2018-05-19 21:51:00

1 files changed, 43 insertions, 0 deletions

diff --git a/doc/context/sources/general/manuals/luatex/luatex-math.tex b/doc/context/sources/general/manuals/luatex/luatex-math.tex
index 9f99c7ab3..821ef010d 100644
--- a/doc/context/sources/general/manuals/luatex/luatex-math.tex
+++ b/doc/context/sources/general/manuals/luatex/luatex-math.tex
@@ -1466,6 +1466,49 @@ use a step to control the size. A value of zero will suppress the gap. The step
 is divided by 1000 which is the usual way to mimmick floating point factors in
 \TEX.
 
+\subsection {Flattening: \lpr {mathflattenmode}}
+
+\topicindex {math+flattening}
+
+The \TEX\ math engine collapses \type {ord} noads without sub- and superscripts
+and a character as nucleus. and which has the side effect that in \OPENTYPE\ mode
+italic corrections are applied (given that they are enabled).
+
+\startbuffer[sample]
+\switchtobodyfont[modern]
+$V \mathbin{\mathbin{v}} V$\par
+$V \mathord{\mathord{v}} V$\par
+\stopbuffer
+
+\typebuffer[sample]
+
+This renders as:
+
+\blank \start \mathflattenmode\plusone \getbuffer[sample] \stop \blank
+
+When we set \lpr {mathflattenmode} to 31 we get:
+
+\blank \start \mathflattenmode\numexpr1+2+4+8+16\relax \getbuffer[sample] \stop \blank
+
+When you see no difference, then the font probably has the proper character
+dimensions and no italic correction is needed. For Latin Modern (at least till
+2018) there was a visual difference. In that respect this parameter is not always
+needed unless of course you want efficient math lists anyway.
+
+You can influence flattening by adding the appropriate number to the value of the
+mode parameter. The default value is~1.
+
+\starttabulate[|Tc|c|]
+\DB mode \BC class \NC \NR
+\TB
+\NC  1   \NC ord   \NC \NR
+\NC  2   \NC bin   \NC \NR
+\NC  4   \NC rel   \NC \NR
+\NC  8   \NC punct \NC \NR
+\NC 16   \NC inner \NC \NR
+\LL
+\stoptabulate
+
 \subsection {Tracing}
 
 \topicindex {math+tracing}