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
12pt 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,
non-display mode). Both LATEX boxing commands \mbox and
\makebox exist. The latter is associated with
class makebox, which is empty by default and can be redefined
by the user.
Similarly, the boxing-with-frame commands \fbox and
\framebox are recognized. Here both, long and short forms
refer to class framebox, which also can be redefined by the
user.
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.
No other box-related commands are implemented.