What is the C++ feature being used in this Nana demo code?

On their webpage, the Nana GUI people give this example:

#include<nana/gui.hpp>

int main()
{
     using namespace nana;
     form fm;
     drawing{fm}.draw([](paint::graphics& graph){
         graph.string({10, 10}, L"Hello, world!", colors::red);
     });
     fm.events().click(API::exit);
     fm.show();
     exec();
}

What is the C++ feature that is being used in the line that starts: drawing{fm}.draw...

I have never seen {} used like that.