Try add a new class QXlsx::Document

src/xlsx/xlsxdocument_p.h

@@ -0,0 +1,24 @@
+#ifndef XLSXDOCUMENT_P_H
+#define XLSXDOCUMENT_P_H
+
+#include "xlsxdocument.h"
+
+namespace QXlsx {
+
+class DocumentPrivate
+{
+    Q_DECLARE_PUBLIC(Document)
+public:
+    DocumentPrivate(Document *p);
+
+    bool loadPackage(QIODevice *device);
+
+    Document *q_ptr;
+    const QString defaultPackageName; //default name when package name not specified
+    QString packageName; //name of the .xlsx file
+
+};
+
+}
+
+#endif // XLSXDOCUMENT_P_H