Make QgsLayoutExporter::generateFileName virtual, so exporter

subclasses can be made which customise the generated file names

python/core/layout/qgslayoutexporter.sip

@@ -21,11 +21,42 @@ class QgsLayoutExporter
 %End
   public:
 
+    struct PageExportDetails
+    {
+      QString directory;
+%Docstring
+Target folder
+%End
+
+      QString baseName;
+%Docstring
+Base part of filename (i.e. file name without extension or '.')
+%End
+
+      QString extension;
+%Docstring
+File suffix/extension (without the leading '.')
+%End
+
+      int page;
+%Docstring
+Page number, where 0 = first page.
+%End
+    };
+
     QgsLayoutExporter( QgsLayout *layout );
 %Docstring
 Constructor for QgsLayoutExporter, for the specified ``layout``.
 %End
 
+    virtual ~QgsLayoutExporter();
+
+    QgsLayout *layout() const;
+%Docstring
+ Returns the layout linked to this exporter.
+ :rtype: QgsLayout
+%End
+
     void renderPage( QPainter *painter, int page ) const;
 %Docstring
 Renders a full page to a destination ``painter``.
@@ -207,6 +238,15 @@ Resolution to export layout at
  The ``dpi`` argument can be set to the actual DPI of exported file, or left as -1 to use the layout's default DPI.
 %End
 
+  protected:
+
+    virtual QString generateFileName( const PageExportDetails &details ) const;
+%Docstring
+ Generates the file name for a page during export.
+
+ Subclasses can override this method to customise page file naming.
+ :rtype: str
+%End
 
 };
 

src/core/layout/qgslayoutexporter.cpp

@@ -31,6 +31,11 @@ QgsLayoutExporter::QgsLayoutExporter( QgsLayout *layout )
 
 }
 
+QgsLayout *QgsLayoutExporter::layout() const
+{
+  return mLayout;
+}
+
 void QgsLayoutExporter::renderPage( QPainter *painter, int page ) const
 {
   if ( !mLayout )
@@ -169,9 +174,11 @@ QgsLayoutExporter::ExportResult QgsLayoutExporter::exportToImage( const QString
   }
 
   QFileInfo fi( filePath );
-  QString path = fi.path();
-  QString baseName = fi.baseName();
-  QString extension = fi.completeSuffix();
+
+  PageExportDetails pageDetails;
+  pageDetails.directory = fi.path();
+  pageDetails.baseName = fi.baseName();
+  pageDetails.extension = fi.completeSuffix();
 
   LayoutContextSettingsRestorer dpiRestorer( mLayout );
   ( void )dpiRestorer;
@@ -207,7 +214,8 @@ QgsLayoutExporter::ExportResult QgsLayoutExporter::exportToImage( const QString
     if ( skip )
       continue; // should skip this page, e.g. null size
 
-    QString outputFilePath = generateFileName( path, baseName, extension, page );
+    pageDetails.page = page;
+    QString outputFilePath = generateFileName( pageDetails );
 
     if ( image.isNull() )
     {
@@ -215,7 +223,7 @@ QgsLayoutExporter::ExportResult QgsLayoutExporter::exportToImage( const QString
       return MemoryError;
     }
 
-    if ( !saveImage( image, outputFilePath, extension ) )
+    if ( !saveImage( image, outputFilePath, pageDetails.extension ) )
     {
       mErrorFileName = outputFilePath;
       return FileError;
@@ -509,15 +517,15 @@ QImage QgsLayoutExporter::createImage( const QgsLayoutExporter::ImageExportSetti
   }
 }
 
-QString QgsLayoutExporter::generateFileName( const QString &path, const QString &baseName, const QString &suffix, int page ) const
+QString QgsLayoutExporter::generateFileName( const PageExportDetails &details ) const
 {
-  if ( page == 0 )
+  if ( details.page == 0 )
   {
-    return path + '/' + baseName + '.' + suffix;
+    return details.directory + '/' + details.baseName + '.' + details.extension;
   }
   else
   {
-    return path + '/' + baseName + '_' + QString::number( page + 1 ) + '.' + suffix;
+    return details.directory + '/' + details.baseName + '_' + QString::number( details.page + 1 ) + '.' + details.extension;
   }
 }
 

src/core/layout/qgslayoutexporter.h

@@ -38,11 +38,34 @@ class CORE_EXPORT QgsLayoutExporter
 
   public:
 
+    //! Contains details of a page being exported by the class
+    struct PageExportDetails
+    {
+      //! Target folder
+      QString directory;
+
+      //! Base part of filename (i.e. file name without extension or '.')
+      QString baseName;
+
+      //! File suffix/extension (without the leading '.')
+      QString extension;
+
+      //! Page number, where 0 = first page.
+      int page = 0;
+    };
+
     /**
      * Constructor for QgsLayoutExporter, for the specified \a layout.
      */
     QgsLayoutExporter( QgsLayout *layout );
 
+    virtual ~QgsLayoutExporter() = default;
+
+    /**
+     * Returns the layout linked to this exporter.
+     */
+    QgsLayout *layout() const;
+
     /**
      * Renders a full page to a destination \a painter.
      *
@@ -219,6 +242,14 @@ class CORE_EXPORT QgsLayoutExporter
      */
     void computeWorldFileParameters( const QRectF &region, double &a, double &b, double &c, double &d, double &e, double &f, double dpi = -1 ) const;
 
+  protected:
+
+    /**
+     * Generates the file name for a page during export.
+     *
+     * Subclasses can override this method to customise page file naming.
+     */
+    virtual QString generateFileName( const PageExportDetails &details ) const;
 
   private:
 
@@ -228,8 +259,6 @@ class CORE_EXPORT QgsLayoutExporter
 
     QImage createImage( const ImageExportSettings &settings, int page, QRectF &bounds, bool &skipPage ) const;
 
-    QString generateFileName( const QString &path, const QString &baseName, const QString &suffix, int page ) const;
-
     /**
      * Saves an image to a file, possibly using format specific options (e.g. LZW compression for tiff)
     */

tests/src/python/test_qgslayoutexporter.py

@@ -317,6 +317,20 @@ class TestQgsLayoutExporter(unittest.TestCase):
         self.assertAlmostEqual(values[4], 1925.000000000000, 2)
         self.assertAlmostEqual(values[5], 3050.000000000000, 2)
 
+    def testPageFileName(self):
+        l = QgsLayout(QgsProject.instance())
+        exporter = QgsLayoutExporter(l)
+        details = QgsLayoutExporter.PageExportDetails()
+        details.directory = '/tmp/output'
+        details.baseName = 'my_maps'
+        details.extension = 'png'
+        details.page = 0
+        self.assertEqual(exporter.generateFileName(details), '/tmp/output/my_maps.png')
+        details.page = 1
+        self.assertEqual(exporter.generateFileName(details), '/tmp/output/my_maps_2.png')
+        details.page = 2
+        self.assertEqual(exporter.generateFileName(details), '/tmp/output/my_maps_3.png')
+
 
 if __name__ == '__main__':
     unittest.main()