How is the UI of LibreOffice built?

Is the UI of libreOffice built with XML or are the menus hardcoded? What does the syntax look like?

All code can be seen here: http://opengrok.libreoffice.org/

Best,
Joel

Very useful link. Thank You.

The dialogs are in the process of being fully ported to an XML layout: https://wiki.documentfoundation.org/Development/WidgetLayout