Re: Fix needed for communication with gpg-agent

[Chong Yidong <cyd@stupidchicken.com>]

Richard Stallman <rms@gnu.org> writes:

> Would someone please implement this code, needed for correct
> redisplay after running pinentry?  Then please ack.
>
> ...
>
> Without X, Pinentry falls back to a curses implementation (there is
> also a curses only version of Pinentry).  This works pretty reliable
> but poses one problem: The screen needs a redraw as there is no
> portable way to save and restore the old screen content.  What can be
> done is to redraw the screen every time after calling a crypto
> operation which uses gpg or gpgsm.  This is of course not optimal as
> in most cases the passphrase has been cached and an expensive redraw
> is not required.

I don't see any reasonable way to do this.

Roughly speaking, when Emacs is run in a console (i.e. as a curses
program), it monopolizes terminal input and output.  I don't know of
any way to call the curses version of pinentry, have it temporarily
"take over" the terminal, and return control to Emacs once it's done.

I suggest filing this in TODO or PROBLEMS.  There is a kind of
workaround: if you first use gpg-agent outside of Emacs to cache your
passphrase, subsequent use of gpg-agent from in Emacs will work since
gpg-agent no longer needs to prompt for your passphrase.