2020-12-04 20:21:00

1 files changed, 42 insertions, 20 deletions

diff --git a/doc/context/sources/general/manuals/luametatex/luametatex-enhancements.tex b/doc/context/sources/general/manuals/luametatex/luametatex-enhancements.tex
index f4dbfb15d..057fddde4 100644
--- a/doc/context/sources/general/manuals/luametatex/luametatex-enhancements.tex
+++ b/doc/context/sources/general/manuals/luametatex/luametatex-enhancements.tex
@@ -19,7 +19,7 @@ and there will be no \type {luametatex} variants. This is because we consider
 \LUAMETATEX\ to be \LUATEX 2\high{+}.
 
 Contrary to the \LUATEX\ engine \LUAMETATEX\ enables all its primitives. You can
-clone (a selection of) primitives with a different prefix, like:
+clone (a selection of) primitives with a different prefix, like this:
 
 \starttyping
 \directlua { tex.enableprimitives('normal',tex.extraprimitives()) }
@@ -27,8 +27,11 @@ clone (a selection of) primitives with a different prefix, like:
 
 The \type {extraprimitives} function returns the whole list or a subset,
 specified by one or more keywords \type {core}, \type {tex}, \type {etex} or
-\type {luatex}. \footnote {At some point this function might be changed to return
-the whole list always}.
+\type {luatex}. When you clone all primitives you can also do this:
+
+\starttyping
+\directlua { tex.enableprimitives('normal',true) }
+\stoptyping
 
 But be aware that the curly braces may not have the proper \prm {catcode}
 assigned to them at this early time (giving a \quote {Missing number} error), so
@@ -42,23 +45,8 @@ it may be needed to put these assignments before the above line:
 More fine|-|grained primitives control is possible and you can look up the
 details in \in {section} [luaprimitives]. There are only three kinds of
 primitives: \type {tex}, \type {etex} and \type {luatex} but a future version
-might drop this and no longer make that distinction as it no longer serves
-a purpose.
-
-\stopsubsection
-
-\startsubsection[title={Experiments}]
-
-There are a few extensions to the engine regarding the macro machinery. Some are
-already well tested but others are (still) experimental. Although they are likely
-to stay, their exact behaviour might evolve. Because \LUAMETATEX\ is also used
-for experiments, this is not a problem. We can always decide to also add some of
-what is discussed here to \LUATEX, but it will happen with a delay.
-
-There are all kinds of small improvements that might find their way into stock
-\LUATEX: a few more helpers, some cleanup of code, etc. We'll see. In any case,
-if you play with these before they are declared stable, unexpected side effects
-are what you have to accept.
+might drop this and no longer make that distinction as it no longer serves a
+purpose apart from the fact that it reveals some history.
 
 \stopsubsection
 
@@ -231,6 +219,34 @@ Fonts are loaded via \LUA\ and a minimal amount of information is kept at the
 about what a character (or glyph) number represents (a \UNICODE\ or index) as it
 only is interested in dimensions.
 
+In \TEX\ the number of registers is 256 and \ETEX\ bumped that to 32K. One reason
+for a fixed number is that these registers are fast ways to store data and
+therefore are part of the main lookup table (used for data and pointers to data
+as well as save and restore housekeeping). In \LUATEX\ the number was bumped to
+64K but one can argue that less would also do. In order to keep the default
+memory footprint reasonable, in \LUAMETATEX\ the number of languages, fonts and
+marks is limited. The size of some tables can be limited by configuration
+settings, so they can start out small and grow till configured maximum which is
+smaller than the absolute maximum. The following table shows all kind of defaults
+as reported by \typ {status.getconstants()}.
+
+\startluacode
+    context.starttabulate { "|T|r|" }
+    for k, v in table.sortedhash(status.getconstants()) do
+        context.NC() context(k) context.NC() context(v) context.NC() context.NR()
+    end
+    context.stoptabulate()
+\stopluacode
+
+Because we have additional ways to store integers, dimensions and glue, we might
+actually decide to decrease the maximum of the registers: if 64K is not enough,
+and you work around it, then likely 32K might do as well. Also, we have \LUA\ to
+store massive amounts of data. One can argue that saving some 1.5MB memory (when
+we go halfway) is not worth the effort in a time when you have to close a browser
+in order to free the gigabytes it consumes, but there is no reason not to be lean
+and mean: a more conservative approach to start with creates headroom for going
+wild later.
+
 \stopsubsection
 
 \stopsection
@@ -276,6 +292,12 @@ language related information, the expansion factor, etc. Now that we have access
 to these nodes from \LUA\ it makes sense to be able to carry more information
 with a node and this is where attributes kick in.
 
+It is important to keep in mind that there are situations where nodes get created
+in the current context. For instance, when \TEX\ builds a paragraph or page or
+constructs math formulas, it does add nodes and giving these the current
+attributes makes no sense and can even give weird side effects. In these cases,
+the attributes are inherited from neighbouring nodes.
+
 \stopsubsection
 
 \startsubsection[title={Attribute registers}]