Re: Possible problem with Gnus

[Richard Stallman <rms@gnu.org>]

Andy, we have been talking about problems in Emacs code
to display postscript in the middle of a document.

    >     The sane thing to do is to serialize the whole GhostScript
    >     operation to have at most one GhostScript process running, and
    >     to not restart this process as long as images remain to be
    >     rendered.
    > 
    > That does sound desirable.  However,
    > 
    >       For this to work, one has to stop passing the information
    >     through an XPixMap but has to go through a file or pipe.
    > 
    > Using a pixmap is preferable, in general.  Why do you think
    > using a single Ghostscript process is incompatible with using
    > a pixmap?

    Because the interface to GhostScript that is used for passing the
    XPixMap Id and the respective sizes is queried just at the start of
    GhostScript.

I think the solution for this is to make a new interface
to allow Emacs to specify the pixmap to an existing GhostScript
process when reusing it for another image.

Andy, can you implement such an interface for Emacs to use?

    >       In contrast, preview-latex first deals with on-screen images.
    >     Once they are dealt with, it reverts to rendering the rest
    >     off-screen.
    > 
    > That would be a good optimization to add.

    Rendering off-screen material is actually not as much an optimization,
    but an interactivity feature.  It means that once GhostScript is
    through, scrolling through the file is not computationally expensive.

    However, if some document has thousands of images, it would be saner
    to render them just to disk in case you'll need them, but not burden
    Emacs' memory with them unless one actually moves there.

That makes sense.  Can that be done easily with reuse of a
single GhostScript process, with the existing GhostScript features?
If not, what new feature do we need?