"pure virtual method called" Under rasperberry pi with eglfs

        Dear LibreCAD developers:
    I have crosscompiled LibreCAD2.1.3 for rasperberry pi with eglfs. Following by this instruction:
https://wiki.qt.io/RaspberryPi2EGLFS
    I want LibreCAD running without X11 and under eglfs. Off course I failed and got this message after "main: app.exec()".
    pure virtual method called
    It seems that LibreCAD's event loop does not works under eglfs.
    Does any one have any hints?