All length commands are ignored, things go smoothly when LATEX syntax is
used (using the \newlength, \setlength, etc. commands,
which are null macros).
Of course, if lengths are really important to the document, rendering
will be poor.
Note that TEX length syntax is not at all recognised. As a
consequence, writing things like \textwidth=10cm will clobber
the output.
Users can correct such misbehaviour by adopting LATEX syntax, here
they should write
\setlength{\textwidth}{10cm}.
The \hspace, \vspace and \addvspace spacing
commands and their starred versions recognise positive explicit length
arguments. Such arguments get converted to a number of non-breaking
spaces or line breaks.
Basically, the value of 1em or 1ex is one space or one
line-break. For other length units, a simple conversion based upon a
10pt font is used.
HEVEA cannot interpret more complicated length arguments or perform negative spacing. In these situations, a warning is issued and no output is done.
Spacing commands without arguments are recognised.
The \enspace, \quad and \qquad commands output
one, two and four non-breaking spaces, while the \smallskip,
\medskip and \bigskip output one, one, and two line
breaks.
Stretchable lengths do not exist, thus the \hfill and
\vfill macros are undefined.
Box contents is typeset in text mode (i.e. non-math and non-display
mode).
Both LATEX boxing commands \mbox and \makebox
commands exist.
However \makebox generates a specific warning, since HEVEA
ignore the length and positioning instructions given as optional
argument.
Similarly, the boxing with frame \fbox and \framebox
commands are recognised and
\framebox issues a warning.
When in display mode, \fbox frames its argument by
enclosing it in a
table with borders. Otherwise, \fbox calls the \textfbox
command, which issues a warning and typesets its argument
inside a \mbox (and thus no frame is drawn).
Users can alter the behaviour of \fbox in non-display mode by
redefining \textfbox.
Boxes can be saved for latter usage by storing them in bins.
New bins are defined by \newsavebox{cmd}.
Then some text can be saved into cmd by
\sbox{cmd}{text} or
\begin{lrbox}{cmd} text \end{lrbox}.
The text is translated to html, as if it was inside a \mbox
and the resulting output is stored.
It is retrieved (and outputted) by the command
\usebox{cmd}.
The \savebox command reduces to \sbox, ignoring its
optional arguments.
The \rule commands translate to a html horizontal rule
(<HR>) regardless of its arguments.
All other box-related commands do not exist.