Code refactoring: add saveToXmlData() to Theme

src/xlsx/xlsxpackage.cpp

@@ -337,11 +337,7 @@ void Package::writeStylesFiles(ZipWriter &zipWriter)
 
 void Package::writeThemeFile(ZipWriter &zipWriter)
 {
-    QByteArray data;
-    QBuffer buffer(&data);
-    buffer.open(QIODevice::WriteOnly);
-    m_workbook->theme()->saveToXmlFile(&buffer);
-    zipWriter.addFile(QStringLiteral("xl/theme/theme1.xml"), data);
+    zipWriter.addFile(QStringLiteral("xl/theme/theme1.xml"), m_workbook->theme()->saveToXmlData());
 }
 
 void Package::writeRootRelsFile(ZipWriter &zipWriter)

src/xlsx/xlsxtheme.cpp

@@ -213,6 +213,14 @@ void Theme::saveToXmlFile(QIODevice *device)
         device->write(xmlData);
 }
 
+QByteArray Theme::saveToXmlData() const
+{
+    if (xmlData.isEmpty())
+        return defaultXmlData;
+    else
+        return xmlData;
+}
+
 void Theme::loadFromXmlData(const QByteArray &data)
 {
     xmlData = data;

src/xlsx/xlsxtheme_p.h

@@ -47,6 +47,7 @@ public:
     Theme();
 
     void saveToXmlFile(QIODevice *device);
+    QByteArray saveToXmlData() const;
     void loadFromXmlData(const QByteArray &data);
 
     QByteArray xmlData;