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Microtype—An interface to the micro-typographic features of pdfTeX - Atelierele Albe
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Acum cîţiva ani am căzut pe spate cînd am citit prima versiune a acestui superb utilitar. Atunci am încercat să-l folosesc cu Adobe Myriad însă complexitatea fişierelor de configurare m-au făcut să mă las păgubaş. Plus că pentru a folosi programul la întreaga sa valoare era absolut necesar să ai Linux şi fonturi multiple master. Zilele trecute însă mi-am adus aminte de el şi, spre marea mea surpriză, am aflat că între timp microtype a evoluat extraordinar, avînd îmbunătăţiri la care nici nu visam.

Singura problemă pe care o întrevăd este una legată de nivelul teoretic: aproape toate facilitaţile pentru care microtype oferă o interfaţă sînt strîns legate de pdfTeX. Portarea acestora către xetex reprezintă o muncă sisifică şi, probabil, pe alocuri imposibilă. Iar pdfTeX nu ştie unicode. Punctul comun ar fi luaTeX care însă, momentan, este încă în anii tinereţii.

Este ferma mea convingere că, actualmente, optimum în tipografia limbii române se atinge folosind pdf[La]TeX, ajutat de microtype să conlucreze cu fonturi postscript, eventual generate din cele opentype.

Urmează un extras din documentaţia microtype ce poate fi accesată în întregime pe ctan.

pdfTeX , the TeX extension written by Hàn Thê Thành, introduces a number of microtypographic features that make it the tool of choice not only for the creation of electronic documents but also of works of outstanding time-honoured typography: most prominently, character protrusion (also known as margin kerning) and font expansion. Quoting Hàn Thê Thành’s thesis:

Margin kerning is the adjustments of the characters at the margins of a typeset text. A simplified employment of margin kerning is hanging punctuation. Margin kerning is needed for optical alignment of the margins of a typeset text, because mechanical justification of the margins makes them look rather ragged. Some characters can make a line appear shorter to the human eye than others. Shifting such characters by an appropriate amount into the margins would greatly improve the appearance of a typeset text.

Composing with font expansion is the method to use a wider or narrower variant of a font to make interword spacing more even. A font in a loose line can be substituted by a wider variant so the interword spaces are stretched by a smaller amount. Similarly, a font in a tight line can be replaced by a narrower variant to reduce the amount that the interword spaces are shrunk by. There is certainly a potential danger of font distortion when using such manipulations, thus they must be used with extreme care. The potentiality to adjust a line width by font expansion can be taken into consideration while a paragraph is being broken into lines, in order to choose better breakpoints.

Both these features have been lacking a simple LaTeX user interface for quite some time. Then, the pdfcprot package was released, which allowed LaTeX users to employ character protrusion without having to mess much with the internals.

Font expansion, however, was still most difficult to utilise, since it required that the font metrics are available for all levels of expansion. Therefore, anybody who wanted to make use of this feature had to create multiple instances of the fonts in advance. Shell scripts to partly relieve the user from this burden were available—however, it remained a cumbersome task. Furthermore, all fonts were still being physically created, thus wasting compilation time and disk space.

In the summer of 2004, Hàn Thê Thành implemented a feature that has proven as a major facilitation for TeX and LaTeX users: font expansion can now take place automatically. That is, pdfTeX no longer needs the expanded font metrics but will calculate them at run-time and completely in memory.

After this great leap in usability had been taken, the development did not stop. On the contrary, pdfTeX was extended with even more features: version 1.30 introduced the possibility to disable all ligatures, version 1.40 a robust letterspacing command, the adjustment of interword spacing and the possibility to specify additional character kerning.

Robust and hyphenatable letterspacing (tracking) has always been extremely difficult to achieve in TeX . Although the soul package undertook great efforts in making this possible, it could still fail in certain circumstances; even to adjust the tracking of a font throughout the document remained impossible. Employing pdfTeX ’s new extension, this no longer poses a problem. The microtype package provides the possibility to change the tracking of customisable sets of fonts, e.g., all small capitals. It also introduces two new commands textls and lsstyle for ad-hoc letterspacing, which can be used like the normal text commands. Note that letterspacing only works in PDF mode.

Adjustment of interword spacing is based upon the idea that in order to achieve a uniform greyness of the text, the space between words should also depend on the surrounding characters. For example, if a word ends with an ‘r’, the following space should be a tiny bit smaller than that following, say, an ‘m’. You can think of this concept as an extension to TeX ’s ‘space factors’. However, while space factors will influence all three parameters of interword space (or glue) by the same amount—the kerning, the maximum amount that the space may be stretched and the maximum amount that it may be shrunk—pdfTeX provides the possibility to modify these parameters independently from one another. Furthermore, the values may be set differently for each font. And, probably most importantly, the parameters may not only be increased but also decreased. This feature may enhance the appearance of paragraphs even more. Emphasis in the last sentence is on the word ‘may’: this extension is still highly experimental—in particular, only ending characters will currently have an influence on the interword space. Also, the settings that are shipped with microtype are but a first approximation, and I would welcome corrections and improvements very much.

Setting additional kerning for characters of a font is especially useful for languages whose typographical tradition requires certain characters to be separated by a space. For example, it is customary in French typography to add a small space before question mark, exclamation mark and semi-colon, and a bigger space before the colon and the guillemets. Until now, this could only be achieved by making these characters active (for example by the babel package), which may not always be a robust solution. In contrast to the standard kerning that is built into the fonts (which will of course apply as usual), this additional kerning is based on single characters, not on character pairs.

The possibility, finally, to disable all ligatures of a font may be useful for typewriter fonts.

The microtype package provides an interface to all these micro-typographic extensions. All micro-typographic aspects may be customised to your taste and needs in a straight-forward manner.