Merge pull request #6782 from wonder-sk/required-layers

Mark layers as required in the project

python/core/qgsproject.sip.in

@@ -952,6 +952,26 @@ Sets the project's ``metadata`` store.
 .. seealso:: :py:func:`metadata`
 
 .. seealso:: :py:func:`metadataChanged`
+%End
+
+    QSet<QgsMapLayer *> requiredLayers() const;
+%Docstring
+Returns a set of map layers that are required in the project and therefore they should not get
+removed from the project. The set of layers may be configured by users in project properties.
+and it is mainly a hint for the user interface to protect users from removing layers that important
+in the project. The removeMapLayer(), removeMapLayers() calls do not block removal of layers listed here.
+
+.. versionadded:: 3.2
+%End
+
+    void setRequiredLayers( const QSet<QgsMapLayer *> &layers );
+%Docstring
+Configures a set of map layers that are required in the project and therefore they should not get
+removed from the project. The set of layers may be configured by users in project properties.
+and it is mainly a hint for the user interface to protect users from removing layers that important
+in the project. The removeMapLayer(), removeMapLayers() calls do not block removal of layers listed here.
+
+.. versionadded:: 3.2
 %End
 
   signals:

src/app/qgisapp.cpp

@@ -9298,15 +9298,17 @@ void QgisApp::removeLayer()
     return;
   }
 
-  Q_FOREACH ( QgsMapLayer *layer, mLayerTreeView->selectedLayers() )
+  const QList<QgsMapLayer *> selectedLayers = mLayerTreeView->selectedLayers();
+
+  for ( QgsMapLayer *layer : selectedLayers )
   {
     QgsVectorLayer *vlayer = qobject_cast<QgsVectorLayer *>( layer );
     if ( vlayer && vlayer->isEditable() && !toggleEditing( vlayer, true ) )
       return;
   }
 
   QStringList activeTaskDescriptions;
-  Q_FOREACH ( QgsMapLayer *layer, mLayerTreeView->selectedLayers() )
+  for ( QgsMapLayer *layer : selectedLayers )
   {
     QList< QgsTask * > tasks = QgsApplication::taskManager()->tasksDependentOnLayer( layer );
     if ( !tasks.isEmpty() )
@@ -9318,6 +9320,16 @@ void QgisApp::removeLayer()
     }
   }
 
+  // extra check for required layers
+  // In theory it should not be needed because the remove action should be disabled
+  // if there are required layers in the selection...
+  const QSet<QgsMapLayer *> requiredLayers = QgsProject::instance()->requiredLayers();
+  for ( QgsMapLayer *layer : selectedLayers )
+  {
+    if ( requiredLayers.contains( layer ) )
+      return;
+  }
+
   if ( !activeTaskDescriptions.isEmpty() )
   {
     QMessageBox::warning( this, tr( "Active Tasks" ),
@@ -11573,7 +11585,7 @@ void QgisApp::selectionChanged( QgsMapLayer *layer )
 
 void QgisApp::legendLayerSelectionChanged()
 {
-  QList<QgsLayerTreeLayer *> selectedLayers = mLayerTreeView ? mLayerTreeView->selectedLayerNodes() : QList<QgsLayerTreeLayer *>();
+  const QList<QgsLayerTreeLayer *> selectedLayers = mLayerTreeView ? mLayerTreeView->selectedLayerNodes() : QList<QgsLayerTreeLayer *>();
 
   mActionDuplicateLayer->setEnabled( !selectedLayers.isEmpty() );
   mActionSetLayerScaleVisibility->setEnabled( !selectedLayers.isEmpty() );
@@ -11599,6 +11611,19 @@ void QgisApp::legendLayerSelectionChanged()
       mLegendExpressionFilterButton->setChecked( exprEnabled );
     }
   }
+
+  // remove action - check for required layers
+  bool removeEnabled = true;
+  const QSet<QgsMapLayer *> requiredLayers = QgsProject::instance()->requiredLayers();
+  for ( QgsLayerTreeLayer *nodeLayer : selectedLayers )
+  {
+    if ( requiredLayers.contains( nodeLayer->layer() ) )
+    {
+      removeEnabled = false;
+      break;
+    }
+  }
+  mActionRemoveLayer->setEnabled( removeEnabled );
 }
 
 void QgisApp::layerEditStateChanged()

src/app/qgsapplayertreeviewmenuprovider.cpp

@@ -87,7 +87,8 @@ QMenu *QgsAppLayerTreeViewMenuProvider::createContextMenu()
 
       menu->addSeparator();
       menu->addAction( actions->actionAddGroup( menu ) );
-      menu->addAction( QgsApplication::getThemeIcon( QStringLiteral( "/mActionRemoveLayer.svg" ) ), tr( "&Remove Group…" ), QgisApp::instance(), SLOT( removeLayer() ) );
+      QAction *removeAction = menu->addAction( QgsApplication::getThemeIcon( QStringLiteral( "/mActionRemoveLayer.svg" ) ), tr( "&Remove Group…" ), QgisApp::instance(), SLOT( removeLayer() ) );
+      removeAction->setEnabled( removeActionEnabled() );
       menu->addSeparator();
 
       menu->addAction( QgsApplication::getThemeIcon( QStringLiteral( "/mActionSetCRS.png" ) ),
@@ -171,7 +172,8 @@ QMenu *QgsAppLayerTreeViewMenuProvider::createContextMenu()
 
       // duplicate layer
       QAction *duplicateLayersAction = menu->addAction( QgsApplication::getThemeIcon( QStringLiteral( "/mActionDuplicateLayer.svg" ) ), tr( "&Duplicate Layer" ), QgisApp::instance(), SLOT( duplicateLayers() ) );
-      menu->addAction( QgsApplication::getThemeIcon( QStringLiteral( "/mActionRemoveLayer.svg" ) ), tr( "&Remove Layer…" ), QgisApp::instance(), SLOT( removeLayer() ) );
+      QAction *removeAction = menu->addAction( QgsApplication::getThemeIcon( QStringLiteral( "/mActionRemoveLayer.svg" ) ), tr( "&Remove Layer…" ), QgisApp::instance(), SLOT( removeLayer() ) );
+      removeAction->setEnabled( removeActionEnabled() );
 
       menu->addSeparator();
 
@@ -708,3 +710,15 @@ void QgsAppLayerTreeViewMenuProvider::setSymbolLegendNodeColor( const QColor &co
     layer->emitStyleChanged();
   }
 }
+
+bool QgsAppLayerTreeViewMenuProvider::removeActionEnabled()
+{
+  const QList<QgsLayerTreeLayer *> selectedLayers = mView->selectedLayerNodes();
+  const QSet<QgsMapLayer *> requiredLayers = QgsProject::instance()->requiredLayers();
+  for ( QgsLayerTreeLayer *nodeLayer : selectedLayers )
+  {
+    if ( requiredLayers.contains( nodeLayer->layer() ) )
+      return false;
+  }
+  return true;
+}

src/app/qgsapplayertreeviewmenuprovider.h

@@ -67,6 +67,9 @@ class QgsAppLayerTreeViewMenuProvider : public QObject, public QgsLayerTreeViewM
     void setVectorSymbolColor( const QColor &color );
     void editSymbolLegendNodeSymbol();
     void setSymbolLegendNodeColor( const QColor &color );
+
+  private:
+    bool removeActionEnabled();
 };
 
 #endif // QGSAPPLAYERTREEVIEWMENUPROVIDER_H

src/app/qgsprojectproperties.cpp

@@ -831,6 +831,7 @@ QgsProjectProperties::QgsProjectProperties( QgsMapCanvas *mapCanvas, QWidget *pa
   connect( titleEdit, &QLineEdit::textChanged, mMetadataWidget, &QgsMetadataWidget::setTitle );
 
   projectionSelectorInitialized();
+  populateRequiredLayers();
   restoreOptionsBaseUi();
   restoreState();
 }
@@ -1283,6 +1284,8 @@ void QgsProjectProperties::apply()
     canvas->refresh();
   }
   QgisApp::instance()->mapOverviewCanvas()->refresh();
+
+  applyRequiredLayers();
 }
 
 void QgsProjectProperties::showProjectionsTab()
@@ -2122,3 +2125,37 @@ void QgsProjectProperties::showHelp()
   }
   QgsHelp::openHelp( link );
 }
+
+void QgsProjectProperties::populateRequiredLayers()
+{
+  const QSet<QgsMapLayer *> requiredLayers = QgsProject::instance()->requiredLayers();
+  QStandardItemModel *model = new QStandardItemModel( mViewRequiredLayers );
+  QList<QgsLayerTreeLayer *> layers = QgsProject::instance()->layerTreeRoot()->findLayers();
+  std::sort( layers.begin(), layers.end(), []( QgsLayerTreeLayer * layer1, QgsLayerTreeLayer * layer2 ) { return layer1->name() < layer2->name(); } );
+  for ( const QgsLayerTreeLayer *l : layers )
+  {
+    QStandardItem *item = new QStandardItem( l->name() );
+    item->setCheckable( true );
+    item->setCheckState( requiredLayers.contains( l->layer() ) ? Qt::Checked : Qt::Unchecked );
+    item->setData( l->layerId() );
+    model->appendRow( item );
+  }
+
+  mViewRequiredLayers->setModel( model );
+}
+
+void QgsProjectProperties::applyRequiredLayers()
+{
+  QSet<QgsMapLayer *> requiredLayers;
+  QAbstractItemModel *model = mViewRequiredLayers->model();
+  for ( int i = 0; i < model->rowCount(); ++i )
+  {
+    if ( model->data( model->index( i, 0 ), Qt::CheckStateRole ).toInt() == Qt::Checked )
+    {
+      QString layerId = model->data( model->index( i, 0 ), Qt::UserRole + 1 ).toString();
+      if ( QgsMapLayer *layer = QgsProject::instance()->mapLayer( layerId ) )
+        requiredLayers << layer;
+    }
+  }
+  QgsProject::instance()->setRequiredLayers( requiredLayers );
+}

src/app/qgsprojectproperties.h

@@ -224,4 +224,7 @@ class APP_EXPORT QgsProjectProperties : public QgsOptionsDialogBase, private Ui:
     void updateGuiForMapUnits();
 
     void showHelp();
+
+    void populateRequiredLayers();
+    void applyRequiredLayers();
 };

src/core/qgsproject.cpp

@@ -2660,3 +2660,25 @@ void QgsProject::setMetadata( const QgsProjectMetadata &metadata )
 
   setDirty( true );
 }
+
+QSet<QgsMapLayer *> QgsProject::requiredLayers() const
+{
+  QSet<QgsMapLayer *> layers;
+  const QStringList lst = readListEntry( QStringLiteral( "RequiredLayers" ), QStringLiteral( "Layers" ) );
+  for ( const QString &layerId : lst )
+  {
+    if ( QgsMapLayer *layer = mapLayer( layerId ) )
+      layers.insert( layer );
+  }
+  return layers;
+}
+
+void QgsProject::setRequiredLayers( const QSet<QgsMapLayer *> &layers )
+{
+  QStringList layerIds;
+  for ( QgsMapLayer *layer : layers )
+  {
+    layerIds << layer->id();
+  }
+  writeEntry( QStringLiteral( "RequiredLayers" ), QStringLiteral( "Layers" ), layerIds );
+}

src/core/qgsproject.h

@@ -928,6 +928,24 @@ class CORE_EXPORT QgsProject : public QObject, public QgsExpressionContextGenera
      */
     void setMetadata( const QgsProjectMetadata &metadata );
 
+    /**
+     * Returns a set of map layers that are required in the project and therefore they should not get
+     * removed from the project. The set of layers may be configured by users in project properties.
+     * and it is mainly a hint for the user interface to protect users from removing layers that important
+     * in the project. The removeMapLayer(), removeMapLayers() calls do not block removal of layers listed here.
+     * \since QGIS 3.2
+     */
+    QSet<QgsMapLayer *> requiredLayers() const;
+
+    /**
+     * Configures a set of map layers that are required in the project and therefore they should not get
+     * removed from the project. The set of layers may be configured by users in project properties.
+     * and it is mainly a hint for the user interface to protect users from removing layers that important
+     * in the project. The removeMapLayer(), removeMapLayers() calls do not block removal of layers listed here.
+     * \since QGIS 3.2
+     */
+    void setRequiredLayers( const QSet<QgsMapLayer *> &layers );
+
   signals:
     //! emitted when project is being read
     void readProject( const QDomDocument & );

src/ui/qgsprojectpropertiesbase.ui

@@ -1443,7 +1443,7 @@
              </property>
             </widget>
            </item>
-           <item row="2" column="0">
+           <item row="3" column="0">
             <widget class="QCheckBox" name="mTrustProjectCheckBox">
              <property name="toolTip">
               <string>Speed up project loading by skipping data checks. Useful in qgis server context or project with huge database views or materialized views.</string>
@@ -1453,6 +1453,28 @@
              </property>
             </widget>
            </item>
+           <item row="4" column="0" colspan="2">
+            <widget class="QgsCollapsibleGroupBox" name="groupBox_5">
+             <property name="title">
+              <string>Required layers</string>
+             </property>
+             <layout class="QGridLayout" name="gridLayout_19">
+              <item row="0" column="0" colspan="2">
+               <widget class="QLabel" name="label_31">
+                <property name="text">
+                 <string>Checked layers in this list are protected from inadvertent removal from the project.</string>
+                </property>
+                <property name="wordWrap">
+                 <bool>true</bool>
+                </property>
+               </widget>
+              </item>
+              <item row="2" column="0" colspan="2">
+               <widget class="QListView" name="mViewRequiredLayers"/>
+              </item>
+             </layout>
+            </widget>
+           </item>
           </layout>
          </widget>
          <widget class="QWidget" name="mTabRelations">

tests/src/core/testqgsproject.cpp

@@ -40,6 +40,7 @@ class TestQgsProject : public QObject
     void testPathResolverSvg();
     void testProjectUnits();
     void variablesChanged();
+    void testRequiredLayers();
 };
 
 void TestQgsProject::init()
@@ -347,6 +348,40 @@ void TestQgsProject::variablesChanged()
   delete prj;
 }
 
+void TestQgsProject::testRequiredLayers()
+{
+  QString dataDir( TEST_DATA_DIR ); //defined in CmakeLists.txt
+  QString layerPath = dataDir + "/points.shp";
+  QgsVectorLayer *layer1 = new QgsVectorLayer( layerPath, QStringLiteral( "points 1" ), QStringLiteral( "ogr" ) );
+  QgsVectorLayer *layer2 = new QgsVectorLayer( layerPath, QStringLiteral( "points 2" ), QStringLiteral( "ogr" ) );
+
+  QgsProject prj;
+  prj.addMapLayer( layer1 );
+  prj.addMapLayer( layer2 );
+
+  QSet<QgsMapLayer *> reqLayers;
+  reqLayers << layer2;
+  prj.setRequiredLayers( reqLayers );
+
+  QSet<QgsMapLayer *> reqLayersReturned = prj.requiredLayers();
+  QCOMPARE( reqLayersReturned.count(), 1 );
+  QCOMPARE( *reqLayersReturned.constBegin(), layer2 );
+
+  QTemporaryFile f;
+  QVERIFY( f.open() );
+  f.close();
+  prj.setFileName( f.fileName() );
+  prj.write();
+
+  // test reading required layers back
+  QgsProject prj2;
+  prj2.setFileName( f.fileName() );
+  QVERIFY( prj2.read() );
+  QSet<QgsMapLayer *> reqLayersReturned2 = prj2.requiredLayers();
+  QCOMPARE( reqLayersReturned2.count(), 1 );
+  QCOMPARE( ( *reqLayersReturned.constBegin() )->name(), QString( "points 2" ) );
+}
+
 
 QGSTEST_MAIN( TestQgsProject )
 #include "testqgsproject.moc"