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+% language=uk
+
+\environment luatex-style
+
+\startcomponent luatex-preamble
+
+\startchapter[reference=preamble,title={Preamble}]
+
+\topicindex{nodes}
+\topicindex{boxes}
+\topicindex{\LUA}
+
+This is a reference manual, not a tutorial. This means that we discuss changes
+relative to traditonal \TEX\ and also present new functionality. As a consequence
+we will refer to concepts that we assume to be known or that might be explained
+later.
+
+The average user doesn't need to know much about what is in this manual. For
+instance fonts and languages are normally dealt with in the macro package that
+you use. Messing around with node lists is also often not really needed at the
+user level. If you do mess around, you'd better know what you're dealing with.
+Reading \quotation {The \TEX\ Book} by Donald Knuth is a good investment of time
+then also because it's good to know where it all started. A more summarizing
+overview is given by \quotation {\TEX\ by Topic} by Victor Eijkhout. You might
+want to peek in \quotation {The \ETEX\ manual} and documentation about \PDFTEX.
+
+But \unknown\ if you're here because of \LUA, then all you need to know is that
+you can call it from within a run. The macro package that you use probably will
+provide a few wrapper mechanisms but the basic \lpr {directlua} command that
+does the job is:
+
+\starttyping
+\directlua{tex.print("Hi there")}
+\stoptyping
+
+You can put code between curly braces but if it's a lot you can also put it in a
+file and load that file with the usual \LUA\ commands.
+
+If you still decide to read on, then it's good to know what nodes are, so we do a
+quick introduction here. If you input this text:
+
+\starttyping
+Hi There
+\stoptyping
+
+eventually we will get a linked lists of nodes, which in \ASCII\ art looks like:
+
+\starttyping
+H <=> i <=> [glue] <=> T <=> h <=> e <=> r <=> e
+\stoptyping
+
+When we have a paragraph, we actually get something:
+
+\starttyping
+[localpar] <=> H <=> i <=> [glue] <=> T <=> h <=> e <=> r <=> e <=> [glue]
+\stoptyping
+
+Each character becomes a so called glyph node, a record with properties like the
+current font, the character code and the current language. Spaces become glue
+nodes. There are many node types that we will discuss later. Each node points
+back to a previous node or next node, given that these exist.
+
+It's also good to know beforehand that \TEX\ is basically centered around
+creating paragraphs and pages. The par builder takes a list and breaks it into
+lines. We turn horizontal material into vertical. Lines are so called boxes and
+can be separated by glue, penalties and more. The page builder accumulates lines
+and when feasible triggers an output routine that will take the list so far.
+Constructing the actual page is not part of \TEX\ but done using primitives that
+permit manipulation of boxes. The result is handled back to \TEX\ and flushed to
+a (often \PDF) file.
+
+The \LUATEX\ engine provides hooks for \LUA\ code at nearly every reasonable
+point in the process: collecting content, hyphenating, applying font features,
+breaking into lines, etc. This means that you can overload \TEX's natural
+behaviour, which still is the benchmark. When we refer to \quote {callbacks} we
+means these hooks.
+
+Where plain \TEX\ is basically a basic framework for writing a specific style,
+macro packages like \CONTEXT\ and \LATEX\ provide the user a whole lot of
+additional tools to make documents look good. They hide the dirty details of font
+management, language demands, turning structure into typeset results, wrapping
+pages, including images, and so on. You should be aware of the fact that when you
+hook in your own code to manipulate lists, this can interfere with the macro
+package that you use.
+
+When you read about nodes in the following chapters it's good to keep in mind their
+commands that relate to then. Here are a few:
+
+\starttabulate[|l|l|p|]
+\DB command                \BC node          \BC explanation \NC \NR
+\TB
+\NC \prm {hbox}            \NC \nod {hlist} \NC horizontal box \NC \NR
+\NC \prm {vbox}            \NC \nod {vlist} \NC vertical box with the baseline at the bottom \NC \NR
+\NC \prm {vtop}            \NC \nod {vlist} \NC vertical box with the baseline at the top \NC \NR
+\NC \prm {hskip}           \NC \nod {glue}  \NC horizontal skip with optional stretch and shrink \NC \NR
+\NC \prm {vskip}           \NC \nod {glue}  \NC vertical skip with optional stretch and shrink \NC \NR
+\NC \prm {kern}            \NC \nod {kern}  \NC horizontal or vertical fixed skip \NC \NR
+\NC \prm {discretionary}   \NC \nod {disc}  \NC hyphenation point (pre, post, replace) \NC \NR
+\NC \prm {char}            \NC \nod {glyph} \NC a character \NC \NR
+\NC \prm {hrule}           \NC \nod {rule}  \NC a horizontal rule \NC \NR
+\NC \prm {vrule}           \NC \nod {rule}  \NC a vertical rule \NC \NR
+\NC \prm {textdir(ection)} \NC \nod {dir}   \NC a change in text direction \NC \NR
+\LL
+\stoptabulate
+
+For now this should be enough to enable you to understand the next chapters.
+
+\stopchapter
+
+\stopcomponent