:date: 2016-05-12

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Thursday, May 12, 2016
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I worked on :ticket:`910` : a course (in :ref:`voga`) now has an
"Export" button which generates and opens an xlsx file designed to be
printed on paper for manually noting the presences of participants.

This document has a special challenge: when there are more than 20
events (or some configurable maximum number), then colums don't fit on
a single page, and in that case it is necessary to split the document
vertically, i.e. print remaining columns to a second page (or set of
pages, if there are many participants).

I believe that the first implementation using wkhtmltopdf had no
future because wkhtmltopdf fails fundamentally with defining page
headers and footers.

This is also a new style of build method for printables: it has a
target file to be generated and rendered to the request, but does not
use any template at all. This is :class:`CustomBuildMethod
<lino.modlib.printing.utils.CustomBuildMethod>`.

Also TIL that `xlwt` has been replaced by `openpyxl`.

We had a case of `AttributeError: 'NoneType' object has no attribute
'number_of_events'`::

    File "/lino_voga/lib/courses/models.py", line 257, in __init__
      if obj.product.number_of_events:


Alexa reported another subtle use case which I classify as part of
:ticket:`909`:


    Im Kurs 001 sind Leute eingeschrieben, die in ein paar Tagen
    beginnen. Also Startdatum steht auf 17. Mai. Lino zeigt aber am
    Bildschirm an (und druckt im Belegstatus aus), dass diese Plätze
    noch frei sind. Wenn sich heute noch jemand anmeldet, dann sehen
    wir nicht, dass der Kurs schon voll ist.
  
I fixed it and wrote some test cases into
:ref:`voga.specs.courses`. To get these test cases I had to enhance
the demo fixture (:mod:`lino_voga.lib.voga.fixtures.buche`).

I did something which I should have done eariler: I changed the
default English date formatting done by :mod:`lino.utils.date_format`
from US to UK.  This causes of course lots of changes in doctests.
But it is just too impossible to get used to the American date format.