Hack is still required, but maybe using non-deprecated api will help?

nyalldawson · nyalldawson · commit 388f9e204c06 · 2018-07-31T10:24:02.000+10:00
Sometimes qt is great, sometimes I want to punch it in it's silly little cute face (cherry-picked from df05369)
diff --git a/src/core/layout/qgslayoutexporter.cpp b/src/core/layout/qgslayoutexporter.cpp
@@ -1108,8 +1108,11 @@ void QgsLayoutExporter::updatePrinterPageSize( QgsLayout *layout, QPrinter &prin
 {
   QgsLayoutSize pageSize = layout->pageCollection()->page( page )->sizeWithUnits();
   QgsLayoutSize pageSizeMM = layout->renderContext().measurementConverter().convert( pageSize, QgsUnitTypes::LayoutMillimeters );
-  printer.setOrientation( layout->pageCollection()->page( page )->orientation() == QgsLayoutItemPage::Portrait ? QPrinter::Portrait : QPrinter::Landscape );
-  printer.setPaperSize( pageSizeMM.toQSizeF(), QPrinter::Millimeter );
+
+  QPageLayout pageLayout( QPageSize( pageSizeMM.toQSizeF(), QPageSize::Millimeter ),
+                          QPageLayout::Portrait,
+                          QMarginsF( 0, 0, 0, 0 ) );
+  printer.setPageLayout( pageLayout );
 }
 
 QgsLayoutExporter::ExportResult QgsLayoutExporter::renderToLayeredSvg( const SvgExportSettings &settings, double width, double height, int page, QRectF bounds, const QString &filename, int svgLayerId, const QString &layerName, QDomDocument &svg, QDomNode &svgDocRoot, bool includeMetadata ) const

Original file line number	Diff line number	Diff line change
`@@ -1108,8 +1108,11 @@ void QgsLayoutExporter::updatePrinterPageSize( QgsLayout *layout, QPrinter &prin`
`1108`	`1108`	`{`
`1109`	`1109`	`QgsLayoutSize pageSize = layout->pageCollection()->page( page )->sizeWithUnits();`
`1110`	`1110`	`QgsLayoutSize pageSizeMM = layout->renderContext().measurementConverter().convert( pageSize, QgsUnitTypes::LayoutMillimeters );`
`1111`		`- printer.setOrientation( layout->pageCollection()->page( page )->orientation() == QgsLayoutItemPage::Portrait ? QPrinter::Portrait : QPrinter::Landscape );`
`1112`		`- printer.setPaperSize( pageSizeMM.toQSizeF(), QPrinter::Millimeter );`
	`1111`	`+`
	`1112`	`+ QPageLayout pageLayout( QPageSize( pageSizeMM.toQSizeF(), QPageSize::Millimeter ),`
	`1113`	`+ QPageLayout::Portrait,`
	`1114`	`+ QMarginsF( 0, 0, 0, 0 ) );`
	`1115`	`+ printer.setPageLayout( pageLayout );`
`1113`	`1116`	`}`
`1114`	`1117`
`1115`	`1118`	`QgsLayoutExporter::ExportResult QgsLayoutExporter::renderToLayeredSvg( const SvgExportSettings &settings, double width, double height, int page, QRectF bounds, const QString &filename, int svgLayerId, const QString &layerName, QDomDocument &svg, QDomNode &svgDocRoot, bool includeMetadata ) const`