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20140222 (Saturday, 22 February 2014)
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Worked on a reported bug in :ref:`faggio`:
It seems that `courses.Course.update_events` does not always work correctly.
To make this reliable, we need a serious suite of unit tests.

:setting:`demo_date`
:func:`atelier.utils.date_offset`.

Worked with Manuel on `sunto`:

Managing images of a product
----------------------------

How to manage a series of uploadable images per Product?
Our idea after some brainstorming was to use a virtual HtmlBox::

    class Product(dd.Model):
        ...
        @dd.virtualfield(dd.HtmlBox())
        def product_image(self, ar):
            url = self.get_image_url()
            img = E.a(E.img(src=url, width="100%"), href=url, target="_blank")
            sar = ar.spawn(ImagesByProduct, master_instance=self)

            toolbar = ar.renderer.quick_manage_toolbar(sar, self)
            return E.div(E.p(img), toolbar)

        def get_image_url(self):
            try:
                im = ProductImage.objects.get(product=self, default_image=True)
            except ProductImage.DoesNotExist:
                return "placeholder.jpg"
            return im.file.url

Which assumes the following database model and tables::


    class ProductImage(dd.Uploadable):
        product = models.ForeignKey(Product)
        default_image = models.BooleanField(default=False)


    class ProductImages(dd.Table):
        model = ProductImage

        insert_layout = """
        product
        default_image
        file
        """

        detail_layout = """
        product
        default_image
        file
        """


    class ImagesByProduct(ProductImages):
        master_key = "product"


Remarks:

- See :mod:`lino.utils.xmlgen.html`
- `ar` is the calling request, i.e. a web request asking "give me the
  detail information about this product instance"
- `self` is the Product instance
- :meth:`quick_manage_toolbar
  <lino.modlib.extjs.ext_renderer.ExtRenderer.quick_manage_toolbar>`.
  is a new method we added together.