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diff --git a/doc/context/sources/general/manuals/luatex/luatex-nodes.tex b/doc/context/sources/general/manuals/luatex/luatex-nodes.tex index 21ef0232d..8d32ab287 100644 --- a/doc/context/sources/general/manuals/luatex/luatex-nodes.tex +++ b/doc/context/sources/general/manuals/luatex/luatex-nodes.tex @@ -882,212 +882,6 @@ Valid window types are: \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 @@ -1254,16 +1048,21 @@ the \TEX\ level. This function accepts string \type {id} and \type {subtype} values as well. -\subsubsection{\type {node.free}} +\subsubsection{\type {node.free} and \type {node.flush_node}} \startfunctioncall -node.free(<node> n) +<node> next = + node.free(<node> n) +flush_node(<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. +The \type {free} function returns the next field of the freed node, while the +\type {flush_node} alternative returns nothing. + \subsubsection{\type {node.flush_list}} \startfunctioncall @@ -1594,6 +1393,25 @@ See the previous section for details. The change is in the local function \type end \stoptyping +\subsubsection{\type {node.traverse_char}} + +This iterators loops over the glyph nodes in a list. Only nodes with a subtype +less than 256 are seen. + +\startfunctioncall +<node> n = + node.traverse_char(<node> n) +\stopfunctioncall + +\subsubsection{\type {node.has_glyph}} + +This function returns the first glyph or disc node in the given list: + +\startfunctioncall +<node> n = + node.has_glyph(<node> n) +\stopfunctioncall + \subsubsection{\type {node.end_of_math}} \startfunctioncall @@ -1700,7 +1518,7 @@ 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}} +\subsubsection{\type {node.protect_glyphs} and \type {node.protect_glyph}} \startfunctioncall node.protect_glyphs(<node> n) @@ -1708,7 +1526,8 @@ node.protect_glyphs(<node> n) 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. +that \type {characters} will become \type {glyphs} after subtraction of 256. A +single character can be marked by the singular call. \subsubsection{\type {node.last_node}} @@ -1844,6 +1663,253 @@ attributes or attribute|-|value pairs are ignored. If the attribute was actually deleted, returns its old value. Otherwise, returns \type {nil}. +\subsubsection{\type {node.slide}} + +This helper makes sure that the node lists is double linked and returns the found +tail node. + +\startfunctioncall +<node> tail = + node.slide(<node> n) +\stopfunctioncall + +\subsubsection{\type {node.check_discretionary} and \type {node.check_discretionaries}} + +When you fool around with disc nodes you need to be aware of the fact that they +have a special internal data structure. As long as you reassign the fields when +you have extended the lists it's ok because then the tail pointers get updated, +but when you add to list without reassigning you might end up in troubles when +the linebreak routien kicks in. You can call this function to check the list for +issues with disc nodes. + +\startfunctioncall +node.check_discretionary(<node> n) +node.check_discretionaries(<node> head) +\stopfunctioncall + +The plural variant runs over all disc nodes in a list, the singular variant +checks one node only (it also checks if the node is a disc node). + +\subsubsection{\type {node.family_font}} + +When you pass it a proper family identifier the next helper will return the font +currently associated with it. You can normally also access the font with the normal +font field or getter because it will resolve the family automatically for noads. + +\startfunctioncall +<integer> id = + node.family_font(<integer> fam) +\stopfunctioncall + +\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 +\NC getbox \NC gets the given box (a list node) \NC \NR +\stoptabulate + +The direct variants also have setters, where the discretionary setter takes three +(optional) arguments plus an optional fourth indicating the subtype. An additional +setter is \type {setlink} which will link two nodes. + +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 {check_discretionaries}\NC \yes \NC \yes \NC \NR +\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 % was never documented and experimental +\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 {find_attribute} \NC \yes \NC \yes \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 {get_attribute} \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 {getglue} \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_direct} \NC \nop \NC \yes \NC \NR +\NC \type {is_glue_zero} \NC \yes \NC \yes \NC \NR +\NC \type {is_glyph} \NC \yes \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_glyphs} \NC \yes \NC \yes \NC \NR +\NC \type {protect_glyph} \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 \nop \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 {setglue} \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 {subtypes} \NC \yes \NC \nop \NC \NR +\NC \type {subtype} \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_char} \NC \yes \NC \yes \NC \NR +\NC \type {traverse_id} \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 {whatsitsubtypes} \NC \yes \NC \nop \NC \NR +\NC \type {whatsits} \NC \yes \NC \nop \NC \NR +\NC \type {write} \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. + \stopchapter \stopcomponent |