diff options
Diffstat (limited to 'doc/context/sources/general/manuals/luatex/luatex-nodes.tex')
| -rw-r--r-- | doc/context/sources/general/manuals/luatex/luatex-nodes.tex | 1829 |
1 files changed, 1829 insertions, 0 deletions
diff --git a/doc/context/sources/general/manuals/luatex/luatex-nodes.tex b/doc/context/sources/general/manuals/luatex/luatex-nodes.tex new file mode 100644 index 000000000..e90813c33 --- /dev/null +++ b/doc/context/sources/general/manuals/luatex/luatex-nodes.tex @@ -0,0 +1,1829 @@ +% 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 {<node>}. + +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{Attributes} + +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. + +\subsubsection{attribute_list nodes} + +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 \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC next \NC node \NC pointer to the first attribute \NC \NR +\stoptabulate + +\subsubsection{attribute nodes} + +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. + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC next \NC node \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 \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC next \NC node \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. By now most of \TEX's node processing makes sure that the +\type {prev} nodes are valid but there can be exceptions, especially when the +internal magic uses a leading \type {temp} nodes to temporarily store a state. + +\subsubsection{hlist nodes} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC subtype \NC number \NC \showsubtypes{list} \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC width \NC number \NC the width of the box \NC \NR +\NC height \NC number \NC the height of the box \NC \NR +\NC depth \NC number \NC the depth of the box \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 0 = \type {normal}, 1 = \type {stretching}, 2 = \type {shrinking} \NC \NR +\NC head/list \NC node \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} + +This node is similar to \type {hlist}, except that \quote {shift} is a displacement +perpendicular to the line progression direction, and \quote {subtype} only has +the values 0, 4, and~5. + +\subsubsection{rule nodes} + +Contrary to traditional \TEX, \LUATEX\ has more subtypes because we also use +rules to store reuseable objects and images. User nodes are invisible and can be +intercepted by a callback. + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC subtype \NC number \NC \showsubtypes{rule} \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC width \NC number \NC the width of the rule where 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 \NC \NR +\stoptabulate + +\subsubsection{ins nodes} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC subtype \NC number \NC the insertion class \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC cost \NC number \NC the penalty associated with this insert \NC \NR +\NC height \NC number \NC height of the insert \NC \NR +\NC depth \NC number \NC depth of the insert \NC \NR +\NC head/list \NC node \NC the first node of the body of this insert \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} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC subtype \NC number \NC unused \NC \NR +\NC attr \NC node \NC list of attributes \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} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC subtype \NC number \NC \showsubtypes{adjust} \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC head/list \NC node \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} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC subtype \NC number \NC \showsubtypes{disc} \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC pre \NC node \NC pointer to the pre|-|break text \NC \NR +\NC post \NC node \NC pointer to the post|-|break text \NC \NR +\NC replace \NC node \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. + +\subsubsection{math nodes} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC subtype \NC number \NC \showsubtypes{math} \NC \NR +\NC attr \NC node \NC list of attributes \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 \rmbf key \NC \bf type \NC \bf explanation \NC \NR +\NC width \NC number \NC the horizontal or vertical displacement \NC \NR +\NC stretch \NC number \NC extra (positive) displacement or stretch amount \NC \NR +\NC stretch_order \NC number \NC factor applied to stretch amount \NC \NR +\NC shrink \NC number \NC extra (negative) displacement or shrink amount\NC \NR +\NC shrink_order \NC number \NC factor applied to shrink amount \NC \NR +\stoptabulate + +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). + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC subtype \NC number \NC \showsubtypes{glue} \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC leader \NC node \NC pointer to a box or rule for leaders \NC \NR +\stoptabulate + +In addition there are the \type {width}, \type {stretch} \type {stretch_order}, +\type {shrink}, and \type {shrink_order} fields. 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. + +A regular word space also results in a \type {spaceskip} subtype (this used to be +a \type {userskip} with subtype zero). + +\subsubsection{kern nodes} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC subtype \NC number \NC \showsubtypes{kern} \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC kern \NC number \NC fixed horizontal or vertical advance \NC \NR +\stoptabulate + +\subsubsection{penalty nodes} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC subtype \NC number \NC not used \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC penalty \NC number \NC the penalty value \NC \NR +\stoptabulate + +\subsubsection[glyphnodes]{glyph nodes} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \rmbf type \NC \rmbf explanation \NC \NR +\NC subtype \NC number \NC bitfield \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC char \NC number \NC the chatacter index in the font \NC \NR +\NC font \NC number \NC the font identifier \NC \NR +\NC lang \NC number \NC the language identifier \NC \NR +\NC left \NC number \NC the frozen \type {\lefthyphenmnin} value \NC \NR +\NC right \NC number \NC the frozen \type {\righthyphenmnin} value \NC \NR +\NC uchyph \NC boolean \NC the frozen \type {\uchyph} value \NC \NR +\NC components \NC node \NC pointer to ligature components \NC \NR +\NC xoffset \NC number \NC a virtual displacement in horizontal direction \NC \NR +\NC yoffset \NC number \NC a virtual displacement in vertical direction \NC \NR +\NC xadvance \NC number \NC an additional advance after the glyph (experimental) \NC \NR +\NC width \NC number \NC the (original) width of the character \NC \NR +\NC height \NC number \NC the (original) height of the character\NC \NR +\NC depth \NC number \NC the (original) depth of the character\NC \NR +\NC expansion_factor \NC number \NC the to be applied expansion_factor \NC \NR +\stoptabulate + +The \type {width}, \type {height} and \type {depth} values are read|-|only. The +\type {expansion_factor} is assigned in the parbuilder and used in the backend. + +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 \rmbf 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{boundary nodes} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC subtype \NC number \NC \showsubtypes{boundary} \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC value \NC number \NC values 0--255 are reserved \NC \NR +\stoptabulate + +This node relates to the \type {\noboundary}, \type {\boundary}, \type +{\protrusionboundary} and \type {\wordboundary} primitives. + +\subsubsection{local_par nodes} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \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 node \NC the \type {\localleftbox} \NC \NR +\NC box_left_width \NC number \NC width of the \type {\localleftbox} \NC \NR +\NC box_right \NC node \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} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \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 +\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{margin_kern nodes} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC subtype \NC number \NC \showsubtypes{margin_kern} \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC width \NC number \NC the advance of the kern \NC \NR +\NC glyph \NC node \NC the glyph to be used \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 {<kernel>}). + +The \type {next} and \type {prev} fields for these subnodes are unused. + +\subsubsubsection{math_char and math_text_char subnodes} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC char \NC number \NC the character index \NC \NR +\NC fam \NC number \NC the family number \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} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC head/list \NC node \NC list of nodes \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} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC small_char \NC number \NC character index of base character \NC \NR +\NC small_fam \NC number \NC family number of base character \NC \NR +\NC large_char \NC number \NC character index of next larger character \NC \NR +\NC large_fam \NC number \NC family number of next larger character \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} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC subtype \NC number \NC \showsubtypes{noad} \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC nucleus \NC kernel node \NC base \NC \NR +\NC sub \NC kernel node \NC subscript \NC \NR +\NC sup \NC kernel node \NC superscript \NC \NR +\stoptabulate + +\subsubsubsection{accent nodes} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC subtype \NC number \NC \showsubtypes{accent} \NC \NR +\NC nucleus \NC kernel node \NC base \NC \NR +\NC sub \NC kernel node \NC subscript \NC \NR +\NC sup \NC kernel node \NC superscript \NC \NR +\NC accent \NC kernel node \NC top accent \NC \NR +\NC bot_accent \NC kernel node \NC bottom accent \NC \NR +\stoptabulate + +\subsubsubsection{style nodes} + +\starttabulate[|lT|l|p|] +\NC \rmbf 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} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC display \NC node \NC list of display size alternatives \NC \NR +\NC text \NC node \NC list of text size alternatives \NC \NR +\NC script \NC node \NC list of scriptsize alternatives \NC \NR +\NC scriptscript \NC node \NC list of scriptscriptsize alternatives \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} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC subtype \NC number \NC \showsubtypes{radical} \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC nucleus \NC kernel node \NC base \NC \NR +\NC sub \NC kernel node \NC subscript \NC \NR +\NC sup \NC kernel node \NC superscript \NC \NR +\NC left \NC delimiter node \NC \NC \NR +\NC degree \NC kernel node \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. + +\subsubsubsection{fraction nodes} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC width \NC number \NC (optional) width of the fraction \NC \NR +\NC num \NC kernel node \NC numerator \NC \NR +\NC denom \NC kernel node \NC denominator \NC \NR +\NC left \NC delimiter node \NC left side symbol \NC \NR +\NC right \NC delimiter node \NC right side symbol\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} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC subtype \NC number \NC \showsubtypes{fence} \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC delim \NC delimiter node \NC delimiter specification \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{front|-|end whatits} + +\subsubsubsection{open whatsits} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \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 + +\subsubsubsection{write whatsits} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \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 + +\subsubsubsection{close whatsits} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC stream \NC number \NC \TEX's stream id number \NC \NR +\stoptabulate + +\subsubsubsection{user_defined whatits} + +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. + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \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 a \LUA\ number \NC \NR +\NC \NC node \NC a node list \NC \NR +\NC \NC string \NC a \LUA\ string \NC \NR +\NC \NC table \NC a \LUA\ table \NC \NR +\stoptabulate + +The \type {type} can have one of six distinct values. The number is the \ASCII\ +value if the first character if the type name (so you can use string.byte("l") +instead of \type {108}). + +\starttabulate[|lT|p|] +\NC \rmbf value \NC \bf meaning \NC \bf explanation \NC \NR +\NC 97 \NC a \NC list of attributes (a node list) \NC \NR +\NC 100 \NC d \NC a \LUA\ number \NC \NR +\NC 108 \NC l \NC a \LUA\ value (table, number, boolean, etc) \NC \NR +\NC 110 \NC n \NC a node list \NC \NR +\NC 115 \NC s \NC a \LUA\ string \NC \NR +\NC 116 \NC t \NC a \LUA\ token list in \LUA\ table form (a list of triplets) \NC \NR +\stoptabulate + +\subsubsubsection{save_pos whatsits} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\stoptabulate + +\subsubsubsection{late_lua whatsits} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \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{\DVI\ backend whatits} + +\subsubsection{special whatits} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC data \NC string \NC the \type {\special} information \NC \NR +\stoptabulate + +\subsubsection{\PDF\ backend whatits} + +\subsubsubsection{pdf_literal whatits} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \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 + +Possible mode values are: + +\starttabulate[|lT|p|] +\NC \rmbf value \NC \rmbf \PDFTEX\ keyword \NC \NR +\NC 0 \NC setorigin \NC \NR +\NC 1 \NC page \NC \NR +\NC 2 \NC direct \NC \NR +\stoptabulate + +\subsubsubsection{pdf_refobj whatits} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC objnum \NC number \NC the referenced \PDF\ object number \NC \NR +\stoptabulate + +\subsubsubsection{pdf_annot whatits} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC width \NC number \NC the width (not used in calculations) \NC \NR +\NC height \NC number \NC the height (not used in calculations) \NC \NR +\NC depth \NC number \NC the depth (not used in calculations) \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 + +\subsubsubsection{pdf_start_link whatits} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC width \NC number \NC the width (not used in calculations) \NC \NR +\NC height \NC number \NC the height (not used in calculations) \NC \NR +\NC depth \NC number \NC the depth (not used in calculations) \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 node \NC the action to perform \NC \NR +\stoptabulate + +\subsubsubsection{pdf_end_link whatits} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC \NC \NR +\stoptabulate + +\subsubsubsection{pdf_dest whatits} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC width \NC number \NC the width (not used in calculations) \NC \NR +\NC height \NC number \NC the height (not used in calculations) \NC \NR +\NC depth \NC number \NC the depth (not used in calculations) \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 the zoom factor (times 1000) \NC \NR +\NC objnum \NC number \NC the \PDF\ object number \NC \NR +\stoptabulate + +\subsubsubsection{pdf_action whatits} + +These are a special kind of item that only appears inside \PDF\ start link +objects. + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC action_type \NC number \NC the kind of action involved \NC \NR +\NC action_id \NC number or string \NC token list reference or string \NC \NR +\NC named_id \NC number \NC the index of the destination \NC \NR +\NC file \NC string \NC the target filename \NC \NR +\NC new_window \NC number \NC the window state of the target \NC \NR +\NC data \NC string \NC the name of the destination \NC \NR +\stoptabulate + +Valid action types are: + +\starttabulate[|lT|lT|] +\NC 0 \NC page \NC \NR +\NC 1 \NC goto \NC \NR +\NC 2 \NC thread \NC \NR +\NC 3 \NC user \NC \NR +\stoptabulate + +Valid window types are: + +\starttabulate[|lT|lT|] +\NC 0 \NC notset \NC \NR +\NC 1 \NC new \NC \NR +\NC 2 \NC nonew \NC \NR +\stoptabulate + +\subsubsubsection{pdf_thread whatits} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC width \NC number \NC the width (not used in calculations) \NC \NR +\NC height \NC number \NC the height (not used in calculations) \NC \NR +\NC depth \NC number \NC the depth (not used in calculations) \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 + +\subsubsubsection{pdf_start_thread whatits} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC width \NC number \NC the width (not used in calculations) \NC \NR +\NC height \NC number \NC the height (not used in calculations) \NC \NR +\NC depth \NC number \NC the depth (not used in calculations) \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 + +\subsubsubsection{pdf_end_thread whatits} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC \NC \NR +\stoptabulate + +\subsubsubsection{pdf_colorstack whatits} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \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 + +\subsubsubsection{pdf_setmatrix whatits} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\NC data \NC string \NC data \NC \NR +\stoptabulate + +\subsubsubsection{pdf_save whatits} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \NC \NR +\stoptabulate + +\subsubsubsection{pdf_restore whatits} + +\starttabulate[|lT|l|p|] +\NC \rmbf field \NC \bf type \NC \bf explanation \NC \NR +\NC attr \NC node \NC list of attributes \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 too. +Each node gets a number that is in fact an index in the memory table and that +number often gets reported when you print node related information. + +There are two access models, a robust one using a so called user data object that +provides a virtual interface to the internal nodes, and a more direct access which +uses the node numbers directly. The first model provide key based access while +the second always accesses fields via functions: + +\starttyping +nodeobject.char +getfield(nodenumber,"char") +\stoptyping + +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, multiplying a node number makes no sense. + +So our advice is: use the indexed (table) approach when possible and investigate +the direct one when speed might be an real 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 getters for all fields, also because some are not +unique to one node type. 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: + +% \startcolumns[balance=yes] + +\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 {get_attribute} \NC \yes \NC \yes \NC \NR +\NC \type {find_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 + +% \stopcolumns + +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. + +\section{The \type {node} library} + +The \type {node} library contains functions that facilitate dealing with (lists +of) nodes and their values. They allow you to create, alter, copy, delete, and +insert \LUATEX\ node objects, the core objects within the typesetter. + +\LUATEX\ nodes are represented in \LUA\ as userdata with the metadata type +\type {luatex.node}. The various parts within a node can be accessed using +named fields. + +Each node has at least the three fields \type {next}, \type {id}, and \type +{subtype}: + +\startitemize[intro] + +\startitem + The \type {next} field returns the userdata object for the next node in a + linked list of nodes, or \type {nil}, if there is no next node. +\stopitem + +\startitem + The \type {id} indicates \TEX's \quote{node type}. The field \type {id} has a + numeric value for efficiency reasons, but some of the library functions also + accept a string value instead of \type {id}. +\stopitem + +\startitem + The \type {subtype} is another number. It often gives further information + about a node of a particular \type {id}, but it is most important when + dealing with \quote {whatsits}, because they are differentiated solely based + on their \type {subtype}. +\stopitem + +\stopitemize + +The other available fields depend on the \type {id} (and for \quote {whatsits}, +the \type {subtype}) of the node. Further details on the various fields and their +meanings are given in~\in{chapter}[nodes]. + +Support for \type {unset} (alignment) nodes is partial: they can be queried and +modified from \LUA\ code, but not created. + +Nodes can be compared to each other, but: you are actually comparing indices into +the node memory. This means that equality tests can only be trusted under very +limited conditions. It will not work correctly in any situation where one of the +two nodes has been freed and|/|or reallocated: in that case, there will be false +positives. + +At the moment, memory management of nodes should still be done explicitly by the +user. Nodes are not \quote {seen} by the \LUA\ garbage collector, so you have to +call the node freeing functions yourself when you are no longer in need of a node +(list). Nodes form linked lists without reference counting, so you have to be +careful that when control returns back to \LUATEX\ itself, you have not deleted +nodes that are still referenced from a \type {next} pointer elsewhere, and that +you did not create nodes that are referenced more than once. + +There are statistics available with regards to the allocated node memory, which +can be handy for tracing. + +\subsection{Node handling functions} + +\subsubsection{\type {node.is_node}} + +\startfunctioncall +<boolean> t = + node.is_node(<any> item) +\stopfunctioncall + +This function returns true if the argument is a userdata object of +type \type {<node>}. + +\subsubsection{\type {node.types}} + +\startfunctioncall +<table> t = + node.types() +\stopfunctioncall + +This function returns an array that maps node id numbers to node type strings, +providing an overview of the possible top|-|level \type {id} types. + +\subsubsection{\type {node.whatsits}} + +\startfunctioncall +<table> t = + node.whatsits() +\stopfunctioncall + +\TEX's \quote{whatsits} all have the same \type {id}. The various subtypes are +defined by their \type {subtype} fields. The function is much like \type +{node.types}, except that it provides an array of \type {subtype} mappings. + +\subsubsection{\type {node.id}} + +\startfunctioncall +<number> id = + node.id(<string> type) +\stopfunctioncall + +This converts a single type name to its internal numeric representation. + +\subsubsection{\type {node.subtype}} + +\startfunctioncall +<number> subtype = + node.subtype(<string> type) +\stopfunctioncall + +This converts a single whatsit name to its internal numeric representation (\type +{subtype}). + +\subsubsection{\type {node.type}} + +\startfunctioncall +<string> type = + node.type(<any> n) +\stopfunctioncall + +In the argument is a number, then this function converts an internal numeric +representation to an external string representation. Otherwise, it will return +the string \type {node} if the object represents a node, and \type {nil} +otherwise. + +\subsubsection{\type {node.fields}} + +\startfunctioncall +<table> t = + node.fields(<number> id) +<table> t = + node.fields(<number> id, <number> subtype) +\stopfunctioncall + +This function returns an array of valid field names for a particular type of +node. If you want to get the valid fields for a \quote {whatsit}, you have to +supply the second argument also. In other cases, any given second argument will +be silently ignored. + +This function accepts string \type {id} and \type {subtype} values as well. + +\subsubsection{\type {node.has_field}} + +\startfunctioncall +<boolean> t = + node.has_field(<node> n, <string> field) +\stopfunctioncall + +This function returns a boolean that is only true if \type {n} is +actually a node, and it has the field. + +\subsubsection{\type {node.new}} + +\startfunctioncall +<node> n = + node.new(<number> id) +<node> n = + node.new(<number> id, <number> subtype) +\stopfunctioncall + +Creates a new node. All of the new node's fields are initialized to either zero +or \type {nil} except for \type {id} and \type {subtype} (if supplied). If you +want to create a new whatsit, then the second argument is required, otherwise it +need not be present. As with all node functions, this function creates a node on +the \TEX\ level. + +This function accepts string \type {id} and \type {subtype} values as well. + +\subsubsection{\type {node.free}} + +\startfunctioncall +node.free(<node> n) +\stopfunctioncall + +Removes the node \type {n} from \TEX's memory. Be careful: no checks are done on +whether this node is still pointed to from a register or some \type {next} field: +it is up to you to make sure that the internal data structures remain correct. + +\subsubsection{\type {node.flush_list}} + +\startfunctioncall +node.flush_list(<node> n) +\stopfunctioncall + +Removes the node list \type {n} and the complete node list following \type {n} +from \TEX's memory. Be careful: no checks are done on whether any of these nodes +is still pointed to from a register or some \type {next} field: it is up to you +to make sure that the internal data structures remain correct. + +\subsubsection{\type {node.copy}} + +\startfunctioncall +<node> m = + node.copy(<node> n) +\stopfunctioncall + +Creates a deep copy of node \type {n}, including all nested lists as in the case +of a hlist or vlist node. Only the \type {next} field is not copied. + +\subsubsection{\type {node.copy_list}} + +\startfunctioncall +<node> m = + node.copy_list(<node> n) +<node> m = + node.copy_list(<node> n, <node> m) +\stopfunctioncall + +Creates a deep copy of the node list that starts at \type {n}. If \type {m} is +also given, the copy stops just before node \type {m}. + +Note that you cannot copy attribute lists this way, specialized functions for +dealing with attribute lists will be provided later but are not there yet. +However, there is normally no need to copy attribute lists as when you do +assignments to the \type {attr} field or make changes to specific attributes, the +needed copying and freeing takes place automatically. + +\subsubsection{\type {node.next}} + +\startfunctioncall +<node> m = + node.next(<node> n) +\stopfunctioncall + +Returns the node following this node, or \type {nil} if there is no such node. + +\subsubsection{\type {node.prev}} + +\startfunctioncall +<node> m = + node.prev(<node> n) +\stopfunctioncall + +Returns the node preceding this node, or \type {nil} if there is no such node. + +\subsubsection{\type {node.current_attr}} + +\startfunctioncall +<node> m = + node.current_attr() +\stopfunctioncall + +Returns the currently active list of attributes, if there is one. + +The intended usage of \type {current_attr} is as follows: + +\starttyping +local x1 = node.new("glyph") +x1.attr = node.current_attr() +local x2 = node.new("glyph") +x2.attr = node.current_attr() +\stoptyping + +or: + +\starttyping +local x1 = node.new("glyph") +local x2 = node.new("glyph") +local ca = node.current_attr() +x1.attr = ca +x2.attr = ca +\stoptyping + +The attribute lists are ref counted and the assignment takes care of incrementing +the refcount. You cannot expect the value \type {ca} to be valid any more when +you assign attributes (using \type {tex.setattribute}) or when control has been +passed back to \TEX. + +Note: this function is somewhat experimental, and it returns the {\it actual} +attribute list, not a copy thereof. Therefore, changing any of the attributes in +the list will change these values for all nodes that have the current attribute +list assigned to them. + +\subsubsection{\type {node.hpack}} + +\startfunctioncall +<node> h, <number> b = + node.hpack(<node> n) +<node> h, <number> b = + node.hpack(<node> n, <number> w, <string> info) +<node> h, <number> b = + node.hpack(<node> n, <number> w, <string> info, <string> dir) +\stopfunctioncall + +This function creates a new hlist by packaging the list that begins at node \type +{n} into a horizontal box. With only a single argument, this box is created using +the natural width of its components. In the three argument form, \type {info} +must be either \type {additional} or \type {exactly}, and \type {w} is the +additional (\type {\hbox spread}) or exact (\type {\hbox to}) width to be used. The +second return value is the badness of the generated box. + +Caveat: at this moment, there can be unexpected side|-|effects to this function, +like updating some of the \type {\marks} and \type {\inserts}. Also note that the +content of \type {h} is the original node list \type {n}: if you call \type +{node.free(h)} you will also free the node list itself, unless you explicitly set +the \type {list} field to \type {nil} beforehand. And in a similar way, calling +\type {node.free(n)} will invalidate \type {h} as well! + +\subsubsection{\type {node.vpack}} + +\startfunctioncall +<node> h, <number> b = + node.vpack(<node> n) +<node> h, <number> b = + node.vpack(<node> n, <number> w, <string> info) +<node> h, <number> b = + node.vpack(<node> n, <number> w, <string> info, <string> dir) +\stopfunctioncall + +This function creates a new vlist by packaging the list that begins at node \type +{n} into a vertical box. With only a single argument, this box is created using +the natural height of its components. In the three argument form, \type {info} +must be either \type {additional} or \type {exactly}, and \type {w} is the +additional (\type {\vbox spread}) or exact (\type {\vbox to}) height to be used. + +The second return value is the badness of the generated box. + +See the description of \type {node.hpack()} for a few memory allocation caveats. + +\subsubsection{\type {node.dimensions}} + +\startfunctioncall +<number> w, <number> h, <number> d = + node.dimensions(<node> n) +<number> w, <number> h, <number> d = + node.dimensions(<node> n, <string> dir) +<number> w, <number> h, <number> d = + node.dimensions(<node> n, <node> t) +<number> w, <number> h, <number> d = + node.dimensions(<node> n, <node> t, <string> dir) +\stopfunctioncall + +This function calculates the natural in|-|line dimensions of the node list starting +at node \type {n} and terminating just before node \type {t} (or the end of the +list, if there is no second argument). The return values are scaled points. An +alternative format that starts with glue parameters as the first three arguments +is also possible: + +\startfunctioncall +<number> w, <number> h, <number> d = + node.dimensions(<number> glue_set, <number> glue_sign, <number> glue_order, + <node> n) +<number> w, <number> h, <number> d = + node.dimensions(<number> glue_set, <number> glue_sign, <number> glue_order, + <node> n, <string> dir) +<number> w, <number> h, <number> d = + node.dimensions(<number> glue_set, <number> glue_sign, <number> glue_order, + <node> n, <node> t) +<number> w, <number> h, <number> d = + node.dimensions(<number> glue_set, <number> glue_sign, <number> glue_order, + <node> n, <node> t, <string> dir) +\stopfunctioncall + +This calling method takes glue settings into account and is especially useful for +finding the actual width of a sublist of nodes that are already boxed, for +example in code like this, which prints the width of the space in between the +\type {a} and \type {b} as it would be if \type {\box0} was used as-is: + +\starttyping +\setbox0 = \hbox to 20pt {a b} + +\directlua{print (node.dimensions( + tex.box[0].glue_set, + tex.box[0].glue_sign, + tex.box[0].glue_order, + tex.box[0].head.next, + node.tail(tex.box[0].head) +)) } +\stoptyping + +You need to keep in mind that this is one of the few places in \TEX\ where floats +are used, which means that you can get small differences in rounding when you +compare the width repported by \type {hpack} with \type {dimensions}. + +\subsubsection{\type {node.mlist_to_hlist}} + +\startfunctioncall +<node> h = + node.mlist_to_hlist(<node> n, <string> display_type, <boolean> penalties) +\stopfunctioncall + +This runs the internal mlist to hlist conversion, converting the math list in +\type {n} into the horizontal list \type {h}. The interface is exactly the same +as for the callback \type {mlist_to_hlist}. + +\subsubsection{\type {node.slide}} + +\startfunctioncall +<node> m = + node.slide(<node> n) +\stopfunctioncall + +Returns the last node of the node list that starts at \type {n}. As a +side|-|effect, it also creates a reverse chain of \type {prev} pointers between +nodes. + +\subsubsection{\type {node.tail}} + +\startfunctioncall +<node> m = + node.tail(<node> n) +\stopfunctioncall + +Returns the last node of the node list that starts at \type {n}. + +\subsubsection{\type {node.length}} + +\startfunctioncall +<number> i = + node.length(<node> n) +<number> i = + node.length(<node> n, <node> m) +\stopfunctioncall + +Returns the number of nodes contained in the node list that starts at \type {n}. +If \type {m} is also supplied it stops at \type {m} instead of at the end of the +list. The node \type {m} is not counted. + +\subsubsection{\type {node.count}} + +\startfunctioncall +<number> i = + node.count(<number> id, <node> n) +<number> i = + node.count(<number> id, <node> n, <node> m) +\stopfunctioncall + +Returns the number of nodes contained in the node list that starts at \type {n} +that have a matching \type {id} field. If \type {m} is also supplied, counting +stops at \type {m} instead of at the end of the list. The node \type {m} is not +counted. + +This function also accept string \type {id}'s. + +\subsubsection{\type {node.traverse}} + +\startfunctioncall +<node> t = + node.traverse(<node> n) +\stopfunctioncall + +This is a \LUA\ iterator that loops over the node list that starts at \type {n}. +Typically code looks like this: + +\starttyping +for n in node.traverse(head) do + ... +end +\stoptyping + +is functionally equivalent to: + +\starttyping +do + local n + local function f (head,var) + local t + if var == nil then + t = head + else + t = var.next + end + return t + end + while true do + n = f (head, n) + if n == nil then break end + ... + end +end +\stoptyping + +It should be clear from the definition of the function \type {f} that even though +it is possible to add or remove nodes from the node list while traversing, you +have to take great care to make sure all the \type {next} (and \type {prev}) +pointers remain valid. + +If the above is unclear to you, see the section \quote {For Statement} in the +\LUA\ Reference Manual. + +\subsubsection{\type {node.traverse_id}} + +\startfunctioncall +<node> t = + node.traverse_id(<number> id, <node> n) +\stopfunctioncall + +This is an iterator that loops over all the nodes in the list that starts at +\type {n} that have a matching \type {id} field. + +See the previous section for details. The change is in the local function \type +{f}, which now does an extra while loop checking against the upvalue \type {id}: + +\starttyping + local function f(head,var) + local t + if var == nil then + t = head + else + t = var.next + end + while not t.id == id do + t = t.next + end + return t + end +\stoptyping + +\subsubsection{\type {node.end_of_math}} + +\startfunctioncall +<node> t = + node.end_of_math(<node> start) +\stopfunctioncall + +Looks for and returns the next \type {math_node} following the \type {start}. If +the given node is a math endnode this helper return that node, else it follows +the list and return the next math endnote. If no such node is found nil is +returned. + +\subsubsection{\type {node.remove}} + +\startfunctioncall +<node> head, current = + node.remove(<node> head, <node> current) +\stopfunctioncall + +This function removes the node \type {current} from the list following \type +{head}. It is your responsibility to make sure it is really part of that list. +The return values are the new \type {head} and \type {current} nodes. The +returned \type {current} is the node following the \type {current} in the calling +argument, and is only passed back as a convenience (or \type {nil}, if there is +no such node). The returned \type {head} is more important, because if the +function is called with \type {current} equal to \type {head}, it will be +changed. + +\subsubsection{\type {node.insert_before}} + +\startfunctioncall +<node> head, new = + node.insert_before(<node> head, <node> current, <node> new) +\stopfunctioncall + +This function inserts the node \type {new} before \type {current} into the list +following \type {head}. It is your responsibility to make sure that \type +{current} is really part of that list. The return values are the (potentially +mutated) \type {head} and the node \type {new}, set up to be part of the list +(with correct \type {next} field). If \type {head} is initially \type {nil}, it +will become \type {new}. + +\subsubsection{\type {node.insert_after}} + +\startfunctioncall +<node> head, new = + node.insert_after(<node> head, <node> current, <node> new) +\stopfunctioncall + +This function inserts the node \type {new} after \type {current} into the list +following \type {head}. It is your responsibility to make sure that \type +{current} is really part of that list. The return values are the \type {head} and +the node \type {new}, set up to be part of the list (with correct \type {next} +field). If \type {head} is initially \type {nil}, it will become \type {new}. + +\subsubsection{\type {node.first_glyph}} + +\startfunctioncall +<node> n = + node.first_glyph(<node> n) +<node> n = + node.first_glyph(<node> n, <node> m) +\stopfunctioncall + +Returns the first node in the list starting at \type {n} that is a glyph node +with a subtype indicating it is a glyph, or \type {nil}. If \type {m} is given, +processing stops at (but including) that node, otherwise processing stops at the +end of the list. + +\subsubsection{\type {node.ligaturing}} + +\startfunctioncall +<node> h, <node> t, <boolean> success = + node.ligaturing(<node> n) +<node> h, <node> t, <boolean> success = + node.ligaturing(<node> n, <node> m) +\stopfunctioncall + +Apply \TEX-style ligaturing to the specified nodelist. The tail node \type {m} is +optional. The two returned nodes \type {h} and \type {t} are the new head and +tail (both \type {n} and \type {m} can change into a new ligature). + +\subsubsection{\type {node.kerning}} + +\startfunctioncall +<node> h, <node> t, <boolean> success = + node.kerning(<node> n) +<node> h, <node> t, <boolean> success = + node.kerning(<node> n, <node> m) +\stopfunctioncall + +Apply \TEX|-|style kerning to the specified node list. The tail node \type {m} is +optional. The two returned nodes \type {h} and \type {t} are the head and tail +(either one of these can be an inserted kern node, because special kernings with +word boundaries are possible). + +\subsubsection{\type {node.unprotect_glyphs}} + +\startfunctioncall +node.unprotect_glyphs(<node> n) +\stopfunctioncall + +Subtracts 256 from all glyph node subtypes. This and the next function are +helpers to convert from \type {characters} to \type {glyphs} during node +processing. + +\subsubsection{\type {node.protect_glyphs}} + +\startfunctioncall +node.protect_glyphs(<node> n) +\stopfunctioncall + +Adds 256 to all glyph node subtypes in the node list starting at \type {n}, +except that if the value is 1, it adds only 255. The special handling of 1 means +that \type {characters} will become \type {glyphs} after subtraction of 256. + +\subsubsection{\type {node.last_node}} + +\startfunctioncall +<node> n = + node.last_node() +\stopfunctioncall + +This function pops the last node from \TEX's \quote{current list}. It returns +that node, or \type {nil} if the current list is empty. + +\subsubsection{\type {node.write}} + +\startfunctioncall +node.write(<node> n) +\stopfunctioncall + +This is an experimental function that will append a node list to \TEX's \quote +{current list} The node list is not deep|-|copied! There is no error checking +either! + +\subsubsection{\type {node.protrusion_skippable}} + +\startfunctioncall +<boolean> skippable = + node.protrusion_skippable(<node> n) +\stopfunctioncall + +Returns \type {true} if, for the purpose of line boundary discovery when +character protrusion is active, this node can be skipped. + +\subsection{Glue handling} + +\subsubsection{\type {node.setglue}} + +You can set the properties of a glue in one go. If you pass no values, the glue +will become a zero glue. + +\startfunctioncall +node.setglue(<node> n) +node.setglue(<node> n,width,stretch,shrink,stretch_order,shrink_order) +\stopfunctioncall + +When you pass values, only arguments that are numbers +are assigned so + +\starttyping +node.setglue(n,655360,false,65536) +\stoptyping + +will only adapt the width and shrink. + +\subsubsection{\type {node.getglue}} + +The next call will return 5 values (or northing when no glue is passed). + +\startfunctioncall +<integer> width, <integer> stretch, <integer> shrink, <integer> stretch_order, + <integer> shrink_order = node.getglue(<node> n) +\stopfunctioncall + +\subsubsection{\type {node.is_zero_glue}} + +This function returns \type {true} when the width, stretch and shrink properties +are zero. + +\startfunctioncall +<boolean> isglue = + node.is_zero_glue(<node> n) +\stopfunctioncall + +\subsection{Attribute handling} + +Attributes appear as linked list of userdata objects in the \type {attr} field of +individual nodes. They can be handled individually, but it is much safer and more +efficient to use the dedicated functions associated with them. + +\subsubsection{\type {node.has_attribute}} + +\startfunctioncall +<number> v = + node.has_attribute(<node> n, <number> id) +<number> v = + node.has_attribute(<node> n, <number> id, <number> val) +\stopfunctioncall + +Tests if a node has the attribute with number \type {id} set. If \type {val} is +also supplied, also tests if the value matches \type {val}. It returns the value, +or, if no match is found, \type {nil}. + +\subsubsection{\type {node.get_attribute}} + +\startfunctioncall +<number> v = + node.get_attribute(<node> n, <number> id) +\stopfunctioncall + +Tests if a node has an attribute with number \type {id} set. It returns the +value, or, if no match is found, \type {nil}. + +\subsubsection{\type {node.find_attribute}} + +\startfunctioncall +<number> v, <node> n = + node.find_attribute(<node> n, <number> id) +\stopfunctioncall + +Finds the first node that has attribute with number \type {id} set. It returns +the value and the node if there is a match and otherwise nothing. + +\subsubsection{\type {node.set_attribute}} + +\startfunctioncall +node.set_attribute(<node> n, <number> id, <number> val) +\stopfunctioncall + +Sets the attribute with number \type {id} to the value \type {val}. Duplicate +assignments are ignored. {\em [needs explanation]} + +\subsubsection{\type {node.unset_attribute}} + +\startfunctioncall +<number> v = + node.unset_attribute(<node> n, <number> id) +<number> v = + node.unset_attribute(<node> n, <number> id, <number> val) +\stopfunctioncall + +Unsets the attribute with number \type {id}. If \type {val} is also supplied, it +will only perform this operation if the value matches \type {val}. Missing +attributes or attribute|-|value pairs are ignored. + +If the attribute was actually deleted, returns its old value. Otherwise, returns +\type {nil}. + +\stopchapter + +\stopcomponent |