Add BackendEmacs so sage-mode can have it's own playground for typesetting output

[gvol]

With the inclusion of #17234, we have a framework of creating typeset output in emacs without interfering with other systems, or piggy backing on things like EMBEDDED_MODE.

This ticket is only for the Sage half of the work.

Component: user interface

Keywords: sage-mode, emacs

Author: Ivan Andrus

Branch/Commit: 20aed33

Reviewer: Volker Braun

Issue created by migration from https://trac.sagemath.org/ticket/18115

[gvol]

comment:1

For those, like me, who don't fully understand the display_manager stuff, try this recipe

from sage.repl.rich_output.backend_emacs import BackendEmacs
from sage.repl.rich_output import get_display_manager
emacsdm = BackendEmacs()
get_display_manager().switch_backend(emacsdm,shell=get_ipython())

Then you can use

%display text latex

to test it out. Of course it will look rather ugly since sage-mode isn't formatting it for you.

[sagetrac-git]

Changed commit from e3e3247 to 20aed33

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

20aed33

Add EmacsBackend

[vbraun]

Reviewer: Volker Braun

[vbraun]

Changed branch from u/iandrus/emacs-typeset-output to 20aed33