[dxf] use a struct instead of QPair for layers

there was a crash in Python in QgsDxfExport.addLayers due to a bad conversion

python/core/dxf/qgsdxfexport.sip.in

@@ -20,6 +20,18 @@ class QgsDxfExport
 #include "qgsdxfexport.h"
 %End
   public:
+
+    struct DxfLayer
+    {
+      DxfLayer( QgsVectorLayer *vl, int layerOutputAttributeIndex = -1 );
+
+      QgsVectorLayer *layer() const;
+      int layerOutputAttributeIndex() const;
+
+      QgsVectorLayer *mLayer;
+      int mLayerOutputAttributeIndex;
+    };
+
     enum SymbologyExport
     {
       NoSymbology,
@@ -64,7 +76,7 @@ Returns the export flags.
 .. seealso:: :py:func:`setFlags`
 %End
 
-    void addLayers( const QList< QPair<QgsVectorLayer *, int > > &layers );
+    void addLayers( const QList< QgsDxfExport::DxfLayer > &layers );
 %Docstring
 Add layers to export
 

src/app/main.cpp

@@ -1357,7 +1357,7 @@ int main( int argc, char *argv[] )
     dxfExport.setExtent( dxfExtent );
 
     QStringList layerIds;
-    QList< QPair<QgsVectorLayer *, int > > layers;
+    QList< QgsDxfExport::DxfLayer > layers;
     if ( !dxfMapTheme.isEmpty() )
     {
       Q_FOREACH ( QgsMapLayer *layer, QgsProject::instance()->mapThemeCollection()->mapThemeVisibleLayers( dxfMapTheme ) )
@@ -1365,7 +1365,7 @@ int main( int argc, char *argv[] )
         QgsVectorLayer *vl = qobject_cast<QgsVectorLayer *>( layer );
         if ( !vl )
           continue;
-        layers << qMakePair<QgsVectorLayer *, int>( vl, -1 );
+        layers << QgsDxfExport::DxfLayer( vl );
         layerIds << vl->id();
       }
     }
@@ -1376,7 +1376,7 @@ int main( int argc, char *argv[] )
         QgsVectorLayer *vl = qobject_cast<QgsVectorLayer *>( ml );
         if ( !vl )
           continue;
-        layers << qMakePair<QgsVectorLayer *, int>( vl, -1 );
+        layers << QgsDxfExport::DxfLayer( vl );
         layerIds << vl->id();
       }
     }

src/app/qgsdxfexportdialog.cpp

@@ -276,9 +276,9 @@ bool QgsVectorLayerAndAttributeModel::setData( const QModelIndex &index, const Q
 }
 
 
-QList< QPair<QgsVectorLayer *, int> > QgsVectorLayerAndAttributeModel::layers() const
+QList< QgsDxfExport::DxfLayer > QgsVectorLayerAndAttributeModel::layers() const
 {
-  QList< QPair<QgsVectorLayer *, int> > layers;
+  QList< QgsDxfExport::DxfLayer > layers;
   QHash< QString, int > layerIdx;
 
   Q_FOREACH ( const QModelIndex &idx, mCheckedLeafs )
@@ -293,7 +293,7 @@ QList< QPair<QgsVectorLayer *, int> > QgsVectorLayerAndAttributeModel::layers()
         if ( !layerIdx.contains( vl->id() ) )
         {
           layerIdx.insert( vl->id(), layers.size() );
-          layers << qMakePair<QgsVectorLayer *, int>( vl, mAttributeIdx.value( vl, -1 ) );
+          layers << QgsDxfExport::DxfLayer( vl, mAttributeIdx.value( vl, -1 ) );
         }
       }
     }
@@ -304,12 +304,12 @@ QList< QPair<QgsVectorLayer *, int> > QgsVectorLayerAndAttributeModel::layers()
       if ( !layerIdx.contains( vl->id() ) )
       {
         layerIdx.insert( vl->id(), layers.size() );
-        layers << qMakePair<QgsVectorLayer *, int>( vl, mAttributeIdx.value( vl, -1 ) );
+        layers << QgsDxfExport::DxfLayer( vl, mAttributeIdx.value( vl, -1 ) );
       }
     }
   }
 
-  QList< QPair<QgsVectorLayer *, int> > layersInROrder;
+  QList< QgsDxfExport::DxfLayer > layersInROrder;
 
   QList<QgsMapLayer *> layerOrder = mRootNode->layerOrder();
 
@@ -549,7 +549,7 @@ void QgsDxfExportDialog::deSelectAll()
 }
 
 
-QList< QPair<QgsVectorLayer *, int> > QgsDxfExportDialog::layers() const
+QList< QgsDxfExport::DxfLayer > QgsDxfExportDialog::layers() const
 {
   const QgsVectorLayerAndAttributeModel *model = dynamic_cast< const QgsVectorLayerAndAttributeModel *>( mTreeView->model() );
   Q_ASSERT( model );

src/app/qgsdxfexportdialog.h

@@ -53,7 +53,7 @@ class QgsVectorLayerAndAttributeModel : public QgsLayerTreeModel
     Qt::ItemFlags flags( const QModelIndex &index ) const override;
     bool setData( const QModelIndex &index, const QVariant &value, int role = Qt::EditRole ) override;
 
-    QList< QPair<QgsVectorLayer *, int> > layers() const;
+    QList< QgsDxfExport::DxfLayer > layers() const;
 
     QgsVectorLayer *vectorLayer( const QModelIndex &index ) const;
     int attributeIndex( const QgsVectorLayer *vl ) const;
@@ -79,7 +79,7 @@ class QgsDxfExportDialog : public QDialog, private Ui::QgsDxfExportDialogBase
     QgsDxfExportDialog( QWidget *parent = nullptr, Qt::WindowFlags f = nullptr );
     ~QgsDxfExportDialog() override;
 
-    QList< QPair<QgsVectorLayer *, int> > layers() const;
+    QList< QgsDxfExport::DxfLayer > layers() const;
 
     double symbologyScale() const;
     QgsDxfExport::SymbologyExport symbologyMode() const;

src/core/dxf/qgsdxfexport.cpp

@@ -398,18 +398,18 @@ QgsDxfExport::Flags QgsDxfExport::flags() const
   return mFlags;
 }
 
-void QgsDxfExport::addLayers( const QList< QPair< QgsVectorLayer *, int > > &layers )
+void QgsDxfExport::addLayers( const QList<DxfLayer> &layers )
 {
   QList<QgsMapLayer *> layerList;
 
   mLayerNameAttribute.clear();
 
-  QList< QPair< QgsVectorLayer *, int > >::const_iterator layerIt = layers.constBegin();
+  QList< DxfLayer >::const_iterator layerIt = layers.constBegin();
   for ( ; layerIt != layers.constEnd(); ++layerIt )
   {
-    layerList << layerIt->first;
+    layerList << layerIt->layer();
-    if ( layerIt->second >= 0 )
+    if ( layerIt->layerOutputAttributeIndex() >= 0 )
-      mLayerNameAttribute.insert( layerIt->first->id(), layerIt->second );
+      mLayerNameAttribute.insert( layerIt->layer()->id(), layerIt->layerOutputAttributeIndex() );
   }
 
   mMapSettings.setLayers( layerList );

src/core/dxf/qgsdxfexport.h

@@ -51,6 +51,25 @@ namespace pal SIP_SKIP
 class CORE_EXPORT QgsDxfExport
 {
   public:
+
+    /**
+     * Layers and optional attribute index to split
+     * into multiple layers using attribute value as layer name.
+     */
+    struct DxfLayer
+    {
+      DxfLayer( QgsVectorLayer *vl, int layerOutputAttributeIndex = -1 )
+        : mLayer( vl )
+        , mLayerOutputAttributeIndex( layerOutputAttributeIndex )
+      {}
+
+      QgsVectorLayer *layer() const {return mLayer;}
+      int layerOutputAttributeIndex() const {return mLayerOutputAttributeIndex;}
+
+      QgsVectorLayer *mLayer;
+      int mLayerOutputAttributeIndex;
+    };
+
     enum SymbologyExport
     {
       NoSymbology = 0, //!< Export only data
@@ -97,7 +116,7 @@ class CORE_EXPORT QgsDxfExport
      * \param layers list of layers and corresponding attribute indexes that determine the layer name (-1 for original layer name or title)
      * \see setLayerTitleAsName
      */
-    void addLayers( const QList< QPair<QgsVectorLayer *, int > > &layers );
+    void addLayers( const QList< QgsDxfExport::DxfLayer > &layers );
 
     /**
      * Export to a dxf file in the given encoding

tests/src/core/testqgsdxfexport.cpp

@@ -94,7 +94,7 @@ void TestQgsDxfExport::cleanup()
 void TestQgsDxfExport::testPoints()
 {
   QgsDxfExport d;
-  d.addLayers( QList< QPair< QgsVectorLayer *, int > >() << qMakePair( mPointLayer, -1 ) );
+  d.addLayers( QList< QgsDxfExport::DxfLayer >() << QgsDxfExport::DxfLayer( mPointLayer ) );
 
   QgsMapSettings mapSettings;
   QSize size( 640, 480 );
@@ -122,7 +122,7 @@ void TestQgsDxfExport::testPoints()
 void TestQgsDxfExport::testLines()
 {
   QgsDxfExport d;
-  d.addLayers( QList< QPair< QgsVectorLayer *, int > >() << qMakePair( mLineLayer, -1 ) );
+  d.addLayers( QList< QgsDxfExport::DxfLayer >() << QgsDxfExport::DxfLayer( mLineLayer ) );
 
   QgsMapSettings mapSettings;
   QSize size( 640, 480 );
@@ -150,7 +150,7 @@ void TestQgsDxfExport::testLines()
 void TestQgsDxfExport::testPolygons()
 {
   QgsDxfExport d;
-  d.addLayers( QList< QPair< QgsVectorLayer *, int > >() << qMakePair( mPolygonLayer, -1 ) );
+  d.addLayers( QList< QgsDxfExport::DxfLayer >() << QgsDxfExport::DxfLayer( mPolygonLayer ) );
 
   QgsMapSettings mapSettings;
   QSize size( 640, 480 );
@@ -189,7 +189,7 @@ void TestQgsDxfExport::testMtext()
   mPointLayer->setLabelsEnabled( true );
 
   QgsDxfExport d;
-  d.addLayers( QList< QPair< QgsVectorLayer *, int > >() << qMakePair( mPointLayer, -1 ) );
+  d.addLayers( QList< QgsDxfExport::DxfLayer >() << QgsDxfExport::DxfLayer( mPointLayer ) );
 
   QgsMapSettings mapSettings;
   QSize size( 640, 480 );
@@ -251,7 +251,7 @@ void TestQgsDxfExport::testText()
   mPointLayer->setLabelsEnabled( true );
 
   QgsDxfExport d;
-  d.addLayers( QList< QPair< QgsVectorLayer *, int > >() << qMakePair( mPointLayer, -1 ) );
+  d.addLayers( QList< QgsDxfExport::DxfLayer >() << QgsDxfExport::DxfLayer( mPointLayer ) );
 
   QgsMapSettings mapSettings;
   QSize size( 640, 480 );