20111111
========

browser-specific UI language
----------------------------

Started support for user-specific language selection.
The basic trick is to add 
Django's `LocaleMiddleware` to 
:setting:`MIDDLEWARE_CLASSES`
as described in 
`How Django discovers language preference
<https://docs.djangoproject.com/en/5.0/topics/i18n/translation/#how-django-discovers-language-preference>`_.
This makes Django ask the user's browser's language 
preferences and set `request.LANGUAGE_CODE`.

Until now I thought that was enough...
but it turns out that there are a few places 
where I need to adapt Lino...

First and most evident was that the server must generate not only 
one file :xfile:`lino.js` at startup, but one for each language.
That wasn't too difficult.

Next problem is that :class:`Choice Lists <lino.utils.choicelists.ChoiceList>` trigger 
translation when filling their `choices` list. 

That's subtile! Check-in 20111111 before touching this problem.

After more than 2 hours of my evening I found the solution, 
which is only one line in 
:meth:`lino.utils.choicelists.ChoiceList.display_text`:
Before::

    @classmethod
    def display_text(cls,bc):
        return unicode(bc)
        
After::        

    from django.utils.functional import lazy
    
    @classmethod
    def display_text(cls,bc):
        return lazy(unicode,unicode)(bc)

That is, this method 
now returns a `Promise` of a call to `unicode()` 
and not already the result of a call to `unicode()`.

And another line of code had to change, 
the `__unicode__()` method 
of :class:`lino.modlib.properties.PropertyOccurence` must 
explicitly call unicode on that `Promise`.

As a side-effect, some unit tests needed to change 
because we use now `LocaleMiddleware`: we cannot any longer use 
:func:`lino.utils.babel.set_language` to select the response 
language, instead we must pass a `HTTP_ACCEPT_LANGUAGE` keyword to
Django's `TestCase.client.get()` function.
The unit tests would break again if for some reason 
we'd remove `LocaleMiddleware` again.

Check-in 20111111b.

Another problem was that many labels were converted to unicode in ext_elems 
when creating the UI widgets. 
Solved in check-in 20111111c.

And a last problem (for today) was that in :mod:`lino.modlib.countries.models` 
I used ugettext and not ugettext_lazy for marking translatable strings.

Check-in 20111111d.

Other changes
-------------

While researching for the above solution I did a few internal optimizations:

- The `few_countries` fixture now adds multilingual country names

- New function :func:`lino.utils.codetime` used by :meth:`lino.ui.extjs3.ext_ui.ExtUI.build_lino_js` 
  to avoid recreating the :xfile:`lino.js` files on each 
  server restart.
  Seems to work, but there may be unexpected surprises...


Closing the top-level window
----------------------------

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