From 4005fc172da021ab3a4ec32f898d52daf1bf387e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marcel=20Fabian=20Kr=C3=BCger?= <tex@2krueger.de>
Date: Wed, 23 Jun 2021 04:39:58 +0200
Subject: [PATCH] gathered support

---
 luamml-amsmath.lua         | 18 +++++++++-------
 luamml-patches-amsmath.sty | 43 ++++++++++++++++++++++++++++++++++----
 2 files changed, 49 insertions(+), 12 deletions(-)

diff --git a/luamml-amsmath.lua b/luamml-amsmath.lua
index c3bfd80..3ef4298 100644
--- a/luamml-amsmath.lua
+++ b/luamml-amsmath.lua
@@ -38,20 +38,21 @@ end
 
 do
   local saved
-  funcid = luatexbase.new_luafunction'__luamml_amsmath_save_inner_table:'
-  token.set_lua('__luamml_amsmath_save_inner_table:', funcid)
+  funcid = luatexbase.new_luafunction'__luamml_amsmath_save_inner_table:n'
+  token.set_lua('__luamml_amsmath_save_inner_table:n', funcid)
   lua.get_functions_table()[funcid] = function()
     -- TODO: Error handling etc
+    local kind = token.scan_argument()
     local mml_table = get_table()
     if not mml_table then return end
     mml_table.displaystyle = true
     local columns = node.count(node.id'align_record', tex.lists.align_head)//2
-    mml_table.columnalign = string.rep('right left', columns, ' ')
+    mml_table.columnalign = kind == 'gathered' and 'center' or string.rep('right left', columns, ' ')
     local spacing = {}
     for n in node.traverse_id(node.id'glue', tex.lists.align_head) do
       spacing[#spacing+1] = n.width == 0 and '0' or string.format('%.3f', n.width/65781.76)
     end
-    mml_table.columnspacing = table.concat(spacing, ' ', 2, #spacing-2)
+    mml_table.columnspacing = #spacing > 3 and table.concat(spacing, ' ', 2, #spacing-2) or nil
     saved = mml_table
   end
 
@@ -70,20 +71,21 @@ do
   end
 end
 
-funcid = luatexbase.new_luafunction'__luamml_amsmath_finalize_table:'
-token.set_lua('__luamml_amsmath_finalize_table:', funcid)
+funcid = luatexbase.new_luafunction'__luamml_amsmath_finalize_table:n'
+token.set_lua('__luamml_amsmath_finalize_table:n', funcid)
 lua.get_functions_table()[funcid] = function()
   -- TODO: Error handling etc
+  local kind = token.scan_argument()
   local mml_table = get_table()
   if not mml_table then return end
   mml_table.displaystyle = true
   local columns = node.count(node.id'align_record', tex.lists.align_head)//2
-  mml_table.columnalign = string.rep('right left', columns, ' ')
+  mml_table.columnalign = kind == 'align' and string.rep('right left', columns, ' ') or nil
   local spacing = {}
   for n in node.traverse_id(node.id'glue', tex.lists.align_head) do
     spacing[#spacing+1] = n.width == 0 and '0' or '.8em'
   end
-  mml_table.columnspacing = table.concat(spacing, ' ', 2, #spacing-2)
+  mml_table.columnspacing = #spacing > 3 and table.concat(spacing, ' ', 2, #spacing-2) or nil
   save_result(mml_table, true)
 end
 
diff --git a/luamml-patches-amsmath.sty b/luamml-patches-amsmath.sty
index f2c9205..93d6a42 100644
--- a/luamml-patches-amsmath.sty
+++ b/luamml-patches-amsmath.sty
@@ -63,9 +63,39 @@
       \ams@return@opt@arg
 }
 
+\renewcommand \gathered [1] [c] {
+  \RIfM@
+  \else
+    \nonmatherr@ { \begin {gathered} }
+  \fi
+  \luamml_annotate:en {
+    nucleus = true, core = false
+  } {
+    \alignedspace@left
+  }
+  \ams@start@box {#1} \bgroup
+    \Let@
+    \chardef \dspbrk@context \@ne
+    \restore@math@cr
+    \spread@equation
+    \ialign \bgroup
+        \hfil
+        \strut@
+        $
+          \m@th
+          \displaystyle
+          ##
+          \luamml_flag_save:Nn \displaystyle {mtd}
+        $
+        \__luamml_amsmath_add_last_to_row:
+        \hfil
+      \crcr
+        \ams@return@opt@arg
+}
+
 \cs_set:Npn \endaligned {
       \crcr
-      \__luamml_amsmath_save_inner_table:
+      \__luamml_amsmath_save_inner_table:n \@currenvir
     \egroup
     \restorecolumn@
   \egroup
@@ -104,8 +134,12 @@
         \strut@
         {##}
       }
+      \dim_compare:nNnF {0pt} = {
+        \box_wd:N \c_zero_int
+      } {
+        \__luamml_amsmath_set_tag:
+      }
       \place@tag@gather
-      \__luamml_amsmath_set_tag:
       \tabskip \iftagsleft@
         \gdisplaywidth@
       \else
@@ -114,6 +148,7 @@
       \crcr
       #1
 }
+
 \cs_new_eq:NN \__luamml_amsmath_original_gmeasure:n \gmeasure@
 \cs_set:Npn \gmeasure@ #1 {
   \exp_last_unbraced:Nno
@@ -125,7 +160,7 @@
 \cs_set:Npn \endgather {
       \math@cr
       \black@ \totwidth@
-      \__luamml_amsmath_finalize_table:
+      \__luamml_amsmath_finalize_table:n {gather}
   \egroup
   $$
   \ignorespacesafterend
@@ -223,7 +258,7 @@
 \cs_set:Npn \endalign {
   \math@cr
   \black@ \totwidth@
-  \__luamml_amsmath_finalize_table:
+  \__luamml_amsmath_finalize_table:n {align}
   \egroup
   \ifingather@
     \restorealignstate@