The VideOC styles 
for dvi, pdf, HEVEA, LATEX2HTML 
(from the VideoC project)
Revision: 1.36

Christian Queinnec
Université Paris 6 --- Pierre et Marie Curie
LIP6, 4 place Jussieu, 75252 Paris Cedex -- France

This documentation is written in English since it it the language for Computer Science as much as French is the official language for fencing, jumping, etc. This allows this documentation as well as the source programs to be read, debugged and enhanced from amateurs or afficionados from many countries. Actually these programs are released under the Gnu Public License version 2.

The overall goal of the VideOC project was to build and experiment tools in order to produce an educational CDrom to teach the C programming language. This long term goal requires several intermediate goals to be fulfilled. One of the main constraint of that project was to be able to derive from the same set of description files:
  1. the entire hierarchy of files/data/programs needed to populate the CDrom,
  2. the data needed for the runtime of the CDrom (which uses its own document server, QCM manager etc.),
  3. a book of selected exercises in C,
  4. some printed material for students in various formats i.e., Postscript, PDF, dvi, html.
Moreover, care has been paid to unify the sources to be more or less independent of the final formats. The styles that are described in this document try to achieve that goal.

As far as I know there are no tools on the market that satisfies all these goals. There are good software products for various tasks but they often use opaque proprietary formats that preclude to use the information entered in these tools in a way not foreseen by the tools. The availability of all these data (text of lectures, exercises and their solutions, programs, etc.) in comprehensible formats makes possible for any teacher in the world to complement, change or experiment with this ``package''.

The documents of the VideOC project are most often written in a limited subset of LATEX and may probably be translated into XML fairly easily. The rules of style for these documents are explained in the present document which, in turn, observes these rules and serves as a test file for these styles. This document may be read in Postscript, HTML. The source of this very document contains a lot of examples of use of the styles and serves as an additional documentation.

The programs of the VideOC project are available for download .

There are many files that are involved with these multiple targets. Here is the big picture:

1   Drawings

Figures are worth thousands words ... when appropriate. Any figure must be able to show on dvi, pdf and HTML documents. The current version of pdflatex only accepts PNG files. In HTML, three formats only are possible: GIF (a non-free format not recommended by GNU), PNG (not every browser recognizes it) or JPEG (not appropriate for schemas with lines, arrows and texts). I decided to mainly use GIF images. GIF images also have the advantage that they may be animated.

There are several ways to create a figure:

The following commands unify the insertion of images independently of the final format (ps, pdf, html).

1.1   The GPICimage environment

A GPIC program should be enclosed within \begin{GPICimage} and \end{GPICimage}. The resulting image does not form a paragraph nor it is centered on its line. You have to specify this explicitly as for the following example:

It is possible to concatenate several images horizontally if separating them with the \subImage command. This command takes as argument the width of the preceding image expressed as an integer percentage of the current line width (i.e., from 0 to 100). The following figures respectively have a 50%, 33% and 14% width (the total which is less than 100% ensures the three figures to be on the same horizontal). To use percentages makes easier to obtain a similar effect in HTML.

The \subImage command may even be used before an image is produced, it simply considers the preceding image to be blank but sets its width according to its argument. It is therefore simple to add intermediate space before, between or after images. The following figure looks like the preceding one except that widths now are 20%, 40%, 20% and 20%.

The last figure was obtained by the following code:
 ellipse "GPIC" "image"
 ellipse "another" "GPIC" "image"


When the \subImage command is used for multiple images, the last image must be followed by such a command so its width is known.

1.2   The URLimage command

The URLimage command specifies an image file to be included. This command does not create a new paragraph nor it centers the produced image. The first argument is the name of the file without extension. The extension will be added by the various processors: Unfortunately, all these processors may take incompatible options that's why the URLimage command is followed by the Postscript options, the PNG options and, the GIF options. The Postscript options are those specified by the includegraphics command of the graphicx package (they are separated by commas). The GIF options are those specified by HTML (they are separated by whitespaces).

For instance, to include the VideoC logo inline, just say:
For instance, to include the 
\URLimage{videoc}{scale=0.25}{}{height=63 alt=VideoC}, 
logo inline, just say: 


Observe the relative pathname used to cite the image file and pay attention to these pathnames since within your HOME directory or on the HTTP server, these may not be the same!

2   URL

An hypertext document is full of links that may be followed. The LATEX version, on paper, does not support these links which must be rendered differently but the pdf and HTML output support them so you can click on them and be teleported. Two commands may be used that hide the various expansions depending on the final format and the next processor: HEVEA, LATEX2HTML or pdflatex.

2.1   The referenceURL command

The referenceURL command takes two arguments. The first one is the text that serves as an anchor to the hyperlink, the second one is the URL. The URL may not contain funny characters such as tilde. The URL is rendered as an hyperlink except in LATEX where it is rendered as a footnote. This command is fragile, you may expect problems when used in title or section commands.

Here are some examples of URLs: This appears in the document as:
Here are some examples of URLs: \begin{itemize}
\item \referenceURL{\videoc{} project page

2.2   The singleURL command

The singleURL command takes an URL as argument. This command may be used to cite explicitly an URL, for instance a mailto URL. It appears in full letters as a clickable link except in TeX. The singleURL command shares the same customisation possibilities offered by referenceURL.

In any case, mail kudos to is written as:
In any case, mail kudos to
\singleURL{} is written as: 

2.3   The defineURL command

Sometimes it is necessary to derive an URL from another base URL. This makes easier to change the base URL and to let all the others be relative to it. This must be explicited since it has to be handled specially (mainly because # is a special character for LATEX and for URLs). The defineURL command also permits URLs to contain funny characters such as tilde.

The defineURL command takes two arguments. The first is a LATEX name (beginning with a backslash), the second is a base URL. The first argument will be defined as a zero-ary command that will expand into the base URL. This command is robust.

Examples are in order. For instance, just write the following to define the \QueinnecURL command:

You may now use the \QueinnecURL command in last argument of \referenceURL or \singleURL. Here is a link towards my home page which is written as:
Here is a link towards my 
\referenceURL{home page}{\QueinnecURL/WWW/Queinnec.html} 
which is written as:


The problem with the two first commands is that they are not robust (this is LATEX jargon that means that you cannot use these commands within other macros, titles for instance). Sometimes you need to find a way to insert an URL in such a context and defineURL may help. I did not succeed to find a portable way to insert a mailto URL in the title so the only possible way seems to clutter source files with conditional code.

3   Citing code snippets

Rendering code snippets depends on the language of the snippet. Code excerpts may also be rendered in line or as paragraphs. Two commands exist for these goals. These commands are revised, improved but compatible versions of the lisp command of the ApocaLIXP package that comes with LiSP2TeX. This tool allows to extract code excerpts from files and to cite them surrounded by appropriate commands. Use the videoc.l2t style file to customize LiSP2TeX.

3.1   The snippet command

Codes excerpts start with the \snippet command and end with \endsnippet. The \snippet command takes an optional argument (embedded within square brackets) that specifies the default language. Among these languages are c and scheme. The language is used to provide a default customization.

Within the excerpt, all characters (including newlines) are copied verbatim. There is however a single exception: commands starting with a backslash are recognized and processed but these commands cannot have arguments. Apart the \endsnippet nullary command that ends the \snippet quasi-environment, there is also the \[ ...\] sequence that typesets its inner text in LATEX.

Observe that these commands do not form pure LATEX environment so you cannot write \begin{snippet} ...\end{snippet}. This is due to TeX and its catcode behavior. It is simpler to recognize the end with a regular command than something containing curly braces. However it is simple to transform one into the other if needed (see the library for instance).

As a matter of style, it is better to start the code to be copied verbatim on the line that follows the snippet command. This is to avoid a first line which is not aligned with the following ones.

Here are some examples. The first one is from Scheme:
;;; Id: snip.scm,v 1.1 1999/01/19 20:42:57 queinnec Exp
(define (fact n)
  (if (> n 1) 
      ;; in TeX: n! = n × n-1!
      (* n (fact (- n 1)))
      1 ) ) 
(define (test)
  ;; A bunch of values with various types:
  `',(#t #f #\a "foo" 3.14) )
This one is a test for me:
(define test "test") ; comment ended by an endsnippet.
The second is from C:
fact (int n)
     if ( n > 1 ) {
          /* in TeX: n! = n × n-1! */
          return n * fact(n-1);
     } else {
          int result = 42/42;  return result;

test ()
     printf("\n\t Test%s", '\0');  \

Here follows the original LATEX code for the two previous examples:
Here are some examples. The first one is from Scheme: 
\snippet[scheme];;; $Id: snip.scm,v 1.1 1999/01/19 20:42:57 queinnec Exp $
(define (fact n)
  (if (> n 1) 
      ;; in \TeX: \fbox{$n! = n \times {n-1}!$}
      (* n (fact (- n 1)))
      1 ) ) 
(define (test)
  ;; A bunch of values with various types:
  `',(#t #f #\a "foo" 3.14) )\endsnippet
This one is a test for me: \snippet[scheme]
(define test "test") ; comment ended by an endsnippet.\endsnippet
The second is from C:
fact (int n)
     if ( n > 1 ) {
          /* in \TeX: \[$n! = n \times {n-1}!$\] */
          return n * fact(n-1);
     } else {
          int result = 42/42; return result;
test ()
     printf("\n\t Test%s", '\0'); \
In fact, I lied in the previous paragraph since the excerpts are automatically extracted from Scheme and C files with the LiSP2TeX tool. Therefore I really wrote:
Here are some examples. The first one is from Scheme: 
\FromFile("snip.scm" fact test)

The second is from C:
\FromCFile("snip.c" "fact" "test") 

The default style (which is, by default, the current value of the snippetDefaultLanguage command i.e., the scheme style) is obtained when one does not mention any language; in this case you even don't need to use the square brackets since there is nothing in it. You thus may write directly:
This    a 
     is   snippet 

This    another 
     is   snippet 

This    a third 
     is   snippet 

The source code for the previous example shows the various possible wordings. It is however encouraged that you always use an explicit language to qualify the snippet because this language will be used to give a class for the DIV section in the generated HTML. Here is the source code:
This    \[a\] 
     is   snippet \endsnippet \snippet[]
This    \[another\] 
     is   snippet \endsnippet \snippet[scheme]
This    \[a third\] 
     is   snippet \endsnippet 
Of course it is possible to define one's own style: see below. Even if it is possible not to mention the language, it is far better to always specify it to obtain a better rendering into HTML. This is because the language is used to give a CLASS tag to the DIV that encloses a snippet. You may then associate to this CLASS some rendering properties via a Cascading Style Sheet file.


There is a number of ways to customize the rendering of snippets. Customization is expressed by hooks. There are general hooks and language-dependent hooks. These later hooks are run after the general ones so they may correct the default behavior for the hook. Therefore there are two different levels of customization depending on whether you want to customize the snippet engine or a particular language rendering.

is run when entering the snippet engine just after the \snippet command (and its optional argument) but before any character is read. By default, it starts a new paragraph.
is run when exiting the snippet engine just before the \endsnippet command. By default, it closes the current paragraph.
is run at the beginning of every line. It may be redefined to print the number of the line for instance. By default, it does nothing.
is run at the end of every line. By default it does nothing.
is run before any TeX inclusion opened by the \[ command. By default it changes the font to italics.
is run after any TeX inclusion closed by the \] command. By default, it closes the math mode if not yet done.
is an internal hook which is run any time the catcode of characters are changed so it is possible to make some characters active. The Scheme environment for instance redefines the semicolon to render comments in italics.
For all these hooks, there may exist a language dependent hook whose name is formed after the name of the hook suffixed by the name of the language (the optional argument of the \snippet command which is recorded in the \snippetLanguage command which, by default, is equal to the current value of the snippetDefaultLanguage) command.

Moreover, styles may be inherited. The exact behavior of the hook mechanism is as follows. Suppose the optional language of the snippet be abc and the hook hook then, hook is run (if defined) then hooka, hookab and hookabc. Therefore if you mention schemeplus as the language of a snippet, you will run the general hooks, the scheme hooks and the schemeplus hooks (and all sort of intermediate hooks such as sch or schemeplus if they are defined).

It is often the case that within these hooks you only toggle some predefined customization habits. Here there are:

defines the macros delimiting an insertion of plain TeX within a snippet. It is custom to use \[ and \] to enter and exit the inclusion.
renders Lisp comments in TeX.
renders Lisp comments verbatim.
(a condition) keeps leading spaces right. after the semi-colons beginning a Lisp comment.
makes \" appear as \".
makes #\c appears as #\c.
makes active a macro after a hash sign.
makes # to be a regular character within comments. This makes easy to talk of true and false!
(in C) makes \n and siblings appear as they stand.
(in C) makes a backslash followed by a newline appears as a backslash alone at the end of a line.
(in Perl) makes \\ stands as it is.
Here is some examples of these various possible customization.

(define (foo)
  ;; one space (and booleans #t and #f)
;; four spaces 'bar )

3.2   The snip command

The \snip command permits the insertion of code within lines. It is somewhat similar to the \verb command except that it shares a number of features of the \snippet command.

A typical use of the \snip command is the following: \snip[file]{file.html} where the word file.html will be typeset according to the convention of the file style. By default, if the optional language parameter is absent, it defaults to the value of the snippetDefaultLanguage command. Therefore to write \snip[\snippetDefaultLanguage]{file.html} is equivalent to write more simply \snip{file.html}.

The following hooks are defined for the \snip command:

which is run right before,
which is run right after.

4   Boxing

The \parbox command in LATEX takes as arguments a width followed by a text that must be typeset in a box of that width. The width is often expressed with absolute units (centimeters, Didot points, etc.). A variant of this command is \subBOX that takes a width expressed in percentage of the current line width. This command may only be used within the BOXES environment.

For instance, this text is typeset in a box that is twice as narrow as the non-empty box that follows. This other box is twice as large as the one to its left. These two boxes should appear on a same line, moreover they are separated by a small empty box. The percentages used here are, from left to right: 30%, 5% and 60%. Once again, the total sum should be a little less than 100% to avoid breaking the horizontal layout.

The previous example is written as:
For instance, this text is typeset in a box that is twice as narrow as
the non-empty box that follows.}
This other box is twice as large as the one to its left. These two
boxes should appear on a same line, moreover they are separated by a
small empty box. The percentages used here are, from left to right:
30%, 5% and 60%. Once again, the total sum should be a little less
than 100% to avoid breaking the horizontal layout. }

5   Texts

All texts, exercises, solutions are written in a extended subset of LATEX: a subset since not all LATEX can be easily turned into html, however this subset is extended by the macros defined in this document. This subset has been chosen to be easily converted into XML some time. Remember that there are a number of ways to combine information to prepare books, lecture, slides, web pages. Therefore, at the lowest level only exist topics and exercises.

5.1   Topic

A topic is a small amount of text on a precise subject. Topics are usually kept in .bk files (I now tend to use .bk for a complete document and .hbk for a file that only contains topics or exercices. These .hbk files need to be included in some other complete documents). A topic appears as a LATEX environment with two mandatory arguments: a label to uniquely identify the topic and title for this topic. The label should only use regular ASCII alphanumeric characters.
\begin{topic}{key}{title} ... \end{topic} 

A topic may contain many parts but primarily a text part that explains the title (this is the body of the topic). This text part contains a LATEX text and appears as a text environment. There must be exactly one text section but it may contain more than one paragraph.

A topic may also contain the mention of some credits (author(s), author(s)'(s) email) as well as some information on the current version of the topic. All these fields are free text for now.
\authorEmail{the author(s)'s email}
\careTakerEmail{the email of the maintainer of the topic}
\keywords{a comma-separated list of keywords}
\begin{credits} ... \end{credits} 

A topic may also contain some pre-requisites that should be read before the current topic. The argument of \required is a sequence of references (more on references below).

Symmetrically a topic may lead to various suggested topics. These are expressed with the following macro.

It is also possible to structure the text section with levels of details. The detail environment isolates a piece of text that should be displayed (interactively) only when the user has enough experience. A level of detail may be programmed to appear automatically after some delay. Levels of details may be embedded at will. Similar to a topic, a detail is introduced with a label and a title (therefore it may be possible to let details appear based on the set of labels qualifying details).

It is mandatory to obtain a correct TeX rendering that the text section be the last section that is, all credits, suggested and required macros appear before it.

Here is a complete example:

\begin{topic}{palmature-canard}{La palmature des canards}
  \required{\referPlace{Les palmipèdes}{cours-palmipede}
            \referPlace{Les ortolans}}{cours-ortolan}
  \suggested{\referPlace{Les mammifères}{dictionnaire-mammifere}}
  \credits{Enrique Instanchi \singleURL{}
           $Revision: 1.36 $ }
  \keywords{canard, bon dieu, enfant}
  \begin{text} Pas grand-chose à en dire! 
     \begin{detail}{petit-rien} et rien de plus!! \end{detail}

5.2   Exercises

An exercise has a structure that looks like a topic. It appears as a LATEX environment with a label and a title. It has a \required component, a \credits part, a text part that presents the exercise followed by one (or more) answer environment(s) containing the answer(s). The text part may use details as well. This is particularly convenient to give some hints to the student.

Here is an example:

\begin{exercise}{cent-sous}{Question à cent sous}
  \required{\referPlace{La palmature des canards}{cours-canard}}
  \suggested{\referPlace{Les mammifères}{dictionnaire-mammifere}
             \referPlace{Le problème du jour}{exercice89}}
  \credits{Enrique Instanchi \singleURL{}
           $Revision: 1.36 $ }
  \keywords{question, cent sous}
  \begin{text} Citez un enfant du bon dieu?
     \begin{detail}{Indice} Pensez à «~sauvage~». \end{detail}
  \begin{answer} «~canard sauvage~» est la bonne réponse. \end{answer}
  \begin{answer} mais on peut aussi pensez au 
                 rousseau-iste «~bon sauvage~». \end{answer}

There may exist additional fields to specify the testing Makefile, the directory where tests should be run, etc.

When typeset, the solution may appear or not depending on the value of the \ifWithSolution LATEX conditional macro. If this macro is not set, it defaults to true.

An exercise is not restricted to a single question. If more than one question is present then use the question environment as in:
\begin{exercise}{cent-sous}{Question à cent sous}
     Cet exercice porte sur l'argent.
     \begin{question} Combien de sous dans un euro ?
        \begin{answer} un certain nombre. \end{answer}
     \begin{question} Combien d'euros dans un sou ?
        \begin{answer} Ca dépend. \end{answer}
        \begin{answer} L'inverse de la réponse précédente. \end{answer}

5.3   Lower structures

The text of both topics and exercices may be further structured into subtopic or subsubtopic environments.

5.4   Higher structures

Above topics and exercises, the structure is free. You may combine them to form a lesson (a kind of LATEX chapter except that a lesson forms a LATEX environment with a title as mandatory argument).
\begin{lesson}{title} ... \end{lesson} 

Then you may combine lessons to form a book.

5.5   References

When a topic or exercice is defined, it may be referred to with a \ref LATEX macro using the label of the topic or exercice.

For an hypertext, another possibility is to refer to a topic or exercise with a \referPlace macro that will be typeset as a clickable link à la \referenceURL.

When expressing \required or \suggested links, there is a need to mark topics or exercises in order to refer to them. These are the analog of \label and \ref except that topics and exercices are automatically marked so you only need to refer to them. This may be done with \referPlace.

It is currently not possible though it may be useful to mark a precise place within a topic or an exercise except using the \label and \ref mechanism.

6   Miscellaneous

The \ttbackslash macro outputs a backslash and its argument in typewriter font.

7   Putting all these styles at work

First, use LATEX2e, then use the videoc package that is, include the following line right after the \documentclass line: \usepackage{videoc}.

To generate HTML pages, use HEVEA and the videoc.hva package.

8   Problems

This section should not exist! Unfortunately, there are at least the following problems that are summed up here so I cannot forget about them.


This document was translated from LATEX by HEVEA.