c++ - Fl_X compile error -

i have been modifying project , when try compile software following error:

in file included main.cpp:32:0: main.h: in member function ‘virtual void fl_root::show()’: main.h:41:17: error: incomplete type ‘fl_x’ used in nested name specifier    if (!shown()) fl_x::set_xid(this, rootwindow(fl_display, fl_screen));                  ^ 

the menu.h file simple , contains following:

extern void showmenu();  class fl_root : public fl_window {     int handle(int); public:     fl_root() : fl_window(0,0,fl::w(),fl::h()) {      }     void show() {         if (!shown()) fl_x::set_xid(this, rootwindow(fl_display, fl_screen));     }     void flush() {     } }; 

any appreciated!

per drew's suggestion!

i found problem! commented out "#define fl_internals 1" call before "#include" statements - oops! wanted post in case helps else.