Re: Overlay mechanic improvements

[Eli Zaretskii <eliz@gnu.org>]

> From: David Kastrup <dak@gnu.org>
> Date: Tue, 30 Sep 2014 18:20:06 +0200
> 
> Since preview-latex is trivial to install via ELPA (as it's included in
> AUCTeX), I am somewhat at a loss figuring out what point people are
> trying to make by stating that they are not going to bother looking at
> it, preferring me to type descriptions for hours.

I doubt that just installing preview-latex would give me the insight
into the issues you were alluding to, without some serious study of
the code.

> Emacs does not offer any default support for rendering images on-demand
> from source code in a buffer.  The pipelines that preview-latex can be
> something like
> 
> buffer -> LaTeX -> Dvips -> Ghostscript -> PNG
> buffer -> PDFLaTeX -> pdftodsc -> Ghostscript -> PNG
> buffer -> LaTeX -> Dvipng -> PNG
> 
> It will also run several of those in parallel, like running
> LaTeX->Dvipng but falling back to Dvips->Ghostscript for those images
> which contain embedded PostScript.  The Ghostscript pipeline will render
> the on-screen images first to make for better interactive response.  In
> addition to the images, LaTeX produces geometry, baseline, source
> location and various other info (for example, default font size in order
> to match the rendering scale to the current default screen font) which
> is parsed by Emacs and used for integrating the resulting images in the
> right place and scale into the originating buffer.
> 
> So there are prioritized rendering pipelines and information side paths
> that deliver information crucial for tying the image stream back into
> the proper buffer locations, with proper scale and baseline.
> 
> There is other stuff like being able to paste text plus images into MIME
> mails (with the obvious loss of baseline and other formatting
> information, but for display math it is somewhat helpful), and desktop
> mode saving and restoring the images associated with a buffer.
> 
> All of that is not specific to LaTeX, and Emacs does not really provide
> anything helpful for creating that kind of facility apart from the
> display feature itself and the possibility to run processes and process
> filters.

Thanks, this is the information I was missing.