HEVEA output language being html, it is normal for users to insert hypertext constructs their documents, or to control colours.
HEVEA provides high-level commands for generating hypertext constructs. Users are advised to use these commands in the first place, because it is easy to write incorrect html and that writing html directly may interfere in nasty ways with HEVEA internals.
A few commands for hyperlink management and included images are provided, all these commands have appropriate equivalents defined by the hevea package (see section 5.2). Hence, a document that relies on these high-level commands still can be typeset by LATEX, provided it loads the hevea package.
| Macro | HEVEA | LATEX | |
\ahref{url}{text} | make text an hyperlink to url | echo text | |
\footahref{url}{text} | make text an hyperlink to url | make url a footnote to text, url is shown in typewriter font | |
\ahrefurl{url} | make url an hyperlink to url. | typeset url in typewriter font | |
\ahrefloc{label}{text} | make text an hyperlink to label inside the document | echo text | |
\aname{label}{text} | make text an hyperlink target with label label | echo text | |
\mailto{address} | make address a “mailto” link to address | typeset address in typewriter font | |
\imgsrc[attr]{url} | insert url as an image, attr are attributes in the html sense | do nothing | |
\home{text} | produce a home-dir url both for output and links, output aspect is: “~text” | ||
It is important to notice that all arguments
are processed.
For instance, to insert a link to
my home page, (http://pauillac.inria.fr/~maranget/index.html),
you should do something like this:
\ahref{http://pauillac.inria.fr/\home{maranget}/index.html}{his home page}
Given the frequency of ~, # etc. in urls,
this is annoying. Moreover, the immediate solution, using \verb,
\ahref{\verb" ... /~maranget/..."}{his home page}
does not work, since LATEX forbids verbatim formatting
inside command arguments.
Fortunately, the url package provides a very convenient
\url command that acts like \verb and can appear in
other command arguments
(unfortunately, this is not the full story, see section B.17.11).
Hence, provided the url package is loaded,
a more convenient reformulation of the example above is:
\ahref{\url{http://pauillac.inria.fr/~maranget/index.html}}{his home page}
Or even better:
\urldef{\lucpage}{\url}{http://pauillac.inria.fr/~maranget/index.html}
\ahref{\lucpage}{his home page}
It may seem complicated, but this is a safe way to have a document processed both by LATEX and HEVEA. Drawing a line between url typesetting and hyperlinks is correct, because users may sometime want urls to be processed and some other times not. Moreover, HEVEA (optionally) depends on only one third party package: url, which is as correct as it can be and well-written.
In case the \url command is undefined
at the time \begin{document} is processed, the commands
\url, \oneurl and \footurl are defined as
synonymous for
\ahref, \ahrefurl and \footahref, thereby
ensuring
some compatibility with older versions of HEVEA.
Note that this usage of \url is deprecated.
Specifying colours both for LATEX and HEVEA should be done using the color package (see section B.14.2). However,one can also specify text color using special type style declarations. The hevea.sty style file define no equivalent for these declarations, which therefore are for HEVEA consumption only.
Those declarations follow html conventions for colours. There are sixteen predefined colours:
\black,
\silver,
\gray,
\white,
\maroon,
\red,
\fuchsia,
\purple,
\green,
\lime,
\olive,
\yellow,
\navy,
\blue,
\teal,
\aqua
|
Additionally, the current text color can be
changed by the declaration \htmlcolor{number},
where number is a six digit hexadecimal number specifying a
color in the RGB space. For instance, the declaration
\htmlcolor{404040}
changes font color to dark gray,
The \imgsrc command becomes handy when one has images both in
Postscript and GIF (or PNG or JPG) format. As explained in
section 6.3, Postscript images can be included in
LATEX documents by using the \epsfbox command from the
epsf package. For instance, if screenshot.ps is an
encapsulated Postscript file, then a doc.tex document can
include it by:
\epsfbox{screenshot.ps}
We may very well also have a GIF version of the screenshot image
(or be able to produce one easily using image converting tools),
let us store it in a screenshot.ps.gif file.
Then, for HEVEA to include a link to the GIF image in its
output, it suffices
to define the \epsfbox command in the macro.hva file
as follows:
\newcommand{\epsfbox}[1]{\imgsrc{#1.gif}}
Then HEVEA has to be run as:
# hevea macros.hva doc.tex
Since it has its own definition of \epsfbox, HEVEA will
silently include a link the GIF image and not to the Postscript image.
If another naming scheme for image files is preferred, there are
alternatives.
For instance, assume that Postscript files are of the kind
name.ps, while GIF files are of the kind
name.gif.
Then, images can be included using
\includeimage{name}, where
\includeimage is a specific user-defined command:
\newcommand{\includeimage}[1]{\ifhevea\imgsrc{#1.gif}\else\epsfbox{#1.ps}\fi}
Note that this method uses the hevea boolean register (see section 5.2.3). If one does not wish to load the hevea.sty file, one can adopt the slightly more verbose definition:
\newcommand{\includeimage}[1]{%
%HEVEA\imgsrc{#1.gif}%
%BEGIN LATEX
\epsfbox{#1.ps}
%END LATEX
}
When the Postscript file has been produced by
translating a bitmap file, this simple method of making a bitmap image and
using the \imgsrc command
is the most adequate.
It should be preferred over using the more automated image file
mechanism (see section 6),
which will translate the image back from
Postscript to bitmap format and will thus degrade it.
In this section a few of HEVEA internal macros are described. Internal macros occur at the final expansion stage of HEVEA and invoke Objective Caml code.
Normally, user source code should not use them, since their behaviour may change from one version of HEVEA to another and because using them incorrectly easily crashes HEVEA. However:
The general principle of HEVEA is that LATEX environments
\begin{env}…
\end{env} get
translated into html block-level elements <block
attributes>… </block>.
More specifically, such block level elements are opened by the
internal macro \@open and closed by the internal macro
\@close.
As a special case, LATEX groups {… }
get translated into html groups, which are shadow block-level
elements with neither opening nor closing tag.
In the following few paragraphs, we sketch the interaction of
\@open…\@close with paragraphs.
Doing so, we intend to warn users about the complexity
of the task of producing correct html, and to encourage
them to use internal macros, which, most of the time, take nasty
details into account.
Paragraphs are rendered by p elements, which are opened and
closed automatically.
More specifically, a first p is opened after
\begin{document}, then paragraph breaks close the active
p and open a new one.
The final \end{document} closes the last p.
In any occasion, paragraphs consisting only of space characters
are discarded silently.
Following html “normative reference [HTML-5a]”, block-level
elements cannot occur inside p; more precisely,
block-level opening tags implicitly close any active p.
As a consequence,
HEVEA closes the active p element when it processes
\@open
and opens a new p when it processes the matching
\@close.
Generally, no p element is opened by default inside block-level
elements, that is, HEVEA does not immediately open p after having
processed \@open.
However, if a paragraph break occurs later, then a new p
element is opened, and will be closed automatically
when the current block is closed.
Thus, the first “paragraph” inside block-level elements
that include several paragraphs is not a p element.
That alone probably prevents the consistent styling
of paragraphs with style sheets.
Groups behave differently, opening or closing them does
not close nor open p elements.
However, processing paragraph breaks inside groups involves temporarily
closing all groups up to the nearest enclosing p, closing it,
opening a new p and finally re-opening all groups.
Opening a block-level element inside a group, similarly
involves closing the active p and opening a new p
when the matching \@close is processed.
Finally, display mode (as introduced by $$) is also
complicated. Displays basically are table elements with one row
(tr), and HEVEA manages to introduce table cells (td)
where appropriate. Processing \@open inside a display
means closing the current cell, starting a new cell, opening the
specified block, and then immediately opening a new display.
Processing the matching \@close closes the internal
display, then the specified block, then the cell and finally opens a
new cell. In many occasions (in particular for groups), either cell
break or the internal display may get cancelled.
It is important to notice that primitive arguments are
processed (except for the \@print primitive, and for some of
the basic style primitives). Thus,
some characters cannot be given directly (e.g. # and
% must be given as \# and \%).
SIZE=3 HOSHADE), while width and
height are length arguments given in the LATEX style
(e.g. 2pt or .5\linewidth).
\@open and \@close must be properly balanced.
p element,
that is if a <p> opening tag is active,
\@out@par first closes it (by emitting </p>),
then formats arg, and then re-open a p element.
Otherwise \@out@par simply formats arg.
This command is adequate when
formatting arg produces block-level elements.
Text-level elements are managed differently. They are not seen
as blocks that must be closed explicitly.
Instead they follow a “declaration” style, similar
to the one of LATEX “text-style declarations” — namely,
\itshape, \em etc.
Block-level elements (and html groups)
delimit the effect of such declarations.
span (with given attributes)
as active.
The text-level element span will get opened as soon as
necessary and closed automatically, when the
enclosing block-level elements get closed.
Enclosed block-level elements are treated properly by closing span
before them, and re-opening span (with given attributes)
inside them.
The following text-level constructs exhibit similar behaviour with respect
to block-level elements.i, tt, etc.;
warning:most of font style elements are depreciated in html5,
and some of them are no longer valid, prefer CSS in span tags)
or phrase elements (em, etc.) in the html terminology.\@span and \@style,
as both a text-level element name name and attributes are specified.
More specifically,
\@span{attr} can be seen as a shorthand for
\@styleattr{span}{attr};
while
\@style{name} can be seen as
a shorthand for
\@styleattr{name}{}.span with attribute
style="font-size:font-size" as active.
The argument
int must be a small integer in the range
1,2, … , 7.
hevea computes font-size, a CSS fontsize value,
from int.
More specifically, font-size will
range from x-small to 120% included in
a xx-large, 3 being the default size medium.
Notice that \@fontsize is deprecated in favour of
\@span with proper fontsize declarations:
\@span{style="font-size=xx-small"},
\@span{style="font-size=x-small"},
\@span{style="font-size=small"},
etc.span with attribute
"style=color" as active.
The argument color must be a color attribute value in the html
style. That is either one of the sixteen conventional colours
black, silver etc, or a RGB hexadecimal color specification
of the form
#XXXXXX.
Note that the argument color is processed, as a consequence
numerical color arguments should be given as \#XXXXXX.The preferred way to style text in new versions of the html “standard”
is using style-sheet specifications. Those can be given as argument to
a “style” attributes of html elements, most noticeably
of the span elements.
For instance, to get italics in old versions of html one used
the text-level “i” element as in
<i>…</i>. Now, for the same results of getting
italics one may write:
<span style="font-style:italic">…</span>.
An indeed hevea styles text in that manner,
starting from version 2.00.
Such (verbose) declarations are then abstracted into style class declarations
by HEVEA optimiser esponja, which is invoked by hevea
when given option “-O”.
Notice that style attributes can be given to elements other than span.
However, combining style attributes requires a little care as only one style
attribute is allowed.
Namely <cite style="font-weight:bold" style="color:red">
is illegal and should be written
<cite style="font-weight:bold;color:red">.
For instance:
Das Kapital.
The command \@addtyle can be handy for adding style to
already style elements:
style attribute is added if necessary. Examples:
\@addstyle{color:red}{href="#"} will produce
href="#" style="color:red", and
\@addstyle{color:red}{href="#" style="font-style:italic"} will
produce href="#" style="font-style:italic;color:red". Note
that an unnecessary extra space can be added in some cases.
As an example, consider the following definition of a command for typesetting citation in bold, written directly in html:
\newcommand{\styledcite}[2][]
{{\@styleattr{cite}{\@addstyle{#1}{style="font-weight:bold"}}#2}}
The purpose of the optional argument is to add style to specific citations, as in:
Two fundamental works: \styledcite{The Holy Bible} and
\styledcite[color:red]{Das Kapital}.
We get: Two fundamental works: The Holy Bible and Das Kapital.
Notice that the example is given for illustrating the usage of the
\@addstyle macros, which is intended for package writers.
A probably simpler way to proceed would be to use
LATEX text-style declarations:
\newcommand{styledcite}[2][]{{\@style{cite}#1\bf{}#2}}
Two fundamental works: \styledcite{The Holy Bible} and
\styledcite[\color{red}]{Das Kapital}.
We get: Two fundamental works: The Holy Bible and Das Kapital.
Any text enclosed between \begin{rawhtml} and
\end{rawhtml} is echoed verbatim into the html output file.
Similarly, \rawhtmlinput{file} echoes the
contents of file file.
In fact, rawhtml is the environment counterpart of the
\@print command, but experience showed it to be much more
error prone.
When HEVEA was less sophisticated then it is now, rawhtml was quite convenient. But, as time went by, numerous pitfalls around rawhtml showed up. Here are a few:
é or é for é.\begin{rawhtml}<table>\end{rawhtml}…
\begin{rawhtml}</table>\end{rawhtml} is
dangerous, because HEVEA is not informed about opening and closing
the block-level element table. In that case, one should use
the internal macros \@open and \@close.\begin{rawhtml}text\end{rawhtml} fragments that
contain block-level elements will almost certainly mix poorly with
p elements (introduced by paragraph breaks) and with active
style declaration (introduced by, for instance, \it).
Safe usage will most of the time means using the internal macros
\@nostyle and \@out@par.As a conclusion, do not use the rawhtml environment! A much safer option is to use the htmlonly environment and to write LATEX code. For instance, in place of writing:
\begin{rawhtml}
A list of links:
<ul>
<li><a href="http://www.apple.com/">Apple</a>.
<li><a href="http://www.sun.com/">Sun</a>.
</ul>
\end{rawhtml}
One can write:
\begin{htmlonly}
A list of links:
\begin{itemize}
\item \ahref{http://www.apple.com/}{Apple}.
\item \ahref{http://www.sun.com/}{Sun}.
\end{itemize}
\end{htmlonly}
A list of links:
If HEVEA is targeted to text or info files (see
Section 11).
The text inside rawhtml environments is ignored.
However there exists a rawtext environment (and a
\rawtextinput command) to echo text verbatim in text or info
output mode.
Additionally, the raw environment and a \rawinput
command echo their contents verbatim, regardless of HEVEA output
mode. Of course, when HEVEA produces html,
the latter environment and command suffer from
the same drawbacks as rawhtml.
As a first example of using internal macros, consider the following
excerpt from the hevea.hva file that
defines the center environment:
\newenvironment{center}{\@open{div}{style="text-align:center"}}{\@close{div}}
Notice that the code above is no longer present and is given here
for explanatory purpose only.
Now HEVEA uses style-sheets and the actual definition of the
center environment is as follows:
\newstyle{.center}{text-align:center;margin-left:auto;margin-right:auto;}%
\setenvclass{center}{center}%
\newenvironment{center}
{\@open{div}{\@getprint{class="\getenvclass{center}"}}
{\@close{div}}%
Basically environments \begin{center}…\end{center} will, by
default, be translated into blocks
<div class="center">…</div>.
Additionally, the style class associated to center environments
is managed through an indirection, using the
commands \setenvclass and \getenvclass.
See section 9.3 for more explanations.
Another example is the definition of the \purple
color declaration (see section 8.1.2):
\newcommand{\purple}{\@fontcolor{purple}}
HEVEA does not feature all text-level elements by default. However one can easily use them with internal macros. For instance this is how you can make all emphasised text blink:
\renewcommand{\em}{\@styleattr{em}{style="text-decoration:blink"}}
Here is an example of this questionable blinking feature:
Then, here is the definition of a simplified \imgsrc
command (see section 8.1.1), without its optional argument:
\newcommand{\imgsrc}[1]
{\@print{<img src="}\@getprint{#1}\@print{">}}
Here, \@print and \@getprint are used to output
html text, depending upon whether this text requires processing or not.
Note that \@open{img}{src="#1"} is not correct,
because the element img consists in a single tag, without a
closing tag.
Another interesting example is the definition of the command
\@doaelement,
which HEVEA uses internally to output A elements.
\newcommand{\@doaelement}[2]
{{\@nostyle\@print{<a }\@getprint{#1}\@print{>}}{#2}{\@nostyle\@print{</a>}}
The command \@doaelement takes two arguments: the first
argument contains the opening tag attributes; while the second element is
the textual content of the A element.
By contrast with the \imgsrc example above,
tags are emitted inside groups where styles are cancelled by using the
\@nostyle declaration.
Such a complication is needed, so as to avoid breaking proper nesting
of text-level elements.
Here is another example of direct block opening. The bgcolor environment from the color package locally changes background color (see section B.14.2.1). This environment is defined as follows:
\newenvironment{bgcolor}[2][style="padding:1em"]
{\@open{table}{}\@open{tr}{}%
\@open{td}{\@addstyle{background-color:\@getcolor{#2}}{#1}}}
{\@close{td}\@close{tr}\@close{table}}
The bgcolor environment operates by opening a html table
(table) with only one row (tr) and cell (td) in
its opening command, and closing all these elements in its closing
command. In my opinion, such a style of opening block-level elements
in environment opening commands and closing them in environment
closing commands is good style.
The one cell background color is forced with a background-color
property in a style attribute.
Note that the mandatory argument to \begin{bgcolor} is the
background color expressed as a high-level color, which therefore
needs to be translated into a low-level color by using the
\@getcolor internal macro from the color package.
Additionally, \begin{bgcolor} takes html attributes
as an optional argument. These attributes are the ones of the
table element.
If you wish to output a given Unicode character whose value you know,
the recommended technique is to define an ad-hoc command
that simply call the \@print@u command.
For instance, “blackboard sigma” is Unicode U+02140 (hexa).
Hence you can define the command \bbsigma as follows:
\newcommand{\bbsigma}{\@print@u{X2140}}
Then, “\bbsigma” will output “⅀”
According to standards, as far as I understand them, html pages are made of Unicode (ISO 10646) characters. By contrast, a file in any operating system is usually considered as being made of bytes.
To account for that fact, html pages usually specify a document charset that defines a translation from a flow of bytes to a flow of characters. For instance, the byte 0xA4 means Unicode 0x00A4 (¤) in the ISO-8859-1 (or latin1) encoding, and 0x20AC (€) in the ISO-8859-15 (or latin9) encoding. Notice that HEVEA has no difficulty to output both symbols, in fact they are defined as Unicode characters:
\newcommand{\textcurrency}{\@print@u{XA4}}
\newcommand{\texteuro}{\@print@u{X20AC}}
But the \@print@u command may output the specified character as
a byte, when possible, by the means of the output translator.
If not possible, \@print@u outputs a numerical character
references (for instance €).
Of course, the document charset and the output translator
must be synchronised. The command \@def@charset takes a
charset name as argument and performs the operation of specifying the
document character set and the output translator. It should occur in
the document preamble.
Valid charset names are ISO-8859-n where n is a
number in 1…15,
KOI8-R, US-ASCII (the
default),
windows-n where n is
1250, 1251, 1252 or 1257,
or macintosh, or UTF-8.
In case those charsets do not suffice, you may ask the author for
other document charsets. Notice however that document charset is not
that important, the default US-ASCII works everywhere!
Input encoding of source files is another, although
related, issue — see Section B.17.4.
If wished so, the charset can be extracted from the current locale environment, provided this yields a valid (to HEVEA) charset name. This operation is performed by a companion script: xxcharset.exe. It thus suffices to launch HEVEA as: