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diff --git a/doc/context/sources/general/manuals/canbedone/canbedone-periods.tex b/doc/context/sources/general/manuals/canbedone/canbedone-periods.tex new file mode 100644 index 000000000..3ddb4545c --- /dev/null +++ b/doc/context/sources/general/manuals/canbedone/canbedone-periods.tex @@ -0,0 +1,157 @@ +% language=us runpath=texruns:manuals/canbedone + +\environment canbedone-style + +% \showframe + +\startdocument + [title=periods, + color=middlered] + +\startsectionlevel[title=Introduction] + +When the \TEX\ program showed up there were not many fonts that could be used so +it came with its own fonts and because the number of slots in the encoding was +limited (first to 127, later to 255) there was no space characters. It was not +needed anyway because the engine uses a model of glue between words. So, instead +of fixed spacing, \TEX\ uses flexible spacing. In addition to what is normally +considered a word space, spacing is also determined by the so called space factor +of characters preceding spaces. But, especially after abbreviations with periods +you might want something different depending on the usage of the period. Here we +discuss how that can be done. + +\stopsectionlevel + +\startsectionlevel[title=Font related spacing] + +Spacing is controlled by the amount specified in the font in the so called +font dimensions. In \CONTEXT\ these can be accessed via macros: + +\starttabulate[||c|c|c|c|] +\BC \NC \tf normal space + \NC \bf bold space + \NC \it italic space + \NC \bi bolditalic space \NC \NR +\NC \tex{interwordspace} \NC {\tf \expandafter}\the\interwordspace + \NC {\bf \expandafter}\the\interwordspace + \NC {\it \expandafter}\the\interwordspace + \NC {\bi \expandafter}\the\interwordspace \NC \NR +\NC \tex{interwordstretch} \NC {\tf \expandafter}\the\interwordstretch + \NC {\bf \expandafter}\the\interwordstretch + \NC {\it \expandafter}\the\interwordstretch + \NC {\bi \expandafter}\the\interwordstretch \NC \NR +\NC \tex{interwordshrink} \NC {\tf \expandafter}\the\interwordshrink + \NC {\it \expandafter}\the\interwordshrink + \NC {\bi \expandafter}\the\interwordshrink + \NC {\bf \expandafter}\the\interwordshrink \NC \NR +\stoptabulate + +The differences in the three components are subtle but often of no concern to the +user. Stretch and shrink kicks in when we align the left and right edge, +otherwise they are basically ignored. These spacing properties are very specific +for \TEX\ fonts, they don't come with for instance \OPENTYPE\ fonts. There we +derive the stretch and shrink from the regular font space (\UNICODE\ slot U+00020 +or \ASCII\ value 32). + +A user can tweak the interword spacing with \type {\spaceskip} and \type +{\xspaceskip} which works together with the \type {\spacefactor} and (character +specific)\type {\sfcode} values. And as it is somewhat hard to explain the +details involved I just refer to Chapter~25 (Spacing) of \TEX\ by Topic. + +\stopsectionlevel + +\startsectionlevel[title=Spacing after periods] + +For this manual it's only important to know that the space factors influence the +spacing after uppercase letters and punctuation and the later aspect is what this +is about. + +\startbuffer[a] +\frenchspacing This is a t.e.s.t. for periods. Does it work? +\vskip-.8\lineheight +\nonfrenchspacing \blue This is a t.e.s.t. for periods. Does it work? +\stopbuffer + +\startbuffer[b] +\frenchspacing This is a t.e.s.t.\ for periods. Does it work? +\vskip-.8\lineheight +\nonfrenchspacing \green This is a t.e.s.t.\ for periods. Does it work? +\stopbuffer + +\startbuffer[c] +\frenchspacing This is a t.e.s.t\fsp. for periods. Does it work? +\vskip-.8\lineheight +\nonfrenchspacing \red This is a t.e.s.t\fsp. for periods. Does it work? +\stopbuffer + +\startbuffer[d] +\setperiodkerning[zerospaceperiods] +\frenchspacing This is a t.e.s.t. for periods. Does it work? +\vskip-.8\lineheight +\nonfrenchspacing \red This is a t.e.s.t. for periods. Does it work? +\stopbuffer + +\typebuffer[a] \start \forgetall \resetperiodkerning \getbuffer[a] \stop + +You will notice that the spacing after \type {t.e.s.t.} is as flexible as +the space after \type {periods.} but what if you don't want that? There are +several ways to influence the following space: + +\typebuffer[b] \start \forgetall \resetperiodkerning \getbuffer[b] \stop + +The \type {\fsp} macro looks ahead and adapts the space factor: + +\typebuffer[c] \start \forgetall \resetperiodkerning \getbuffer[c] \stop + +\stopsectionlevel + +\startsectionlevel[title=Automation] + +Where the manual (explicit) making sure we get spacing right is quite +robust and predictable a user might be willing to delegate the task to +\CONTEXT, and here is the trick: + +\typebuffer[d] \start \forgetall \resetperiodkerning \getbuffer[d] \stop + +This features has been present from mid 2017 but I admit that till now I never +used it. Reasons are that it makes no sense to adapt existing documents and when +a text is for instance meant for a user group journal too, you cannot expect this +automatic feature to be present in the macro package used for typesetting it. But +maybe it's time to change that policy. I also admit that I seldom have this +situation, probably the only few cases are abbreviations like \type {e.g.} (for +example) and \type {c.q.} (casu quo). + +There are a few predefined period kerning variants and you can define more if you +want: + +\starttyping +\defineperiodkerning [zerospaceperiods] [factor=0] +\defineperiodkerning [smallspaceperiods] [factor=.25] +\defineperiodkerning [halfspaceperiods] [factor=.5] +\stoptyping + +\startbuffer[e] +\setperiodkerning[zerospaceperiods] +\frenchspacing How about c.q. and e.g. within a sentence? +\vskip-.8\lineheight +\nonfrenchspacing \red How about c.q. and e.g. within a sentence? +\stopbuffer + +\typebuffer[e] \start \forgetall \getbuffer[e] \stop + +Of course one needs to keep an eye on the results because one never knows if the +heuristics are flawed. And if needed it can be improved. + +\stopsectionlevel + +\startsectionlevel[title=Todo] + +{\em more spacing related features} + +% optionalspace +% autoinsertspace +% ~ + +\stopsectionlevel + +\stopdocument |