feat: New force read only option for vector layer

To be able to open vector layer in a read-only mode, a new vector layer option has been defined to do it.

This option is used to open world_map.gpkg and fixes #35383

python/core/auto_generated/vector/qgsvectorlayer.sip.in

@@ -1842,7 +1842,9 @@ If you need only the count of committed features call this method on this layer'
 %Docstring
 Makes layer read-only (editing disabled) or not
 
-:return: ``False`` if the layer is in editing yet
+:return: ``False`` if the layer is in editing yet or if the data source is in read-only mode
+
+.. seealso:: :py:func:`readOnlyChanged`
 %End
 
     virtual bool supportsEditing() const;
@@ -3015,6 +3017,8 @@ Will be emitted whenever the edit form configuration of this layer changes.
 Emitted when the read only state of this layer is changed.
 Only applies to manually set readonly state, not to the edit mode.
 
+.. seealso:: :py:func:`setReadOnly`
+
 .. versionadded:: 3.0
 %End
 

src/app/qgsstatusbarcoordinateswidget.cpp

@@ -255,7 +255,8 @@ void QgsStatusBarCoordinatesWidget::world()
   }
   const QString fileName = QgsApplication::pkgDataPath() + QStringLiteral( "/resources/data/world_map.gpkg|layername=countries" );
   const QFileInfo fileInfo = QFileInfo( fileName );
-  const QgsVectorLayer::LayerOptions options { QgsProject::instance()->transformContext() };
+  QgsVectorLayer::LayerOptions options { QgsProject::instance()->transformContext() };
+  options.forceReadOnly = true;
   QgsVectorLayer *layer = new QgsVectorLayer( fileInfo.absoluteFilePath(),
       tr( "World Map" ), QStringLiteral( "ogr" ), options );
   // Register this layer with the layers registry
@@ -384,4 +385,3 @@ void QgsStatusBarCoordinatesWidget::ensureCoordinatesVisible()
     mLineEdit->setMaximumWidth( width );
   }
 }
-

src/core/vector/qgsvectorlayer.cpp

@@ -189,6 +189,7 @@ QgsVectorLayer::QgsVectorLayer( const QString &vectorLayerPath,
     if ( options.forceReadOnly )
     {
       providerFlags |= QgsDataProvider::ForceReadOnly;
+      mDataSourceReadOnly = true;
     }
     setDataSource( vectorLayerPath, baseName, providerKey, providerOptions, providerFlags );
   }
@@ -272,6 +273,7 @@ QgsVectorLayer *QgsVectorLayer::clone() const
   {
     dataSource = source();
   }
+  options.forceReadOnly = mDataSourceReadOnly;
   QgsVectorLayer *layer = new QgsVectorLayer( dataSource, name(), mProviderKey, options );
   if ( mDataProvider && layer->dataProvider() )
   {
@@ -1573,6 +1575,7 @@ bool QgsVectorLayer::readXml( const QDomNode &layer_node, QgsReadWriteContext &c
     mProviderKey = QStringLiteral( "ogr" );
   }
 
+  const QDomElement elem = layer_node.toElement();
   QgsDataProvider::ProviderOptions options { context.transformContext() };
   QgsDataProvider::ReadFlags flags;
   if ( mReadFlags & QgsMapLayer::FlagTrustLayerMetadata )
@@ -1585,7 +1588,6 @@ bool QgsVectorLayer::readXml( const QDomNode &layer_node, QgsReadWriteContext &c
     {
       QgsDebugMsg( QStringLiteral( "Could not set data provider for layer %1" ).arg( publicSource() ) );
     }
-    const QDomElement elem = layer_node.toElement();
 
     // for invalid layer sources, we fallback to stored wkbType if available
     if ( elem.hasAttribute( QStringLiteral( "wkbType" ) ) )
@@ -1594,6 +1596,7 @@ bool QgsVectorLayer::readXml( const QDomNode &layer_node, QgsReadWriteContext &c
   if ( mReadFlags & QgsMapLayer::FlagForceReadOnly )
   {
     flags |= QgsDataProvider::ForceReadOnly;
+    mDataSourceReadOnly = true;
   }
 
   QDomElement pkeyElem = pkeyNode.toElement();
@@ -3750,7 +3753,7 @@ bool QgsVectorLayer::isSpatial() const
 
 bool QgsVectorLayer::isReadOnly() const
 {
-  return mReadOnly;
+  return mDataSourceReadOnly || mReadOnly;
 }
 
 bool QgsVectorLayer::setReadOnly( bool readonly )
@@ -3759,6 +3762,10 @@ bool QgsVectorLayer::setReadOnly( bool readonly )
   if ( readonly && mEditBuffer )
     return false;
 
+  // exit if the data source is in read-only mode
+  if ( !readonly && mDataSourceReadOnly )
+    return false;
+
   mReadOnly = readonly;
   emit readOnlyChanged();
   return true;
@@ -3769,6 +3776,9 @@ bool QgsVectorLayer::supportsEditing() const
   if ( ! mDataProvider )
     return false;
 
+  if ( mDataSourceReadOnly )
+    return false;
+
   return mDataProvider->capabilities() & QgsVectorDataProvider::EditingCapabilities && ! mReadOnly;
 }
 

src/core/vector/qgsvectorlayer.h

@@ -486,6 +486,18 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
        */
       bool skipCrsValidation = false;
 
+      /**
+       * Controls whether the layer is forced to be load as Read Only
+       *
+       * If TRUE, then the layer's provider will only check read capabilities.
+       * Write capabilities will be skipped.
+       *
+       * If FALSE (the default), the layer's provider will check the
+       * edition capabilities based on user rights or file rights or
+       * others.
+       * \since QGIS 3.28
+       */
+      bool forceReadOnly = false;
     };
 
     /**
@@ -1725,7 +1737,9 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
 
     /**
      * Makes layer read-only (editing disabled) or not
-     * \returns FALSE if the layer is in editing yet
+     * \returns FALSE if the layer is in editing yet or if the data source is in read-only mode
+     *
+     * \see readOnlyChanged()
      */
     bool setReadOnly( bool readonly = true );
 
@@ -2792,6 +2806,8 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
      * Emitted when the read only state of this layer is changed.
      * Only applies to manually set readonly state, not to the edit mode.
      *
+     * \see setReadOnly()
+     *
      * \since QGIS 3.0
      */
     void readOnlyChanged();
@@ -2830,7 +2846,13 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
     void updateDefaultValues( QgsFeatureId fid, QgsFeature feature = QgsFeature() );
 
     /**
-     * Returns TRUE if the provider is in read-only mode
+     * Returns TRUE if the layer is in read-only mode
+     *
+     * \note the layer can be in read-only mode by construction or by action
+     * \see QgsVectorLayer::LayerOptions.forceReadOnly
+     * \see QgsMapLayer::FlagForceReadOnly
+     * \see setReadOnly()
+     * \see readOnlyChanged()
      */
     bool isReadOnly() const FINAL;
 
@@ -2893,7 +2915,15 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
     //! The user-defined actions that are accessed from the Identify Results dialog box
     QgsActionManager *mActions = nullptr;
 
-    //! Flag indicating whether the layer is in read-only mode (editing disabled) or not
+    //! Flag indicating whether the layer has been created in read-only mode (editing disabled) or not
+    bool mDataSourceReadOnly = false;
+
+    /**
+     * Flag indicating whether the layer has been converted in read-only mode (editing disabled) or not
+     * \see setReadOnly()
+     * \see readOnlyChanged()
+     * \see isReadOnly()
+     */
     bool mReadOnly = false;
 
     /**

src/gui/qgscoordinateboundspreviewmapwidget.cpp

@@ -35,7 +35,9 @@ QgsCoordinateBoundsPreviewMapWidget::QgsCoordinateBoundsPreviewMapWidget( QWidge
   setDestinationCrs( srs );
 
   const QString layerPath = QgsApplication::pkgDataPath() + QStringLiteral( "/resources/data/world_map.gpkg|layername=countries" );
-  mLayers << new QgsVectorLayer( layerPath );
+  QgsVectorLayer::LayerOptions options;
+  options.forceReadOnly = true;
+  mLayers << new QgsVectorLayer( layerPath, tr( "World Map" ), QStringLiteral( "ogr" ), options );
   setLayers( mLayers );
   mPanTool = new QgsMapToolPan( this );
   setMapTool( mPanTool );