sort of unclear indeed
these big things are tricky as in plain tex they depends on font dimensions and forced scaling but in context we have abit more control over these sizes
you can add this to cont-new.mkiv
\unprotect
\unexpanded\def\math_fenced_fenced_indeed[#1]#2% {\iffirstargument\setupcurrentmathfence[#1]\fi \math_fenced_fenced_common \edef\p_size{\mathfenceparameter\c!size}% \ifx\p_size\empty\else
\attribute\mathsizeattribute\numexpr\bigmathdelimitervariant *\plushundred+\p_size\relax \fi \math_fenced_left #2% \math_fenced_right \stopusemathstyleparameter \endgroup \advance\c_math_fenced_nesting\minusone}
\protect
and then do
\setupbodyfont[lucidaot]
\definemathfence[Set][left="007B,right="007D,command=yes]
\startTEXpage[offset=1ex] \startformula \Set{x\in\mathbb R~:~x^2=1} \stopformula \startformula \Set[size=2]{x\in\mathbb R~:~x^2=1} \stopformula \startformula \Set[size=3]{x\in\mathbb R~:~x^2=1} \stopformula \startformula \Set[size=4]{x\in\mathbb R~:~x^2=1} \stopformula \stopTEXpage
Many thanks for your answer, I appreciate it! If you look at the example below (output attached), you see that the version with \bigl and \bigr has a different size than the other ones. So my question boils down to: Is it possible, by using fences, to have the same size as the \big, \Big, \bigg etc would give? If not, is it possible to implement? I think it would make the already very nice fencing system even more usable. The reason is to be able to use this instead of not using fences at all in the few cases where the size from the fencing is not optimal. /Mikael \unprotect \unexpanded\def\math_fenced_fenced_indeed[#1]#2% {\iffirstargument\setupcurrentmathfence[#1]\fi \math_fenced_fenced_common \edef\p_size{\mathfenceparameter\c!size}% \ifx\p_size\empty\else \attribute\mathsizeattribute\numexpr\bigmathdelimitervariant*\plushundred+\p_size\relax \fi \math_fenced_left #2% \math_fenced_right \stopusemathstyleparameter \endgroup \advance\c_math_fenced_nesting\minusone} \protect \setupbodyfont[lucidaot] \definemathfence[Set][left="007B,right="007D,command=yes] \startTEXpage[offset=1ex] \startformula \{x\in\mathbb R~:~x^2=1\}\quad\text{Here the braces are too small} \stopformula \startformula \bigl\{x\in\mathbb R~:~x^2=1\bigr\}\quad\text{I like this size} \stopformula \startformula \Set{x\in\mathbb R~:~x^2=1}\quad\text{Here the braces are too big} \stopformula \startformula \Set[size=2]{x\in\mathbb R~:~x^2=1}\quad\text{Here the braces are too big} \stopformula \stopTEXpage