1 files changed, 564 insertions, 252 deletions
diff --git a/Master/texmf-dist/tex/context/base/mkiv/math-ali.mkiv b/Master/texmf-dist/tex/context/base/mkiv/math-ali.mkiv
index ebb20e33e31..49a343ba0b6 100644
--- a/Master/texmf-dist/tex/context/base/mkiv/math-ali.mkiv
+++ b/Master/texmf-dist/tex/context/base/mkiv/math-ali.mkiv
@@ -25,26 +25,28 @@
 %D Modules may provide additional alignment features. The following
 %D mechanisms are provided by the core.
 
+% why all these spans
+
 % n>1 ### needed, strange # interaction in recurse
 
-\newtoks\c_math_align_a
-\newtoks\c_math_align_b
-\newtoks\c_math_align_c
+\newtoks\t_math_align_a
+\newtoks\t_math_align_b
+\newtoks\t_math_align_c
 
 \def\displayopenupvalue{.25\bodyfontsize}
 
 \def\math_build_eqalign
   {\scratchtoks\emptytoks
    \dorecurse{\mathalignmentparameter\c!m}\math_build_eqalign_step
-   \normalexpanded{\scratchtoks{\the\scratchtoks\the\c_math_align_c}}}
+   \normalexpanded{\scratchtoks{\the\scratchtoks\the\t_math_align_c}}}
 
-\def\math_build_eqalign_step
+\unexpanded\def\math_build_eqalign_step % make sure no expansion in tracing
   {\ifnum\recurselevel>\plusone
      \scratchtoks\expandafter{\the\scratchtoks\tabskip\mathalignmentparameter\c!distance\aligntab\tabskip\zeropoint}%
    \fi
-   \normalexpanded{\scratchtoks{\the\scratchtoks\the\c_math_align_a}}%
+   \normalexpanded{\scratchtoks{\the\scratchtoks\the\t_math_align_a}}%
    \dorecurse{\numexpr\mathalignmentparameter\c!n-\plusone\relax}
-     {\normalexpanded{\scratchtoks{\the\scratchtoks\the\c_math_align_b}}}}
+     {\normalexpanded{\scratchtoks{\the\scratchtoks\the\t_math_align_b}}}}
 
 \def\math_math_in_eqalign#1%
   {\startforceddisplaymath
@@ -83,70 +85,141 @@
 
 % use zeroskipplusfill
 
-% i really need to redo this eqno mess ... in lua
-
 \def\math_prepare_r_eqalign_no
-  {\c_math_align_a{\strut\math_first_in_eqalign\hfil\math_left_of_equalign\span\math_math_in_eqalign{\alignmark\alignmark}\math_right_of_eqalign\tabskip\zeropoint}%
-   \c_math_align_b{\aligntab\math_next_in_eqalign\math_left_of_equalign\span\math_math_in_eqalign{\alignmark\alignmark}\math_right_of_eqalign\tabskip\zeropoint}%
+  {\t_math_align_a
+     {\strut
+      \tabskip\zeropoint
+      \alignmark\alignmark % for picking up the number
+      \aligntab
+      \math_first_in_eqalign
+      \hfil
+      \math_left_of_equalign
+      \span
+      \math_math_in_eqalign{\alignmark\alignmark}%
+      \math_right_of_eqalign
+      \tabskip\zeropoint}%
+   \t_math_align_b
+     {\aligntab
+      \math_next_in_eqalign
+      \math_left_of_equalign
+      \span
+      \math_math_in_eqalign{\alignmark\alignmark}%
+      \math_right_of_eqalign
+      \tabskip\zeropoint}%
    \ifnum\mathraggedstatus=\plusone
-     \c_math_align_c{\hfil\aligntab\span\math_text_in_eqalign{\alignmark\alignmark}\tabskip\zeropoint}%
+     \t_math_align_c
+       {\hfil
+        \aligntab
+        \span
+        \math_text_in_eqalign{\alignmark\alignmark}%
+        \tabskip\zeropoint}%
    \else\ifnum\mathraggedstatus=\plusthree
-     \c_math_align_c{\hfil\tabskip\zeropoint\s!plus 1\s!fill\aligntab\span\math_text_in_eqalign{\alignmark\alignmark}\tabskip\zeropoint}%
+     \t_math_align_c
+       {\hfil
+        \tabskip\zeropoint\s!plus 1\s!fill
+        \aligntab
+        \span
+        \math_text_in_eqalign{\alignmark\alignmark}%
+        \tabskip\zeropoint}%
    \else
-     \c_math_align_c{\hfil\tabskip\centering\aligntab\llap{\span\math_text_in_eqalign{\alignmark\alignmark}}\tabskip\zeropoint}%
+     \t_math_align_c
+       {\hfil
+        \tabskip\centering
+        \aligntab
+        \span
+        \llap{\math_text_in_eqalign{\alignmark\alignmark}}%
+        \tabskip\zeropoint}%
    \fi\fi
-   \global\mathnumberstatus\zerocount
    \math_build_eqalign
    \the\mathdisplayaligntweaks
    \tabskip\centering}
 
 \def\math_prepare_l_eqalign_no  % \checkeddisplaymath
-  {\c_math_align_a{\strut\math_first_in_eqalign\hfil\math_left_of_equalign\span\math_math_in_eqalign{\alignmark\alignmark}\math_right_of_eqalign\tabskip\zeropoint}%
-   \c_math_align_b{\aligntab\math_next_in_eqalign\math_left_of_equalign\span\math_math_in_eqalign{\alignmark\alignmark}\math_right_of_eqalign\tabskip\zeropoint}%
-   % problem: number is handled after rest and so ends up in the margin
+  {\t_math_align_a
+     {\strut
+      \tabskip\zeropoint
+      \alignmark\alignmark % for picking up the number
+      \aligntab
+      \math_first_in_eqalign
+      \hfil
+      \math_left_of_equalign
+      \span
+      \math_math_in_eqalign{\alignmark\alignmark}%
+      \math_right_of_eqalign
+      \tabskip\zeropoint}%
+   \t_math_align_b
+     {\aligntab
+      \math_next_in_eqalign
+      \math_left_of_equalign
+      \span
+      \math_math_in_eqalign{\alignmark\alignmark}%
+      \math_right_of_eqalign
+      \tabskip\zeropoint}%
    \ifnum\mathraggedstatus=\plusone
-     \c_math_align_c{\hfil\aligntab\kern-\displaywidth\rlap{\span\math_text_in_eqalign{\alignmark\alignmark}}\tabskip\displaywidth}%
+     \t_math_align_c
+       {\hfil
+        \aligntab
+        \kern-\displaywidth
+        \span
+        \rlap{\math_text_in_eqalign{\alignmark\alignmark}}%
+        \tabskip\displaywidth}%
    \else\ifnum\mathraggedstatus=\plusthree
-     \c_math_align_c{\hfil\tabskip\zeropoint\s!plus 1\s!fill\aligntab\kern-\displaywidth\span\math_rlap{\span\math_text_in_eqalign{\alignmark\alignmark}}\tabskip\displaywidth}%
+     \t_math_align_c
+       {\hfil
+        \tabskip\zeropoint\s!plus 1\s!fill
+        \aligntab
+        \kern-\displaywidth
+        \span
+        \math_rlap{\math_text_in_eqalign{\alignmark\alignmark}}%
+        \tabskip\displaywidth}%
    \else
-     \c_math_align_c{\hfil\tabskip\centering\aligntab\kern-\displaywidth\rlap{\span\math_text_in_eqalign{\alignmark\alignmark}}\tabskip\displaywidth}%
+     \t_math_align_c
+       {\hfil
+        \tabskip\centering
+        \aligntab
+        \kern-\displaywidth
+        \span
+        \rlap{\math_text_in_eqalign{\alignmark\alignmark}}%
+        \tabskip\displaywidth}%
    \fi\fi
-   \global\mathnumberstatus\zerocount
    \math_build_eqalign
    \the\mathdisplayaligntweaks
    \tabskip\centering}
 
+\def\math_halign_checked
+   {\halign \ifcase\eqalignmode \or to \checkeddisplaywidth \fi}
+
 \def\math_both_eqalign_no_normal#1#2%
   {\ifmmode
-     \the\mathdisplayaligntweaks % \let\strc_formulas_place_number\relax % strange hack
+     \the\mathdisplayaligntweaks
      \vcenter\bgroup
      \let\math_finish_eqalign_no\egroup
    \else
      \let\math_finish_eqalign_no\relax
    \fi
    #1%
-   \halign \ifcase\eqalignmode \or to \checkeddisplaywidth \fi \expandafter {\the\scratchtoks\crcr#2\crcr}%
+   \math_halign_checked\expandafter\bgroup\the\scratchtoks\crcr#2\crcr\egroup
    \math_finish_eqalign_no}
 
 \def\math_both_eqalign_no_aligned#1%
   {\ifmmode
-    \the\mathdisplayaligntweaks
-    \global\mathnumberstatus\plusone
-    \ifcase\mathraggedstatus
+     \the\mathdisplayaligntweaks
+     \global\mathnumberstatus\plusone
+     \ifcase\mathraggedstatus
        \def\math_finish_eqalign_no{\crcr\egroup}%
-    \else
+     \else
        % we're in a mathbox
        \vcenter\bgroup
        \def\math_finish_eqalign_no{\crcr\egroup\egroup}%
-    \fi
+     \fi
    \fi
    #1%
-   \halign \ifcase\eqalignmode \or to \checkeddisplaywidth \fi \expandafter \bgroup\the\scratchtoks\crcr}
+   \math_halign_checked\expandafter\bgroup\the\scratchtoks\crcr}
 
 \def\math_rlap#1%
   {\setbox\scratchbox\hbox{#1}%
-   \ifdim\wd\scratchbox>\mathnumbercorrection
-     \xdef\mathnumbercorrection{\the\wd\scratchbox}%
+   \ifdim\wd\scratchbox>\d_math_number_correction
+     \global\d_math_number_correction\wd\scratchbox
    \fi
    \box\scratchbox
    \global\mathnumberstatus\plustwo}
@@ -157,12 +230,9 @@
 \def\math_handle_eqalign_no_l_aligned{\math_both_eqalign_no_aligned\math_prepare_l_eqalign_no}
 \def\math_finish_eqalign_no          {\crcr\egroup}
 
-\let     \reqalignno \math_handle_eqalign_no_r_normal
-\let     \leqalignno \math_handle_eqalign_no_l_normal
-\let\alignreqalignno \math_handle_eqalign_no_r_aligned
-\let\alignleqalignno \math_handle_eqalign_no_l_aligned
-\let      \eqalignno \math_handle_eqalign_no_r_normal
-\let \aligneqalignno \math_handle_eqalign_no_r_aligned
+\let\reqalignno\relax
+\let\leqalignno\relax
+\let\eqalignno \relax
 
 %D Here we implement the user interface part. We start with basic math alignments:
 
@@ -170,26 +240,28 @@
 
 \newtoks \everymathalignment
 
-\def\math_alignment_NR_indeed[#1][#2]%
-  {\strc_formulas_place_number_nested{#1}{#2}% to be tagged (better an attribute)
+\def\math_alignment_NC_first#1\NR
+  {\glet\math_alignment_NC\math_alignment_NC_rest
+   \scratchtoks{\math_number_left_of_eqalign\aligntab#1\NR}% \math_number_left_of_eqalign not used yet
+   \dodoubleempty\math_alignment_NC_first_indeed}
+
+\def\math_alignment_NC_first_indeed[#1][#2]%
+  {\strc_formulas_place_number_nested{#1}{#2}\the\scratchtoks}
+
+\def\math_alignment_NR
+  {\aligntab
+   \dostoptagged % finish cell
+   \math_number_right_of_eqalign
    \crcr
    \dostoptagged % finish row
    \noalign{\glet\math_alignment_NC\math_alignment_NC_first}} % noalign used for change state, conditional does not work here
 
-\def\math_alignment_NC_first
-  {\glet\math_alignment_NC\math_alignment_NC_rest}
-
 \def\math_alignment_NC_rest
   {\aligntab}
 
 \def\math_alignment_EQ
   {\NC=}
 
-\def\math_alignment_NR
-  {\aligntab
-   \dostoptagged % finish cell
-   \dodoubleempty\math_alignment_NR_indeed} % use xx from tabulate
-
 \appendtoks
    \glet\math_alignment_NC\math_alignment_NC_first
    \unexpanded\def\NC{\math_alignment_NC}% messy, due to lookahead (we cannot use a flag)
@@ -227,7 +299,7 @@
    \the\everymathalignment
    \c_math_eqalign_column\zerocount
    \processcommacommand
-     [\mathalignmentparameter\c!align]
+     [\mathalignmentparameter\c!align]%
      {\advance\c_math_eqalign_column\plusone\math_eqalign_set_column}% takes argument
    \global\c_math_eqalign_column\plusone
    \dostarttagged\t!math\empty
@@ -311,15 +383,33 @@
 
 \def\math_left_of_equalign
   {\ifcsname\??mathalignmentvariant\number\c_math_eqalign_column\endcsname
-     \ifcase\csname\??mathalignmentvariant\number\c_math_eqalign_column\endcsname\or
-       \relax \or \hfill \or \hfill
-     \fi
+     \ifcase\lastnamedcs \or \relax \or \hfill \or \hfill \fi
    \fi}
 
 \def\math_right_of_eqalign
   {\ifcsname\??mathalignmentvariant\number\c_math_eqalign_column\endcsname
-     \ifcase\csname\??mathalignmentvariant\number\c_math_eqalign_column\endcsname\or
-       \hfill \or \relax \or \hfill
+     \ifcase\lastnamedcs \or \hfill \or \relax \or \hfill \fi
+   \fi}
+
+\newconditional\c_math_alignment_local_number % not used but when true puts in front (todo)
+
+\def\math_number_right_of_eqalign
+  {\ifcase\wd\b_strc_formulas_number\else
+     \ifconditional\c_math_alignment_local_number
+       \ifcase\c_strc_math_number_location\or\or
+         \box\b_strc_formulas_number
+       \fi
+     \else
+       \box\b_strc_formulas_number
+     \fi
+   \fi}
+
+\def\math_number_left_of_eqalign
+  {\ifcase\wd\b_strc_formulas_number\else
+     \ifconditional\c_math_alignment_local_number
+       \ifcase\c_strc_math_number_location\or
+         \box\b_strc_formulas_number
+       \fi
      \fi
    \fi}
 
@@ -677,8 +767,10 @@
 
 \def\math_matrix_stop
   {\crcr
-   \mathstrut\crcr
-   \noalign{\kern-\baselineskip}%
+ % \ifgridsnapping \else
+     \mathstrut\crcr
+     \noalign{\vskip-\baselineskip}%
+ % \fi
    \egroup
    \popmacro\math_matrix_NC
    \egroup
@@ -689,19 +781,19 @@
 \definemathmatrix[\v!mathmatrix]
 
 \def\math_matrix_prepare
-  {\c_math_align_a{\strut\math_first_in_eqalign\math_left_of_equalign\span
+  {\t_math_align_a{\strut\math_first_in_eqalign\math_left_of_equalign\span
             \math_text_in_eqalign{\mathmatrixparameter\c!style\alignmark\alignmark}\math_right_of_eqalign}%
-   \c_math_align_b{\aligntab\hskip\mathmatrixparameter\c!distance
+   \t_math_align_b{\aligntab\hskip\mathmatrixparameter\c!distance
             \math_next_in_eqalign\math_left_of_equalign\span
             \math_text_in_eqalign{\mathmatrixparameter\c!style\alignmark\alignmark}\math_right_of_eqalign}%
-   \c_math_align_c{\aligntab\aligntab\hskip\mathmatrixparameter\c!distance
+   \t_math_align_c{\aligntab\aligntab\hskip\mathmatrixparameter\c!distance
             \math_left_of_equalign\span
             \math_text_in_eqalign{\mathmatrixparameter\c!style\alignmark\alignmark}\math_right_of_eqalign}%
    \scratchtoks\emptytoks
-   \normalexpanded{\scratchtoks{\the\scratchtoks\the\c_math_align_a}}%
+   \normalexpanded{\scratchtoks{\the\scratchtoks\the\t_math_align_a}}%
    \dorecurse{\numexpr\scratchcounter-\plusone\relax}
-     {\normalexpanded{\scratchtoks{\the\scratchtoks\the\c_math_align_b}}}%
-   \normalexpanded{\scratchtoks{\the\scratchtoks\the\c_math_align_c}}%
+     {\normalexpanded{\scratchtoks{\the\scratchtoks\the\t_math_align_b}}}%
+   \normalexpanded{\scratchtoks{\the\scratchtoks\the\t_math_align_c}}%
    \halign \expandafter \bgroup\the\scratchtoks \crcr}
 
 \unexpanded\def\math_matrix_NC_indeed
@@ -1023,9 +1115,8 @@
 
 %D The following code comes from \type {math-str.mkiv}.
 %D
-%D Here we implement a basic math alignment mechanism. Numbers
-%D are also handled. The macros \type {\startinnermath} and
-%D \type {\stopinnermath} can be overloaded in specialized
+%D Here we implement a basic math alignment mechanism. Numbers are also handled. The macros
+%D \type {\startinnermath} and \type {\stopinnermath} can be overloaded in specialized
 %D modules.
 
 \installcorenamespace{mathinnerstart}
@@ -1052,223 +1143,444 @@
 \newconstant\mathraggedstatus % normal left center  right
 \newconstant\mathnumberstatus % nothing normal shift_right
 
-\let\mathnumbercorrection\!!zeropoint
-
-\let\math_the_r_eq_no\empty
-\let\math_the_l_eq_no\empty
-
-\unexpanded\def\startmathbox#1%
-  {\hsize\displaywidth % \checkeddisplaymath
-   \global\mathnumberstatus\plusone
-   \mathraggedstatus#1\relax
-   \let\mathnumbercorrection\!!zeropoint
-   \global\let\math_the_r_eq_no\empty
-   \global\let\math_the_l_eq_no\empty
-   \def\reqno{\gdef\math_the_r_eq_no}%
-   \def\leqno{\gdef\math_the_l_eq_no}%
-   \let\eqno\reqno
-   % added
-   \let\normalreqno\reqno
-   \let\normalleqno\leqno
-   \let\normaleqno \eqno
-   % added
-   \strc_formulas_place_number
-   \setbox\scratchbox\math_hbox to \displaywidth\bgroup % \checkeddisplaymath
-     \mathinnerstrut
-     \startforceddisplaymath
-     \ifcase\mathraggedstatus\or\hfill\or\hfill\fi}
+\newdimen\d_math_number_correction
 
 \def\math_box_llapped_math_no
   {\ifcase\mathraggedstatus\or
-     \math_the_r_eq_no
+     \box\b_strc_formulas_number
    \or
-     \llap{\math_the_r_eq_no}%
+     \llap{\box\b_strc_formulas_number}%
    \or
-     \llap{\math_the_r_eq_no}%
+     \llap{\box\b_strc_formulas_number}%
    \fi}
 
 \def\math_box_rlapped_math_no
   {\ifcase\mathraggedstatus\or
-     \rlap{\math_the_l_eq_no}%
+     \rlap{\box\b_strc_formulas_number}%
    \or
-     \rlap{\math_the_l_eq_no}%
+     \rlap{\box\b_strc_formulas_number}%
    \or
-     \math_the_l_eq_no
+     \box\b_strc_formulas_number
+   \fi}
+
+\newconditional\c_strc_math_has_number
+\newconditional\c_strc_math_display_overflow
+\newconstant   \c_strc_math_number_location
+\newdimen      \d_strc_math_number_width
+\newdimen      \d_strc_math_display_width
+\newbox        \b_strc_math_display
+\newconstant   \c_strc_formulas_frame_mode
+
+\let\d_strc_math_framed_width\displaywidth
+
+\setvalue{\??formulaoption\v!frame}%
+  {\edef\p_frame{\formulaparameter\c!frame}%
+   \ifx\p_frame\v!number
+     \c_strc_formulas_frame_mode\plustwo % inside frame
+   \else
+     \c_strc_formulas_frame_mode\plusone % outside frame
+   \fi}
+
+% mode: 0=no frame | 1=number inside frame | 2=number outside frame
+
+\def\strc_math_flush_aligned
+  {\ifcase\mathraggedstatus\or\hfill\or\hfill\fi
+   \box\b_strc_math_display
+   \ifcase\mathraggedstatus\or\or\hfill\or\hfill\fi}
+
+\def\strc_math_flush_box_normal
+  {\hbox to \displaywidth\bgroup
+     \strc_math_flush_aligned
+   \egroup}
+
+\def\strc_math_flush_box_framed_common
+  {\setformulaframedparameter\c!align{\formulaparameter\c!align}%
+   \letformulaframedparameter\c!strut\v!no
+   \d_framed_formula\ht\b_strc_math_display
+   \ifcase\mathraggedstatus\or\hfill\or\hfill         \fi
+   \inheritedformulaframedframed{\box\b_strc_math_display}%
+   \ifcase\mathraggedstatus\or      \or\hfill\or\hfill\fi}
+
+% \def\strc_math_flush_box_framed_inline
+%   {\letformulaframedparameter\c!location\empty
+%    \letformulaframedparameter\c!width\displaywidth
+%    \strc_math_flush_box_framed_common}
+
+\def\strc_math_flush_box_framed_display
+  {\let\currentformulaframed\currentformula
+   \letformulaframedparameter\c!location\v!formula
+   \setformulaframedparameter\c!width{\d_strc_math_framed_width}%
+   \strc_math_flush_box_framed_common}
+
+\def\strc_math_flush_box_framed_fit_inline
+  {\let\currentformulaframed\currentformula
+   \letformulaframedparameter\c!location\empty
+   \letformulaframedparameter\c!width\v!fit
+   \strc_math_flush_box_framed_common}
+
+\def\strc_math_flush_box_framed_fit_display
+  {\let\currentformulaframed\currentformula
+   \letformulaframedparameter\c!location\v!formula
+   \letformulaframedparameter\c!width\v!fit
+   \strc_math_flush_box_framed_common}
+
+% combiners
+
+\def\strc_math_flush_box
+  {\ifcase\c_strc_formulas_frame_mode
+     \strc_math_flush_box_normal
+   \else
+     \strc_math_flush_box_framed_display
+   \fi}
+
+\def\strc_math_number_right_normal
+  {\strc_math_flush_aligned
+   \hss % hss makes room for number
+   \math_box_llapped_math_no}
+
+\def\strc_math_number_left_normal
+  {\math_box_rlapped_math_no
+   \strc_math_flush_aligned
+   \hss} % hss makes room for number
+
+\def\strc_math_number_right_normal_outside
+  {\ifconditional\c_strc_formulas_tight
+     \strc_math_flush_box_framed_fit_display
+   \else
+     \strc_math_flush_box_framed_display
+   \fi
+   \hss % hss makes room for number
+   \math_box_llapped_math_no}
+
+\def\strc_math_number_left_normal_outside
+  {\math_box_rlapped_math_no
+   \hss % hss makes room for number
+   \ifconditional\c_strc_formulas_tight
+     \strc_math_flush_box_framed_fit_display
+   \else
+     \strc_math_flush_box_framed_display
+   \fi}
+
+\def\strc_math_number_right_normal_inside
+  {\setbox\b_strc_math_display\hpack to \dimexpr\displaywidth-\d_framed_locator_lo-\d_framed_locator_ro\relax\bgroup
+     \strc_math_flush_aligned
+     \hss
+     \math_box_llapped_math_no
+   \egroup
+   \strc_math_flush_box_framed_fit_inline}
+
+\def\strc_math_number_left_normal_inside
+  {\setbox\b_strc_math_display\hpack to \dimexpr\displaywidth-\d_framed_locator_lo-\d_framed_locator_ro\relax\bgroup
+     \math_box_rlapped_math_no
+     \hss
+     \strc_math_flush_aligned
+   \egroup
+   \strc_math_flush_box_framed_fit_inline}
+
+\def\strc_math_number_right_overflow
+  {\vpack\bgroup
+     \strc_math_flush_box
+     \par
+     \hpack to \displaywidth\bgroup
+       \hss
+       \math_box_llapped_math_no
+     \egroup
+   \egroup}
+
+\def\strc_math_number_left_overflow
+  {\vpack\bgroup
+     \hpack to \displaywidth\bgroup
+       \math_box_rlapped_math_no
+       \hss
+     \egroup
+     \strc_math_flush_box
+   \egroup}
+
+\def\strc_math_number_right_overflow_outside
+  {\vpack\bgroup
+     \strc_math_flush_box_framed_fit_inline
+%      \hskip\zeropoint % nicely breaks the line without introducing funny vertical spacing ... why o why
+     \hpack to \displaywidth\bgroup
+       \hss
+       \math_box_llapped_math_no
+     \egroup
+   \egroup}
+
+\def\strc_math_number_left_overflow_outside
+  {\vpack\bgroup
+     \hpack to \dimexpr\displaywidth-\d_framed_locator_lo\relax\bgroup
+       \math_box_rlapped_math_no
+       \hss
+     \egroup
+     \hskip\zeropoint % nicely breaks the line without introducing funny vertical spacing ... why o why
+     \strc_math_flush_box_framed_fit_inline
+   \egroup}
+
+\def\strc_math_number_right_overflow_inside
+  {\setbox\b_strc_math_display\vpack\bgroup
+     \box\b_strc_math_display
+     \hpack to \displaywidth\bgroup
+       \hss
+       \math_box_llapped_math_no
+       \hskip\d_framed_locator_ro
+     \egroup
+   \egroup
+   \strc_math_flush_box_framed_fit_inline}
+
+\def\strc_math_number_left_overflow_inside
+  {\setbox\b_strc_math_display\vpack\bgroup
+     \hpack to \displaywidth\bgroup
+     % \hskip\d_framed_locator_lo
+       \math_box_rlapped_math_no
+       \hss
+     \egroup
+     \box\b_strc_math_display
+   \egroup
+   \strc_math_flush_box_framed_fit_inline}
+
+% checkers
+
+\def\strc_math_number_check
+  {\d_strc_math_display_width\wd\b_strc_math_display
+   \ifconditional\c_strc_formulas_tight
+     \ifdim\d_strc_math_display_width>\displaywidth
+       \settrue\c_strc_math_display_overflow
+     \else
+       \displaywidth\d_strc_math_display_width
+       \setfalse\c_strc_math_display_overflow
+     \fi
+   \else
+     \ifdim\d_strc_math_display_width>\displaywidth
+       \settrue\c_strc_math_display_overflow
+     \else
+       \setfalse\c_strc_math_display_overflow
+     \fi
    \fi}
 
-\unexpanded\def\stopmathbox
+\def\strc_math_number_check_outside
+  {\d_strc_math_display_width\naturalwd\b_strc_math_display
+   \ifdim\dimexpr\d_strc_math_display_width+\d_framed_locator_lo+\d_framed_locator_ro\relax>\displaywidth
+     \settrue\c_strc_math_display_overflow
+   \else
+     \setfalse\c_strc_math_display_overflow
+   \fi
+   % still ok?
+   \ifnum\mathraggedstatus=\plustwo
+     \edef\d_strc_math_framed_width{\the\dimexpr\displaywidth-2\wd\b_strc_formulas_number\relax}%
+   \else
+     \edef\d_strc_math_framed_width{\the\dimexpr\displaywidth-\wd\b_strc_formulas_number\relax}%
+   \fi}
+
+\let\strc_math_number_check_inside\strc_math_number_check_outside
+
+% offsets
+
+\def\strc_math_number_check_offsets
+  {\begingroup
+     \setbox\scratchbox\hbox
+       {\inheritedformulaframedframed
+          {\pack_framed_locator_set_lo\pack_framed_locator_set_ro}}%
+   \endgroup}
+
+% tracing
+
+\def\strc_math_traced_state_yes
+  {\llap{\setbox\scratchbox\hbox{\infofont
+   \ifcase\mathraggedstatus unset\or right\or middle\or left\fi
+   \space
+   \ifcase\c_strc_formulas_frame_mode no\or out\or in\fi
+   \space
+   \ifconditional\c_strc_math_display_overflow overflow\else fit\fi
+   \quad}\ht\scratchbox\zeropoint\dp\scratchbox\zeropoint\box\scratchbox}}
+
+\let\strc_math_traced_state\relax
+
+\installtextracker
+  {formulas.framed}
+  {\let\strc_math_traced_state\strc_math_traced_state_yes}
+  {\let\strc_math_traced_state\relax}
+
+% packaging
+
+\unexpanded\def\strc_math_box_start#1%
+  {\hsize\displaywidth % \checkeddisplaymath
+   \global\mathnumberstatus\plusone
+   \mathraggedstatus#1\relax
+   %
+   \global\d_math_number_correction\zeropoint
+   %
+   \edef\p_location{\formulaparameter\c!location}%
+   \useformulacolorparameter\c!color
+   \c_strc_math_number_location\ifx\p_location\v!left\plusone\else\ifx\p_location\v!right\plustwo\else\zerocount\fi\fi
+   %
+  %\strc_formulas_place_number % not here as we can have inner alignment numbers
+   \dontcomplain
+   \setbox\b_strc_math_display\math_hbox\bgroup % \checkeddisplaymath
+     \mathinnerstrut
+     \startforceddisplaymath}
+
+\def\strc_math_flush_number_no
+  {\ifconditional\c_strc_math_display_overflow
+     \ifcase\c_strc_formulas_frame_mode
+       \strc_math_flush_box_normal
+     \else
+       \strc_math_flush_box_framed_fit_inline
+     \fi
+   \else
+     \ifcase\c_strc_formulas_frame_mode
+      %\ifconditional\c_strc_formulas_tight
+      %  \strc_math_flush_box_normal
+      %\else
+         \strc_math_flush_box_normal
+      %\fi
+     \else
+       \ifconditional\c_strc_formulas_tight
+         \strc_math_flush_box_framed_fit_inline
+       \else
+         \strc_math_flush_box_framed_display
+       \fi
+     \fi
+   \fi}
+
+\def\strc_math_flush_number_left
+  {\ifconditional\c_strc_math_display_overflow
+     \ifcase\c_strc_formulas_frame_mode
+       \strc_math_number_left_overflow
+     \or
+       \strc_math_number_left_overflow_outside
+     \or
+       \strc_math_number_left_overflow_inside
+     \fi
+   \else
+     \ifcase\c_strc_formulas_frame_mode
+       \strc_math_number_left_normal
+     \or
+       \strc_math_number_left_normal_outside
+     \or
+       \strc_math_number_left_normal_inside
+     \fi
+   \fi}
+
+\def\strc_math_flush_number_right
+  {\ifconditional\c_strc_math_display_overflow
+     \ifcase\c_strc_formulas_frame_mode
+       \strc_math_number_right_overflow
+     \or
+       \strc_math_number_right_overflow_outside
+     \or
+       \strc_math_number_right_overflow_inside
+     \fi
+   \else
+     \ifcase\c_strc_formulas_frame_mode
+       \strc_math_number_right_normal
+     \or
+       \strc_math_number_right_normal_outside
+     \or
+       \strc_math_number_right_normal_inside
+     \fi
+   \fi}
+
+\unexpanded\def\strc_math_box_stop
   {\stopforceddisplaymath
-   \ifcase\mathraggedstatus\or\or\hfill\or\hfill\fi
    \egroup
-   \setbox0\hbox{\unhcopy\scratchbox}%
-   \scratchdimen\wd0
-  % to be tested: \scratchdimen\naturalwd\scratchbox
-   \ifdim\scratchdimen>\displaywidth % \checkeddisplaymath
-     \donetrue
+ % % not needed, attribute driven
+ % \ifgridsnapping
+ %   \snaptogrid[\v!math]\vbox
+ % \fi
+ % \bgroup
+   % check number
+   \d_strc_math_number_width\wd\b_strc_formulas_number
+   %
+   \ifcase\mathnumberstatus
+     \setfalse\c_strc_math_has_number
+   \or\ifzeropt\d_strc_math_number_width
+     \setfalse\c_strc_math_has_number
    \else
-     \donefalse
+     \settrue\c_strc_math_has_number
+   \fi\fi
+   % preroll left and right offsets
+   \ifcase\c_strc_formulas_frame_mode
+     % no frame
+   \else
+     \strc_math_number_check_offsets
+   \fi
+   \ifcase\c_strc_formulas_frame_mode
+     \strc_math_number_check
+   \or
+     \strc_math_number_check_outside
+   \else
+     \strc_math_number_check_inside
    \fi
-   \hbox to \displaywidth\bgroup
+   \noindent % \noindentation % not \dontleavehmode
+   \hskip\d_strc_formulas_display_margin_left % was kern but that doesn't indent
+   \strc_math_traced_state
+   \hbox to \displaywidth \bgroup
      \ifcase\mathnumberstatus
-       \box\scratchbox
-     \or
-       \ifx\math_the_l_eq_no\empty
-         \ifx\math_the_r_eq_no\empty
-           \box\scratchbox
+       \strc_math_flush_box
+     \or % status 1
+       \ifcase\c_strc_math_number_location
+         \strc_math_flush_box
+       \or % number left
+         \ifzeropt\wd\b_strc_formulas_number
+           \strc_math_flush_number_no
          \else
-           \ifdone
-             \vpack{\box\scratchbox\hpack to \displaywidth{\hss\math_box_llapped_math_no}}% \checkeddisplaymath
-           \else
-             \hss\box\scratchbox\math_box_llapped_math_no % hss makes room for number
-           \fi
+           \strc_math_flush_number_left
          \fi
-       \else
-         \ifdone
-           \vpack{\hpack to \displaywidth{\math_box_rlapped_math_no\hss}\box\scratchbox}% \checkeddisplaymath
+       \else % number right
+         \ifzeropt\wd\b_strc_formulas_number
+           \strc_math_flush_number_no
          \else
-           \math_box_rlapped_math_no\box\scratchbox\hss % hss makes room for number
+           \strc_math_flush_number_right
          \fi
        \fi
-     \or
-        \hskip\mathnumbercorrection
-        \box\scratchbox
+     \or % status 2
+        \hskip\d_math_number_correction % probably no longer used
+        \strc_math_flush_box
         \hss
      \else
-        \box\scratchbox
+       \strc_math_flush_box
      \fi
+ % \egroup
    \egroup}
 
-\defineinnermathhandler\v!left      {\startmathbox\plusone  }{\stopmathbox}
-\defineinnermathhandler\v!middle    {\startmathbox\plustwo  }{\stopmathbox}
-\defineinnermathhandler\v!right     {\startmathbox\plusthree}{\stopmathbox}
-\defineinnermathhandler\v!flushleft {\startmathbox\plusthree}{\stopmathbox}
-\defineinnermathhandler\v!center    {\startmathbox\plustwo  }{\stopmathbox}
-\defineinnermathhandler\v!flushright{\startmathbox\plusone  }{\stopmathbox}
-\defineinnermathhandler\v!normal    {}                       {}
+\defineinnermathhandler\v!left      {\strc_math_box_start\plusone  }{\strc_math_box_stop}
+\defineinnermathhandler\v!middle    {\strc_math_box_start\plustwo  }{\strc_math_box_stop}
+\defineinnermathhandler\v!right     {\strc_math_box_start\plusthree}{\strc_math_box_stop}
+\defineinnermathhandler\v!flushleft {\strc_math_box_start\plusthree}{\strc_math_box_stop}
+\defineinnermathhandler\v!center    {\strc_math_box_start\plustwo  }{\strc_math_box_stop}
+\defineinnermathhandler\v!flushright{\strc_math_box_start\plusone  }{\strc_math_box_stop}
+\defineinnermathhandler\v!normal    {\strc_math_box_start\plustwo  }{\strc_math_box_stop}
 
-%defineinnermathhandler\v!normal    {\startmathbox\plustwo  }{\stopmathbox}
+%D Some inline math tweak.
 
-%D [The examples below are in english and don't process in the
-%D  documentation style, which will be english some day.]
-%D
-%D Normally a formula is centered, but in case you want to
-%D align it left or right, you can set up formulas to behave
-%D that way. Normally a formula will adapt is left indentation
-%D to the environment:
-%D
-%D \startbuffer
-%D \fakewords{20}{40}\epar
-%D \startitemize
-%D \item \fakewords{20}{40}\epar
-%D       \placeformula \startformula \fakeformula \stopformula
-%D \item \fakewords{20}{40}\epar
-%D \stopitemize
-%D \fakewords{20}{40}\epar
-%D \stopbuffer
-%D
-%D % \getbuffer
-%D
-%D In the next examples we explicitly align formulas to the
-%D left (\type {\raggedleft}), center and right (\type
-%D {\raggedright}):
-%D
-%D \startbuffer
-%D \setupformulas[align=left]
-%D \startformula\fakeformula\stopformula
-%D \setupformulas[align=middle]
-%D \startformula\fakeformula\stopformula
-%D \setupformulas[align=right]
-%D \startformula\fakeformula\stopformula
-%D \stopbuffer
-%D
-%D \typebuffer
-%D
-%D Or in print:
-%D
-%D % {\getbuffer}
-%D
-%D With formula numbers these formulas look as follows:
-%D
-%D \startbuffer
-%D \setupformulas[align=left]
-%D \placeformula \startformula\fakeformula\stopformula
-%D \setupformulas[align=middle]
-%D \placeformula \startformula\fakeformula\stopformula
-%D \setupformulas[align=right]
-%D \placeformula \startformula\fakeformula\stopformula
-%D \stopbuffer
-%D
-%D % {\getbuffer}
-%D
-%D This was keyed in as:
-%D
-%D \typebuffer
-%D
-%D When tracing is turned on (\type {\tracemathtrue}) you can
-%D visualize the bounding box of the formula,
-%D
-%D % {\tracemathtrue\getbuffer}
-%D
-%D As you can see, the dimensions are the natural ones, but if
-%D needed you can force a normalized line:
-%D
-%D \startbuffer
-%D \setupformulas[strut=yes]
-%D \placeformula \startformula \fakeformula \stopformula
-%D \stopbuffer
-%D
-%D \typebuffer
-%D
-%D This time we get a more spacy result.
-%D
-%D % {\tracemathtrue\getbuffer}
-%D
-%D We will now show a couple of more settings and combinations
-%D of settings. In centered formulas, the number takes no space
-%D
-%D \startbuffer
-%D \setupformulas[align=middle]
-%D \startformula \fakeformula \stopformula
-%D \placeformula \startformula \fakeformula \stopformula
-%D \stopbuffer
-%D
-%D \typebuffer % {\tracemathtrue\getbuffer}
-%D
-%D You can influence the placement of the whole box with the
-%D parameters \type {leftmargin} and \type {rightmargin}.
-%D
-%D \startbuffer
-%D \setupformulas[align=right,leftmargin=3em]
-%D \startformula \fakeformula \stopformula
-%D \placeformula \startformula \fakeformula \stopformula
-%D
-%D \setupformulas[align=left,rightmargin=1em]
-%D \startformula \fakeformula \stopformula
-%D \placeformula \startformula \fakeformula \stopformula
-%D \stopbuffer
-%D
-%D \typebuffer % {\tracemathtrue\getbuffer}
-%D
-%D You can also inherit the margin from the environment.
-%D
-%D \startbuffer
-%D \setupformulas[align=right,margin=standard]
-%D \startformula \fakeformula \stopformula
-%D \placeformula \startformula \fakeformula \stopformula
-%D \stopbuffer
-%D
-%D \typebuffer % {\tracemathtrue\getbuffer}
-%D
-%D The distance between the formula and the number is only
-%D applied when the formula is left or right aligned.
-%D
-%D \startbuffer
-%D \setupformulas[align=left,distance=2em]
-%D \startformula \fakeformula \stopformula
-%D \placeformula \startformula \fakeformula \stopformula
-%D \stopbuffer
-%D
-%D \typebuffer % {\tracemathtrue\getbuffer}
+\appendtoks
+    \ifcase\mathnestinglevel\or
+        % 4=disable 6=only when no spaces
+        \mathsurroundskip\mathematicsparameter\c!textdistance\relax
+        \ifzeropt\mathsurroundskip
+        \ifdim\gluestretch\mathsurroundskip=\zeropoint
+            \ifdim\glueshrink\mathsurroundskip=\zeropoint
+            \mathsurroundmode\plussix
+            \else
+            \mathsurroundskip\zeropoint
+            \mathsurroundmode\plusfour
+            \fi
+        \else
+            \mathsurroundmode\plussix
+        \fi
+        \else
+        \mathsurroundmode\plussix
+        \fi
+    \else
+        \mathsurroundmode\plusfour
+        \mathsurroundskip\zeropoint
+    \fi
+\to \everymathematics
+
+\setupmathematics
+  [\c!textdistance=\zeropoint]
+
+%D For documentation, see \type {math-mkiv.tex}.
 
 \protect \endinput