1 files changed, 23 insertions, 1 deletions
diff --git a/doc/context/sources/general/manuals/luametatex/luametatex-fonts.tex b/doc/context/sources/general/manuals/luametatex/luametatex-fonts.tex
index 917ebfeb8..7cea6f865 100644
--- a/doc/context/sources/general/manuals/luametatex/luametatex-fonts.tex
+++ b/doc/context/sources/general/manuals/luametatex/luametatex-fonts.tex
@@ -140,7 +140,6 @@ For example, here is the character \quote {f} (decimal 102) in the font \type
 }
 \stoptyping
 
-
 Two very special string indexes can be used also: \type {left_boundary} is a
 virtual character whose ligatures and kerns are used to handle word boundary
 processing. \type {right_boundary} is similar but not actually used for anything
@@ -589,6 +588,29 @@ font.current(<number> i)
 %
 % \stopsubsection
 
+\startsubsection[title={\type{\glyphdimensionsmode}}]
+
+Already in the early days of \LUATEX\ the decision was made to calculate the
+effective height and depth of glyphs in a way that reflected the applied vertical
+offset. The height got that offset added, the depth only when the offset was
+larger than zero. We can now control this in more detail with this mode
+parameter. An offset is added to the height and|/|or subtracted from the depth.
+The effective values are never negative. The zero mode is the default.
+
+\starttabulate[|l|pl|]
+\DB value     \BC effect \NC\NR
+\TB
+\NC \type {0} \NC the old behavior: add the offset to the height and only subtract
+                  the offset only from the depth when it is positive \NC \NR
+\NC \type {1} \NC add the offset to the height and subtract it from the depth \NC \NR
+\NC \type {2} \NC add the offset to the height and subtract it from the depth but
+                  keep the maxima of the current and previous results \NC \NR
+\NC \type {3} \NC use the height and depth of the glyph, so no offset is applied \NC \NR
+\LL
+\stoptabulate
+
+\stopsubsection
+
 \stopsection
 
 \stopchapter