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% language=us
\usemodule[present-boring,abbreviations-logos]
\definecolor[maincolor] [r=.4,g=.4]
\definecolor[extracolor][s=.1]
\startdocument
[title={PARAGRAPHS},
banner={a bit of an upgrade},
location={context\enspace {\bf 2021}\enspace meeting}]
\starttitle[title=Note]
\startitemize
\startitem
Some of the following already is present for a while and has been discussed
at previous meetings.
\stopitem
\startitem
But \unknown\ occasionally some minor tweak gets added so consider this to be
an update.
\stopitem
\stopitemize
\starttitle[title=Spacing]
\startitemize
\startitem
Spaces in \TEX\ become glue nodes (with optional stretch and shrink).
\stopitem
\startitem
In traditional \TEX\ these glue nodes are ref counted copies of the current
spacing related variables.
\stopitem
\startitem
In \LUATEX\ we make real copies so that when we mess with the node list
changes to glue don't affect other instances.
\stopitem
\stopitemize
\starttitle[title=Parameters]
\startitemize
\startitem
In traditional \TEX\ the paragraphs bound properties that are in effect
when \type {\par} happens are used when breaking into lines.
\stopitem
\startitem
In \LUAMETATEX\ the paragraphs bound properties are stored with the
paragraph and can be frozen when they are set.
\stopitem
\startitem
This gives a more predictable (and robust) way of manipulating a
paragraph.
\stopitem
\startitem
We can for instance get rid of grouping side effects that interfere with
\type {\everypar}.
\stopitem
\startitem
Currently three dozen parameters are tracked but they are grouped in
categories.
\stopitem
\blank[2*big] {\em (show code and examples)}
\stopitemize
\stoptitle
\starttitle[title=Wrapping]
\startitemize
\startitem
Doing something in front of a paragraph is taken care of by good old
\type {\everypar}.
\stopitem
\startitem
In \LUAMETATEX\ we also have \type {\everybeforepar} but so far in \CONTEXT\
we haven't used that.
\stopitem
\startitem
Adding something to the end of a paragraph can be tricky so we have
a wrapper mechanism: \type {\wrapuppar}.
\stopitem
\startitem
The \type {\wrapuppar} primitive is similar to \type {\atendofgroup} in the
sense that it accumulates tokens (so no \type {\endofpar}).
\stopitem
\startitem
Normally these primitives are not used directly but managed by a more general
system of handling paragraphs.
\stopitem
\stopitemize
\blank[2*big] {\em (show code and examples)}
\stoptitle
\starttitle[title=Normalizing]
\startitemize
\startitem
In order to see consistent paragraphs at the \LUA\ end in \LUAMETATEX\
we can normalize the lines that come from the paragraph builder.
\stopitem
\startitem
Normalization results in:
\startitemize
\startitem
the first line having: indent skip
\stopitem
\startitem
each line having: left hang, left skip, right skip, right hang
\stopitem
\startitem
the last line having: left parfill skip, right parfill skip
\stopitem
\stopitemize
\stopitem
\startitem
It is controlled by \type {\normalizelinemode} which has additional flags for
swapping hanging indentation and par shapes, breaking after dir nodes,
removing margin kerns and clipping the line width.
\stopitem
\startitem
The clipping options avoids the side effects of \TEX\ using shifts which has
the side effect of unreal dimensions. This is one of the tricks|/|properties
of the traditional engine that is perfectly fine until we open up things.
\stopitem
\stopitemize
\blank[2*big] {\em (show code and examples)}
\stoptitle
\stopdocument
|
