We start with making a .per screenform for our window:

DATABASE FORMONLY

SCREEN {

 [editfield               ]

}

ATTRIBUTES
Edit editfield = FORMONLY.editfield;

Compile this example with “fcompile -xml style.per”
And now we create our window:

MAIN

IF aclfgl_sendfile_to_ui("default.4st") THEN END IF

OPEN WINDOW w_1 WITH FORM "style"

MENU "Navi"
   COMMAND "Ok"
   COMMAND "End"
      EXIT MENU
END MENU

END MAIN

The default.4st can be downloaded here. You need to place the default.4st file in the same folder as the program.