[api] Add QgsLayoutDesignerInterface.layoutExported signal

Emitted whenever the layout is exported from the designer

python/gui/auto_generated/layout/qgslayoutdesignerinterface.sip.in

@@ -457,6 +457,16 @@ Toggles whether or not the rulers should be ``visible`` in the designer.
 .. versionadded:: 3.4
 %End
 
+  signals:
+
+    void layoutExported();
+%Docstring
+Emitted whenever a layout is exported from the layout designer.
+
+The results of the export can be retrieved by calling :py:func:`~QgsLayoutDesignerInterface.lastExportResults`.
+
+.. versionadded:: 3.20
+%End
 
 };
 

src/app/layout/qgslayoutdesignerdialog.cpp

@@ -113,7 +113,9 @@ bool QgsLayoutDesignerDialog::sInitializedRegistry = false;
 QgsAppLayoutDesignerInterface::QgsAppLayoutDesignerInterface( QgsLayoutDesignerDialog *dialog )
   : QgsLayoutDesignerInterface( dialog )
   , mDesigner( dialog )
-{}
+{
+  connect( mDesigner, &QgsLayoutDesignerDialog::layoutExported, this, &QgsLayoutDesignerInterface::layoutExported );
+}
 
 QWidget *QgsAppLayoutDesignerInterface::window()
 {
@@ -4904,6 +4906,8 @@ void QgsLayoutDesignerDialog::storeExportResults( QgsLayoutExporter::ExportResul
     qDeleteAll( mLastExportLabelingResults );
     mLastExportLabelingResults.clear();
   }
+
+  emit layoutExported();
 }
 
 void QgsLayoutDesignerDialog::selectItems( const QList<QgsLayoutItem *> &items )

src/app/layout/qgslayoutdesignerdialog.h

@@ -338,6 +338,12 @@ class QgsLayoutDesignerDialog: public QMainWindow, public Ui::QgsLayoutDesignerB
      */
     void aboutToClose();
 
+    /**
+     * Emitted whenever a layout is exported from the layout designer.
+     *
+     */
+    void layoutExported();
+
   protected:
 
     void closeEvent( QCloseEvent * ) override;

src/gui/layout/qgslayoutdesignerinterface.h

@@ -398,6 +398,16 @@ class GUI_EXPORT QgsLayoutDesignerInterface: public QObject
      */
     virtual void showRulers( bool visible ) = 0;
 
+  signals:
+
+    /**
+     * Emitted whenever a layout is exported from the layout designer.
+     *
+     * The results of the export can be retrieved by calling lastExportResults().
+     *
+     * \since QGIS 3.20
+     */
+    void layoutExported();
 
 };