Smooth migration with traditional UI mode

IBM® Informix® 4GL (I4GL) and Genero Business Development Language (BDL) handle windows and form content rendering differently. I4GL is designed to write applications for dumb terminals, while Genero BDL uses real GUI rendering, with resizable windows and proportional fonts. To simplify migration from TUI-style products, Genero BDL supports the traditional GUI mode.