nm... I guess LoadFont needs to fallback on *something* if say, Lucida, isn't on the system...
Yep, LoadGuiFont() should return the most suitable font even if the given name isn't available, to mimic the behaviour on Windows or OS X. FLTK just uses Helvetica if it can't match one, iirc.
Regarding LookupGuiFont(), check out the FLTKMaxGUI source (TFLTKGUIDriver.LibraryFont()) or the MaxGUI docs for more info. If GTK has the capability, it is better if the GUI driver overrides the LibraryFont() method, as otherwise hard-coded font names (specified in MaxGUI.MaxGUI) are returned for each platform.
Cheers