Photo crash on project switch

app/attributes/attributecontroller.cpp

@@ -359,59 +359,59 @@ void AttributeController::clearAll()
 void AttributeController::updateOnLayerChange()
 {
   clearAll();
+  QgsVectorLayer *layer = mFeatureLayerPair.layer();
+  if ( !layer )
+    return;
 
   // 1) DATA
-  QgsVectorLayer *layer = mFeatureLayerPair.layer();
-  if ( layer )
+  if ( layer->editFormConfig().layout() == Qgis::AttributeFormLayout::DragAndDrop )
   {
-    if ( layer->editFormConfig().layout() == Qgis::AttributeFormLayout::DragAndDrop )
+    QgsAttributeEditorContainer *root = layer->editFormConfig().invisibleRootContainer();
+    if ( root->columnCount() > 1 )
     {
-      QgsAttributeEditorContainer *root = layer->editFormConfig().invisibleRootContainer();
-      if ( root->columnCount() > 1 )
-      {
-        qDebug() << "root tab in manual config has multiple columns. not supported on mobile devices!";
-        root->setColumnCount( 1 );
-      }
+      qDebug() << "root tab in manual config has multiple columns. not supported on mobile devices!";
+      root->setColumnCount( 1 );
+    }
 
-      mHasTabs = allowTabs( root );
-      if ( mHasTabs )
+    mHasTabs = allowTabs( root );
+    if ( mHasTabs )
+    {
+      for ( QgsAttributeEditorElement *element : root->children() )
       {
-        for ( QgsAttributeEditorElement *element : root->children() )
+        if ( element->type() == Qgis::AttributeEditorType::Container )
         {
-          if ( element->type() == Qgis::AttributeEditorType::Container )
+          QgsAttributeEditorContainer *container = static_cast<QgsAttributeEditorContainer *>( element );
+          if ( container->columnCount() > 1 )
           {
-            QgsAttributeEditorContainer *container = static_cast<QgsAttributeEditorContainer *>( element );
-            if ( container->columnCount() > 1 )
-            {
-              qDebug() << "tab " << container->name() << " in manual config has multiple columns. not supported on mobile devices!";
-              container->setColumnCount( 1 );
-            }
-            createTab( container );
+            qDebug() << "tab " << container->name() << " in manual config has multiple columns. not supported on mobile devices!";
+            container->setColumnCount( 1 );
           }
+          createTab( container );
         }
       }
-      else
-      {
-        createTab( root );
-      }
     }
     else
     {
-      // Auto-Generated Layout
-      // We create fake root tab
-      QgsAttributeEditorContainer *tab = autoLayoutTabContainer();
-
-      // We need to look for relations and include them into form,
-      // in auto-generated layout they are not included in form config
-      discoverRelations( tab );
-
-      createTab( tab );
+      createTab( root );
     }
+  }
+  else
+  {
+    // Auto-Generated Layout
+    // We create fake root tab
+    QgsAttributeEditorContainer *tab = autoLayoutTabContainer();
+
+    // We need to look for relations and include them into form,
+    // in auto-generated layout they are not included in form config
+    discoverRelations( tab );
 
-    if ( mRememberAttributesController )
-      mRememberAttributesController->storeLayerFields( layer );
+    createTab( tab );
   }
 
+  if ( mRememberAttributesController )
+    mRememberAttributesController->storeLayerFields( layer );
+
+
   // 2) MODELS
   // for all other models, ownership is managed by Qt parent system
   AttributeTabModel *tabModel = new AttributeTabModel( mAttributeTabProxyModel.get(), this, mTabItems.size() );
@@ -462,6 +462,9 @@ void AttributeController::updateOnLayerChange()
 
 void AttributeController::updateOnFeatureChange()
 {
+  if ( !mFeatureLayerPair.layer() )
+    return;
+
   const QgsFeature feature = mFeatureLayerPair.feature();
 
   QMap<QUuid, std::shared_ptr<FormItem>>::iterator formItemsIterator = mFormItems.begin();

app/inpututils.h

@@ -470,7 +470,7 @@ class InputUtils: public QObject
     Q_INVOKABLE static QString featureTitle( const FeatureLayerPair &pair, QgsProject *project );
 
     //! Creates featureLayerPair from geometry and layer, evaluates its expressions and returns it.
-    Q_INVOKABLE static FeatureLayerPair createFeatureLayerPair( QgsVectorLayer *layer, const QgsGeometry &geometry, VariablesManager *variablesmanager, QgsExpressionContextScope *additionalScope = nullptr );
+    Q_INVOKABLE static FeatureLayerPair createFeatureLayerPair( QgsVectorLayer *layer = nullptr, const QgsGeometry &geometry = QgsGeometry(), VariablesManager *variablesmanager = nullptr, QgsExpressionContextScope *additionalScope = nullptr );
 
     Q_INVOKABLE static void createEditBuffer( QgsVectorLayer *layer );
 

app/qml/FormsStackManager.qml

@@ -83,6 +83,11 @@ Item {
   }
 
   function _getActiveForm() {
+    if (formsStack.depth === 0) {
+      // no active form on empty form stack
+      return null
+    }
+
     if ( root.activeFormIndex >= 0 && root.activeFormIndex < formsStack.depth ) {
       return formsStack.get( activeFormIndex )
     }
@@ -137,7 +142,25 @@ Item {
   }
 
   function reload() {
-    formsStack.clear() // removes all objects thanks to Qt parent system
+    // Even after formStack.clear() is called,
+    // forms in the formStack will still
+    // receive and evaluate some signals
+    // and most importantly in some scenarios
+    // featureLayerPair could contain already
+    // dangling pointer to layer and crash the app
+    // https://github.com/MerginMaps/input/issues/2879
+    for ( let i = 0; i < formsStack.depth; i++ ) {
+      let form = formsStack.get( i )
+      form.featureLayerPair = __inputUtils.createFeatureLayerPair()
+      form.relationToApply = null
+      form.controllerToApply = null
+      form.project = null
+      form.linkedRelation = null
+      form.parentController = null
+    }
+
+    // removes all objects thanks to Qt parent system
+    formsStack.clear(StackView.Immediate)
   }
 
   function openLinkedFeature( linkedFeature ) {

app/qml/form/FormWrapper.qml

@@ -34,7 +34,7 @@ Item {
   property real previewHeight
   property real panelHeight
 
-  property bool isReadOnly: featureLayerPair ? featureLayerPair.layer.readOnly : false
+  property bool isReadOnly: featureLayerPair?.layer?.readOnly ?? false
 
   signal closed()
   signal editGeometry( var pair )