20130124
========

Validation errors during 
:func:`form2obj_and_save <lino.ui.extjs3.views.form2obj_and_save>`
didn't always lead in a visible user message.
Fixed. 

Invested another hour into documenting what Lino is and why I love it:
:lino:`/about/index` and :lino:`/topics/ui`.

Checkin.


Worked on the documentation of 
:lino:`/topics/mti`.
:mod:`lino.utils.mti`
and :mod:`lino.test_apps.mti`.
tests.py is now in a separate file which does a `literalinclude` of models.py 

Added an MTI example to
:lino:`/tutorials/layouts`.


Removed `person_model` and `company_model` attributes
-----------------------------------------------------

These are no longer necessary.


AttributeError: 'ChildCollector' object has no attribute 'add_batch'
--------------------------------------------------------------------

This happens when running the 
:mod:`lino.test_apps.mti` 
suite using the newest Django development version. 
Yes, they changed code in 
:mod:`django.db.models.deletion.Collector`,
and yes I am using undocumented features.


Hiding a field in all layouts
-----------------------------

New method
:meth:`lino.core.model.Model.hide_element`
and new decorator
:meth:`dd.when_prepared <lino.core.inject.when_prepared>`.

Together they allow us to have :mod:`lino.projects.cosi` 
hide the `region` field::

  @dd.when_prepared('contacts.Partner')
  def hide_region(model):
      model.hide_elements('region')

(:mod:`lino.projects.cosi` is for Belgians, and Belgians 
don't use this field. 
But :mod:`lino.modlib.contacts` is not only for Belgians)