How does qtxlsx insert string to footer or header in xlsx file?

[fcy2016]

Hello,
I want to know how does qtxlsx insert string to footer or header in xlsx file?
I have writen footer in xlsx file , but after saveas by qt+qtxlsx the footer is nothing.
how i insert new string to footer or do some setting that won't let the footer disappear?
i see the Qt Xlsx C++ Classes on http://qtxlsx.debao.me/,and i don't find anything function about footer or header,my english is very bad,maybe i lost some thing.
please,
thank you.

[VSRonin]

It's basically the same as VSRonin#27