1 files changed, 47 insertions, 28 deletions
diff --git a/tex/context/base/mkiv/strc-mat.mkiv b/tex/context/base/mkiv/strc-mat.mkiv
index c6b277991..775d2aca1 100644
--- a/tex/context/base/mkiv/strc-mat.mkiv
+++ b/tex/context/base/mkiv/strc-mat.mkiv
@@ -566,7 +566,7 @@
 \newconstant\c_strc_math_vertical % experiment
 
 \c_strc_formulas_mode       \plustwo   % 0=native 1=simple (old) 2=align (new)
-\c_strc_formulas_space_model\plusthree % replaces \plusone
+\c_strc_formulas_space_model\plusthree % replaces \plusone, we might use \plusfour in the future
 
 \newconditional\c_strc_formulas_tight
 
@@ -641,33 +641,6 @@
      \directvspacing\p_spaceafter
    \fi}
 
-% \def\strc_math_obey_depth
-%   {\ifvmode\ifdim\prevdepth<\zeropoint\else\ifdim\prevdepth<\strutdp
-%      % maybe add a tracing option here
-%      \ifgridsnapping
-%        \directvspacing\v!depth
-%      \else
-%        \kern\dimexpr\strutdp-\prevdepth\relax
-%        \prevdepth\strutdp
-%      \fi
-%    \fi\fi\fi}
-%
-% \setvalue{\??mathdisplayspacemodel\v!before:3}%
-%   {% not ok, try \stopformula\par\startformula vs \stopformula\startformula
-%    \ifdim\lastskip>\zeropoint
-%      % bah
-%    \else
-%      \strc_math_obey_depth % somehow \fakenextstrutline doesn't work here
-%      \nointerlineskip
-%    \fi
-%    \ifx\p_spacebefore\v!none
-%      % nothing
-%    \else\ifx\p_spacebefore\empty
-%      \directvspacing\currentvspacing
-%    \else
-%      \directvspacing\p_spacebefore
-%    \fi\fi}
-
 \setvalue{\??mathdisplayspacemodel\v!before:3}%
   {% not ok, try \stopformula\par\startformula vs \stopformula\startformula
    \let\m_spacebefore\empty
@@ -714,6 +687,49 @@
      \directvspacing\p_spaceafter
    \fi\fi}
 
+\newconditional\c_math_model_four_indeed
+
+\setvalue{\??mathdisplayspacemodel\v!before:4}%
+  {% not ok, try \stopformula\par\startformula vs \stopformula\startformula
+   \ifvmode
+     \ifinner
+        \csname\??mathdisplayspacemodel\v!before:3\endcsname
+     \else
+       \settrue\c_math_model_four_indeed
+       \forcestrutdepth
+       \nointerlineskip
+       \ifx\p_spacebefore\v!none
+         % nothing
+       \else\ifx\p_spacebefore\empty
+         \directvspacing\currentvspacing
+       \else
+         \directvspacing{\p_spacebefore,\the\scratchdimen}%
+       \fi\fi
+     \fi
+  \else
+     \csname\??mathdisplayspacemodel\v!before:3\endcsname
+  \fi}
+
+\setvalue{\??mathdisplayspacemodel\v!after:4}%
+  {\ifconditional\c_math_model_four_indeed
+     \setfalse\c_math_model_four_indeed
+     \forcestrutdepth
+   \else
+     \prevdepth\strutdp % \directvspacing\v!depth
+   \fi
+   \ifx\p_spaceafter\v!none
+     % nothing
+   \else\ifx\p_spaceafter\empty
+     \directvspacing\currentvspacing
+   \else
+     \directvspacing\p_spaceafter
+   \fi\fi}
+
+\unexpanded\def\setdisplaymathspacemodel[#1]%
+  {\ifcsname\??mathdisplayspacemodel\v!before:\number#1\endcsname
+     \c_strc_formulas_space_model#1\relax
+   \fi}
+
 % \newtoks\everybeforedisplay
 % \appendtoks\page_sides_check_floats_indeed\to\everybeforedisplay
 
@@ -785,6 +801,9 @@
   {\d_strc_formulas_display_skip_left \zeropoint
    \d_strc_formulas_display_skip_right\zeropoint}
 
+\setvalue{\??formulaoption\v!depth}%
+  {\c_strc_formulas_space_model\plusfour}
+
 \setvalue{\??formulaoption\v!line}%
   {\ifgridsnapping
      \setformulaparameter\c!grid{\v!math:\v!line}%