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author | Karl Berry <karl@freefriends.org> | 2009-05-22 23:51:44 +0000 |
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committer | Karl Berry <karl@freefriends.org> | 2009-05-22 23:51:44 +0000 |
commit | 566f5207d7e3cafb0633d31277067336ccd9cca7 (patch) | |
tree | 7af53e7ac405185168bc1dc38c4e820f442b78d0 /Master/texmf-dist/doc/generic/FAQ-en/html/FAQ-overfull.html | |
parent | b0beea26ffffd915bb6d9b82f2d65a0a05b7e23b (diff) |
move generic english documents out of texmf-doc
git-svn-id: svn://tug.org/texlive/trunk@13396 c570f23f-e606-0410-a88d-b1316a301751
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diff --git a/Master/texmf-dist/doc/generic/FAQ-en/html/FAQ-overfull.html b/Master/texmf-dist/doc/generic/FAQ-en/html/FAQ-overfull.html new file mode 100644 index 00000000000..b518a27bc39 --- /dev/null +++ b/Master/texmf-dist/doc/generic/FAQ-en/html/FAQ-overfull.html @@ -0,0 +1,133 @@ +<head> +<title>UK TeX FAQ -- question label overfull</title> +</head><body> +<h3>(La)TeX makes overfull lines</h3> +<p/>When TeX is building a paragraph, it can make several attempts to +get the line-breaking right; on each attempt it runs the same +algorithm, but gives it different parameters. You can affect the way +TeX’s line breaking works by adjusting the parameters: this answer +deals with the “tolerance” and stretchability parameters. The other +vital ‘parameter’ is the set of hyphenations to be applied: see +“<a href="FAQ-nohyph.html">my words aren’t being hyphenated</a>” +(and the questions it references) for advice. +<p/>If you’re getting an undesired “overfull box”, what has happened is +that TeX has given up: the parameters you gave it don’t allow it to +produce a result that <em>doesn’t</em> overfill. In this circumstance, +Knuth decided the best thing to do was to produce a warning, and to +allow the user to solve the problem. (The alternative, silently to go +beyond the envelope of “good taste” defined for this run of TeX, +would be distasteful to any discerning typographer.) The user can +almost always address the problem by rewriting the text that’s +provoking the problem — but that’s not always possible, and in some +cases it’s impossible to solve the problem without adjusting the +parameters. This answer discusses the approaches one might take to +resolution of the problem, on the assumption that you’ve got the +hyphenation correct. +<p/>The simplest case is where a ‘small’ word fails to break at the end of +a line; pushing the entire word to a new line isn’t going to make much +difference, but it might make things just bad enough that TeX won’t +do it by default. In such a case on can <em>try</em> the LaTeX +<code>\</code><code>linebreak</code> command: it may solve the problem, and if it does, it +will save an awful lot of fiddling. Otherwise, one needs to adjust +parameters: to do that we need to recap the details of TeX’s line +breaking mechanisms. +<p/>TeX’s first attempt at breaking lines is performed without even +trying hyphenation: TeX sets its “tolerance” of line breaking +oddities to the internal value <code>\</code><code>pretolerance</code>, and sees what +happens. If it can’t get an acceptable break, TeX adds the +hyphenation points allowed by the current patterns, and tries again +using the internal <code>\</code><code>tolerance</code> value. If this pass also fails, and +the internal <code>\</code><code>emergencystretch</code> value is positive, TeX will try +a pass that allows <code>\</code><code>emergencystretch</code> worth of extra stretchability +to the spaces in each line. +<p/>In principle, therefore, there are three parameters (other than +hyphenation) that you can change: <code>\</code><code>pretolerance</code>, <code>\</code><code>tolerance</code> +and <code>\</code><code>emergencystretch</code>. Both the <code>tolerance</code> values are +simple numbers, and should be set by TeX primitive count +assignment — for example +<blockquote> +<pre> +\pretolerance=150 +</pre> +</blockquote><p> +For both, an “infinite” tolerance is represented by the value +<code>10</code><code>000</code>, but infinite tolerance is rarely +appropriate, since it can lead to very bad line breaks indeed. +<p/><code>\</code><code>emergencystretch</code> is a TeX-internal ‘dimen’ register, and can +be set as normal for dimens in Plain TeX; in LaTeX, use +<code>\</code><code>setlength</code> — for example: +<blockquote> +<pre> +\setlength{\emergencystretch}{3em} +</pre> +</blockquote><p> +<p/>The choice of method has time implications — each of the +passes takes time, so adding a pass (by changing +<code>\</code><code>emergencystretch</code>) is less desirable than suppressing one (by +changing <code>\</code><code>pretolerance</code>). However, it’s unusual nowadays to find a +computer that’s slow enough that the extra passes are really +troublesome. +<p/>In practice, <code>\</code><code>pretolerance</code> is rarely used other than to manipulate +the use of hyphenation; Plain TeX and LaTeX both set its value +to <code>100</code>. To suppress the first scan of paragraphs, set +<code>\</code><code>pretolerance</code> to <code>-1</code>. +<p/><code>\</code><code>tolerance</code> is often a good method for adjusting spacing; +Plain TeX and LaTeX both set its value to <code>200</code>. LaTeX’s +<code>\</code><code>sloppy</code> command sets it to <code>9999</code>, as does the +<code>sloppypar</code> environment. This value is the largest +available, this side of infinity, and can allow pretty poor-looking +breaks (this author rarely uses <code>\</code><code>sloppy</code> “bare”, though he does +occasionally use <code>sloppypar</code> — that way, the change of +<code>\</code><code>tolerance</code> is confined to the environment). More satisfactory is +to make small changes to <code>\</code><code>tolerance</code>, incrementally, and then to look to +see how the change affects the result; very small increases can often +do what’s necessary. Remember that <code>\</code><code>tolerance</code> is a paragraph +parameter, so you need to ensure it’s actually applied — see +“<a href="FAQ-paraparam.html">ignoring paragraph parameters</a>”. +LaTeX users could use an environment like: +<blockquote> +<pre> +\newenvironment{tolerant}[1]{% + \par\tolerance=#1\relax +}{% + \par +} +</pre> +</blockquote><p> +enclosing entire paragraphs (or set of paragraphs) in it. +<p/>The value of <code>\</code><code>emergencystretch</code> is added to the assumed +stretchability of each line of a paragraph, in a further run of the +paragraph formatter in case that the paragraph can’t be made to look +right any other way. (The extra scan happens if +<code>\</code><code>emergencystretch>0pt</code> — if it’s zero or negative, no gain +could be had from rerunning the paragraph setter.) The example above +set it to <code>3em</code>; the Computer Modern fonts ordinarily fit three +space skips to the <code>em</code>, so the change would allow anything up +to the equivalent of nine extra spaces in each line. In a line with +lots of spaces, this could be reasonable, but with (say) only three +spaces on the line, each could stretch to four times its natural +width. It is therefore clear that <code>\</code><code>emergencystretch</code> needs to be +treated with a degree of caution. +<p/>More subtle (but more tricky to manage) are the microtypographic +extensions provided by PDFTeX. Since PDFTeX is the default +‘engine’ for LaTeX and ConTeXt work in all distributions, +nowadays, the extensions are available to all. There are two +extensions, margin kerning and font expansion; margin kerning only +affects the visual effect of the typeset page, and has little effect +on the ability of the paragraph setter to “get things right”. +Font expansion works like a subtler version of the trick that +<code>\</code><code>emergencystretch</code> plays: PDFTeX ‘knows’ that your current font +may be stretched (or shrunk) to a certain extent, and will do that +“on the fly” to optimise the setting of a paragraph. This is a +powerful tool in the armoury of the typesetter. +<p/>As mentioned above, the microtypographic extensions are tricky beasts +to control; however, the <i>microtype</i> package relieves the user +of the tedious work of specifying how to perform margin adjustments +and how much to scale each font ... for the fonts the package +knows about; it’s a good tool, and users who can take on the +specification of adjustments for yet more fonts are always welcome. +<dl> +<dt><tt><i>microtype.sty</i></tt><dd><a href="ftp://cam.ctan.org/tex-archive/macros/latex/contrib/microtype.zip">macros/latex/contrib/microtype</a> (<a href="ftp://cam.ctan.org/tex-archive/macros/latex/contrib/microtype.tar.gz">gzipped tar</a>, <a href="http://www.tex.ac.uk/tex-archive/macros/latex/contrib/microtype/">browse</a>) +</dl> +<p/><p>This question on the Web: <a href="http://www.tex.ac.uk/cgi-bin/texfaq2html?label=overfull">http://www.tex.ac.uk/cgi-bin/texfaq2html?label=overfull</a> +</body> |