motivation for recent bug reports on overlays and properties like before-string, display, after-string, and face (was: linum.el and display properties)

[Joe Wells <jbw@macs.hw.ac.uk>]

Markus Triska <markus.triska@gmx.at> writes:

> Hi Joe,
>
> I've been (loosely) following your recent bug-reports on
> Emacs-devel;

I hope you don't mind that I CC emacs-devel for my reply.  I think it
might help people to understand better why I've been trying to use
this stuff.

> is it correct that fixing these problems will also help linum.el?

Possibly.  I suspect linum.el is probably affected by the problem
where an overlay's before-string is affected by the face of the
character in the buffer after the overlay start (which isn't even
inside the overlay in the case of a zero-length overlay like linum.el
uses).

> Also, what exactly is it that you want to do with LaTeX and folding?

I've been making the code in tex-fold.el work better with the code in
preview.el (latex-preview).  (Both of these are part of AUCTeX.)  The
code in tex-fold allows viewing something like

  \textbf{XYZ \textit{ABC} 123}

as:

  XYZ ABC 123

This picks up anything that font-latex.el has already done, so the
appropriate fonts will be used.  In this case, that means the XYZ and
123 will be in bold font, and the ABC will be in bold italic font.

The code in preview.el allows viewing something like

  $\Omega^2_3$

as an image in the buffer, so you can see what the TeX typesetting
will look like.  It looks roughly like Ω²₃, except that the
superscript will be directly above the subscript, and it will use the
TeX fonts.

However, without any of the changes I have been making, these don't
work together, so you can get

  \textbf{XYZ $\Omega^2_3$ 123}

to display as either

  XYZ $\Omega^2_3$ 123

(where the XYZ and 123 are in bold font) or as

  \textbf{XYZ Ω²₃ 123}

but not as

  XYZ Ω²₃ 123

which is the most desired version.

If you want to see for yourself, I posted a version of my changes to
the auctex-devel mailing list.  (I've continued to work on making them
better since then.)

> Thank you for pursuing these issues!

Sure.  I'm just trying to use the text and overlay properties as they
are documented.  :-)

-- 
Joe