Implementing the Content-Language header according to RFC 3282 for better multi-language support

[Jorg Knobloch]

Hi all,

as announced on tb-planning in January 2016 (see below), I'd like to
improve multi-language support in TB a little. I write e-mail in four
languages and despite using my add-on "Dictionary for recipient
<https://addons.mozilla.org/en-us/thunderbird/addon/dictionary-for-recipient/>",
there are situations where I have to change the composition language
manually, or even more annoying, I have to change it a second time after
returning to a saved draft.

The first step would be to support the Content-Language header according to
RFC 3282 (https://tools.ietf.org/html/rfc3282). MS products already support
that and and looking through my e-mail store I see: es-ES, es-cr, ca-ES
(Catalan), de-DE, de-ch, cz-CZ, en-US, en-au, en-nz, en-za, en-US, it-IT,
etc.

This header would store the dictionary of the composition and would be used
for the following:

- When opening a saved draft or template, it would restore the language (Bug
1169184 <https://bugzilla.mozilla.org/show_bug.cgi?id=1169184>)
- It would also communicate the used language to the recipient (Bug
1201836 <https://bugzilla.mozilla.org/show_bug.cgi?id=1201836>). If such
a header is found, it could also preset the language when replying or
forwarding. Maybe that could be driven by a preference, since the language
information sent by other clients isn't always accurate. It seems that
Outlook transmits the language of the installed program but not the
language of the content.

Comments?

Jörg.
--
Jörg Knobloch - jo...@jorgk.com - www.jorgk.com
Thunderbird Developer <http://www.jorgk.com/misc/Mozilla-work.pdf> (Compose
peer) <https://wiki.mozilla.org/Modules/Thunderbird#Compose> - Member of
the Thunderbird Council
<https://wiki.mozilla.org/Modules/Thunderbird#Thunderbird_Council>

On 19/01/2016 23:56, Jörg Knobloch wrote:

Hi all,

Now that the features for TB 45 are more or less complete, I'm thinking
about work in 2016 and TB 52 due for Christmas.

For the next major release I'd like to tackle these three areas:

1) Better (multi-)language support:
+ https://bugzilla.mozilla.org/show_bug.cgi?id=1169184
Save spell checking language with draft
+ https://bugzilla.mozilla.org/show_bug.cgi?id=1201836
Communicate content language of e-mail (Content-Language header,
https://tools.ietf.org/html/rfc3282)
(can be used to set dictionary when replying/forwarding)
+ https://bugzilla.mozilla.org/show_bug.cgi?id=1020181
Store preferred spell check language in address book
+ https://bugzilla.mozilla.org/show_bug.cgi?id=728775
Make language display consistent in a) option b) spell checker c) context
menu d) spelling button.

<snip>

[R Kent James]

Sounds like an excellent idea to me!


Kent

[Magnus Melin]

Like I wrote on the bug, the value you get from adding Content-Language
is not much, since Outlook misuses it and doesn't look at the actual
content language (but installation language). Yes, it could be used for
internal language like drafts, but nobody on the receiving end could
really trust it for anything. The alternative, setting the lang value in
the HTML does not have this problem, and would work for multi-language
content as well.

-Magnus