this time I started as instructed, in 'build' directory and not in src root.
Build nearly finishes, but ..
[ 83%] Building CXX object src/tools/CMakeFiles/oyranos-xforms-fltk.dir/oforms/oyranos_xforms_fltk.cxx.o
In file included from /home/guest/botva/src/src/oyranos/src/include_private/Oy_Fl_Double_Window.h:5,
from /home/guest/botva/src/src/oyranos/src/tools/oforms/oyranos_xforms_fltk.cxx:33:
/home/guest/botva/src/src/oyranos/src/include_private/Oy_Fl_Window_Base.h: In static member function 'static float Oy_Fl_Window_Base::getScaleFactor()':
/home/guest/botva/src/src/oyranos/src/include_private/Oy_Fl_Window_Base.h:93:7: error: 'Fl_Preferences' was not declared in this scope
93 | Fl_Preferences pref( Fl_Preferences::USER, *scale_factor_pref_org(), *scale_factor_pref_app() );
| ^~~~~~~~~~~~~~
/home/guest/botva/src/src/oyranos/src/include_private/Oy_Fl_Window_Base.h:94:22: error: expected ';' before 'app_pref'
94 | Fl_Preferences app_pref( pref, *scale_factor_pref_app() );
| ^~~~~~~~
/home/guest/botva/src/src/oyranos/src/include_private/Oy_Fl_Window_Base.h:95:7: error: 'app_pref' was not declared in this scope
95 | app_pref.get( "user_scale", scale_factor_(), 1.0f );
| ^~~~~~~~
/home/guest/botva/src/src/oyranos/src/include_private/Oy_Fl_Window_Base.h: In static member function 'static void Oy_Fl_Window_Base::setScaleFactor(float)':
/home/guest/botva/src/src/oyranos/src/include_private/Oy_Fl_Window_Base.h:103:7: error: 'Fl_Preferences' was not declared in this scope
103 | Fl_Preferences pref( Fl_Preferences::USER, *scale_factor_pref_org(), *scale_factor_pref_app() );
| ^~~~~~~~~~~~~~
/home/guest/botva/src/src/oyranos/src/include_private/Oy_Fl_Window_Base.h:104:22: error: expected ';' before 'app_pref'
104 | Fl_Preferences app_pref( pref, *scale_factor_pref_app() );
| ^~~~~~~~
/home/guest/botva/src/src/oyranos/src/include_private/Oy_Fl_Window_Base.h:105:7: error: 'app_pref' was not declared in this scope
105 | app_pref.set( "user_scale", scale_factor_() );
| ^~~~~~~~
make[2]: *** [src/tools/CMakeFiles/oyranos-xforms-fltk.dir/build.make:104: src/tools/CMakeFiles/oyranos-xforms-fltk.dir/oforms/oyranos_xforms_fltk.cxx.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:4782: src/tools/CMakeFiles/oyranos-xforms-fltk.dir/all] Error 2
make: *** [Makefile:136: all] Error 2
fltk-config --version
1.1.9
this time I started as instructed, in 'build' directory and not in src root.
Build nearly finishes, but ..
fltk-config --version
1.1.9