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diff --git a/doc/context/sources/general/manuals/lowlevel/lowlevel-paragraphs.tex b/doc/context/sources/general/manuals/lowlevel/lowlevel-paragraphs.tex index 0521a43de..65b36da94 100644 --- a/doc/context/sources/general/manuals/lowlevel/lowlevel-paragraphs.tex +++ b/doc/context/sources/general/manuals/lowlevel/lowlevel-paragraphs.tex @@ -999,6 +999,375 @@ examples are visualized in \in {figure} [fig:flow]. \stopsectionlevel +\startsectionlevel[title=Leaders] + +Leaders are a basic feature that users probably never run into directly. They +repeat content till it fits the specified width which can be stretched out. The +content is typeset once and it is the backend that does the real work of +repetition. + +\startbuffer +\strut\leaders \hbox{!}\hfill\strut +\strut\xleaders\hbox{!}\hfill\strut +\strut\cleaders\hbox{!}\hfill\strut +\strut\gleaders\hbox{!}\hfill\strut +\stopbuffer + +\typebuffer + +Here \type {\leaders} starts at the left edge and are repeats the box as long as +it fits, \type {\xleaders} spreads till the edges and \type {\cleaders} centers +the lot. The \type {\gleaders} primitive (which is not in orginal \TEX) takes the +outer box as reference and further behaves like \type {\cleaders}. + +\startlines \showmakeup[line] \getbuffer \stoplines + +The leader primitives take box or rule but in \LUAMETATEX\ a glyph can also be +specified, which saves wrapping in a box. + +\startbuffer +\ruledvbox \bgroup \hsize 10cm + \strut\cleaders\hbox{!}\hfill\strut +\egroup + +\ruledvbox \bgroup \hsize 10cm + \strut\cleaders\hrule\hfill\strut +\egroup + +\ruledvbox \bgroup \hsize 10cm + \strut\cleaders\glyph`!\hfill\strut +\egroup +\stopbuffer + +\typebuffer + +\getbuffer + +The \LUAMETATEX\ engine also introduced \type {\uleaders} + +\definecolor[tred] [r=.6,a=1,t=.5] +\definecolor[tgreen][g=.6,a=1,t=.5] +\definecolor[tblue] [b=.6,a=1,t=.5] + +\startbuffer[one] + x xx xxx xxxx + \ruledhbox{L\hss R}\space + x xx xxx xxxx +\stopbuffer + +\startbuffer[two] + x xx xxx xxxx + \uleaders\backgroundhbox[gray]{L\hss R}\hskip\zeropoint plus 100pt\relax\space + x xx xxx xxxx +\stopbuffer + +\startbuffer[three] + x xx xxx xxxx + \uleaders\ruledhbox{L\hss R}\hskip\zeropoint plus 100pt\relax\space + x xx xxx xxxx +\stopbuffer + +We show three boxes, a regular one first (red): + +\typebuffer[one] + +The second one (blue) is also a box but one that stretches upto 100pt and is in a +later stage, when the paragraph has been built, is repackaged to the effective +width. The third example (green) leaves out the background. + +\startlinecorrection +\startoverlay + {\vbox{\color[tgreen]{\small\dorecurse {20} {\getbuffer[three]}}}} + {\vbox{\color[tblue] {\small\dorecurse {20} {\getbuffer [two]}}}} + {\vbox{\color[tred] {\small\dorecurse {20} {\getbuffer [one]}}}} +\stopoverlay +\stoplinecorrection + +In \CONTEXT\ we have wrapped this feature in the adaptive box mechanism, so here +a few a few examples: + +\setupexternalfigures[location={default,local,global}] + +\startbuffer +\startsetups adaptive:test:a + \setbox\usedadaptivebox\vbox to \usedadaptivetotal \bgroup + \externalfigure + [cow.pdf] + [width=\framedmaxwidth, + frame=on, + height=\usedadaptivetotal]% + \egroup +\stopsetups + +\startsetups adaptive:test:b + \setbox\usedadaptivebox\vbox to \usedadaptivetotal \bgroup + \externalfigure + [cow.pdf] + [width=\usedadaptivewidth, + frame=on, + height=\usedadaptivetotal]% + \egroup +\stopsetups +\stopbuffer + +\typebuffer \getbuffer + +We use this as follows (see \in {figure} [fig:adaptive] for the result): + +\startbuffer +\framed[height=18cm,align=middle,adaptive=yes,top=,bottom=] {% + \begstrut \samplefile{tufte} \endstrut + \par + \adaptivevbox + [strut=yes,setups=adaptive:test:a] + {\showstruts\strut\hsize5cm\hss}% + \par + \adaptivevbox + [strut=yes,setups=adaptive:test:b] + {\showstruts\strut\hsize5cm\hss}% + \par + \begstrut \samplefile{tufte} \endstrut +} +\stopbuffer + +\typebuffer + +\startplacefigure[reference=fig:adaptive] + \getbuffer +\stopplacefigure + +Here is one that you can test yourself: + +\starttyping +\startsetups adaptive:test + \setbox\usedadaptivebox\vbox to \usedadaptivetotal \bgroup + \externalfigure + [cow.pdf] + [width=\usedadaptivewidth, + height=\usedadaptivetotal]% + \egroup +\stopsetups + +\ruledvbox to \textheight { + \par \begstrut \samplefile{tufte} \endstrut \par + \adaptivevbox[strut=yes,setups=adaptive:test]{\hsize\textwidth\hss} + \par \begstrut \samplefile{tufte} \endstrut +} +\stoptyping + +The next example comes from the test suite (where it runs over many pages in +order to illustrate the idea): + +\startbuffer +\startMPdefinitions + def TickTock = + interim linecap := squared; + save p ; path p ; + p := fullsquare xysized(AdaptiveWidth,.9(AdaptiveHeight+AdaptiveDepth)) ; + fill p withcolor AdaptiveColor ; + draw bottomboundary (p enlarged (-AdaptiveThickness) ) + withdashes (3*AdaptiveThickness) + withpen pencircle scaled AdaptiveThickness + withcolor white ; + enddef ; +\stopMPdefinitions + +\startsetups adaptive:test + \setbox\usedadaptivebox\hbox + to \usedadaptivewidth + yoffset -.9\usedadaptivedepth + \bgroup + \hss + \startMPcode + TickTock ; + \stopMPcode + \hss + \egroup +\stopsetups + +\definecolor[adaptive:tick][.25(blue,green)] +\definecolor[adaptive:tock][.75(blue,green)] + +\defineadaptive + [tick] + [setups=adaptive:test, + color=adaptive:tick, + foregroundcolor=white, + foregroundstyle=\infofont, + strut=yes] + +\defineadaptive + [tock] + [tick] + [color=adaptive:tock] + +\dostepwiserecurse{8}{12}{1}{% + \dostepwiserecurse{5}{15}{1}{% + this~#1.##1 is~#1.##1 test~#1.##1 + \ifodd##1\relax + \adaptivebox[tick]{\hss tick #1.##1\hss} + \else + \adaptivebox[tock]{\hss tock #1.##1\hss} + \fi + } +} +\stopbuffer + +\typebuffer \getbuffer + +In the next example the graphics adapt to the available space: + +\startbuffer +\startsetups adaptive:test + \setbox\usedadaptivebox\hbox + to \usedadaptivewidth + yoffset -\usedadaptivedepth + \bgroup + \externalfigure + [cow.pdf] + [width=\usedadaptivewidth, + height=\dimexpr\usedadaptivetotal\relax]% + \egroup +\stopsetups + +\dostepwiserecurse{1}{50}{1}{% + this~#1 is~#1 test~#1 + {\adaptivebox[strut=yes,setups=adaptive:test]{}} +} +\stopbuffer + +\typebuffer \getbuffer + +\stopsectionlevel + +\startsectionlevel[title=Prevdepth] + +The depth of a box is normally positive but rules can have a negative depth in +order to get a rule above the baseline. When \TEX\ was written the assumption was +that a negative depth of more than 1000 point made no sense at all. The last +depth on a vertical list is registered in the \type {\prevdepth} variable. This +is basically a reference into the current list. In order to illustrate some +interesting side effects of setting this \type {\prevdepth} and especially when +we set it to -1000pt. In order to illustrate this this special value can be set +to a different value in \LUAMETATEX. However, as dealing with the property is +somewhat special in the engine you should not set it unless you know that the +macro package is ware of it. + +\startbuffer +line 1\par line 2 \par \nointerlineskip line 3 \par +\stopbuffer + +\typebuffer + +Assuming that we haven't set any inter paragraph spacing this gives: + +\startlinecorrection +\ruledvbox{\setupwhitespace[none]\showmakeup[line]\getbuffer} +\stoplinecorrection + +Here \type {\nointerlineskip} is (normally) defined as: + +\starttyping +\prevdepth-1000pt +\stoptyping + +although in \CONTEXT\ we use \type {\ignoredepthcriterium} instead of the hard +coded dimension. We now give a more extensive example: + +\startbuffer[definition-1] +\def\PrevTest#1% + {\setbox0\ruledhbox{\strut$\tf#1$}% + \dp0=#1 + \vbox\bgroup\hsize4em + FIRST\par + \unhbox0\par + LAST\par + \egroup} +\stopbuffer + +\startbuffer[definition-2] +\def\PrevTest#1% + {\setbox0\ruledhbox{\strut$\tf#1$}% + \dp0=#1 + \vbox\bgroup + \ruledhbox{FIRST}\par + \box0\par + \ruledhbox{LAST}\par + \egroup} +\stopbuffer + +\startbuffer[example] +\ruledhbox \bgroup + \PrevTest{-10.0pt}\quad + \PrevTest{-20.0pt}\quad + \PrevTest{-49.9pt}\quad + \PrevTest{-50.0pt}\quad + \PrevTest{-50.1pt}\quad + \PrevTest{-60.0pt}\quad + \PrevTest{-80.0pt}% +\egroup +\stopbuffer + +In this example we set \type {\ignoredepthcriterium} to $\tf-50.0pt$ instead of the +normal $\tf -1000pt$. The helper is defined as: + +\typebuffer[option=TEX][definitions-1] + +or + +\typebuffer[option=TEX][definitions-2] + +The result of the following example is shown in \in {figures} [fig:prevdepth-1] +\in {and} [fig:prevdepth-2]. The first case is what we normally have in text and +we haven't set \type {prevdepth} explicitly between lines so \TEX\ will just look +at the depth of the lines. In the second case the depth is ignored when less than +the criterium which is why, when we set the depth of the box to a negative value +we get somewhat interesting skips. + +\startplacefigure[reference=fig:prevdepth-1] + \showmakeup[line] + \ignoredepthcriterium-50pt + \setupwhitespace[none] + \getbuffer[definition-1,example] +\stopplacefigure + +\startplacefigure[reference=fig:prevdepth-2] + \showmakeup[line] + \ignoredepthcriterium-50pt + \setupwhitespace[none] + \getbuffer[definition-2,example] + \blank[5*line] +\stopplacefigure + +I'm sure one can use this effect otherwise than intended but I doubt is any user +is willing to do this but the fact that we can lower the criterium makes for nice +experiments. Just for the record, in \in {figure} [fig:prevdepth-3] you see what +we get with positive values: + +\startbuffer[example] +\ruledhbox \bgroup + \PrevTest{10.0pt}\quad + \PrevTest{20.0pt}\quad + \PrevTest{49.9pt}\quad + \PrevTest{50.0pt}\quad + \PrevTest{50.1pt}\quad + \PrevTest{60.0pt}\quad + \PrevTest{80.0pt}% +\egroup +\stopbuffer + +\startplacefigure[reference=fig:prevdepth-3] + \showmakeup[line] + \ignoredepthcriterium50pt + \setupwhitespace[none] + \getbuffer[definition-2,example] +\stopplacefigure + +Watch the interline skip kicking in when we make the depth larger than in +\type {\ignoredepthcriterium} being $\tf 50pt$. + +\stopsectionlevel + \startsectionlevel[title=Normalization] {\em todo: users don't need to bother about this but it might be interesting anyway} |