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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-ifpdf.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
Diffstat (limited to 'Master/texmf-dist/doc/generic/FAQ-en/html/FAQ-ifpdf.html')
-rw-r--r-- | Master/texmf-dist/doc/generic/FAQ-en/html/FAQ-ifpdf.html | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/Master/texmf-dist/doc/generic/FAQ-en/html/FAQ-ifpdf.html b/Master/texmf-dist/doc/generic/FAQ-en/html/FAQ-ifpdf.html new file mode 100644 index 00000000000..7f26397e5c5 --- /dev/null +++ b/Master/texmf-dist/doc/generic/FAQ-en/html/FAQ-ifpdf.html @@ -0,0 +1,80 @@ +<head> +<title>UK TeX FAQ -- question label ifpdf</title> +</head><body> +<h3>Am I using PDFTeX?</h3> +<p/>It’s often useful to know whether your macros are operating within +PDFTeX or within (“normal”) TeX; getting the right answer is +surprisingly tricky. +<p/>Suppose you need to test whether your output will be PDF or +DVI. The natural thing is to check whether you have access to +some PDFTeX-only primitive; a good one to try (not least because it +was present in the very first releases of PDFTeX) is +<code>\</code><code>pdfoutput</code>. So you try +<blockquote> +<pre> +\ifx\pdfoutput\undefined + <not running PDFTeX> +\else + <running PDFTeX> +\fi +</pre> +</blockquote><p> +Except that neither branch of this conditional is rock-solid. The +first branch can be misleading, since the “awkward” user could have +written: +<blockquote> +<pre> +\let\pdfoutput\undefined +</pre> +</blockquote><p> +so that your test will falsely choose the first alternative. While +this is a theoretical problem, it is unlikely to be a major one. +<p/>More important is the user who loads a package that uses +LaTeX-style testing for the command name’s existence (for example, +the LaTeX <i>graphics</i> package, which is useful even to the +Plain TeX user). Such a package may have gone ahead of you, so the +test may need to be elaborated: +<blockquote> +<pre> +\ifx\pdfoutput\undefined + <not running PDFTeX> +\else + \ifx\pdfoutput\relax + <not running PDFTeX> + \else + <running PDFTeX> + \fi +\fi +</pre> +</blockquote><p> +If you only want to know whether some PDFTeX extension (such as +marginal kerning) is present, you can stop at this point: you know as +much as you need. +<p/>However, if you need to know whether you’re creating PDF +output, you also need to know about the value of <code>\</code><code>pdfoutput</code>: +<blockquote> +<pre> +\ifx\pdfoutput\undefined + <not running PDFTeX> +\else + \ifx\pdfoutput\relax + <not running PDFTeX> + \else + <running PDFTeX, with...> + \ifnum\pdfoutput>0 + <...PDF output> + \else + <...DVI output> + \fi + \fi +\fi +</pre> +</blockquote><p> +The above is, in essence, what Heiko Oberdiek’s <i>ifpdf</i> +package does; the reasoning is the FAQ’s interpretation of +Heiko’s explanation. +<dl> +<dt><tt><i>ifpdf.sty</i></tt><dd>Distributed with Heiko Oberdiek’s packages <a href="ftp://cam.ctan.org/tex-archive/macros/latex/contrib/oberdiek.zip">macros/latex/contrib/oberdiek</a> (<a href="ftp://cam.ctan.org/tex-archive/macros/latex/contrib/oberdiek.tar.gz">gzipped tar</a>, <a href="http://www.tex.ac.uk/tex-archive/macros/latex/contrib/oberdiek/">browse</a>) +</dl> +<p/><p>This question on the Web: <a href="http://www.tex.ac.uk/cgi-bin/texfaq2html?label=ifpdf">http://www.tex.ac.uk/cgi-bin/texfaq2html?label=ifpdf</a> +</body> |