8 |
Generating HTML constructs |
|
HEVEA output language being HTML, it is normal for users to insert
hypertext constructs their documents, or to control colors.
HEVEA provides high-level commands for doing this.
Users are advised to use these macros in the first place,
because it is easy to write incorrect HTML and that writting
HTML directly may interfeer in nasty ways with HEVEA internals.
8.1.1 |
Commands for Hyperlinks |
|
A few commands for hyperlink management and included images
are provided, all these
commands have approriate 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
\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.17.6).
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 (optionnaly) depends on only one third party package:
url, which 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 colors 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 colors.
There are sixteen predefined colors:
\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 following declarations
change font color to dark gray:
\htmlcolor{404040}
8.2 |
More on included images |
|
The \imgsrc
command
becomes handy when one has images both in Postscript and GIF 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 prefered, 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 GIF image and
using the \imgsrc
command
is the most adequate.
It should be prefered 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.
8.3 |
The rawhtml environment |
|
Any text enclosed between \begin{rawhtml}
and
\end{rawhtml}
is echoed verbatim into the HTML output file.
For avoiding to break HTML element nesting, the rawhtml
environment should be used only at toplevel (i.e. not within another
environment), and it should contain only HTML text that makes sense
alone
(e.g. \begin{rawhtml}<TABLE><ALIGN=right>\end{rawhtml}
...
\begin{rawhtml}</TABLE>\end{rawhtml}
is
dangerous. In that case,
use the internal macros \@open
and \@close
of
the following section instead).
When HEVEA is given the command line option ``-O'',
checking and optimization of text-level elements in the whole document
takes place.
As a consequence, incorrect HTML introduced by using the rawhtml
environment may be detected at a later stage.
For the document to remain processable by LATEX, it must load the
hevea.sty style file (see section 5.2).
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 behavior may change from one version of HEVEA to another and
because using them incorrectly easily
crashes HEVEA.
However:
-
Internal macros
are almost mandatory for writing supplementary base style files.
- Casual usage is a convenient (but dangerous) way to finely control
output (cf. the examples in the next section).
- Knowing a little about internal macros helps in understanding how
HEVEA works.
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 tag nor closing tag.
It is important to notice that primitive arguments are
processed (except for the \@print
primitive). Thus,
some characters cannot be given directly (e.g. #
and
%
must be given as \#
and \%
).
-
\@print{text}
-
Echo text verbatim.
- \@getprint{text}
-
Process text using a special output mode that strips off
HTML tags. This macro is the one to use for processed attributes of
HTML tags.
- \@hr[attr]{width}{height}
-
Ouput an HTML horizontal rule, attr is attributes given
directly (e.g.
SIZE=3 HOSHADE
), while width and
height are length arguments given in the LATEX style
(e.g. 2pt
or .5\linewidth
).
- \@open{BLOCK}{attributes}
-
Open HTML block-level element BLOCK with attributes
attributes. The block name BLOCK must be
uppercase.
As a special case BLOCK may be the empty string, then a HTML
group is opened.
- \@close{BLOCK}
-
Close HTML block-level element BLOCK.
Note that
\@open
and \@close
must be properly balanced.
Text-level elements are managed differently. They are not seen
as blocks that must be closed explicitely and they are replaced by the
internal text-level declarations \@style
, \@fontsize
and
\@fontcolor
. Block-level elements (and HTML groups)
delimit the effect of such declarations.
-
\@style{SHAPE}
-
Declare the text shape SHAPE (which must be uppercase)
as active. Text shapes are known as font style elements (
I
, TT
,
etc.) or phrase elements (EM
, etc.) in the
HTML terminology, they are part of the more general class of
text-level elements.
The text-level element SHAPE 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 SHAPE before them, and re-opening SHAPE inside them.
The next text-level constructs exhibit similar behavior with respect
to block-level elements.
- \@fontsize{int}
-
Declare the text-level element
FONT
with attribute
SIZE=
int as active. Note that int must
be a small integer in the range 1,2, ... , 7.
- \@fontcolor{color}
-
Declare the text-level element
FONT
with attribute
COLOR=
color as active.
Note that color must be a color attribute value in the HTML
style. That is either one of the sixteen conventional colors
black
, silver
etc, or a RGB hexadecimal color specification
of the form
"#
XXXXXX"
(yes, quotes are needed).
Note that the argument color is processed, as a consequence
numerical color arguments should be given as "\#
XXXXXX"
.
- \@nostyle
-
Close active text-level declarations and ignore further text-level
declarations (such as
\@style
, etc).
The effect stops when the enclosing block-level element is closed.
As a first example of using internal macros, consider the following
excerpt from the hevea.hva file that
defines the LATEX center
environment:
\newenvironment{center}{\@open{DIV}{ALIGN=center}}{\@close{DIV}}
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 the internal macro
\@style
.
For instance this is how you can make all emphasized text blink:
\renewcommand{\em}{\@style{EM}\@style{BLINK}}
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 wether 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 internaly 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
exemple above,
tags are emitted inside groups where styles are canceled by using the
\@nostyle
declaration.
Such a complication is needed, so as to avoid breaking proper nesting
of text-level elements.
Finally, here is an 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][CELLPADDING=10]
{\@open{TABLE}{#1}\@open{TR}{}\@open{TD}{BGCOLOR=\@getcolor{#2}}}
{\@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 BGCOLOR
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.