Add a clone method to QgsLayout

python/core/layout/qgslayout.sip

@@ -56,6 +56,12 @@ called on the new layout.
 
     ~QgsLayout();
 
+    virtual QgsLayout *clone() const /Factory/;
+%Docstring
+Creates a clone of the layout. Ownership of the return layout
+is transferred to the caller.
+%End
+
     void initializeDefaults();
 %Docstring
 Initializes an empty layout, e.g. by adding a default page to the layout. This should be called after creating

python/core/layout/qgsprintlayout.sip

@@ -26,6 +26,9 @@ class QgsPrintLayout : QgsLayout
 Constructor for QgsPrintLayout.
 %End
 
+    virtual QgsPrintLayout *clone() const /Factory/;
+
+
     QgsLayoutAtlas *atlas();
 %Docstring
 Returns the print layout's atlas.

src/core/composer/qgslayoutmanager.cpp

@@ -283,16 +283,8 @@ QgsComposition *QgsLayoutManager::duplicateComposition( const QString &name, con
 
 QgsLayout *QgsLayoutManager::duplicateLayout( const QgsLayout *layout, const QString &newName )
 {
-  QDomDocument currentDoc;
+  std::unique_ptr< QgsLayout > newLayout( layout->clone() );
-
+  if ( !newLayout )
-  QgsReadWriteContext context;
-  QDomElement elem = layout->writeXml( currentDoc, context );
-  currentDoc.appendChild( elem );
-
-  std::unique_ptr< QgsLayout > newLayout = qgis::make_unique< QgsPrintLayout >( mProject );
-  bool ok = false;
-  newLayout->loadFromTemplate( currentDoc, context, true, &ok );
-  if ( !ok )
   {
     return nullptr;
   }

src/core/layout/qgslayout.cpp

@@ -75,6 +75,25 @@ QgsLayout::~QgsLayout()
   mItemsModel.reset(); // manually delete, so we can control order of destruction
 }
 
+QgsLayout *QgsLayout::clone() const
+{
+  QDomDocument currentDoc;
+
+  QgsReadWriteContext context;
+  QDomElement elem = writeXml( currentDoc, context );
+  currentDoc.appendChild( elem );
+
+  std::unique_ptr< QgsLayout > newLayout = qgis::make_unique< QgsLayout >( mProject );
+  bool ok = false;
+  newLayout->loadFromTemplate( currentDoc, context, true, &ok );
+  if ( !ok )
+  {
+    return nullptr;
+  }
+
+  return newLayout.release();
+}
+
 void QgsLayout::initializeDefaults()
 {
   // default to a A4 landscape page

src/core/layout/qgslayout.h

@@ -83,6 +83,12 @@ class CORE_EXPORT QgsLayout : public QGraphicsScene, public QgsExpressionContext
 
     ~QgsLayout() override;
 
+    /**
+     * Creates a clone of the layout. Ownership of the return layout
+     * is transferred to the caller.
+     */
+    virtual QgsLayout *clone() const SIP_FACTORY;
+
     /**
      * Initializes an empty layout, e.g. by adding a default page to the layout. This should be called after creating
      * a new layout.

src/core/layout/qgsprintlayout.cpp

@@ -16,6 +16,7 @@
 
 #include "qgsprintlayout.h"
 #include "qgslayoutatlas.h"
+#include "qgsreadwritecontext.h"
 
 QgsPrintLayout::QgsPrintLayout( QgsProject *project )
   : QgsLayout( project )
@@ -23,6 +24,25 @@ QgsPrintLayout::QgsPrintLayout( QgsProject *project )
 {
 }
 
+QgsPrintLayout *QgsPrintLayout::clone() const
+{
+  QDomDocument currentDoc;
+
+  QgsReadWriteContext context;
+  QDomElement elem = writeXml( currentDoc, context );
+  currentDoc.appendChild( elem );
+
+  std::unique_ptr< QgsPrintLayout > newLayout = qgis::make_unique< QgsPrintLayout >( project() );
+  bool ok = false;
+  newLayout->loadFromTemplate( currentDoc, context, true, &ok );
+  if ( !ok )
+  {
+    return nullptr;
+  }
+
+  return newLayout.release();
+}
+
 QgsLayoutAtlas *QgsPrintLayout::atlas()
 {
   return mAtlas;

src/core/layout/qgsprintlayout.h

@@ -38,6 +38,8 @@ class CORE_EXPORT QgsPrintLayout : public QgsLayout
      */
     QgsPrintLayout( QgsProject *project );
 
+    QgsPrintLayout *clone() const override SIP_FACTORY;
+
     /**
      * Returns the print layout's atlas.
      */

tests/src/core/testqgslayout.cpp

@@ -26,6 +26,8 @@
 #include "qgslayoutitempolyline.h"
 #include "qgslayoutitemhtml.h"
 #include "qgslayoutframe.h"
+#include "qgsprintlayout.h"
+#include "qgslayoutatlas.h"
 
 class TestQgsLayout: public QObject
 {
@@ -54,6 +56,7 @@ class TestQgsLayout: public QObject
     void pageIsEmpty();
     void clear();
     void georeference();
+    void clone();
 
   private:
     QString mReport;
@@ -844,6 +847,44 @@ void TestQgsLayout::georeference()
   t.reset();
 }
 
+void TestQgsLayout::clone()
+{
+  QgsProject proj;
+  QgsLayout l( &proj );
+  QgsLayoutItemPage *page = new QgsLayoutItemPage( &l );
+  page->setPageSize( "A4" );
+  l.pageCollection()->addPage( page );
+  QgsLayoutItemPage *page2 = new QgsLayoutItemPage( &l );
+  page2->setPageSize( "A4" );
+  l.pageCollection()->addPage( page2 );
+  QgsLayoutItemPage *page3 = new QgsLayoutItemPage( &l );
+  page3->setPageSize( "A4" );
+  l.pageCollection()->addPage( page3 );
+
+  //add some items to the composition
+  QgsLayoutItemShape *label1 = new QgsLayoutItemShape( &l );
+  l.addLayoutItem( label1 );
+  QgsLayoutItemShape *label2 = new QgsLayoutItemShape( &l );
+  l.addLayoutItem( label2 );
+  QgsLayoutItemShape *label3 = new QgsLayoutItemShape( &l );
+  l.addLayoutItem( label3 );
+
+  // clone and check a few poperties
+  std::unique_ptr< QgsLayout > cloned( l.clone() );
+  QVERIFY( cloned.get() );
+  QCOMPARE( cloned->pageCollection()->pageCount(), 3 );
+  QList< QgsLayoutItem * > items;
+  cloned->layoutItems( items );
+  QCOMPARE( items.count(), 6 ); // 3 pages + 3 items
+
+  // clone a print layout
+  QgsPrintLayout pl( &proj );
+  pl.atlas()->setPageNameExpression( QStringLiteral( "not a real expression" ) );
+  std::unique_ptr< QgsPrintLayout > plClone( pl.clone() );
+  QVERIFY( plClone.get() );
+  QCOMPARE( plClone->atlas()->pageNameExpression(), QStringLiteral( "not a real expression" ) );
+}
+
 
 QGSTEST_MAIN( TestQgsLayout )
 #include "testqgslayout.moc"