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### 6.1.1 Package options

The package is included with the customary

 \usepackage[options]{preview}

You should usually load this package as the last one, since it redefines several things that other packages may also provide.

The following options are available:

active

is the most essential option. If this option is not specified, the preview package will be inactive and the document will be typeset as if the preview package were not loaded, except that all declarations and environments defined by the package are still legal but have no effect. This allows defining previewing characteristics in your document, and only activating them by calling LaTeX as

 latex '\PassOptionsToPackage{active}{preview} \input{filename}'
noconfig

Usually the file ‘prdefault.cfg’ gets loaded whenever the preview package gets activated. ‘prdefault.cfg’ is supposed to contain definitions that can cater for otherwise bad results, for example, if a certain document class would otherwise lead to trouble. It also can be used to override any settings made in this package, since it is loaded at the very end of it. In addition, there may be configuration files specific for certain preview options like auctex which have more immediate needs. The noconfig option suppresses loading of those option files, too.

psfixbb

Dvips determines the bounding boxes from the material in the DVI file it understands. Lots of PostScript specials are not part of that. Since the TeX boxes do not make it into the DVI file, but merely characters, rules and specials do, Dvips might include far too small areas. The option psfixbb will include ‘/dev/null’ as a graphic file in the ultimate upper left and lower right corner of the previewed box. This will make Dvips generate an appropriate bounding box.

dvips

If this option is specified as a class option or to other packages, several packages pass things like page size information to Dvips, or cause crop marks or draft messages written on pages. This seriously hampers the usability of previews. If this option is specified, the changes will be undone if possible.

pdftex

If this option is set, PDFTeX is assumed as the output driver. This mainly affects the tightpage option.

xetex

If this option is set, XeTeX is assumed as the output driver. This mainly affects the tightpage option.

displaymath

will make all displayed math environments subject to preview processing. This will typically be the most desired option.

floats

will make all float objects subject to preview processing. If you want to be more selective about what floats to pass through to a preview, you should instead use the \PreviewSnarfEnvironment command on the floats you want to have previewed.

textmath

will make all text math subject to previews. Since math mode is used throughly inside of LaTeX even for other purposes, this works by redefining \(, \) and \$ and the math environment (apparently some people use that). Only occurences of these text math delimiters in later loaded packages and in the main document will thus be affected.

graphics

will subject all \includegraphics commands to a preview.

sections

will subject all section headers to a preview.

delayed

will delay all activations and redefinitions the preview package makes until \begin{document}. The purpose of this is to cater for documents which should be subjected to the preview package without having been prepared for it. You can process such documents with

 latex '\RequirePackage[active,delayed,options]{preview} \input{filename}'

This relaxes the requirement to be loading the preview package as last package.

driver

loads a special driver file ‘prdriver.def’. The remaining options are implemented through the use of driver files.

auctex

This driver will produce fake error messages at the start and end of every preview environment that enable the Emacs package preview-latex in connection with AUCTeX to pinpoint the exact source location where the previews have originated. Unfortunately, there is no other reliable means of passing the current TeX input position in a line to external programs. In order to make the parsing more robust, this option also switches off quite a few diagnostics that could be misinterpreted.

You should not specify this option manually, since it will only be needed by automated runs that want to parse the pseudo error messages. Those runs will then use \PassOptionsToPackage in order to effect the desired behaviour. In addition, ‘prauctex.cfg’ will get loaded unless inhibited by the noconfig option. This caters for the most frequently encountered problematic commands.

showlabels

During the editing process, some people like to see the label names in their equations, figures and the like. Now if you are using Emacs for editing, and in particular preview-latex, I’d strongly recommend that you check out the RefTeX package which pretty much obliterates the need for this kind of functionality. If you still want it, standard LaTeX provides it with the showkeys package, and there is also the less encompassing showlabels package. Unfortunately, since those go to some pain not to change the page layout and spacing, they also don’t change preview’s idea of the TeX dimensions of the involved boxes. So if you are using preview for determing bounding boxes, those packages are mostly useless. The option showlabels offers a substitute for them.

tightpage

It is not uncommon to want to use the results of preview as graphic images for some other application. One possibility is to generate a flurry of EPS files with

 dvips -E -i -Pwww -o outputfile.000 inputfile

However, in case those are to be processed further into graphic image files by Ghostscript, this process is inefficient since all of those files need to be processed one by one. In addition, it is necessary to extract the bounding box comments from the EPS files and convert them into page dimension parameters for Ghostscript in order to avoid full-page graphics. This is not even possible if you wanted to use Ghostscript in a single run for generating the files from a single PostScript file, since Dvips will in that case leave no bounding box information anywhere.

The solution is to use the tightpage option. That way a single command line like

 ‘gs -sDEVICE=png16m -dTextAlphaBits=4 -r300 -dGraphicsAlphaBits=4 -dSAFER -q -dNOPAUSE -sOutputFile=outputfile%d.png inputfile.ps’

will be able to produce tight graphics from a single PostScript file generated with Dvips without use of the options -E -i, in a single run.

The tightpage option actually also works when using the pdftex option and generating PDF files with PDFTeX. The resulting PDF file has separate page dimensions for every page and can directly be converted with one run of Ghostscript into image files.

If neither dvips or pdftex have been specified, the corresponding option will get autodetected and invoked.

If you need this in a batch environment where you don’t want to use preview’s automatic extraction facilities, no problem: just don’t use any of the extraction options, and wrap everything to be previewed into preview environments. This is how LyX does its math previews.

If the pages under the tightpage option are just too tight, you can adjust by setting the length \PreviewBorder to a different value by using \setlength. The default value is ‘0.50001bp’, which is half of a usual PostScript point, rounded up. If you go below this value, the resulting page size may drop below 1bp, and Ghostscript does not seem to like that. If you need finer control, you can adjust the bounding box dimensions individually by changing the macro \PreviewBbAdjust with the help of \renewcommand. Its default value is

 \newcommand \PreviewBbAdjust {-\PreviewBorder -\PreviewBorder \PreviewBorder \PreviewBorder}

This adjusts the left, lower, right and upper borders by the given amount. The macro must contain 4 TeX dimensions after another, and you may not omit the units if you specify them explicitly instead of by register. PostScript points have the unit bp.

lyx

This option is for the sake of LyX developers. It will output a few diagnostics relevant for the sake of LyX’ preview functionality (at the time of writing, mostly implemented for math insets, in versions of LyX starting with 1.3.0).

counters

This writes out diagnostics at the start and the end of previews. Only the counters changed since the last output get written, and if no counters changed, nothing gets written at all. The list consists of counter name and value, both enclosed in {} braces, followed by a space. The last such pair is followed by a colon (:) if it is at the start of the preview snippet, and by a period (‘.’) if it is at the end. The order of different diagnostics like this being issued depends on the order of the specification of the options when calling the package.

Systems like preview-latex use this for keeping counters accurate when single previews are regenerated.

footnotes

This makes footnotes render as previews, and only as their footnote symbol. A convenient editing feature inside of Emacs.

The following options are just for debugging purposes of the package and similar to the corresponding TeX commands they allude to:

tracingall

causes lots of diagnostic output to appear in the log file during the preview collecting phases of TeX’s operation. In contrast to the similarly named TeX command, it will not switch to \errorstopmode, nor will it change the setting of \tracingonline.

showbox

This option will show the contents of the boxes shipped out to the DVI files. It also sets \showboxbreadth and \showboxdepth to their maximum values at the end of loading this package, but you may reset them if you don’t like that.

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This document was generated by Mosè Giordano on November 13, 2015 using texi2html 1.82.