T_TH: a ``T_EX to HTML'' translator.

Abstract

Contents

1  Capabilities

1.1  Plain T_EX

1.1.1  Mathematics

Almost all of T_EX's mathematics is supported with the exception of a few obscure symbols that are absent from the fonts normally available to browsers. Support includes, for example, in-line equations with subscripts and superscripts, display equations with built-up fractions, over accents, large delimiters, operators with limits; matrix, pmatrix, cases, [but not bordermatrix]; over/underbrace [but using a rule, not a brace].

1.1.2  Formatting and Macro Support

• Font styles: \it, \bf, \sl, \uppercase, everywhere, \rm in equations¹.
• Accented characters written like \"o or \'{e}.
• Guess the intent of font definitions, i.e. \font commands [optionally, remove contruct].
• Macro definitions that are global: \gdef, \xdef, \global\def, \global\edef; or local to the current group: \def, \edef.
• Definitions with delimited arguments.
• Input of files [see 9.2].
• Newcount, number, advance and counter setting [global counter setting only].
• Conditionals: iftrue, iffalse, ifnum, ifodd, ifcase, if [for defined commands and plain characters, not some internals] ², ifx [only for defined commands and counters; internals appear undefined], ifvmode, ifmmode, newif.
• Centerline, beginsection, item, itemitem, obeylines; hang, hangindent, narrower [for entire paragraphs, hangafter ignored]. Headline is made into a title, footnote{}{}. Comments: removed.
• Tables: halign [uses border style if the template contains vrule.]. Settabs, \+.
• Simple uses of \hbox,\vbox and \hsize to align text and make boxes with restricted widths, but these are discouraged.

1.2  L^AT_EX

1.2.1  Environments:

1.2.2  L^AT_EX Commands:

These cover most of the vital L^AT_EX constructs. Internal hypertext cross-references are automatically generated (e.g. by ref and tableofcontents) provided L^AT_EX has previously been run on the document and the appropriate command-line switch is used.

1.3  Special T_EX usage for T_TH

\epsfbox{file.[e]ps} Puts in an anchor called "Figure" linked to 
    file.[e]ps (default), or alternatively calls user-supplied script 
    to convert the [e]ps file to a gif image and optionally inline it.  
\special{html:"tags"} inserts ``tags'' into the HTML e.g. for images etc.  
\href{reference}{anchor} highlights ``anchor'' with href=``reference''.
\url{URL} like \href but with URL providing both reference and anchor.
\begin{[raw]html} ... \end{[raw]html} environment passed direct to output.
\tthdump{...} The group is omitted by tth. Define \tthdump as a nop for TeX.
%%tth:... The rest of the comment line is passed to tth (not TeX) for parsing.

1.4  Unsupported Commands

When T_TH encounters T_EX constructs that it cannot handle either because there is no HTML equivalent, or because it is not clever enough, it tries to remove the mess they would otherwise cause in the HTML code, generally giving a warning of the action if it is not sure what it is doing. The following are not translated.

 \magnification \magstep etc : Removes the whole construct.
 New or non-standard dimension tokens: removed.
 Some boxes in equations.
 \raisebox, \lowerbox and similar usages.

2  Installation

The source for T_TH is flex code which is processed to produce a C program tth.c which comprises the distribution. This file is compiled by

	gcc -o tth tth.c

The executable should then be copied to whatever directory you want (preferably on your path of course). That's all!

Alternatively you may be able to obtain a precompiled executable from wherever you accessed this file. The Wind@ws executable comes with a batch file for installation. Just run it by the command ``install''.

3  Usage

Command line is as follows. The order of the parts is irrelevant. Switches (preceded by a minus sign -) can appear anywhere on the line. Square brackets should not be entered, they simply indicate optional parts of the command line.

Either filter style (the < and > are file redirection operators):
  tth [-a -c -d ... ] <file.tex [>file.html] [2>err]

Or, specifying the input file as an argument (output is then implied):
  tth [-a -c -d ... ] file[.tex] [2>err]

Switches:
   -a automatic picture environment conversion using latex2gif (default omit). 
   -c prefix header "Content-type: text/HTML" (for direct web serving).
   -d disable delimited definitions.
   -e? epsfbox handling: -e1 convert figure to gif using user-supplied ps2gif.
       -e2 convert and include inline. -e0 (default) no conversion, just ref. 
   -f? sets the depth of grouping to which fractions are constructed built-up
    f5 (default) allows five levels built-up, f0 none, f9 lots. 
   -g don't guess an HTML equivalent for font definitions, just remove.
   -h print help. -? print usage.
   -i use italic as default math font.
   -Lfile  tells tth the base file (no extension) for LaTeX auxiliary input, 
      enables LaTeX commands (e.g. \frac) without a \documentclass line.
   -ppath specify additional directories (path) to search for input files.
   -r output raw HTML (no preamble or postlude) for inclusion in other HTML.
	-r2 omit just the time stamp. -r1 is equivalent to -r.
   -t display built-up items in textstyle equations (default in-line).
   -w? html writing style: 0 no title construction. 1 insert head/body.
   -xmakeindx  specify a non-standard makeindex command line.
   -v give verbose commentary. 

If a non-switch argument is present, it is assumed to be the name of the input file. The file must have extension ``.tex'' but the extension may be omitted. The output file is then constructed from the argument by removing the extension ``.tex'' if specified, and adding ``.html''.

T_TH is extremely fast in default mode on any reasonable hardware. Conversion of even large T_EX files should be a matter of a second or two. This makes it possible to use T_TH in a CGI script to output HTML directly from T_EX source if desired; (stderr may then need to be redirected.)

To discuss how to get the best from T_TH, you can subscribe to a mailing list by sending an email containing the message subscribe tth_mailing_list to majordomo@hutchinson.belmont.ma.us. Then you can send messages to tth_mailing_list@hutchinson.belmont.ma.us.

4  Messages

Messages about T_TH's state and its assessment of the T_EX it is translating are output always to the stderr stream, which normally displays on the console, but under Un*x type systems can be redirected to a file if necessary. Normally these messages are one of three types:

Error Messages

Warnings

Informational and external

The switch -v causes more verbose messages to be output, which may be helpful for understanding why errors are reported. A higher level of verbosity -V can be invoked, but is intended primarily for internal debugging of T_TH and will rarely be comprehensible!

The presumption that lies behind T_TH message design is that the file being translated has been debugged using T_EX or L^AT_EX to remove syntax errors. T_TH is not good at understanding or reporting T_EX syntax errors and does not keep an exact count of line numbers (especially when \input is used). Therefore error reporting by T_TH does not reach even the low standard of clarity set by T_EX and L^AT_EX error messages. Although T_EX files can be debugged using T_TH alone, since it is very fast, the process is not recommended for inexpert T_EX users. Moreover, since T_TH understands both T_EX and L^AT_EX simultaneously, it can parse some files that T_EX or L^AT_EX  separately cannot.

5  Mathematics

5.1  Equations

Equations are translated internally into HTML3.2 as much as it allows. T_TH uses HTML3.2 tables for layout of built-up fractions in display equations. It also uses the HTML tag < font face=``symbol'' > , part of the HTML4.0 specification, to render Greek and large delimiters etc. Untranslatable T_EX math tokens are inserted verbatim.

The internal approach to equation translation is a major area where T_TH departs from the philosophy of L^AT_EX2html and its derivatives. T_TH  does not use any images to try to represent hard-to-translate constructs like equations. Instead it uses the native ability of HTML to the fullest in providing a semantically correct rendering of the equation. The aesthetic qualities obtained are in practice no worse on average than L^AT_EX2html's inlined images, which are generally slightly misaligned and of uncertain scaling relative to the text. Some limitations in the HTML code are inevitable, of course, but one ends up with a compact representation that can be rendered directly by the browser without the visitor having to download any additional helper code (e.g. Java equation renderer).

The option [-i]   to T_TH makes italic the default font within equations, and thus the style more T_EX-like. The italic font appearance in browsers is not as satisfactory as T_EX's math italic, so for many documents roman looks better.

Spacing   in equations is handled slightly differently by T_TH than by T_EX. The reason is that most browsers use fonts that will crowd the characters horizontally too close for comfort in many cases (for example: M_||/2). Also, built-up HTML equations are more spread out vertically than in T_EX. Therefore T_TH equations look better if spaces are added between some characters. So T_TH  does not remove spaces in the original T_EX file between characters in equations. The author is thus able to control this detail of layout in the HTML without messing up their T_EX file - since T_EX will ignore any spaces inserted. Legacy T_EX code that contains a lot of spurious whitespace (ignored by T_EX) may, as a result, occasionally become too spread-out when translated.

5.2  In-line Equation Limitations

Some T_EX capabilities are extremely difficult or impossible to translate into HTML, because of browser limitations, and are best avoided if possible. Arrays or matrices in in-line equations cannot be properly supported because tables cannot be placed in-line in HTML. T_TH output often will be strangely disjointed. Likewise built-up fractions, most over- and under-accents, and indeed anything that requires specific placement on the page other than simple subscript or superscript and underline, cannot be rendered in-line in HTML, although T_TH will render them well in displaystyle. These latter constructs are nevertheless commonly used in in-line T_EX. T_TH adopts the default policy of indicating in an unambiguous and relatively intuitive way what construct is being used (as opposed to simply omitting it). For example $\hat{a}$ is rendered [^a]. The result is rarely elegant. Therefore in authoring T_EX that is known to be destined for HTML translation, one should bear in mind these limitations, and use an appropriate style.

As an option, T_TH provides switch -t to convert inline equations that use built-up constructs into a sort of half display, half in-line equation. Each time a new in-line equation is encountered [$ ... $ or \( ... \)] that needs to be built up, an HTML table that starts a new line is begun, and the text then flows on afterwards. For example

1 2 + n

This option gives a slightly disjointed layout for simple equations but is a big improvement for some situations, e.g. in-line matrices.

6  Features dependent on external programs.

6.1  Independence of [La]T_EX installation and the -L switch.

Forward references in L^AT_EX are handled by multiple passes that write auxiliary files. T_TH does only a single pass through the source. If you want T_TH to use L^AT_EX constructs (e.g. tableofcontents, bibliographic commands, etc.) that depend on auxiliary files, then you do need to run L^AT_EX on the code so that these files are generated.

When run specifying a filename on the command line as a non-switch argument, T_TH constructs the name of the expected auxiliary L^AT_EX files in the usual way and looks for them in the same directory as the file. If you are using T_TH as a filter, you must tell T_TH, using the switch -Lfilename, the base file name of these auxiliary files (which is the name of the original file omitting the extension). If T_TH cannot find the relevant auxiliary file because you didn't run L^AT_EX and generate the files or didn't include the switch, then it will omit the construct and warn you. Forward references via ref will not work if the .aux file is unavailable, but backward references will. The -L switch with no filename may be used to tell T_TH that the document being translated is to be interpreted as a L^AT_EX file even though it lacks the usual L^AT_EXheader commands. This may be useful for translating single equations that (unwisely) use the \frac command.

6.2  BibT_EX bibliographies

T_TH supports bibliographies that are created by hand using \begin{thebibliography} etc. Such bibliographies do not require anything beyond the .aux file. T_TH also supports bibliographies created using BibT_EX from a biblography database. The filename.bbl file is input at the correct place in the document. However, this filename.bbl is not created automatically either by L^AT_EX or T_TH. In addition to running L^AT_EX on the source file to create the auxiliary file, you must also execute bibtex filename in the same directory, to create the filename.bbl file, and then run L^AT_EX again to get the references right. (This is, of course, no more than the standard procedure for using BibT_EX with L^AT_EX but it must be done if you want T_TH to get your bibliography right). If you don't create the .bbl file, or if you create it somewhere else that T_TH does not search, then naturally T_TH won't find it.

There are many different styles for bibliographies and a large number of different L^AT_EX extension packages has grown up to implement them, which T_TH does not support. More recently, a significant rationalization of the situation has been achieved by the package natbib. T_TH has rudimentary support built in for its commands \citep and citet in the default author-date form without a second optional argument. A style file for natbib is distributed with T_THgold which makes it possible to accommodate most of its more useful styles and commands and easily switch from author-date citation to numeric citation.

6.3  Indexing

Indexing an HTML document is different from indexing a printed document, because a printed index refers to page numbers, which have no meaning in HTML because there are no page breaks. T_TH indexes L^AT_EX documents by section number rather than by page; assuming, of course, that they have been prepared with index entries in the standard L^AT_EX fashion.

When processing a L^AT_EX file that contains the \makeindex command in its preamble, T_TH will construct an appropriately cross-hyperlinked index that will be input when the command \printindex is encountered, which must be after all the index references \index{ ... } in the document. T_TH does this independently of L^AT_EX, but not of the subsidiary program makeindex that is normally used with L^AT_EX to produce the final index ``file.ind''. T<sub>T</sub>H creates its index entries in a file with extension .tid (Tth InDex). Because of makeindex program limitations, T<sub>T</sub>H currently removes all the page-number formatting that is present in the index entry (but not the reference formatting). It also uses the section reference style ``1-2'', separated by a dash, because this is the standard form that makeindex expects and it is cumbersome to change it. The actual reference is less important to the reader than the fact that T_TH inserts a link to the actual place in the document indexed. When the \printindex command is encountered, T_TH closes this file and runs makeindex on it, which creates by default a file with extension .ind, and then T_TH reads the .ind file in as its index. Because the .ind file that T_TH produces may well be incompatible with running L^AT_EX itself on the file, T_TH deletes the .ind file that it creates (and hence one is left without such a file at the end). If, instead of creating an index file during T_TH processing, one wants to use with T_TH an index file already created, all that is needed is to remove the \makeindex command from the top of the L^AT_EX source. Any existing .ind file will still be input by \printindex but no indexing files will be written or deleted.

If you run T_TH on a file that contains both a \makeindex command and a \printindex it will overwrite your file.ind. In the unusual situation where your index, file.ind, was created laboriously by hand and cannot be recreated, you should be very careful to remove the \makeindex command from the .tex file. For safety, of course, also save a copy of your file.ind somewhere else.

The \makeindex command, if present, will also cause T_TH to add a linked entry called ``Index'' to the end of any table of contents. This entry is a highly desirable feature for an HTML file, but if there is no \printindex command at the end of the document, the index will not exist, so the reference will be non-existent.

On some operating systems with file name length restrictions, the makeindex program is called makeindx. Therefore a T_TH switch is provided: -xcommandline, which substitutes commandline for the default call makeindex. Therefore, -xmakeindx will switch to the correct program name on one of these limited operating systems. This switch also allows additional parameters or switches to be passed to makeindex via e.g.  -x"makeindex -s style.sty". If you don't have the makeindex program, you can't create indexes with T_TH or L^AT_EX, except by hand.

All of the index file processing naturally requires that T_TH have write permission for the directory in which the original L^AT_EX file (specified by the -L switch) resides.

6.4  Graphics Inclusion: epsfbox/includegraphics

Optionally T_TH can use a more appropriate graphics format, possibly using a user-supplied (script or) program called ps2png or ps2gif to convert the postscript file to a png⁴ or gif file, ``file.png'' or ``file.gif''. [``file'' is the name of the original postscript file without the extension and png or gif are interchangeable as far as matters for this description]. When the switch -e1 or -e2 is specified, if ``file.png'', ``file.gif'' or ``file.jpg'' already exists in the same directory as implied by the reference to ``file.ps'' then no conversion is done and the file found is used instead. That graphics file is then automatically either linked (-e1) or inlined (-e2) in the document. If no such file is found, T_TH tries to find a postscript file with extension that starts either .ps or .eps and convert it, first using ps2png then, if unsuccessful, ps2gif. Linux (un*x) ps2png and ps2gif scripts using Ghostscript and the netpbm utilities for this purpose are included with the distribution. A comparable batch program can be constructed to work under other operating systems ⁵ or else the conversion can be done by hand. Naturally you need these utility programs or their equivalent on your system to do the conversion. The calling command-line for whatever ps2png (or gif) is supplied must be of the form:

ps2png inputfile.ext outputfile.ext

By popular request, a third graphics option -e3 for generating icons is now available. If no previously translated graphics file, e.g. ``file.png'' exists, T<sub>T</sub>H passes to ps2gif (or png) a third argument consisting of the name, ``file_icon.gif'', of an icon file. ps2gif is expected to create it from the same postscript file. In other words the call becomes

ps2gif file.eps file.gif file_icon.gif

The L^AT_EX2e command \includegraphics{...} and the older \[e]psfig{file=...} are treated the same as \epsfbox. Their optional arguments are ignored.

If the extension is omitted for the graphics file specification, then .ps or .eps is tried. If the extension of the file specified is non-null and not .ps or .eps, no conversion is done but the file is referenced or in-lined as an image. In effect, then, T_TH supports postscript, encapsulated postscript, gif, and jpeg, plus any future formats that become supported by common browsers. However, L^AT_EX does not support these other formats, so it will give an error message if it can't find a postscript file, unless you specify the bounding box, thus preventing L^AT_EX interrogating the file.

6.5  Picture Environments

7  Tabular Environment or Halign for Tables

7.1  Tabular

• HTML tables have either all cells bordered with rules or none. T_TH therefore decides whether to use a bordered table by examining the first character of the alignment argument. If is it |, then the table is bordered, otherwise not.
• HTML tables are not capable of simultaneously aligning part of a cell's contents to the right and part to the left, which is automatically done by L^AT_EX on some occasions when @-strings are used. For example if the alignment argument is |l@{~units}|r|, L^AT_EX will align ``units'' to the right of the first cell. T_TH can't. In some unbordered cases T_TH will try for the same effect by putting the closing @-string in the following cell. This won't always give a good result.
• @-strings and *{num} code repetition are not permitted in the alignment argument to \multicolumn, but they are in the main tabular alignment argument.

7.2  Halign

• T_TH decides whether to use a bordered table in Plain T_EX by examining the entire halign template (i.e. the material up to the first \cr of the halign). If it contains the command \vrule T_TH makes the table bordered, otherwise not.
• T_TH decides on the alignment of the cell contents by looking for \hfill or \hss commands in the cell template. The default is to left-align the cell. If one of these spacing commands is present in the template prior to the # for this cell, then the cell will be right-aligned unless such a command also appears after the #, in which case the cell is centered. Again HTML is not capable of applying different alignments to different parts of a cell. So results may sometimes be different from T_EX. However, if most of this paragraph sounds totally obscure to you, don't worry; T_TH will probably do the right thing.
• The \multispan command is supported, giving a centered multicolumn cell, and \omit is treated as \multispan1. However, \span is currently not supported.

7.3  Longtables

• The longtable environment is supported, but it is always centered. It is converted into a standard tabular inside a table environment because there is no need to accommodate page breaks (the main point of longtable) in HTML.
• The caption (including caption*) command is translated correctly but set as part of the HTML table; so, if the caption is longer than the longest row of the table, it will cause the whole table width to expand, possibly up to 100% of the line-width.
• The commands endhead, endfirsthead, endfoot, endlastfoot, are ignored, but their immediately preceding commands are therefore inserted into the table. That is probably not desirable for the foot commands. Longtable footers are not translated into footers.
• The \kill command is ignored. Its text is spuriously inserted.

8  Boxes, Dimensions, and fills

Boxes, dimensions, and fills are rarely appropriate for web documents because they imply an attempt to control the fine details of layout. Browsers make their own choices about layout of a document in HTML. For example they make the lines fit whatever size of window happens to be present. This dynamic formatting makes mincemeat of most detailed T_EX layout. Therefore the best advice is to avoid these constructions as far as possible.

There are nevertheless many cases when a T_EX document containing boxes, dimensions, and fills needs to be translated. Earlier versions of T_TH made a point of trying to intercept the dimensions and drop them, so as not to clutter the HTML with rubbish. From version 2.5 onwards, limited translation of these constructs is supported. They are translated, where appropriate and possible, into HTML tables with widths and vertical skips estimated to give a reasonable result on a browser. It must be stressed that accurate translation is inherently impossible because browsers deal in pixel sizes and default font sizes that vary and are out of the control of the publisher.

The types of box usage that translate quite well are when things like

\hbox to \hsize{The left \hfil the Right}
\vbox{\hsize=2in Matter to be set in horizontal mode to a 
  limited hsize}
\makebox[0.6\hsize][r]{Stuff to the right of the makebox.}
\framebox{check}

The left

the Right

Matter to be set in horizontal mode to a limited hsize

Stuff to the right of the makebox.

check

Usages that translate poorly tend to be boxes within a line of text. That is because current HTML table implementations have to start a new line unless they happen to be adjacent to a table already. Thus an hbox in a line will give a line break that you might not have wanted. This behaviour is really a bug in the browsers, but we are currently stuck with it. The behaviour of HTML tables is buggy [see 12.6] when their alignment is specified, which means that strange results are likely if more than one box on a line is being set. Boxes in equations are troublesome. The only type that is reasonably supported is \mbox which is often used in L^AT_EX for introducing text inside equations.

Usages that are currently not supported at all include negative skips, \newdimen new dimensions.

The only important dimension parameter that is currently supported is \hsize. This can be reset using the plain T_EX format e.g. \hsize = 3in but only within a group, because it makes no sense for the HTML file to try to specify the width of the line at the outermost level, which is the browser's business.

T_TH trys valiantly to mimic the sort of text alignment that is obtained using glue such as \hfil and \hss, provided it is inside a box. However, the alignment algorithm of HTML tables makes it impossible to obtain fills with exactly equal sizes. So don't be surprised if some results looks disagreeable. Moreover, T_TH will completely ignore the glue outside an hbox, and it doesn't know the difference between \hfil and \hfill, etc.

9  T_EX command definitions and other extensions

9.1  Delimited-parameter macros and Conditionals

Delimited parameter definitions are fully supported. However, macros in some style files are written in such a way that the recognition of the delimited parameter depends on other T_EX behaviour (e.g. dimensions) that are not supported by T_TH. In such cases it is all too possible for the delimited parameter not to be matched, resulting in a runaway argument situation. Thus, delimited parameter macros are especially dangerous when using T_TH, or indeed any process other than T_EX itself. (And they are never exactly ``safe T_EX''). The recognition of these definitions can be disabled using the -d switch, in which case the definitions are simply discarded.

Conditionals such as \if, \ifnum and so on are supported, as listed above (1.1.2). In T_TH they have one syntax limitation. Further `if' commands are not permitted in, or as part of a command expanded in, the tokens, characters, or numbers being tested. Thus, an example of truly perverse usage such as
\ifnum 1=\if ab 1\else 2\fi True \else False \fi
will likely break. Nested `if' constructs are permitted in the conditional text, however, so
\ifnum 1=1 True\if ab -true\else -false\fi \else False \fi
is fine. Because T_TH does not internally resemble T_EX, whereas the result of conditionals such as \if and \ifx may depend on internal representations, there cannot be 100% compatibility of such tests at the lowest level. Still, tests on externally defined commands ought generally to give correct results. When authoring documents in T_EX one is generally well advised to avoid conditionals.

Although T_TH supports a remarkably complete subset of L^AT_EX, it does not support all of the complicated primitive details of T_EX, partly because that would be unnecessary. For example, practically any T_EX that redefines category codes (other than @ which T_TH treats universally as a letter) will break because T_TH knows nothing about the concept of category codes. (If you don't know much either, about this unfortunate aspect of T_EX, join the vast majority of T_EX users!) A related example is that T_TH expects only letters or @ in user-defined command names, not punctuation characters etc.

9.2  Macro- and Style-file inclusion

T_TH will find an input file if

1. the full path is specified relative to the directory from which T_TH is run, e.g.
   \input /home/myhome/mytexdir/mymacro.tex
   
2. the -p switch specifies a path on which the file is found, or
3. the TTHINPUTS environment variable is defined to be a path on which the file is found.

This policy provides a mechanism for making available the alternative package for T_TH, without alteration of the original T_EXfiles, by placing the (simplified) version of the macro package on the path T_TH searches. An example using the -p switch might be

tth >file.html <file.tex -p/usr/local/tthinputs:~/mytthinputs

Since it is impossible to anticipate all style file incompatibilities, it must be the responsibility of the user (or the journal) to decide how to translate the concepts implemented in the original complicated macro package into simpler, T_TH-compatible, T_EXmacros.

9.3  Layout to include arguments of unknown commands

Unrecognized or undefined commands of the form \dothis{one}{two}{three}, are treated by discarding all the following adjacent brace groups. A space between the close and open braces will terminate the discarded arguments and cause the following brace group(s) to be scanned as if just the text. This makes it possible to use formatting to make T_EX code come out right in both T_EX and HTML. For example if T_TH encounters a command written ``\boxthis{width} {boxed material}'' which might be designed in T_EX to provide a width to a defined command, written with a space after the first argument, it will ignore the width and scan the boxed material into the text.

9.4  Restrictions on redefinition of internal commands

In T_TH (unlike T_EX) most internal commands can not normally be redefined; any redefinition will simply be ignored (except inside edef and a few other places). This prevents T_TH from safely allowing use of major packages that redefine standard T_EX commands. For example amsT_EX redefines footnote to have just one argument, which will cause problems. This particular example is potentially a problem with L^AT_EX too, which also redefines footnote. T_TH handles this by keeping track of whether the file is L^AT_EX or T_EX; therefore you should not mix the two dialects in a single file even though there is no need to tell T_TH explicitly which type the file is. (Besides, a mixed file will play havoc with T_EX itself.)

9.4.1  Footnotes

10  Color

10.1  L^AT_EX Color

The L^AT_EX syntax is recommended because the 68 standard named colors⁷ are directly supported internally by T_TH using the named model. Any numerical CMYK, RGB and Gray color can also be prescribed. For example the following commands are enclosed in themselves: \textcolor[named]{BrickRed}{...}, \textcolor[rgb]{0.,.5,0.}{...}, \textcolor[cmyk]{0.,.5,0.,0.3}{...}. You can define custom colors in the usual way using, for example

{\definecolor{Puce}{rgb}{1.,.5,.8}
\color{Puce} This is my own Puce.}

The command \pagecolor is supported but discouraged. It is highly likely to give rise to an HTML file that will fail validation because it inserts an HTML tag <body bgcolor=...> which will not be in its correct position (immediately following the title). The only way to be certain to produce an HTML file that passes validation is to put the title and body commands in by hand, using e.g. \special{html:<title>...</title><body ...>} Netscape seems not to mind a body tag out of order, but only the first one is able to set the page background color.

The commands \colorbox and \fcolorbox are supported via CSS style sheet commands. They will only work to set the background color of included text if the browser is set to use style sheets. ``This sentence'' is the result of the command \colorbox{green}{``This sentence''}. If it is colored, then your browser supports style sheets to this extent. If not, check your preferences settings.

10.2  Plain Color

The Plain T_EX syntax using commands such as \Red{red text} requires the file colordvi.tex to be input prior to their use. But because T_TH does not search the standard T_EX paths, that file will not usually be found unless the full path is explicitly specified. If the file is not found, only the 8 standard colors

\Red, \Green, \Blue, \Cyan, \Magenta, \Yellow, \Black, and \White

\Color{0. .5 .5 0.}{pale red}

\def\redcolor{0. .5 .5 0.}
\Color{\redcolor}{The stuff that is red.}

Another difficulty with the colordvi command \textColor (which is the color switch - L^AT_EX syntax reversed that usage and changed to comma-delimited arguments just to confuse us) is that it is a global setting. It then becomes almost impossible to maintain proper nesting of the closure of the font commands used for colors in HTML. As a result, use of \textColor often gives HTML files that won't pass HTML validation.

10.3  Limitations

11  HTML and output

11.1  Formal HTML validation

One reason for violation arises because HTML4.0 requires a <title>...</title> for every document. A title is constructed from L^AT_EX files that contain the \title{...} command, in which case HTML conformance is ensured by putting the \title command before any text (i.e. in the preamble, where it belongs). If the \title command is not desired in the T_EX file, for example because it is a plain T_EX document, a title can be provided by the author for the HTML document by putting a line like this at the top of the T_EX file.

%%tth:\begin{html}<title>Put the title here</title>\end{html}

If commands like \item, that output material to the HTML file occur before the title has been constructed, the HTML title command will be out of order and the formal standard will be violated.

In the case where the title construction fails, or if some other T_EX usage causes a violation of the formal standard, browsers will still render the output correctly if this manual is followed.

11.2  HTML Styles

12  Browser Problems

T_TH translates T_EX into standard HTML and takes account as far as possible of the idiosyncrasies of the major browsers. Nevertheless, there are several problems that are associated with the browsers. Authors and publishers should recognize that these are not T_TH bugs.

12.1  MacIntosh browser font problems

The characters with codes higher than 127 in the Mac fonts are in a different order from the standard ISO-8859-1 (sometimes called ISO Latin-1). If Netscape or IE on Macs have their document encoding set to the standard, then in versions 3 onwards they are programmed to access the glyph where they think the corresponding accented Latin character will be in the Mac font. This is fine if one really wants an accented Latin character. However, for mathematics, using the symbol font (which is ordered the SAME on the Mac as on other platforms) the result is that one gets the wrong symbol glyph. This is a particular problem with large delimiters. The fix is that the Mac browser must be set to use the Options/Document-encoding ``MacRoman". This tells the browser not to do the permutation to access the accented Latin characters in the Mac places; hence, for eight-bit characters, it accesses the symbol font correctly. This would break the Latin accented characters except for the fact that (most current versions of) the browsers still access characters in the Mac order if they are specified numerically using the HTML syntax ``&#???;". So T_TH documents will in most cases display both accented characters and symbols correctly on Macs if the document-encoding is set to MacRoman.

In addition, NS4.0 has under Edit Preferences Fonts a choice between ``use document fonts'' and ``use my fonts overriding document''. You need to set ``use document fonts''. This necessity is obvious if you think about it. You can make any document into garbage by specifying your own font (e.g. Greek or Cyrilic) that happens not to be what the document is written in. The same is true for the symbols of mathematics. The reader must permit the document to specify the font. Browsers should always set ``use document fonts'' as the default.

In summary, you might want to tell people viewing your documents to set their browsers to View Encoding MacRoman, and Edit Preferences Fonts Use-document-fonts (NS 4.0).

12.2  Netscape Composer

[Unconfirmed reports indicate that P*gemill has problems of the same type.]

12.3  X font problems

Symbol fonts are not normally enabled for Netscape running under X, because of the way Netscape groups its fonts. A fix for this is to install some aliases in the fonts directories or else to add a line to your .Xdefaults file. See http://hutchinson.belmont.ma.us/tth/Xfonts.html. You might want to put these notes on your site for people viewing your documents.

A font rendering problem exists for small size single-symbol overbar in the Xfree86 server. The overbar symbol may or may not appear, depending on the direction in which its window uncovered. (Yes, this is a really bizarre bug but can be demonstrated with the xfd program.) It is strictly not a Netscape bug but an X-server, or perhaps font, bug. This symbol is used by T_TH only as a fall-back for \bar in situations like in-line equations where it can't render the construct using tables.

12.4  Internet Expl*der

12.5  Printing

In Netscape 3.0 and 4.x under X, for example, the printing fonts are hard coded into the browser and the font-changing commands are ignored when printing. For that reason, visitors viewing T_TH documents will often not be able to print readable versions of documents with lots of mathematics. This problem could, and should, be fixed in the browsers. However, if you want your readers to be able to print a high-quality paper copy of the file, then you probably want to make available to them either the T_EX source or a common page-description format such as Postscript or PDF. Since HTML documents download and display so much faster and better than these other formats on the screen, T_TH's translation provides the natural medium for people to browse, but not necessarily the best medium for paper production.

12.6  Other Browser Bugs

Under Wind*ws, both Netscape (3.0) and Internet Expl*rer (3.02) incorrectly size or space vertically the symbol glyphs so that small gaps appear between the parts of large symbols and delimiters. This occurs only at certain font sizes (different between the two browsers!) but causes a slightly annoying degradation of the appearance.

Both Netscape and IE fail (although somewhat differently) to carry font changing commands from cell to cell of HTML3.2 tables. In rendering equations (using tables) T_TH circumvents this bug at the cost of significant extra effort and slightly verbose HTML. However, for tables generated by \halign or \begin{tabular} T_TH takes no special steps to avoid this bug. Therefore you cannot, for example, increase the font size of an entire table by enclosing it in {\large ... } and indeed the table will revert to the default size even if it is inside a different sized section of text. Moreover, a change of font face in a cell, for example by \it will not carry over to the next cell. A document containing this problem will not pass some HTML validations. It is prevented if every cell of a T_EX table is enclosed in braces and the required style applied separately to every cell - a serious annoyance.

IE can become confused about its vertical alignment in tables, with the result that symbols float above or below the horizontal line in built-up equations. This sometimes fixes itself if you simply refresh the page!

Tables are incapable of being properly embedded within a line of text. They generally force a new line. This is quite a significant handicap when translating in-line material that could use a table. It can be argued that this behaviour is required by the HTML standard. Specifically, the <p> element is defined as having in-line attributes which prevent it from containing any elements defined as being block type, of which <table> is one. However, here the standard seems to be very unhelpful.

Nested tables in Netscape 4.x are not properly cleared by the <br clear=all> attribute. It appears that the next line is shifted down only by the height of the last innermost table in the nest. If this happens not to be the tallest table, the subsequent text will overwrite that tallest table. This sometimes the cause of problems when putting more than one box on a line.

On Macintosh Netscape, the standard HTML entity &times; for a multiplication sign is not recognised. There seems to be no good reason for this omission. Complain to the browser manufacturer!

12.7  Cascading Style Sheets and Unicode

The facilities offered by style sheets make it possible in principle, but not currently in practice, to solve several of the outstanding layout problems that T_EX translation encounters. Unfortunately, in practice, the latest versions of the popular graphical browsers offer only incredibly buggy and broken implementations of the parts of CSS that are needed for mathematics layout, and they are essentially unusable for this purpose. (Here Netscape is the worse offender.) The use of unicode is advocated by purists instead of using the symbol font. However, again, there is no practical way to use it reliably in the current browsers.

13  Code Critique

If you think you have found a bug, you can report it to the mailing list mentioned in section 3. You are most likely to get help if your report is accompanied by the brief section of T_EX code that causes the problem. But please don't send L^AT_EX2.09 files or files that do not conform to the latest (1994) L^AT_EX users' guide. And please check this manual and especially the FAQ (B) first.

The code has been compiled and run on Linux, MSDOS, Wind*ws, Open VMS, and sundry other operating systems. See http://hutchinson.belmont.ma.us/tth/platform.html.

14  License

T_TH is copyright © Ian Hutchinson, 1997-2000.

You may freely use T_TH for non-commercial purposes. It may not be used for commercial purposes. If you distribute any copies, you must include this file and these conditions must apply to the recipient. T_THgold may be used for commercial purposes according to its license. No warranty of fitness for any purpose whatever is given, intended, or implied. You use this software entirely at your own risk. If you choose to use T_TH, or T_THgold, by your actions you acknowledge that any direct or consequential damage whatever is your responsibility, not mine.

15  Acknowledgements

Many thanks for useful discussions and input to Robert Curtis, Ken Yap, Paul Gomme, Michael Sanders, Michael Patra, Bryan Anderson, Wolfram Gloger, Ray Mines, John Murdie, David Johnson, Jonathan Barron, Michael Hirsch, Jon Nimmo, Alan Flavell, Ron Kumon, Magne Rudshaug, Rick Mabry, Andrew Trevorrow, Guy Albertelli II, and for bug reports from others too numerous to mention.

A  Appendix: Non-Standard T_EX Macros

The following macro definitions, although not needed for T_TH, will enable a T_EX file that uses the non-standard T_TH commands to be correctly parsed by Plain T_EX.

\def\hyperlink#1#2{\special{html:<a href="\##1">}#2\special{html:</a>}}
  % Incorrect link name in \TeX\ because # can't be passed properly to a special.
\def\hypertarget#1#2{\special{html:<a name="#1">}#2\special{html:</a>}}
\long\def\tthdump#1{#1} % Do nothing. The following are not done for TtH.
\tthdump{%
\def\title#1{\bgroup\leftskip 0 pt plus1fill \rightskip 0 pt plus1fill
\pretolerance=100000 \lefthyphenmin=20 \righthyphenmin=20
\noindent #1 \par\egroup}% Centers a possibly multi-line title.
 \let\author=\title % Actually smaller font than title in \LaTeX.
 \input epsf     % PD package defines \epsfbox for figure inclusion
  % Macro for http reference inclusion, per hypertex.
 \def\href#1#2{\special{html:<a href="#1">}#2\special{html:</a>}}
 \def\urlend#1{#1\endgroup}
 \def\url{\begingroup \tt 
  \catcode`\_=13 % Don't know why this works.
  \catcode`\~=11 \catcode`\#=11 \catcode`\^=11 
  \catcode`\$=11 \catcode`\&=11 \catcode`\%=11
\urlend}% \url for plain \TeX.
}

B  Appendix: Frequently Asked Questions

Why won't T_TH run under DOS? Something about DPMI.
It will, but the distributed DOS executable needs DPMI memory extension support to run. Plain old DOS doesn't have that unless you specifically load it. All Wind*ws versions from 3.1 on support it at the DOS prompt.

Why won't T_TH run from Program Manager in Wind*ws?
You need a command line. Call up the DOS prompt.

T_TH does not recognize tableofcontents, backward references, listoffigures, ...
Yes it does, see section 6.1, and use the -L switch.

T_TH does not insert my picture environments.
If picture environment pictures are to be included, conversion to a gif file is needed. See 6.5.

T_TH messes up my tabbing environment.
Tabbing is not currently supported. It is alien to the HTML document mark-up approach. See section 7.

How do I make T_TH border my tabular table?
T_TH looks in the format string argument of the begin{tabular} environment and if it begins with a | (vertical bar) then the HTML table is bordered.

T_TH inserts the title and author even without the maketitle command
True, T_TH inserts them when you define them. This gives you a chance to fine-tune the presentation if you wish.

Why doesn't \frac work in equations?
It does, but only in L^AT_EX documents because \frac is not a plain T_EX command. The document you are presenting to T_TH doubtless has no \documentclass command and other L^AT_EX blurb at the top. If you insist on having L^AT_EX commands available in such a document, you can use the -L switch. But note that other changes in interpretation (e.g. in footnotes) are implied by using this switch to tell T_TH that this is a L^AT_EX file.

What is this strange result using \dot \hat \tilde \frac \vec ... in in-line equations?
Neither over and under accents nor built-up constructs such as fractions can be rendered in-line (i.e. in a textstyle equation produced by $ ... $) in HTML. Therefore, T_TH outputs something that is not elegant but reasonably indicates the original intention. Additional brackets are inserted to ensure that fractions are unambiguous. T_TH will render all these built-up constructs correctly in a display equation. See also 5.2 for an option.

Why does the large square root sign look so ugly?
There are some things that browser symbol fonts can't do well.

Why does a dagger sign come out strange?
Browsers don't generally have a dagger sign in their fonts. T_TH uses a kludge.

How do I insert code that is used only by T_TH, not T_EX?
Use %%tth: followed by the material you wish to pass to T_TH. T_EX omits this line as a comment. Alternatively, insert \newif\iftth at the top of your document, then use a conditional: \iftth \TtH\ material \fi. TtH recognizes \iftth as a special `if' that is always true, whereas to T<sub>E</sub>X it is simply a new `if', which by default is false when defined.

How do I insert HTML tags into my file without T_EX knowing?
Use %%tth: then on this line put \begin{html} tags \end{html}. Do not try to continue this html onto a second line with a second %%tth: before the \end{HTML} because the html environment will output the %%tth:, which it probably not what you want. Another way to pass codes directly to the output is the \special{html: ... } command. Do not use \begin{verbatim} to pass HTML tags. It will convert the greater than and less than signs to make them appear in the display and not be interpreted as tags.

How do I insert code that is used only by T_EX, not T_TH?
Insert \newif\iftth at the top of the file and then use the conditional constr uction:

\iftth\beginsection{The \TtH\ Header}\par\else\beginsection{The \TeX\ Header}\fi

\def\tthdump#1{#1}
%%tth:\begin{html}<H1>The HTML Header</H1>\end{html}
\tthdump{\beginsection{The \TeX\ Header}\par}

How do I include the style file ...sty for the T_EX paper I prepared for... journal?
If you are wise, you probably don't. T_TH often can't handle complicated journal formats for [La]T_EX without modification, because they frequently use newdimens, and category code modification or other unsupported constructs. Instead, look at your T_EX file, or the T_TH messages telling you which commands are unknown. Decide which of the journal's specific commands or environments you used or need. Write a little style file that defines them to do something simple and sensible, or translates them into standard L^AT_EX commands. Or ask the journal to provide such a style file! If you are a journal publisher, distribute your simplified style file to your authors.

Why does T_TH not recognize my ends of lines properly?
If you transfer a file from one operating system to another as a binary file, the line-end codes are likely to be messed up. They use different codes on Un*x, DOS, and Mac. Usually T_EX is not bothered by this. T_TH is somewhat more sensitive. Use ASCII transfer.

T_TH does not recognize evironment ... even though it claims to.
Probably you left a spurious space, e.g. \begin {enumerate} between the \begin and the following brace. T_TH occasionally won't accept that, even though L^AT_EX does. It is bad style.

Why does T_TH not recognize ... command from ... style package?
Let's be perfectly clear here. T_TH does not currently recognize \usepackage and, with the exception of commands explicitly mentioned in this manual, does not support any of the zillions of extensions to L^AT_EX that exist, even if they are part of the ``standard distribution''.

The file I ``published'' using Netscape Composer looks messed up when viewed on a Mac.
Don't use Composer on T_TH documents. See section 12.2.

In bordered tables I want an empty cell to look empty. How do I make T_TH do that?
HTML tables by default ``fill in'' an empty cell, so that it gives the visual impression of being absent. This is sometimes useful, so T_TH does not prevent it. If you want it to look like an empty cell, put a non-break space in it by &~& in the T_EX.

Why does T_TH mess up my \fbox, minipage, etc?
The whole concept of a ``box'' is not really translatable into HTML. T_TH tries to mimic the box using tables. But in some cases, especially in equations, it can't cope.

Why does T_TH complain about my skip, space, ... command?
Dimensions are usually inappropriate for HTML. T_TH tries do something sensible with dimension, space, and glue commands. Usually it is successful. If so, you need do nothing. In some rare cases, you might see some irrelevant left-over characters from the dimension command that have to be removed by hand.

How do I get caligraphic fonts, {\cal E}, AMS fonts, etc?
You can't because browsers don't have access to them. T_TH can only support fonts that are available on the browsers that eventually visit the page. By default T_TH tells the browser to render caligraphic as italic helvetica font. You may, if you wish, define \cal to be something different, such as %%tth:\def\cal{\it\color{red}}.

Why does T_TH turn double-quotes into an accent instead of quotes?
In basic T_EX the double quotes character " is not defined, and hence may do anything that the local installation feels like. Double quotes must be inserted by using two quote '' or back-quote `` characters. In German T_EX implementations, the double-quotes character is used to provide the umlaut over accent and for some other special needs. T_TH supports these German uses in some appropriate contexts. English speakers should adopt proper T_EX quote usage. There is essentially never a situation in L^AT_EX where it is advisable to use a double quote to represent itself outside of a verbatim section (where it will naturally be treated literally). In Plain T_EX you might need it. If so, \char`" is an absolutely fool-proof way to insert it. Here it is:". You can also just enclose it in braces thus:{"}.

How do I include into a macro I am defining a # sign for an HTML reference?
When you do \special{html:<a href="#reference">} T_TH just puts the html tag in the output verbatim. T_EX does essentially the same for its dvi file and the dvi processor later may or may not complain about not understanding it; but generally it is ignored. However if you try to define a macro like \def\localhref{\special{html:<a href="#reference">}} then T_EX will complain as follows:

! Illegal parameter number in definition of \localref.
<to be read again> 
                   r
l.3 \def\localref{\special{html:<a href="#r
                                            eference">}}
?

\def\tthdump#1{#1}
\tthdump{\edef\localref{[a hyperreference]}}
%%tth:\def\localhref{\special{html:<a href="#reference">}}

\def\localhref#1#2{\special{html:<a href="\##1">}#2\special{html:</a>}}

How do I construct a macro to take as a single argument a URL, which may contain special T_EX characters like _ ~ @ & etc, that makes T_TH construct a hyperreference but T_EX just enter it in the text?
Use the built-in command \url{...}. This behaves in essentially the same way as the command defined in L^AT_EX's url.sty. The reference will appear verbatim in the text (in teletype font).

T_TH seems not to work on WinNT when converting included PostScript files, even though my ps2gif program works fine from the command line. What is the problem?
The problem is not T_TH. It appears to be an operating system problem. The batch program ps2gif is breaking for some strange reason when called from T_TH. See footnote 5.

Why doesn't T_TH automatically generate <head> and <body> HTML tags?
First, the <head> and <body> tags are optional in the HTML specification. There is no need for T_TH to generate them to statisfy the standard. Second, T_EX and L^AT_EX files do not have a corresponding structural division into separate head and body sections. It might seem as if L^AT_EX does, with \begin{document} being the divider, but there are many cases where this mapping is incorrect. For example title may not be defined until after \begin{document}, corresponding to the HTML body section, whereas it must be in the head section. Finally, if T_TH automatically entered <head> and <body> tags, then the thoughtful author would not be able to enter them where they ought to be by using, for example:
%%tth: \begin{html} <head> \end{html}
Therefore, the choice not to produce these tags automatically is a deliberate one based on a careful consideration of the advantages and disadvantages. An author can always adjust their T_EX code to include them, if they wish to be pedantic about the division. See also the section on HTML style [11.2].

Why don't T_EX commands get expanded in the HTML title?
In HTML, the stuff that goes in the <title>...</title> of a page is not permitted by the specification to contain HTML tags - things in angle brackets - and tags are not interpreted. If an equation or some other command that T_TH translates into HTML formatting is in the title, then the title will break when expanded. Therefore T_TH never expands commands in the title, but leaves them in the T_EX form that they started as, since that is about as easy to read as any unformatted mathematics.

Can T_TH be made to support BibT_EX bibliographies?
It already does; see 6.2. If T_TH is not finding the .bbl file even though you used the -L switch, then you probably forgot to generate it using L^AT_EX and BibT_EX, or perhaps it is in the wrong place.

Does T_TH support ...?
Probably yes if it is part of L^AT_EX. But if you want a specific additional capability, and find that it is not supported, why not write a TeX macro to support it and translate it into suitable HTML using the functions described in this manual. Then you will have your support and if you send it to tth@hutchinson.belmont.ma.us it may be possible to include it into the standard T_TH executable and you'll have helped all the other users of T_TH.

Index (showing section)

&times;

     Mac browser bug, 12-6

L^AT_EX extension packages, B-0

T_EX-only code, B-0

T_TH-only code, B-0

auxiliary files, 6-1

BibT_EX, 6-2

<body>, B-0

bugs, 13-0

calligraphic, B-0

CGI script, 3-0

charcodes, 9-1

color, 10-0

colordvi, 10-0

commands

     L^AT_EX supported, 1-2

     alternative files, 9-2

     handling unsupported, 1-4

     redefining, 9-4

     renaming, 9-4

     unknown, 9-3

     unsupported, 1-4

compile, 2-0

conditionals, see \if

CSS, 12-7

definitions

     delimited, 9-1

environments, 1-2

equations

     textstyle, see in-line equations, overaccents

Error, 4-0

extensions to L^AT_EX, B-0

flex, 2-0

font

     face="symbol", 5-1

fonts, 1-1

footnotes, 9-4

frac command

     see switch -L, B-0

gif, 6-4

graphics files, 6-4

<head>, B-0

\headline, 1-1

HTML

     3.2, 5-1

     4.0, 5-1

     insertion, 1-3

     tags, B-0

icons, 6-4

\if, 1-1, 9-1

iftth, B-0

in-line equations

     arrays, 5-2

     built-up display, 5-2

     fractions, 5-2

     overaccents, 5-2

\includegraphics, 6-4

indexing, 6-3

\input

     TEXINPUTS, 9-2

     TTHINPUTS, 9-2

italic

     equation style, 5-1

jpeg, 6-4

LaTeX2HTML

     differences, 5-1, 6-1

license, 14-0

limitations, 5-2

longtable, 7-3

Mac browsers, 12-1

macro files, 9-2

macros

     alternate, 9-2

     special use, A-0

makeindex, 6-3

mathematics, 1-1

messages, 4-0

Netscape Composer, 12-2

picture environment, 6-5

portability, 6-1

postscript, 6-4

printing, 12-5

ps2gif, 6-4

ps2png, 6-4

publish

     through composer disallowed, 12-2

references

     forward, 6-1

\rm, 1-1

spacing, 5-1

stderr, 3-0

stdin, 3-0

stdout, 3-0

style sheets, 12-7

switch

     -L, B-0

switches

     -L, 3-0, 6-1

     T_TH, 3-0

symbols, 12-3

Table of Contents

     Index entry, 6-3

tables

     overwriting bug, 12-6

texinputs path, 9-2

title

     HTML construction, 11-1

unknown commands, see commands, unknown

vertical alignment, 12-6

warning, 4-0

X fonts, 12-3

Footnotes:

¹The problem with \rm in text is that HTML has no < rm > tag, and relies on cancelling all previous (e.g.) < i > or < b > tags. T_THgold has a style switch -y that uses Cascading Style Sheets to solve this problem. However not all older browsers support CSS. The best solution is to avoid \rm by using proper grouping of non-roman text. (In equations \rm is essential, but T_TH has a work-around in equations.)

²Conditionals \if and \ifx are not 100% T_EX compatible for cases where they refer to internal T_EX commands because T_TH internals are not identical. Catcodes are also unknown to T_TH.

³See appendix for T_EX macros supporting these commands

⁴The PNG graphics file format is an improved replacement for the GIF standard. Netscape has built in rendering for PNG. The GIF standard is plagued with legal problems related to a ridiculous patent on the type of file compression it uses.

⁵May 1999 reports indicate that there is a batch program in circulation bearing the comment ``:#batchified by cschenk@snafu.de'' that tries to implement the functionality of ps2gif and gives errors on WinNT when called by T_TH but not when called from the command line. This problem appears to be related to memory management or other some operating system inadequacy. It would do everyone running on Wind*ws systems a favor if someone could figure out what the problem is and let me know at tth@hutchinson.belmont.ma.us. Meanwhile, it is reported that removing the pnmmargin command from the ps2gif batch file enables it to run. A Sep 99 report notes that on Win98 the pnmmargin command appears not to be available on the system. Remember, ps2gif is the user's responsibility.

⁶The alignment argument of the math array environment was ignored in T_TH versions earlier than 2.20 but is now honored.

⁷See the file colordvi.tex for a list of the named colors.