Re: [AUCTeX] "No connection to bus" message in Cygwin Emacs

[Tassilo Horn]

Sebastien Vauban <address@hidden> writes:

Hi Sebastien,

>> Possibly there has been an earlier error which already broke the
>> initialization of `TeX-latex-mode' in that buffer.
>
> Yes, the initialization seems broken because, when opening a .tex file,
> the mode stays in "Fundamental", hence the warning when I still tried to
> execute `C-c C-c' the first time.

Ok, I see.

>> Yes, indeed.  There's a predicate `TeX-evince-dbus-p' which should
>> never error and test if DBUS is available on the system and supported
>> by Emacs, and if the relevant Evince DBUS interfaces are available.
>>
>> In case you can reproduce the issue, you could edebug that function to
>> see where the error occurs.
>
> I've edebug'ed the function `TeX-evince-dbus-p' from tex.el.
>
> The `and' returns `nil' on the 3rd line:
>
>        (dbus-ignore-errors (dbus-get-unique-name :session))
>
> See http://screencast.com/t/2QHtttjSm.

Ok, so DBus should not be used on your system.  But AUCTeX never
accesses the DBus without being protected by (when (TeX-evince-dbus-p)
...) except for in `TeX-evince-sync-view' which is only used as View
command in case the viewer is Evince and DBus is available.  In any
case, it shouldn't have to do anything with errors at initialization.

> What's not clear to me at this instant is that `C-h f
> TeX-evince-dbus-p' doesn't return me a link to the file where the
> function is defined, as you can see on
> http://screencast.com/t/7HSPqoXIJm.

That's indeed strange.  Is than only with this function, also with other
AUCTeX functions, or also with functions of other packages?  At least in
the last case I'd guess it's a general emacs problem (on cygwin).

> Installation problem?  I'm using the ELPA version!

I've also checked with 11.88.6 from ELPA and Emacs 24.5, and there the
link is there.

> `C-h v AUCTeX-version' returns "11.88.6"...
>
> And `M-x locate-library RET tex-site' returns "Library is file
> ~/.emacs.d/elpa/auctex-11.88.6/tex-site.elc".
>
> So, it seems well installed, nope?

Yes, that's what's expected.  Locating the libraries tex and latex also
suggests tex.el and latex.el in that directory, right?  (There has been
a problem with some special distribution of Emacs which did some setup
in default.el and thereby overwrote user and package.el settings.
There, the result was that tex-site.el from AUCTeX ELPA eventually
triggered loading of a bundled, system-wide AUCTeX install so
effectively you couldn't upgrade your AUCTeX version.)

> PS- I don't have `evince' installed on my Windows.  I'm using SumatraPDF
>     to view the PDF files.  I don't know about evince, but that one
>     refreshes automatically the PDF after each compilation.

Yes, evince does that, too.  And forward and backward search with evince
as a viewer are implemented using DBus communication if possible in
AUCTeX.

Now I see where the error probably comes from.  When dbus.el gets
loaded, it'll call `dbus--init-bus' defined in dbusbind.c, and that can
possibly throw a "No connection to bus" error.  However, when I test
with cygwin's emacs 24.4.1 and auctex 11.88.6, I get no such error and
the source link in the help buffer is also there.

Anyway, you could try the following things:

  1. Wrap a (let ((dbus-debug nil)) ...) around the (and ...) in
    `TeX-evince-dbus-p'.
  2. If that doesn't help, also wrap the (require 'dbus nil :no-error)
     form in a (dbus-ignore-errors ...).

Then do `M-x byte-recompile-directory' for
~/.emacs.d/elpa/auctex-11.88.6/ and restart emacs.  Do you still get the
error then?

Bye,
Tassilo