

\starttext
\startbuffer[test]
  \startformula
  \hat{xxx} \quad \widehat{xxx} \quad \tilde{xxx} \quad \widetilde{xxx}
  \stopformula
\stopbuffer

\def\test#1{
  \switchtobodyfont[#1]
  \startTEXpage
  #1
  \getbuffer[test]
  \stopTEXpage
}

\test{modern}
\test{cambria}
\test{asana}
\test{xits}
\test{euler}
\stoptext
