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Tuesday, May 20, 2014
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I have still some questions to meditate.

For the end-user there are two types of excerpts: (1) those who were
until now a simple "Print" button (usually together with a "Clear
Cache" button) and (2) those where the user chooses the "excerpt type"
before printing.

For example in :ref:`welfare`, Budgets and Contract are case (1). They
have zero or one "printout". They either have been printed, or they
haven't. There's never more than one printout per Budget or Contract.
`pcsw.Client` is an example of case (2). You cannot simply say "Print"
on a client, you must also specify "what" to print (current choices
are a curriculum vitae, eid-content and a todo list "plan d'action").

For Budgets and Contracts there will be no visible difference for the
user. The advantage of using excerpts is that now these printouts are
visible in the "history" (per client or per user).

Excerpts make it possible to dynamically configure the choice
between (1) and (2).  A concrete use case that drops into mind:
Invoices (in an accounting application) are usually case (1), but a
customer might decide that they want every invoice printed (possibly)
twice, one "internal" version (used e.g. by the packaging team) and
one version for the client. That would be case (2).

With case (1), users just want their "Print" and "Clear cache" buttons.
With case (2) it gets more complex.

Todo:

- Handle case (2) using a ComboButton

- Convert existing data.

- Is there a way do avoid rewriting the existing templates `vse.odt` and
  `art60-7.odt`? Currently they don't work because the printing context
  has changed.



Converted also `cal.Guest` and `cal.Event` to the new system (they are
no longer `Printable`).

I removed the `body_template` functionality from
:class:`ml.notes.NoteType` (which was there from before we had
excerpts).


The following decision took some time (to understand what's happening
and to choose the solution):

I renamed the `get_templates_group` methods in
:mod:`lino.mixins.printable` to `get_template_groups`.  
And accordingly I changed 
lino.utils.config.find_template_config_files

Because I had the following problem: I want Lino to use the same
template `Default.odt` for most excerpts.  This should be in a
template group `excerpts`. But apps must be able to define
model-specific templates (as :file:`cv.odt`, :file:`eid-content.odt`,
:file:`art60-7.odt`). And these should not get mixed up with each
other, so they should use in their model-based template group. So the
list of possible choices for the :attr:`lino.modlib.excerpts.Excerpt.template`
field is a combination of a files found in all groups.

Another question is about the template context of an excerpt: Should
``this`` refer to the `Excerpt` instance? Or rather to the
`Excerpt.owner`, i.e. the object being printed?

Added a subtle new feature: 
If :attr:`master_key` is given, then this field is automatically added to 
:attr:`hidden_columns`.