% language=uk \environment luatex-style \environment luatex-logos \startcomponent luatex-nodes \startchapter[reference=nodes,title={Nodes}] \section{\LUA\ node representation} \TEX's nodes are represented in \LUA\ as userdata object with a variable set of fields. In the following syntax tables, such the type of such a userdata object is represented as \syntax {}. The current return value of \type {node.types()} is: \startluacode for id, name in table.sortedhash(node.types()) do context.type(name) context(" (%s), ",id) end context.removeunwantedspaces() context.removepunctuation() \stopluacode . % period The \type {\lastnodetype} primitive is \ETEX\ compliant. The valid range is still $[-1,15]$ and glyph nodes (formerly known as char nodes) have number~0 while ligature nodes are mapped to~7. That way macro packages can use the same symbolic names as in traditional \ETEX. Keep in mind that these \ETEX\ node numbers are different from the real internal ones and that there are more \ETEX\ node types than~15. You can ask for a list of fields with the \type {node.fields} (which takes an id) and for valid subtypes with \type {node.subtypes} (which takes a string because eventually we might support more used enumerations) . \subsection{Auxiliary items} A few node|-|typed userdata objects do not occur in the \quote {normal} list of nodes, but can be pointed to from within that list. They are not quite the same as regular nodes, but it is easier for the library routines to treat them as if they were. \subsubsection{attribute_list and attribute items} The newly introduced attribute registers are non|-|trivial, because the value that is attached to a node is essentially a sparse array of key|-|value pairs. It is generally easiest to deal with attribute lists and attributes by using the dedicated functions in the \type {node} library, but for completeness, here is the low|-|level interface. An \type {attribute_list} item is used as a head pointer for a list of attribute items. It has only one user-visible field: \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC next \NC \syntax{} \NC pointer to the first attribute \NC \NR \stoptabulate A normal node's attribute field will point to an item of type \type {attribute_list}, and the \type {next} field in that item will point to the first defined \quote {attribute} item, whose \type {next} will point to the second \quote {attribute} item, etc. Valid fields in \type {attribute} items: \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC next \NC \syntax{} \NC pointer to the next attribute \NC \NR \NC number \NC number \NC the attribute type id \NC \NR \NC value \NC number \NC the attribute value \NC \NR \stoptabulate As mentioned it's better to use the official helpers rather than edit these fields directly. For instance the \type {prev} field is used for other purposes and there is no double linked list. \subsection{Main text nodes} These are the nodes that comprise actual typesetting commands. A few fields are present in all nodes regardless of their type, these are: \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC next \NC \syntax{} \NC the next node in a list, or nil \NC \NR \NC id \NC number \NC the node's type (\type {id}) number \NC \NR \NC subtype \NC number \NC the node \type {subtype} identifier \NC \NR \stoptabulate The \type {subtype} is sometimes just a stub entry. Not all nodes actually use the \type {subtype}, but this way you can be sure that all nodes accept it as a valid field name, and that is often handy in node list traversal. In the following tables \type {next} and \type {id} are not explicitly mentioned. Besides these three fields, almost all nodes also have an \type {attr} field, and there is a also a field called \type {prev}. That last field is always present, but only initialized on explicit request: when the function \type {node.slide()} is called, it will set up the \type {prev} fields to be a backwards pointer in the argument node list. \subsubsection{hlist nodes} Valid fields: \showfields{hlist}\crlf Id: \showid{hlist} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC subtype \NC number \NC \type {0} = unknown origin, \type {1} = created by linebreaking, \type {2} = explicit box command, \type {3} = paragraph indentation box, \type {4} = alignment column or row, \type {5} = alignment cell \type {6} = equation \type {7} = equation number \NC \NR \NC attr \NC \syntax{} \NC The head of the associated attribute list \NC \NR \NC width \NC number \NC \NC \NR \NC height \NC number \NC \NC \NR \NC depth \NC number \NC \NC \NR \NC shift \NC number \NC a displacement perpendicular to the character progression direction \NC \NR \NC glue_order \NC number \NC a number in the range $[0,4]$, indicating the glue order \NC \NR \NC glue_set \NC number \NC the calculated glue ratio \NC \NR \NC glue_sign \NC number \NC \type {0} = normal, \type {1} = stretching, \type {2} = shrinking \NC \NR \NC head \NC \syntax{} \NC the first node of the body of this list \NC \NR \NC dir \NC string \NC the direction of this box, see~\in[dirnodes] \NC \NR \stoptabulate A warning: never assign a node list to the \type {head} field unless you are sure its internal link structure is correct, otherwise an error may result. Note: the field name \type {head} and \type {list} are both valid. Sometimes it makes more sense to refer to a list by \type {head}, sometimes \type {list} makes more sense. \subsubsection{vlist nodes} Valid fields: As for hlist, except that \quote {shift} is a displacement perpendicular to the line progression direction, and \quote {subtype} only has subtypes~0, 4, and~5. \subsubsection{rule nodes} \subsubsubsection{normal rules} Valid fields: \showfields{rule}\crlf Id: \showid{rule} We have three subtypes. Subtype~0 is just a normal rule, a rectangle filled with ink. Subtype~1 is a reusable box, while subtype_2 is an image. \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC subtype \NC number \NC 0 upto 3 \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC width \NC number \NC the width of the rule; the special value $-1073741824$ is used for \quote {running} glue dimensions \NC \NR \NC height \NC number \NC the height of the rule (can be negative) \NC \NR \NC depth \NC number \NC the depth of the rule (can be negative) \NC \NR \NC dir \NC string \NC the direction of this rule, see~\in[dirnodes] \NC \NR \NC index \NC number \NC an optional index that can be referred to (only for subtypes 1 and~2 and backend specific). \NC \NR \stoptabulate The subtypes 1 and~2 replace the xform and ximage whatsits and in node lists they behave like rules of subtype_0 when it comes to dimensions. Subtype~3 only has dimensions. \subsubsection{ins nodes} Valid fields: \showfields{ins}\crlf Id: \showid{ins} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC subtype \NC number \NC the insertion class \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC cost \NC number \NC the penalty associated with this insert \NC \NR \NC height \NC number \NC \NC \NR \NC depth \NC number \NC \NC \NR \NC head/list \NC \syntax{} \NC the first node of the body of this insert \NC \NR %NC spec \NC \syntax{} \NC a pointer to the \type {\splittopskip} % glue spec \NC \NR \stoptabulate There is a set of extra fields that concern the associated glue: \type {width}, \type {stretch}, \type {stretch_order}, \type {shrink} and \type {shrink_order}. These are all numbers. A warning: never assign a node list to the \type {head} field unless you are sure its internal link structure is correct, otherwise an error may be result. You can use \type {list} instead (often in functions you want to use local variable swith similar names and both names are equally sensible). \subsubsection{mark nodes} Valid fields: \showfields{mark}\crlf Id: \showid{mark} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC subtype \NC number \NC unused \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC class \NC number \NC the mark class \NC \NR \NC mark \NC table \NC a table representing a token list \NC \NR \stoptabulate \subsubsection{adjust nodes} Valid fields: \showfields{adjust}\crlf Id: \showid{adjust} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC subtype \NC number \NC \type {0} = normal, \type {1} = \quote{pre} \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC head/list \NC \syntax{} \NC adjusted material \NC \NR \stoptabulate A warning: never assign a node list to the \type {head} field unless you are sure its internal link structure is correct, otherwise an error may be result. \subsubsection{disc nodes} Valid fields: \showfields{disc}\crlf Id: \showid{disc} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC subtype \NC number \NC indicates the source of a discretionary: \type {0} = the \type {\discretionary} command, \type {1} = the \type {\-} command, \type {2} = added automatically following a \type {-}, \type {3} = added by the hyphenation algorithm (simple), \type {4} = added by the hyphenation algorithm (hard, first item), \type {5} = added by the hyphenation algorithm (hard, second item) \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC pre \NC \syntax{} \NC pointer to the pre|-|break text \NC \NR \NC post \NC \syntax{} \NC pointer to the post|-|break text \NC \NR \NC replace \NC \syntax{} \NC pointer to the no|-|break text \NC \NR \NC penalty \NC number \NC the penalty associated with the break, normally \type {\hyphenpenalty} or \type {\exhyphenpenalty} \NC \NR \stoptabulate The subtype numbers~4 and~5 belong to the \quote {of-f-ice} explanation given elsewhere. Warning: never assign a node list to the \type {pre}, \type {post} or \type {replace} field unless you are sure its internal link structure is correct, otherwise an error may be result. This limnitation will disappear in the future, \subsubsection{math nodes} Valid fields: \showfields{math}\crlf Id: \showid{math} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC subtype \NC number \NC \type {0} = on, \type {1} = off \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC surround \NC number \NC width of the \type {\mathsurround} kern \NC \NR \stoptabulate There is a set of extra fields that concern the associated glue: \type {width}, \type {stretch}, \type {stretch_order}, \type {shrink} and \type {shrink_order}. These are all numbers. \subsubsection{glue nodes} Skips are about the only type of data objects in traditional \TEX\ that are not a simple value. The structure that represents the glue components of a skip is called a \type {glue_spec}, and it has the following accessible fields: \starttabulate[|lT|l|p|] \NC \ssbf key \NC \bf type \NC \bf explanation \NC \NR \NC width \NC number \NC \NC \NR \NC stretch \NC number \NC \NC \NR \NC stretch_order \NC number \NC \NC \NR \NC shrink \NC number \NC \NC \NR \NC shrink_order \NC number \NC \NC \NR \stoptabulate % These objects are reference counted, so there is actually an extra read|-|only % field named \type {ref_count} as well. This item type will likely disappear in % the future, and the glue fields themselves will become part of the nodes % referencing glue items. The effective width of some glue subtypes depends on the stretch or shrink needed to make the encapsulating box fit its dimensions. For instance, in a paragraph lines normally have glue representing spaces and these stretch of shrink to make the content fit in the available space. The \type {effective_glue} function that takes a glue node and a parent (hlist or vlist) returns the effective width of that glue item. A gluespec node is a special kind of node that is used for storing a set of glue values in registers. Originally they were also used to store properties of glue nodes (using a system of reference counts) but we now keep these properties in the glue nodes themselves, which gives a cleaner interface to \LUA. The indirect spec approach was in fact an optimization in the original \TEX\ code. First of all it can save quite some memory because all these spaces that become glue now share the same specification (only the reference count is incremented), and zero testing is also a bit faster because only the pointer has to be checked (this is no longer true for engines that implement for instance protrusion where we really need to ensure that zero is zero when we test for bounds). Another side effect is that glue specifications are read|-|only, so in the end copies need to be made when they are used from \LUA\ (each assignment to a field can result in a new copy). So in the end the advantages of sharing are not that high (and nowadays memory is less an issue, also given that a glue node is only a few memory words larger than a spec). Valid fields: \showfields{glue}\crlf Id: \showid{glue} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC subtype \NC number \NC \type {0} = \type {\skip}, \type {1-18} = internal glue parameters, \type {98-99} = \quote {math glue} subtypes \type {100-103} = \quote {leader} subtypes \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC leader \NC \syntax{} \NC pointer to a box or rule for leaders \NC \NR \NC width \NC number \NC \NC \NR \NC stretch \NC number \NC \NC \NR \NC stretch_order \NC number \NC \NC \NR \NC shrink \NC number \NC \NC \NR \NC shrink_order \NC number \NC \NC \NR \stoptabulate Note that we use the key \type {width} in both horizontal and vertical glue. This suits the \TEX\ internals well so we decided to stick to that naming. The exact meanings of the subtypes are as follows: \starttabulate[|rT|l|] \NC 1 \NC \type {\lineskip} \NC \NR \NC 2 \NC \type {\baselineskip} \NC \NR \NC 3 \NC \type {\parskip} \NC \NR \NC 4 \NC \type {\abovedisplayskip} \NC \NR \NC 5 \NC \type {\belowdisplayskip} \NC \NR \NC 6 \NC \type {\abovedisplayshortskip} \NC \NR \NC 7 \NC \type {\belowdisplayshortskip} \NC \NR \NC 8 \NC \type {\leftskip} \NC \NR \NC 9 \NC \type {\rightskip} \NC \NR \NC 10 \NC \type {\topskip} \NC \NR \NC 11 \NC \type {\splittopskip} \NC \NR \NC 12 \NC \type {\tabskip} \NC \NR \NC 13 \NC \type {\spaceskip} \NC \NR \NC 14 \NC \type {\xspaceskip} \NC \NR \NC 15 \NC \type {\parfillskip} \NC \NR \NC 16 \NC \type {\mathsurroundskip} \NC \NR \NC 17 \NC \type {\thinmuskip} \NC \NR \NC 18 \NC \type {\medmuskip} \NC \NR \NC 19 \NC \type {\thickmuskip} \NC \NR \NC 98 \NC \type {conditional math skip} \NC \NR \NC 99 \NC \type {muglue} \NC \NR \NC 100 \NC \type {\leaders} \NC \NR \NC 101 \NC \type {\cleaders} \NC \NR \NC 102 \NC \type {\xleaders} \NC \NR \NC 103 \NC \type {\gleaders} \NC \NR \stoptabulate A regular word space also results in a \type {spaceskip} subtype (this used to be a \type {userskip} with subtype zero). For convenience we provide access to the spec fields directly so that you can avoid the spec lookup. So, the following fields can also be queried or set. When you set a field and no spec is set, a spec will automatically be created. \starttabulate[|lT|l|p|] \NC \ssbf key \NC \bf type \NC \bf explanation \NC \NR \NC width \NC number \NC \NC \NR \NC stretch \NC number \NC \NC \NR \NC stretch_order \NC number \NC \NC \NR \NC shrink \NC number \NC \NC \NR \NC shrink_order \NC number \NC \NC \NR \stoptabulate When you assign the properties to a spec using the above keys the advantage is that when needed a new spec is allocated. if you access the spec node directly you can get an error message with respect to a non|-|writable spec node. By using the accessors in the glue node you are more future proof as we might decide at some point to carry all information in the glue nodes themselves. Of course we can then also decide to make the spec field kind of virtual to keep compatibility (for a while). \subsubsection{kern nodes} Valid fields: \showfields{kern}\crlf Id: \showid{kern} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC subtype \NC number \NC \type {0} = from font, \type {1} = from \type {\kern}, \type {2} = from \type {\accent}, \type {3} = from \type {\/} \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC kern \NC number \NC \NC \NR \stoptabulate \subsubsection{penalty nodes} Valid fields: \showfields{penalty}\crlf Id: \showid{penalty} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC subtype \NC number \NC not used \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC penalty \NC number \NC \NC \NR \stoptabulate \subsubsection[glyphnodes]{glyph nodes} Valid fields: \showfields{glyph}\crlf Id: \showid{glyph} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \ssbf type \NC \ssbf explanation \NC \NR \NC subtype \NC number \NC bitfield \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC char \NC number \NC \NC \NR \NC font \NC number \NC \NC \NR \NC lang \NC number \NC \NC \NR \NC left \NC number \NC \NC \NR \NC right \NC number \NC \NC \NR \NC uchyph \NC boolean \NC \NC \NR \NC components \NC \syntax{} \NC pointer to ligature components \NC \NR \NC xoffset \NC number \NC \NC \NR \NC yoffset \NC number \NC \NC \NR \NC width \NC number \NC \NC \NR \NC height \NC number \NC \NC \NR \NC depth \NC number \NC \NC \NR \NC expansion_factor \NC number \NC \NC \NR \stoptabulate A warning: never assign a node list to the components field unless you are sure its internal link structure is correct, otherwise an error may be result. Valid bits for the \type {subtype} field are: \starttabulate[|c|l|] \NC \ssbf bit \NC \bf meaning \NC \NR \NC 0 \NC character \NC \NR \NC 1 \NC ligature \NC \NR \NC 2 \NC ghost \NC \NR \NC 3 \NC left \NC \NR \NC 4 \NC right \NC \NR \stoptabulate See \in {section} [charsandglyphs] for a detailed description of the \type {subtype} field. The \type {expansion_factor} has been introduced as part of the separation between font- and backend. It is the result of extensive experiments with a more efficient implementation of expansion. Early versions of \LUATEX\ already replaced multiple instances of fonts in the backend by scaling but contrary to \PDFTEX\ in \LUATEX\ we now also got rid of font copies in the frontend and replaced them by expansion factors that travel with glyph nodes. Apart from a cleaner approach this is also a step towards a better separation between front- and backend. The \type {is_char} function checks if a node is a glyph node with a subtype still less than 256. This function can be used to determine if applying font logic to a glyph node makes sense. The value \type {nil} gets returned when the node is not a glyph, a character number is returned if the node is still tagged as character and \type {false} gets returned otherwise. When nil is returned, the id is also returned. The \type {is_glyph} variant doesn't check for a subtype being less than 256, so it returns either the character value or nil plus the id. These helpers are not always faster than separate calls but they sometimes permit making more readable tests. \subsubsection{margin_kern nodes} Valid fields: \showfields{margin_kern}\crlf Id: \showid{margin_kern} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC subtype \NC number \NC \type {0} = left side, \type {1} = right side \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC width \NC number \NC \NC \NR \NC glyph \NC \syntax{} \NC \NC \NR \stoptabulate \subsection{Math nodes} These are the so||called \quote {noad}s and the nodes that are specifically associated with math processing. Most of these nodes contain subnodes so that the list of possible fields is actually quite small. First, the subnodes: \subsubsection{Math kernel subnodes} Many object fields in math mode are either simple characters in a specific family or math lists or node lists. There are four associated subnodes that represent these cases (in the following node descriptions these are indicated by the word \type {}). The \type {next} and \type {prev} fields for these subnodes are unused. \subsubsubsection{math_char and math_text_char subnodes} Valid fields: \showfields{math_char}\crlf Id: \showid{math_char} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC char \NC number \NC \NC \NR \NC fam \NC number \NC \NC \NR \stoptabulate The \type {math_char} is the simplest subnode field, it contains the character and family for a single glyph object. The \type {math_text_char} is a special case that you will not normally encounter, it arises temporarily during math list conversion (its sole function is to suppress a following italic correction). \subsubsubsection{sub_box and sub_mlist subnodes} Valid fields: \showfields{sub_box}\crlf Id: \showid{sub_box} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{}\NC \NC \NR \NC head \NC \syntax{}\NC \NC \NR \stoptabulate These two subnode types are used for subsidiary list items. For \type {sub_box}, the \type {head} points to a \quote {normal} vbox or hbox. For \type {sub_mlist}, the \type {head} points to a math list that is yet to be converted. A warning: never assign a node list to the \type {head} field unless you are sure its internal link structure is correct, otherwise an error may be result. \subsubsection{Math delimiter subnode} There is a fifth subnode type that is used exclusively for delimiter fields. As before, the \type {next} and \type {prev} fields are unused. \subsubsubsection{delim subnodes} Valid fields: \showfields{delim}\crlf Id: \showid{delim} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC\bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC small_char \NC number \NC \NC \NR \NC small_fam \NC number \NC \NC \NR \NC large_char \NC number \NC \NC \NR \NC large_fam \NC number \NC \NC \NR \stoptabulate The fields \type {large_char} and \type {large_fam} can be zero, in that case the font that is sed for the \type {small_fam} is expected to provide the large version as an extension to the \type {small_char}. \subsubsection{Math core nodes} First, there are the objects (the \TEX book calls then \quote {atoms}) that are associated with the simple math objects: ord, op, bin, rel, open, close, punct, inner, over, under, vcent. These all have the same fields, and they are combined into a single node type with separate subtypes for differentiation. \subsubsubsection{simple nodes} Valid fields: \showfields{noad}\crlf Id: \showid{noad} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC subtype \NC number \NC see below \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC nucleus \NC \syntax{} \NC \NC \NR \NC sub \NC \syntax{} \NC \NC \NR \NC sup \NC \syntax{} \NC \NC \NR \stoptabulate Operators are a bit special because they occupy three subtypes. \type {subtype}. \starttabulate[|lT|p|] \NC \ssbf number \NC \bf node subtype \NC \NR \NC 0 \NC Ord \NC \NR \NC 1 \NC Op: \type {\displaylimits} \NC \NR \NC 2 \NC Op: \type {\limits} \NC \NR \NC 3 \NC Op: \type {\nolimits} \NC \NR \NC 4 \NC Bin \NC \NR \NC 5 \NC Rel \NC \NR \NC 6 \NC Open \NC \NR \NC 7 \NC Close \NC \NR \NC 8 \NC Punct \NC \NR \NC 9 \NC Inner \NC \NR \NC 10 \NC Under \NC \NR \NC 11 \NC Over \NC \NR \NC 12 \NC Vcent \NC \NR \stoptabulate \subsubsubsection{accent nodes} Valid fields: \showfields{accent}\crlf Id: \showid{accent} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC subtype \NC number \NC the first bit is used for a fixed top accent flag (if the \type {accent} field is present), the second bit for a fixed bottom accent flag (if the \type {bot_accent} field is present); example: the actual value \type {3} means: do not stretch either accent \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC nucleus \NC \syntax{} \NC \NC \NR \NC sub \NC \syntax{} \NC \NC \NR \NC sup \NC \syntax{} \NC \NC \NR \NC accent \NC \syntax{} \NC \NC \NR \NC bot_accent \NC \syntax{} \NC \NC \NR \stoptabulate \subsubsubsection{style nodes} Valid fields: \showfields{style}\crlf Id: \showid{style} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC style \NC string \NC contains the style \NC \NR \stoptabulate There are eight possibilities for the string value: one of \quote {display}, \quote {text}, \quote {script}, or \quote {scriptscript}. Each of these can have a trailing \type {'} to signify \quote {cramped} styles. \subsubsubsection{choice nodes} Valid fields: \showfields{choice}\crlf Id: \showid{choice} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC display \NC \syntax{} \NC \NC \NR \NC text \NC \syntax{} \NC \NC \NR \NC script \NC \syntax{} \NC \NC \NR \NC scriptscript \NC \syntax{} \NC \NC \NR \stoptabulate A warning: never assign a node list to the display, text, script, or scriptscript field unless you are sure its internal link structure is correct, otherwise an error may be result. \subsubsubsection{radical nodes} Valid fields: \showfields{radical}\crlf Id: \showid{radical} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC nucleus \NC \syntax{} \NC \NC \NR \NC sub \NC \syntax{} \NC \NC \NR \NC sup \NC \syntax{} \NC \NC \NR \NC left \NC \syntax{} \NC \NC \NR \NC degree \NC \syntax{} \NC Only set by \type {\Uroot} \NC \NR \stoptabulate A warning: never assign a node list to the nucleus, sub, sup, left, or degree field unless you are sure its internal link structure is correct, otherwise an error may be result. The radical noad is also used for under- and overdelimiters, which is indicated by the subtypes: \starttabulate[|lT|l|] \NC 0 \NC \type {\radical} \NC \NR \NC 1 \NC \type {\Uradical} \NC \NR \NC 2 \NC \type {\Uroot} \NC \NR \NC 3 \NC \type {\Uunderdelimiter} \NC \NR \NC 4 \NC \type {\Uoverdelimiter} \NC \NR \NC 5 \NC \type {\Udelimiterunder} \NC \NR \NC 6 \NC \type {\Udelimiterover} \NC \NR \stoptabulate \subsubsubsection{fraction nodes} Valid fields: \showfields{fraction}\crlf Id: \showid{fraction} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC width \NC number \NC \NC \NR \NC num \NC \syntax{} \NC \NC \NR \NC denom \NC \syntax{} \NC \NC \NR \NC left \NC \syntax{} \NC \NC \NR \NC right \NC \syntax{} \NC \NC \NR \stoptabulate A warning: never assign a node list to the num, or denom field unless you are sure its internal link structure is correct, otherwise an error may be result. \subsubsubsection{fence nodes} Valid fields: \showfields{fence}\crlf Id: \showid{fence} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC subtype \NC number \NC \type {1} = \type {\left}, \type {2} = \type {\middle}, \type {3} = \type {\right} \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC delim \NC \syntax{} \NC \NC \NR \stoptabulate \subsection{whatsit nodes} Whatsit nodes come in many subtypes that you can ask for by running \type {node.whatsits()}: \startluacode for id, name in table.sortedpairs(node.whatsits()) do context.type(name) context(" (%s), ",id) end context.removeunwantedspaces() context.removepunctuation() \stopluacode . % period \subsubsection{open nodes} Valid fields: \showfields{whatsit,open}\crlf Id: \showid{whatsit,open} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC stream \NC number \NC \TEX's stream id number \NC \NR \NC name \NC string \NC file name \NC \NR \NC ext \NC string \NC file extension \NC \NR \NC area \NC string \NC file area (this may become obsolete) \NC \NR \stoptabulate \subsubsection{write nodes} Valid fields: \showfields{whatsit,write}\crlf Id: \showid{whatsit,write} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC stream \NC number \NC \TEX's stream id number \NC \NR \NC data \NC table \NC a table representing the token list to be written \NC \NR \stoptabulate \subsubsection{close nodes} Valid fields: \showfields{whatsit,close}\crlf Id: \showid{whatsit,close} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC stream \NC number \NC \TEX's stream id number \NC \NR \stoptabulate \subsubsection{special nodes} Valid fields: \showfields{whatsit,special}\crlf Id: \showid{whatsit,special} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC data \NC string \NC the \type {\special} information \NC \NR \stoptabulate \subsubsection{boundary nodes} Valid fields: \showfields{boundary}\crlf Id: \showid{boundary} This node relates to the \type {\noboundary} primitive but you can use it for your own purpose too, in which case \type {\boundary} can come in handy. \subsubsection{language nodes} \LUATEX\ does not have language whatsits any more. All language information is already present inside the glyph nodes themselves. This whatsit subtype will be removed in the next release. \subsubsection{local_par nodes} Valid fields: \showfields{local_par}\crlf Id: \showid{local_par} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC pen_inter \NC number \NC local interline penalty (from \type {\localinterlinepenalty}) \NC \NR \NC pen_broken \NC number \NC local broken penalty (from \type {\localbrokenpenalty}) \NC \NR \NC dir \NC string \NC the direction of this par. see~\in [dirnodes] \NC \NR \NC box_left \NC \syntax{} \NC the \type {\localleftbox} \NC \NR \NC box_left_width \NC number \NC width of the \type {\localleftbox} \NC \NR \NC box_right \NC \syntax{} \NC the \type {\localrightbox} \NC \NR \NC box_right_width \NC number \NC width of the \type {\localrightbox} \NC \NR \stoptabulate A warning: never assign a node list to the \type {box_left} or \type {box_right} field unless you are sure its internal link structure is correct, otherwise an error may be result. \subsubsection[dirnodes]{dir nodes} Valid fields: \showfields{dir}\crlf Id: \showid{dir} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC dir \NC string \NC the direction (but see below) \NC \NR \NC level \NC number \NC nesting level of this direction whatsit \NC \NR \NC dvi_ptr \NC number \NC a saved \DVI\ buffer byte offset \NC \NR \NC dir_h \NC number \NC a saved \DVI\ position \NC \NR \stoptabulate A note on \type {dir} strings. Direction specifiers are three|-|letter combinations of \type {T}, \type {B}, \type {R}, and \type {L}. These are built up out of three separate items: \startitemize[packed] \startitem the first is the direction of the \quote{top} of paragraphs. \stopitem \startitem the second is the direction of the \quote{start} of lines. \stopitem \startitem the third is the direction of the \quote{top} of glyphs. \stopitem \stopitemize However, only four combinations are accepted: \type {TLT}, \type {TRT}, \type {RTT}, and \type {LTL}. Inside actual \type {dir} whatsit nodes, the representation of \type {dir} is not a three-letter but a four|-|letter combination. The first character in this case is always either \type {+} or \type {-}, indicating whether the value is pushed or popped from the direction stack. \subsubsection{pdf_literal nodes} Valid fields: \showfields{whatsit,pdf_literal}\crlf Id: \showid{whatsit,pdf_literal} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC mode \NC number \NC the \quote {mode} setting of this literal \NC \NR \NC data \NC string \NC the \type {\pdfliteral} information \NC \NR \stoptabulate Mode values: \starttabulate[|lT|p|] \NC \ssbf value \NC \ssbf corresponding \type {\pdftex} keyword \NC \NR \NC 0 \NC setorigin \NC \NR \NC 1 \NC page \NC \NR \NC 2 \NC direct \NC \NR \stoptabulate \subsubsection{pdf_refobj nodes} Valid fields: \showfields{whatsit,pdf_refobj}\crlf Id: \showid{whatsit,pdf_refobj} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC objnum \NC number \NC the referenced \PDF\ object number \NC \NR \stoptabulate \subsubsection{pdf_annot nodes} Valid fields: \showfields{whatsit,pdf_annot}\crlf Id: \showid{whatsit,pdf_annot} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC width \NC number \NC \NC \NR \NC height \NC number \NC \NC \NR \NC depth \NC number \NC \NC \NR \NC objnum \NC number \NC the referenced \PDF\ object number \NC \NR \NC data \NC string \NC the annotation data \NC \NR \stoptabulate \subsubsection{pdf_start_link nodes} Valid fields: \showfields{whatsit,pdf_start_link}\crlf Id: \showid{whatsit,pdf_start_link} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC width \NC number \NC \NC \NR \NC height \NC number \NC \NC \NR \NC depth \NC number \NC \NC \NR \NC objnum \NC number \NC the referenced \PDF\ object number \NC \NR \NC link_attr \NC table \NC the link attribute token list \NC \NR \NC action \NC \syntax{} \NC the action to perform \NC \NR \stoptabulate \subsubsection{pdf_end_link nodes} Valid fields: \showfields{whatsit,pdf_end_link}\crlf Id: \showid{whatsit,pdf_end_link} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \stoptabulate \subsubsection{pdf_dest nodes} Valid fields: \showfields{whatsit,pdf_dest}\crlf Id: \showid{whatsit,pdf_dest} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC width \NC number \NC \NC \NR \NC height \NC number \NC \NC \NR \NC depth \NC number \NC \NC \NR \NC named_id \NC number \NC is the \type {dest_id} a string value? \NC \NR \NC dest_id \NC number \NC the destination id \NC \NR \NC \NC string \NC the destination name \NC \NR \NC dest_type \NC number \NC type of destination \NC \NR \NC xyz_zoom \NC number \NC \NC \NR \NC objnum \NC number \NC the \PDF\ object number \NC \NR \stoptabulate \subsubsection{pdf_action nodes} Valid fields: \showfields{whatsit,pdf_action}\crlf Id: \showid{whatsit,pdf_action} These are a special kind of item that only appears inside \PDF\ start link objects. \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC action_type \NC number \NC \NC \NR \NC action_id \NC number or string \NC \NC \NR \NC named_id \NC number \NC \NC \NR \NC file \NC string \NC \NC \NR \NC new_window \NC number \NC \NC \NR \NC data \NC string \NC \NC \NR \NC ref_count \NC number \NC read-only \NC \NR \stoptabulate \subsubsection{pdf_thread nodes} Valid fields: \showfields{whatsit,pdf_thread}\crlf Id: \showid{whatsit,pdf_thread} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC width \NC number \NC \NC \NR \NC height \NC number \NC \NC \NR \NC depth \NC number \NC \NC \NR \NC named_id \NC number \NC is \type {tread_id} a string value? \NC \NR \NC tread_id \NC number \NC the thread id \NC \NR \NC \NC string \NC the thread name \NC \NR \NC thread_attr \NC number \NC extra thread information \NC \NR \stoptabulate \subsubsection{pdf_start_thread nodes} Valid fields: \showfields{whatsit,pdf_start_thread}\crlf Id: \showid{whatsit,pdf_start_thread} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC width \NC number \NC \NC \NR \NC height \NC number \NC \NC \NR \NC depth \NC number \NC \NC \NR \NC named_id \NC number \NC is \type {tread_id} a string value? \NC \NR \NC tread_id \NC number \NC the thread id \NC \NR \NC \NC string \NC the thread name \NC \NR \NC thread_attr \NC number \NC extra thread information \NC \NR \stoptabulate \subsubsection{pdf_end_thread nodes} Valid fields: \showfields{whatsit,pdf_end_thread}\crlf Id: \showid{whatsit,pdf_end_thread} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \stoptabulate \subsubsection{save_pos nodes} Valid fields: \showfields{whatsit,save_pos}\crlf Id: \showid{whatsit,save_pos} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \stoptabulate \subsubsection{late_lua nodes} Valid fields: \showfields{whatsit,late_lua}\crlf Id: \showid{whatsit,late_lua} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC data \NC string \NC data to execute \NC \NR \NC string \NC string \NC data to execute \NC \NR \NC name \NC string \NC the name to use for \LUA\ error reporting \NC \NR \stoptabulate The difference between \type {data} and \type {string} is that on assignment, the \type {data} field is converted to a token list, cf. use as \type {\latelua}. The \type {string} version is treated as a literal string. \subsubsection{pdf_colorstack nodes} Valid fields: \showfields{whatsit,pdf_colorstack}\crlf Id: \showid{whatsit,pdf_colorstack} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC stack \NC number \NC colorstack id number \NC \NR \NC command \NC number \NC command to execute \NC \NR \NC data \NC string \NC data \NC \NR \stoptabulate \subsubsection{pdf_setmatrix nodes} Valid fields: \showfields{whatsit,pdf_setmatrix}\crlf Id: \showid{whatsit,pdf_setmatrix} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC data \NC string \NC data \NC \NR \stoptabulate \subsubsection{pdf_save nodes} Valid fields: \showfields{whatsit,pdf_save}\crlf Id: \showid{whatsit,pdf_save} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \stoptabulate \subsubsection{pdf_restore nodes} Valid fields: \showfields{whatsit,pdf_restore}\crlf Id: \showid{whatsit,pdf_restore} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \stoptabulate \subsubsection{user_defined nodes} User|-|defined whatsit nodes can only be created and handled from \LUA\ code. In effect, they are an extension to the extension mechanism. The \LUATEX\ engine will simply step over such whatsits without ever looking at the contents. Valid fields: \showfields{whatsit,user_defined}\crlf Id: \showid{whatsit,user_defined} \starttabulate[|lT|l|p|] \NC \ssbf field \NC \bf type \NC \bf explanation \NC \NR \NC attr \NC \syntax{} \NC \NC \NR \NC user_id \NC number \NC id number \NC \NR \NC type \NC number \NC type of the value \NC \NR \NC value \NC number \NC \NC \NR \NC \NC string \NC \NC \NR \NC \NC \syntax{} \NC \NC \NR \NC \NC table \NC \NC \NR \stoptabulate The \type {type} can have one of five distinct values: \starttabulate[|lT|p|] \NC \ssbf value \NC \bf explanation \NC \NR \NC 97 \NC the value is an attribute node list \NC \NR \NC 100 \NC the value is a number \NC \NR \NC 110 \NC the value is a node list \NC \NR \NC 115 \NC the value is a string \NC \NR \NC 116 \NC the value is a token list in \LUA\ table form \NC \NR \stoptabulate \section{Two access models} Deep down in \TEX\ a node has a number which is an numeric entry in a memory table. In fact, this model, where \TEX\ manages memory is real fast and one of the reasons why plugging in callbacks that operate on nodes is quite fast. So, if you use the direct model, even if you know that you deal with numbers, you should not depend on that property but treat it an abstraction just like traditional nodes. In fact, the fact that we use a simple basic datatype has the penalty that less checking can be done, but less checking is also the reason why it's somewhat faster. An important aspect is that one cannot mix both methods, but you can cast both models. So our advice is: use the indexed (table) approach when possible and investigate the direct one when speed might be an issue. For that reason we also provide the \type {get*} and \type {set*} functions in the top level node namespace. There is a limited set of getters. When implementing this direct approach the regular index by key variant was also optimized, so direct access only makes sense when we're accessing nodes millions of times (which happens in some font processing for instance). We're talking mostly of getters because setters are less important. Documents have not that many content related nodes and setting many thousands of properties is hardly a burden contrary to millions of consultations. Normally you will access nodes like this: \starttyping local next = current.next if next then -- do something end \stoptyping Here \type {next} is not a real field, but a virtual one. Accessing it results in a metatable method being called. In practice it boils down to looking up the node type and based on the node type checking for the field name. In a worst case you have a node type that sits at the end of the lookup list and a field that is last in the lookup chain. However, in successive versions of \LUATEX\ these lookups have been optimized and the most frequently accessed nodes and fields have a higher priority. Because in practice the \type {next} accessor results in a function call, there is some overhead involved. The next code does the same and performs a tiny bit faster (but not that much because it is still a function call but one that knows what to look up). \starttyping local next = node.next(current) if next then -- do something end \stoptyping If performance matters you can use an function instead: \starttabulate[|T|p|] \NC getnext \NC parsing nodelist always involves this one \NC \NR \NC getprev \NC used less but is logical companion to \type {getnext} \NC \NR \NC getboth \NC returns the next and prev pointer of a node \NC \NR \NC getid \NC consulted a lot \NC \NR \NC getsubtype \NC consulted less but also a topper \NC \NR \NC getfont \NC used a lot in \OPENTYPE\ handling (glyph nodes are consulted a lot) \NC \NR \NC getchar \NC idem and also in other places \NC \NR \NC getdisc \NC returns the \type {pre}, \type {post} and \type {replace} fields and optionally when true is passed also the tail fields. \NC \NR \NC getlist \NC we often parse nested lists so this is a convenient one too (only works for hlist and vlist!) \NC \NR \NC getleader \NC comparable to list, seldom used in \TEX\ (but needs frequent consulting like lists; leaders could have been made a dedicated node type) \NC \NR \NC getfield \NC generic getter, sufficient for the rest (other field names are often shared so a specific getter makes no sense then) \NC \NR \stoptabulate The direct variants also have setters, where the discretionary setter takes three (optional) arguments plus an optional fourth indicating the subtype. It doesn't make sense to add more. Profiling demonstrated that these fields can get accesses way more times than other fields. Even in complex documents, many node and fields types never get seen, or seen only a few times. Most functions in the \type {node} namespace have a companion in \type {node.direct}, but of course not the ones that don't deal with nodes themselves. The following table summarized this: \start \def\yes{$+$} \def\nop{$-$} \starttabulate[|T|c|c|] \HL \NC \bf function \NC \bf node \NC \bf direct \NC \NR \HL \NC \type {copy_list} \NC \yes \NC \yes \NC \NR \NC \type {copy} \NC \yes \NC \yes \NC \NR \NC \type {count} \NC \yes \NC \yes \NC \NR \NC \type {current_attr} \NC \yes \NC \yes \NC \NR \NC \type {dimensions} \NC \yes \NC \yes \NC \NR \NC \type {do_ligature_n} \NC \yes \NC \yes \NC \NR \NC \type {effective_glue} \NC \yes \NC \yes \NC \NR \NC \type {end_of_math} \NC \yes \NC \yes \NC \NR \NC \type {family_font} \NC \yes \NC \nop \NC \NR \NC \type {fields} \NC \yes \NC \nop \NC \NR \NC \type {first_character} \NC \yes \NC \nop \NC \NR \NC \type {first_glyph} \NC \yes \NC \yes \NC \NR \NC \type {flush_list} \NC \yes \NC \yes \NC \NR \NC \type {flush_node} \NC \yes \NC \yes \NC \NR \NC \type {free} \NC \yes \NC \yes \NC \NR \NC \type {getboth} \NC \yes \NC \yes \NC \NR \NC \type {getbox} \NC \nop \NC \yes \NC \NR \NC \type {getchar} \NC \yes \NC \yes \NC \NR \NC \type {getdisc} \NC \yes \NC \yes \NC \NR \NC \type {getfield} \NC \yes \NC \yes \NC \NR \NC \type {getfont} \NC \yes \NC \yes \NC \NR \NC \type {getid} \NC \yes \NC \yes \NC \NR \NC \type {getleader} \NC \yes \NC \yes \NC \NR \NC \type {getlist} \NC \yes \NC \yes \NC \NR \NC \type {getnext} \NC \yes \NC \yes \NC \NR \NC \type {getprev} \NC \yes \NC \yes \NC \NR \NC \type {getsubtype} \NC \yes \NC \yes \NC \NR \NC \type {has_attribute} \NC \yes \NC \yes \NC \NR \NC \type {has_field} \NC \yes \NC \yes \NC \NR \NC \type {has_glyph} \NC \yes \NC \yes \NC \NR \NC \type {hpack} \NC \yes \NC \yes \NC \NR \NC \type {id} \NC \yes \NC \nop \NC \NR \NC \type {insert_after} \NC \yes \NC \yes \NC \NR \NC \type {insert_before} \NC \yes \NC \yes \NC \NR \NC \type {is_char} \NC \yes \NC \yes \NC \NR \NC \type {is_glyph} \NC \yes \NC \yes \NC \NR \NC \type {is_direct} \NC \nop \NC \yes \NC \NR \NC \type {is_node} \NC \yes \NC \yes \NC \NR \NC \type {kerning} \NC \yes \NC \yes \NC \NR \NC \type {last_node} \NC \yes \NC \yes \NC \NR \NC \type {length} \NC \yes \NC \yes \NC \NR \NC \type {ligaturing} \NC \yes \NC \yes \NC \NR \NC \type {mlist_to_hlist} \NC \yes \NC \nop \NC \NR \NC \type {new} \NC \yes \NC \yes \NC \NR \NC \type {next} \NC \yes \NC \nop \NC \NR \NC \type {prev} \NC \yes \NC \nop \NC \NR \NC \type {protect_glyph} \NC \yes \NC \yes \NC \NR \NC \type {protect_glyphs} \NC \yes \NC \yes \NC \NR \NC \type {protrusion_skippable} \NC \yes \NC \yes \NC \NR \NC \type {remove} \NC \yes \NC \yes \NC \NR \NC \type {set_attribute} \NC \yes \NC \yes \NC \NR \NC \type {setboth} \NC \yes \NC \yes \NC \NR \NC \type {setbox} \NC \yes \NC \yes \NC \NR \NC \type {setchar} \NC \yes \NC \yes \NC \NR \NC \type {setdisc} \NC \yes \NC \yes \NC \NR \NC \type {setfield} \NC \yes \NC \yes \NC \NR \NC \type {setlink} \NC \yes \NC \yes \NC \NR \NC \type {setnext} \NC \yes \NC \yes \NC \NR \NC \type {setprev} \NC \yes \NC \yes \NC \NR \NC \type {slide} \NC \yes \NC \yes \NC \NR \NC \type {subtype} \NC \yes \NC \nop \NC \NR \NC \type {subtypes} \NC \yes \NC \nop \NC \NR \NC \type {tail} \NC \yes \NC \yes \NC \NR \NC \type {todirect} \NC \yes \NC \yes \NC \NR \NC \type {tonode} \NC \yes \NC \yes \NC \NR \NC \type {tostring} \NC \yes \NC \yes \NC \NR \NC \type {traverse_id} \NC \yes \NC \yes \NC \NR \NC \type {traverse_char} \NC \yes \NC \yes \NC \NR \NC \type {traverse} \NC \yes \NC \yes \NC \NR \NC \type {types} \NC \yes \NC \nop \NC \NR \NC \type {type} \NC \yes \NC \nop \NC \NR \NC \type {unprotect_glyphs} \NC \yes \NC \yes \NC \NR \NC \type {unset_attribute} \NC \yes \NC \yes \NC \NR \NC \type {usedlist} \NC \yes \NC \yes \NC \NR \NC \type {vpack} \NC \yes \NC \yes \NC \NR \NC \type {whatsits} \NC \yes \NC \nop \NC \NR \NC \type {whatsitsubtypes} \NC \yes \NC \nop \NC \NR \NC \type {write} \NC \yes \NC \yes \NC \NR \NC \type {setglue} \NC \yes \NC \yes \NC \NR \NC \type {getglue} \NC \yes \NC \yes \NC \NR \NC \type {glue_is_zero} \NC \yes \NC \yes \NC \NR \stoptabulate \stop The \type {node.next} and \type {node.prev} functions will stay but for consistency there are variants called \type {getnext} and \type {getprev}. We had to use \type {get} because \type {node.id} and \type {node.subtype} are already taken for providing meta information about nodes. Note: The getters do only basic checking for valid keys. You should just stick to the keys mentioned in the sections that describe node properties. Some nodes have indirect references. For instance a math character refers to a family instead of a font. In that case we provide a virtual font field as accessor. So, \type {getfont} and \type {.font} can be used on them. The same is true for the \type {width}, \type {height} and \type {depth} of glue nodes. These actually access the spec node properties, and here we can set as well as get the values. \stopchapter \stopcomponent