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Diffstat (limited to 'doc/context/sources/general/manuals/luatex/luatex-math.tex')
| -rw-r--r-- | doc/context/sources/general/manuals/luatex/luatex-math.tex | 270 |
1 files changed, 265 insertions, 5 deletions
diff --git a/doc/context/sources/general/manuals/luatex/luatex-math.tex b/doc/context/sources/general/manuals/luatex/luatex-math.tex index cb8d198b1..3c29d9609 100644 --- a/doc/context/sources/general/manuals/luatex/luatex-math.tex +++ b/doc/context/sources/general/manuals/luatex/luatex-math.tex @@ -38,6 +38,99 @@ be used as numeric values, so you can write code like this: \fi \fi \stoptyping +Sometimes you won't get what you expect so a bit of explanation might help to +understand what happens. When math is parsed and expanded it gets turned into a +linked list. In a second pass the formula will be build. This has to do with the +fact that in order to determine the automatically chosen sizes (in for instance +fractions) following content can influence preceding sizes. A side effect of this +is for instance that one cannot change the definition of a font family (and +thereby reusing numbers) because the number that got used is stored and used in +the second pass (so changing \type {\fam 12} mid|-|formula spoils over to +preceding use of that family). + +The style switching primitives like \type {\textstyle} are turned into nodes so +the styles set there are frozen. The \type {\mathchoice} primitive results in +four lists being constructed of which one is used in the second pass. The fact +that some automatic styles are not yet known also means that the \type +{\mathstyle} primitive expands to the current style which can of course be +different from the one really used. It's a snapshot of the first pass state. As a +consequence in the following example you get a style number (first pass) typeset +that can actually differ from the used style (second pass). In the case of a math +choice used ungrouped, the chosen style is used after the choice too, unless you +group. + +\startbuffer[1] + [a:\mathstyle]\quad + \bgroup + \mathchoice + {\bf \scriptstyle (x:d :\mathstyle)} + {\bf \scriptscriptstyle (x:t :\mathstyle)} + {\bf \scriptscriptstyle (x:s :\mathstyle)} + {\bf \scriptscriptstyle (x:ss:\mathstyle)} + \egroup + \quad[b:\mathstyle]\quad + \mathchoice + {\bf \scriptstyle (y:d :\mathstyle)} + {\bf \scriptscriptstyle (y:t :\mathstyle)} + {\bf \scriptscriptstyle (y:s :\mathstyle)} + {\bf \scriptscriptstyle (y:ss:\mathstyle)} + \quad[c:\mathstyle]\quad + \bgroup + \mathchoice + {\bf \scriptstyle (z:d :\mathstyle)} + {\bf \scriptscriptstyle (z:t :\mathstyle)} + {\bf \scriptscriptstyle (z:s :\mathstyle)} + {\bf \scriptscriptstyle (z:ss:\mathstyle)} + \egroup + \quad[d:\mathstyle] +\stopbuffer + +\startbuffer[2] + [a:\mathstyle]\quad + \begingroup + \mathchoice + {\bf \scriptstyle (x:d :\mathstyle)} + {\bf \scriptscriptstyle (x:t :\mathstyle)} + {\bf \scriptscriptstyle (x:s :\mathstyle)} + {\bf \scriptscriptstyle (x:ss:\mathstyle)} + \endgroup + \quad[b:\mathstyle]\quad + \mathchoice + {\bf \scriptstyle (y:d :\mathstyle)} + {\bf \scriptscriptstyle (y:t :\mathstyle)} + {\bf \scriptscriptstyle (y:s :\mathstyle)} + {\bf \scriptscriptstyle (y:ss:\mathstyle)} + \quad[c:\mathstyle]\quad + \begingroup + \mathchoice + {\bf \scriptstyle (z:d :\mathstyle)} + {\bf \scriptscriptstyle (z:t :\mathstyle)} + {\bf \scriptscriptstyle (z:s :\mathstyle)} + {\bf \scriptscriptstyle (z:ss:\mathstyle)} + \endgroup + \quad[d:\mathstyle] +\stopbuffer + +\typebuffer[1] + +% \typebuffer[2] + +This gives: + +\blank $\displaystyle \getbuffer[1]$ \blank +\blank $\textstyle \getbuffer[1]$ \blank + +Using \type {\begingroup} \unknown\ \type {\endgroup} instead gives: + +\blank $\displaystyle \getbuffer[2]$ \blank +\blank $\textstyle \getbuffer[2]$ \blank + +This might look wrong but it's just a side effect of \type {\mathstyle} expanding +to the current (first pass) style and the number being injected in the list that +gets converted in the second pass. It all makes sense and it illustrates the +importance of grouping. In fact, the math choice style being effective afterwards +has advantages. It would be hard to get it otherwise. + \subsection{\type {\Ustack}} There are a few math commands in \TEX\ where the style that will be used is not @@ -174,7 +267,7 @@ are described as follows: \startitemize \startitem In any style superscripts and subscripts are taken from the next smaller style. - Exception: in display style they are taken in script style. + Exception: in display style they are in script style. \stopitem \startitem Subscripts are always in the cramped variant of the style; superscripts are only @@ -314,7 +407,7 @@ needed. The injection of \type {\abovedisplayskip} and \type {\belowdisplayskip} is not symmetrical. An above one is always inserted, also when zero, but the below is -only inserted when larger than zero. Especially the later mkes it sometimes hard +only inserted when larger than zero. Especially the later makes it sometimes hard to fully control spacing. Therefore \LUATEX\ comes with a new directive: \type {\mathdisplayskipmode}. The following values apply: @@ -464,6 +557,86 @@ Note 9: \type {FractionDelimiterDisplayStyleSize} and \type {FractionDelimiterSize} do not actually exist in the \quote {standard} \OPENTYPE\ math font Cambria, but were useful enough to be added. +\section{Nolimit correction} + +There are two extra math parameters \type {\Umathnolimitsupfactor} and \type +{\Umathnolimitsubfactor} that were added to provide some control over how limits +are spaced (for example the position of super and subscripts after integral +operators). They relate to an extra parameter \type {\mathnolimitsmode}. The half +corrections are what happens when scripts are placed on above and below. The +problem with italic corrections is that officially that correction italic is used +for above|/|below placement while advanced kerns are used for placement at the +right end. The question is: how often is this implemented, and if so, does the +kerns assume correction too. Anyway, with this parameter one can control it. + +\starttabulate[|l|ck1|ck1|ck1|ck1|ck1|ck1|] + \NC + \NC \mathnolimitsmode0 $\displaystyle\int\nolimits^0_1$ + \NC \mathnolimitsmode1 $\displaystyle\int\nolimits^0_1$ + \NC \mathnolimitsmode2 $\displaystyle\int\nolimits^0_1$ + \NC \mathnolimitsmode3 $\displaystyle\int\nolimits^0_1$ + \NC \mathnolimitsmode4 $\displaystyle\int\nolimits^0_1$ + \NC \mathnolimitsmode8000 $\displaystyle\int\nolimits^0_1$ + \NC \NR + \TB + \NC \bf mode + \NC \tttf 0 + \NC \tttf 1 + \NC \tttf 2 + \NC \tttf 3 + \NC \tttf 4 + \NC \tttf 8000 + \NC \NR + \NC \bf superscript + \NC 0 + \NC font + \NC 0 + \NC 0 + \NC +ic/2 + \NC 0 + \NC \NR + \NC \bf subscript + \NC -ic + \NC font + \NC 0 + \NC -ic/2 + \NC -ic/2 + \NC 8000ic/1000 + \NC \NR +\stoptabulate + +When the mode is set to one, the math parameters are used. This way a macro +package writer can decide what looks best. Given the current state of fonts in +\CONTEXT\ we currently use mode 1 with factor 0 for the superscript and 750 for +the subscripts. Positive values are used for both parameters but the subscript +shifts to the left. A \type {\mathnolimitsmode} larger that 15 is considered to +be a factor for the subscript correction. This feature can be handy when +experimenting. + +\section{Math italic mess} + +The \type {\mathitalicsmode} parameter can be set to~1 to force italic correction +before noads that represent some more complex structure (read: everything +that is not an ord, bin, rel, open, close, punct or inner). + +\starttexdefinition Whatever #1 + \NC \type{\mathitalicsmode=#1} + \NC \mathitalicsmode#1\ruledhbox{$\left|T^1\right|$} + \NC \mathitalicsmode#1\ruledhbox{$\left|T\right|$} + \NC \mathitalicsmode#1\ruledhbox{$T+1$} + \NC \mathitalicsmode#1\ruledhbox{$T{1\over2}$} + \NC \mathitalicsmode#1\ruledhbox{$T\sqrt{1}$} + \NR \NR +\stoptexdefinition + +\starttabulate[|c|c|c|c|c|c|] + \Whatever0 + \Whatever1 +\stoptabulate + +This kind of parameters relate to the fact that italic correction in \OPENTYPE\ +math is bound to fuzzy rules. So, control is the solution. + \section{Math spacing setting} Besides the parameters mentioned in the previous sections, there are also 64 new @@ -603,7 +776,7 @@ correction takes place. Possible locations are \type {top}, \type {bottom}, \type {both} and \type {center}. When no location is given \type {top} is assumed. An additional parameter \type {fraction} can be specified followed by a number; a value of for -instance 1200 means that the criterium is 1.2 times the width of the nuclues. The +instance 1200 means that the criterium is 1.2 times the width of the nucleus. The fraction only applies to the stepwise selected shapes and is mostly meant for the \type {overlay} location. It also works for the other locations but then it concerns the width. @@ -831,12 +1004,34 @@ For Latin Modern The result looks as follows: \stoptabulate \stop +\section {Last lines} + +There is a new primitive to control the overshoot in the calculation of the +previous line in mid|-|paragraph display math. The default value is 2 times +the em width of the current font: + +\starttyping +\predisplaygapfactor=2000 +\stoptyping + +If you want to have the length of the last line independent of math i.e.\ you don't +want to revert to a hack where you insert a fake display math formula in order to +get the length of the last line, the following will often work too: + +\starttyping +\def\lastlinelength{\dimexpr + \directlua {tex.sprint ( + (nodes.dimensions(node.tail(tex.lists.page_head).list)) + )}sp +\relax} +\stoptyping + \section {Other Math changes} \subsection {Verbose versions of single-character math commands} \LUATEX\ defines six new primitives that have the same function as -\type {^}, \type {_}, \type {$}, and \type {$$}: %$ +\type {^}, \type {_}, \type {$}, and \type {$$}: \starttabulate[|l|l|l|l|] \NC \bf primitive \NC \bf explanation \NC \NR @@ -869,7 +1064,57 @@ Inline math is surrounded by (optional) \type {\mathsurround} spacing but that i dimension. There is now an additional parameter \type {\mathsurroundskip}. When set to a non|-|zero value (or zero with some stretch or shrink) this parameter will replace \type {\mathsurround}. By using an additional parameter instead of changing the nature -of \type {\mathsurround}, we can remain compatible. +of \type {\mathsurround}, we can remain compatible. In the meantime a bit more +control has been added via \type {\mathsurroundmode}. This directive can take 6 values +with zero being the default behaviour. + +\start + +\def\OneLiner#1#2% + {\NC #1 +% \NC \ruledhbox{\mathsurroundmode#1\relax\hsize 100pt x$x$x} +% \NC \ruledhbox{\mathsurroundmode#1\relax\hsize 100pt x $x$ x} + \NC \dontleavehmode\inframed[align=normal,offset=0pt,frame=off]{\mathsurroundmode#1\relax\hsize 100pt x$x$x} + \NC \dontleavehmode\inframed[align=normal,offset=0pt,frame=off]{\mathsurroundmode#1\relax\hsize 100pt x $x$ x} + \NC #2 + \NC \NR} + +\startbuffer +\mathsurround 10pt +\mathsurroundskip20pt +\stopbuffer + +\typebuffer \getbuffer + +\starttabulate[|Tc|c|c|pl|] +\HL +\BC mode \BC \type {x$x$x} \BC \type {x $x$ x} \BC effect \NC \NR +\HL +\OneLiner{0}{obey \type {\mathsurround} when \type {\mathsurroundskip} is 0pt} +\OneLiner{1}{only add skip to the left} +\OneLiner{2}{only add skip to the right} +\OneLiner{3}{add skip to the left and right} +\OneLiner{4}{ignore the skip setting, obey \type {\mathsurround}} +\OneLiner{5}{disable all spacing around math} +\OneLiner{6}{only apply \type {\mathsurroundskip} when also spacing} +\OneLiner{7}{only apply \type {\mathsurroundskip} when no spacing} +\HL +\stoptabulate + +\stop + +Method six omits the surround glue when there is (x)spacing glue present while +method seven does the opposite, the glue is only applied when there is (x)space +glue present too. Anything more fance, like checking the begining or end of a +paragraph (or edges of a box) would not be robust anyway. If you want that you +can write a callback that runs over a list and analyzes a paragraph. Actually, in +that case you could also inject glue (or set the properties of a math node) +explicitly. So, these modes are in practice mostly useful for special purposes +and experiments (they originate in a tracker item). Keep in mind that this glue +is part of the math node and not always treated as normal glue: it travels with +the begin and end math nodes. Also, method 6 and 7 will zero the skip related +fields in a node when applicable in the first occasion that checks them +(linebreaking or packaging). % \section{Math todo} % @@ -980,6 +1225,21 @@ primitive \type {\mathoption} has been introduced (so that we don't end up with many new commands). The approach of options also permits us to see what effect a specific solution has. +\subsubsection {\type {\mathoption old}} + +This option was introduced for testing purposes when the math engine got split +code paths and it forces the engine to treat new fonts as old ones with respect +to italic correction etc. There are no guarantees given with respect to the final +result and unexpected side effects are not seens as bugs as they relate to font +properties. + +\startbuffer +\mathoption old 1 +\stopbuffer + +The \type {oldmath} boolean flag in the \LUA\ font table is the official way to +force old treatment as it's bound to fonts. + \subsubsection {\type {\mathoption noitaliccompensation}} This option compensates placement for characters with a built|-|in italic |