1 files changed, 55 insertions, 9 deletions
diff --git a/tex/context/base/mkiv/math-fen.mkiv b/tex/context/base/mkiv/math-fen.mkiv
index 320dffeb8..a32ea410e 100644
--- a/tex/context/base/mkiv/math-fen.mkiv
+++ b/tex/context/base/mkiv/math-fen.mkiv
@@ -15,6 +15,14 @@
 
 \unprotect
 
+% maybe always "method=auto" for:
+%
+% \switchtobodyfont[cambria]
+% \ruledhbox{$f(x)$}
+% \ruledhbox{\mathdelimitersmode6$f\left(x\right)$}
+% \ruledhbox{\mathdelimitersmode7$f\left(x\right)$}
+% \ruledhbox{$f\left(\frac{1}{x}\right)$}
+
 % todo: mathstyle
 
 % \definemathfence [fancybracket] [bracket] [command=yes,color=blue]
@@ -38,12 +46,14 @@
 \let\setupmathfences\setupmathfence
 
 \setupmathfences
-  [\c!left=,
+  [\c!method=, % maybe always \v!auto
+   \c!left=,
    \c!right=,
    \c!middle=,
    \c!mathstyle=,
    \c!color=,
    \c!command=,
+   \c!mathclass=,
    \c!factor=\v!auto]
 
 \appendtoks
@@ -61,17 +71,40 @@
   {\ifx#1\empty
      #2.%
    \else
+     \edef\p_mathclass{\mathfenceparameter\c!mathclass}%
      \edef\p_factor{\mathfenceparameter\c!factor}%
      \ifx\p_factor\empty
-       #2%
+       \ifx\p_mathclass\empty
+         #2%
+       \else
+         #3%
+         \s!class\p_mathclass
+       \fi
      \else\ifx\p_factor\v!auto
-       #2%
+       \ifx\p_mathclass\empty
+         #2%
+       \else
+         #3%
+         \s!class\p_mathclass
+       \fi
      \else\ifx\p_factor\v!none
-       #3\s!height\zeropoint\s!depth\zeropoint\s!axis
-       #2%
+       #3%
+       \s!height\zeropoint
+       \s!depth\zeropoint
+       \ifx\p_mathclass\empty\else
+         \s!class\p_mathclass
+       \fi
+       \s!axis
+     % #2%
      \else
        \scratchdimen\dimexpr\p_factor\bodyfontsize/2\relax
-       #3\s!height\scratchdimen\s!depth\scratchdimen\s!axis
+       #3%
+       \s!height\scratchdimen
+       \s!depth\scratchdimen
+       \ifx\p_mathclass\empty\else
+         \s!class\p_mathclass
+       \fi
+       \s!axis
      \fi\fi\fi
      \Udelimiter#4\fam#1\relax
    \fi}
@@ -94,7 +127,7 @@
 
 \def\math_fenced_middle
   {\edef\p_middle
-     {\mathfenceparameter\c!middle}%
+    {\mathfenceparameter\c!middle}%
    \mskip\thinmuskip
    \math_fenced_color_push
  % \normalmiddle\ifx\p_middle\empty.\else\Udelimiter\plusfour\fam\p_middle\relax\fi
@@ -771,14 +804,14 @@
 \unexpanded\def\stopcheckedfences
   {\endgroup}
 
-\appendtoks
+% \appendtoks
    % maybe: safeguard against overloading
    %
    % \let\left       \math_fences_used_left
    % \let\right      \math_fences_used_right
    % \let\middle     \math_fences_used_middle
    % \let\leftorright\math_fences_used_both
-\to \everymathematics
+% \to \everymathematics
 
 \appendtoks
     \ifx\currentmathfence\empty
@@ -786,6 +819,19 @@
     \fi
 \to \everysetupmathfence
 
+\newconstant\c_math_fences_delimiters_mode \c_math_fences_delimiters_mode"16 % \numexpr"02+"04+"10\relax
+
+%unexpanded\def\enableautofencemode {\mathdelimitersmode\plussix} % the shift (1) is too fragile
+\unexpanded\def\enableautofencemode {\mathdelimitersmode\c_math_fences_delimiters_mode}
+
+\unexpanded\def\disableautofencemode{\mathdelimitersmode\zerocount}
+
+\appendtoks
+    \ifx\currentmathfence\empty
+        \doifelse{\mathfenceparameter\c!method}\v!auto\enableautofencemode\disableautofencemode
+    \fi
+\to \everysetupmathfence
+
 % some day default: \setupmathfences[\c!state=\v!auto]
 
 %D The next characters were used for constructing nicer extensibles but