[FEATURE] add clone() methods for layers

src/core/qgsmaplayer.cpp

@@ -94,6 +94,43 @@ QgsMapLayer::~QgsMapLayer()
   delete mStyleManager;
 }
 
+void QgsMapLayer::clone( QgsMapLayer *layer, bool deep ) const
+{
+  layer->setBlendMode( blendMode() );
+
+  QMap<QString, QgsMapLayerStyle> styles = styleManager()->mapLayerStyles();
+  for ( QString s : styles.keys() )
+  {
+    layer->styleManager()->addStyle( s, styles.value( s ) );
+  }
+
+  layer->setName( name() );
+  layer->setShortName( shortName() );
+  layer->setMinimumScale( minimumScale() );
+  layer->setMaximumScale( maximumScale() );
+  layer->setScaleBasedVisibility( hasScaleBasedVisibility() );
+  layer->setTitle( title() );
+  layer->setAbstract( abstract() );
+  layer->setKeywordList( keywordList() );
+  layer->setDataUrl( dataUrl() );
+  layer->setDataUrlFormat( dataUrlFormat() );
+  layer->setAttribution( attribution() );
+  layer->setAttributionUrl( attributionUrl() );
+  layer->setMetadataUrl( metadataUrl() );
+  layer->setMetadataUrlType( metadataUrlType() );
+  layer->setMetadataUrlFormat( metadataUrlFormat() );
+  layer->setLegendUrl( legendUrl() );
+  layer->setLegendUrlFormat( legendUrlFormat() );
+  layer->setDependencies( dependencies() );
+  layer->setCrs( crs() );
+  layer->setCustomProperties( mCustomProperties );
+
+  if ( deep )
+  {
+    layer->setId( id() );
+  }
+}
+
 QgsMapLayer::LayerType QgsMapLayer::type() const
 {
   return mLayerType;
@@ -104,6 +141,11 @@ QString QgsMapLayer::id() const
   return mID;
 }
 
+void QgsMapLayer::setId( const QString &id )
+{
+  mID = id;
+}
+
 void QgsMapLayer::setName( const QString &name )
 {
   QString newName = capitalizeLayerName( name );
@@ -1583,6 +1625,11 @@ void QgsMapLayer::setCustomProperty( const QString &key, const QVariant &value )
   mCustomProperties.setValue( key, value );
 }
 
+void QgsMapLayer::setCustomProperties( const QgsObjectCustomProperties &properties )
+{
+  mCustomProperties = properties;
+}
+
 QVariant QgsMapLayer::customProperty( const QString &value, const QVariant &defaultValue ) const
 {
   return mCustomProperties.value( value, defaultValue );

src/core/qgsmaplayer.h

@@ -110,6 +110,13 @@ class CORE_EXPORT QgsMapLayer : public QObject
     //! QgsMapLayer cannot be copied
     QgsMapLayer &operator=( QgsMapLayer const & ) = delete;
 
+    /** Returns a new instance equivalent to this one.
+     * \param deep If true, a deep copy is done
+     * \returns a new layer instance
+     * \since QGIS 3.0
+     */
+    virtual QgsMapLayer *clone( bool deep ) const = 0;
+
     /** Returns the type of the layer.
      */
     QgsMapLayer::LayerType type() const;
@@ -444,6 +451,12 @@ class CORE_EXPORT QgsMapLayer : public QObject
     */
     QVariant customProperty( const QString &value, const QVariant &defaultValue = QVariant() ) const;
 
+    /** Set custom properties for layer.
+     * \param properties The custom properties to set.
+     * \since QGIS 3.0
+     */
+    void setCustomProperties( const QgsObjectCustomProperties &properties );
+
     /** Remove a custom property from layer. Properties are stored in a map and saved in project file.
      * \see setCustomProperty()
      */
@@ -916,6 +929,15 @@ class CORE_EXPORT QgsMapLayer : public QObject
     void metadataChanged();
 
   protected:
+
+    /** Copies attributes like name, short name, ... into another layer. The
+     *  unique ID is copied too if deep parameter is true.
+     * \param layer The copy recipient
+     * \param deep To copy the unique ID or not
+     * \since QGIS 3.0
+     */
+    void clone( QgsMapLayer *layer, bool deep = false ) const;
+
     //! Set the extent
     virtual void setExtent( const QgsRectangle &rect );
 
@@ -1009,6 +1031,11 @@ class CORE_EXPORT QgsMapLayer : public QObject
 
   private:
 
+    /** Set the unique id of the layer.
+     * /param id the new unique id of the layer
+     */
+    void setId( const QString &id );
+
     /**
      * This method returns true by default but can be overwritten to specify
      * that a certain layer is writable.

src/core/qgsmaplayerstylemanager.cpp

@@ -70,6 +70,11 @@ QStringList QgsMapLayerStyleManager::styles() const
   return mStyles.keys();
 }
 
+QMap<QString, QgsMapLayerStyle> QgsMapLayerStyleManager::mapLayerStyles() const
+{
+  return mStyles;
+}
+
 QgsMapLayerStyle QgsMapLayerStyleManager::style( const QString &name ) const
 {
   if ( name == mCurrentStyle )

src/core/qgsmaplayerstylemanager.h

@@ -110,6 +110,13 @@ class CORE_EXPORT QgsMapLayerStyleManager : public QObject
 
     //! Return list of all defined style names
     QStringList styles() const;
+
+    /** Gets available styles for the associated map layer.
+     * \returns A map of map layer style by style name
+     * \since QGIS 3.0
+     */
+    QMap<QString, QgsMapLayerStyle> mapLayerStyles() const;
+
     //! Return data of a stored style - accessed by its unique name
     QgsMapLayerStyle style( const QString &name ) const;
 

src/core/qgspluginlayer.h

@@ -36,6 +36,13 @@ class CORE_EXPORT QgsPluginLayer : public QgsMapLayer
     QgsPluginLayer( const QString &layerType, const QString &layerName = QString() );
     ~QgsPluginLayer();
 
+    /** Returns a new instance equivalent to this one.
+     * \param deep If true, a deep copy is done
+     * \returns a new layer instance
+     * \since QGIS 3.0
+     */
+    virtual QgsPluginLayer *clone( bool deep ) const override = 0;
+
     //! Return plugin layer type (the same as used in QgsPluginLayerRegistry)
     QString pluginLayerType();
 

src/core/qgsvectorlayer.cpp

@@ -85,6 +85,7 @@
 #include "qgsxmlutils.h"
 #include "qgsunittypes.h"
 #include "qgstaskmanager.h"
+#include "qgsreadwritecontext.h"
 
 #include "diagram/qgsdiagram.h"
 
@@ -201,6 +202,63 @@ QgsVectorLayer::~QgsVectorLayer()
   delete mConditionalStyles;
 }
 
+QgsVectorLayer *QgsVectorLayer::clone( bool deep ) const
+{
+  QgsVectorLayer *layer = new QgsVectorLayer( source(), originalName(), mProviderKey );
+  QgsMapLayer::clone( layer, deep );
+
+  QList<QgsVectorLayerJoinInfo> joins = vectorJoins();
+  Q_FOREACH ( QgsVectorLayerJoinInfo join, joins )
+  {
+    layer->addJoin( join );
+  }
+
+  layer->setProviderEncoding( dataProvider()->encoding() );
+  layer->setDisplayExpression( displayExpression() );
+  layer->setMapTipTemplate( mapTipTemplate() );
+  layer->setReadOnly( isReadOnly() );
+  layer->selectByIds( selectedFeatureIds() );
+  layer->setExcludeAttributesWms( excludeAttributesWms() );
+  layer->setExcludeAttributesWfs( excludeAttributesWfs() );
+  layer->setExtent( extent() );
+  layer->setRenderer( renderer()->clone() );
+  layer->setAttributeTableConfig( attributeTableConfig() );
+  layer->setFeatureBlendMode( featureBlendMode() );
+  layer->setLayerTransparency( layerTransparency() );
+
+  if ( labeling() )
+  {
+    layer->setLabeling( labeling()->clone() );
+  }
+  layer->setSimplifyMethod( simplifyMethod() );
+
+  if ( diagramRenderer() )
+  {
+    layer->setDiagramRenderer( diagramRenderer()->clone() );
+  }
+
+  if ( diagramLayerSettings() )
+  {
+    QgsDiagramLayerSettings *dls = new QgsDiagramLayerSettings( *diagramLayerSettings() );
+    layer->setDiagramLayerSettings( *dls );
+  }
+
+  for ( int i = 0; i < fields().count(); i++ )
+  {
+    layer->setFieldAlias( i, attributeAlias( i ) );
+  }
+
+  for ( int i = 0; i < fields().count(); i++ )
+  {
+    if ( fields().fieldOrigin( i ) == QgsFields::OriginExpression )
+    {
+      layer->addExpressionField( expressionField( i ), fields().at( i ) );
+    }
+  }
+
+  return layer;
+}
+
 QString QgsVectorLayer::storageType() const
 {
   if ( mDataProvider )

src/core/qgsvectorlayer.h

@@ -400,6 +400,16 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
     //! QgsVectorLayer cannot be copied.
     QgsVectorLayer &operator=( QgsVectorLayer const &rhs ) = delete;
 
+    /** Returns a new instance equivalent to this one. A new provider is
+     *  created for the same data source and renderers for features and diagrams
+     *  are cloned too. Moreover, each attributes (transparency, extent, selected
+     *  features and so on) are identicals.
+     * \param deep If true, a deep copy is done (unique ID is copied too)
+     * \returns a new layer instance
+     * \since QGIS 3.0
+     */
+    virtual QgsVectorLayer *clone( bool deep = false ) const override SIP_FACTORY;
+
     //! Returns the permanent storage type for this layer as a friendly name.
     QString storageType() const;
 

src/core/raster/qgsrasterlayer.cpp

@@ -144,6 +144,14 @@ QgsRasterLayer::~QgsRasterLayer()
   // Note: provider and other interfaces are owned and deleted by pipe
 }
 
+QgsRasterLayer *QgsRasterLayer::clone( bool deep ) const
+{
+  QgsRasterLayer *layer = new QgsRasterLayer( source(), originalName(), mProviderKey );
+  QgsMapLayer::clone( layer, deep );
+  layer->setRenderer( renderer()->clone() );
+  return layer;
+}
+
 //////////////////////////////////////////////////////////
 //
 // Static Methods and members

src/core/raster/qgsrasterlayer.h

@@ -188,6 +188,14 @@ class CORE_EXPORT QgsRasterLayer : public QgsMapLayer
 
     ~QgsRasterLayer();
 
+    /** Returns a new instance equivalent to this one. A new provider is
+     *  created for the same data source and renderer is cloned too.
+     * \param deep If true, a deep copy is done (unique ID is copy too)
+     * \returns a new layer instance
+     * \since QGIS 3.0
+     */
+    virtual QgsRasterLayer *clone( bool deep = false ) const override SIP_FACTORY;
+
     //! \brief This enumerator describes the types of shading that can be used
     enum ColorShadingAlgorithm
     {