preview-latex: Misplaced previews
6.4 Misplaced previews
======================
If you are reading this section, the first thing is to check that your
problem is not caused by x-symbol in connection with an installation not
supporting 8-bit characters (
x-symbol interoperation). If not,
here's the beef:
As explained previously, Emacs uses pseudo-error messages generated
by the 'preview' package in order to pinpoint the exact source location
where a preview originated. This works in running text, but fails when
preview material happens to lie in macro arguments, like the contents of
'\emph'. Those macros first read in their entire argument, munge it
through, perhaps transform it somehow, process it and perhaps then
typeset something. When they finally typeset something, where is the
location where the stuff originated? TeX, having read in the entire
argument before, does not know and actually there would be no sane way
of defining it.
For previews contained inside such a macro argument, the default
behaviour of preview-latex is to use a position immediately after the
closing brace of the argument. All the previews get placed there, all
at a zero-width position, which means that Emacs displays it in an order
that preview-latex cannot influence (currently in Emacs it is even
possible that the order changes between runs). And since the placement
of those previews is goofed up, you will not be able to regenerate them
by clicking on them. The default behaviour is thus somewhat
undesirable.
The solution (like with other preview problems) is to tell the LaTeX
'preview' package how to tackle this problem (The LaTeX style
file). Simply, you don't need '\emph' do anything at all during
previews! You only want the text math previewed, so the solution is to
use '\PreviewMacro*\emph' in the preamble of your document which will
make LaTeX ignore '\emph' completely as long as it is not part of a
larger preview (in which case it gets typeset as usual). Its argument
thus becomes ordinary text and gets treated like ordinary text.
Note that it would be a bad idea to declare
'\PreviewMacro*[{{}}]\emph' since then both '\emph' as well as its
argument would be ignored instead of previewed. For user-level macros,
this is almost never wanted, but there may be internal macros where you
might want to ignore internal arguments.
The same mechanism can be used for a number of other text-formatting
commands like '\textrm', '\textit' and the like. While they all use the
same internal macro '\text@command', it will not do to redefine just
that, since they call it only after having read their argument in, and
then it already is too late. So you need to disable every of those
commands by hand in your document preamble.
Actually, we wrote all of the above just to scare you. At least all
of the above mentioned macros and a few more are already catered for by
a configuration file 'prauctex.cfg' that gets loaded by default unless
the 'preview' package gets loaded with the 'noconfig' option. You can
make your own copy of this file in a local directory and edit it in case
of need. You can also add loading of a file of your liking to
'preview-default-preamble', or alternatively do the manual disabling of
your favorite macro in 'preview-default-preamble', which is customizable
in the Preview Latex group.
Info Catalog
preview-latex: The preview images
preview-latex: For advanced users