\starttext

    $ \hat{H}  \ruledhbox{$\widehat{H}$}  \ruledhbox{$H$}  \widehat{H} $

    \definemathoverextensible [top] [hoed]  ["FE302]
    \definemathoverextensible [top] [slang] ["FE303]

    $ \hoed{H}  \ruledhbox{$\hoed{\tf H}$}  \slang{H} $

    \definemathaccents   [myaccents] [color=darkred]
    \definemathtopaccent [myaccents] [mywidehat] ["0302]

    $ \hat{H}  \widehat{H}  \mywidehat{H} $

\stoptext
