+  selected << ids.at( 1 ) << ids.at( 3 );
+  mPointsLayer->selectByIds( selected.toSet() );
+
+  mDualView->setFilterMode( QgsAttributeTableFilterModel::ShowSelected );
+  QCOMPARE( mDualView->tableView()->model()->rowCount(), 2 );
+
+  int headingIdx = mPointsLayer->fields().lookupField( "Heading" );
+  QgsField fld = mPointsLayer->fields().at( headingIdx );
+  for ( int i = 0; i < selected.count(); ++i )
+  {
+    mPointsLayer->getFeatures( QgsFeatureRequest().setFilterFid( selected.at( i ) ) ).nextFeature( feature );
+    QModelIndex index = mDualView->tableView()->model()->index( i, headingIdx );
+    QCOMPARE( mDualView->tableView()->model()->data( index ).toString(), fld.displayString( feature.attribute( headingIdx ) ) );
+  }
+
+  // select none
+  mPointsLayer->removeSelection();
+  QCOMPARE( mDualView->tableView()->model()->rowCount(), 0 );
+}
+
 void TestQgsDualView::testSelectAll()
 {
   mDualView->setFilterMode( QgsAttributeTableFilterModel::ShowVisible );