But I want to do the same using only core::stringc/w, so the question is: how correctly (platform independently) format strings of types core:stringc/w ?
OMG, i hope not No, of course it won't work. c_str() returns a const char* string which is not writable. You'll have to use append and stuff to create your string. We do not have variable argument methods in Irrlicht, yet.
Yeah, indeed a nice function. But Windows-only. I think for a proper solution in Irrlicht we will need template specialization here... We have to use vsnprintf or vsnwprintf (resp. the _vs... versions from Microsoft). I wonder if VC6 will do this.