wagtail/docs/building_your_site/frontenddevelopers.rst

For Front End developers
========================

.. contents::

========================
Overview
========================

This page is aimed at non-Django-literate Front End developers.

Wagtail uses Django's templating language. For developers new to Django, start with Django's own template documentation: 
https://docs.djangoproject.com/en/dev/topics/templates/

Python programmers new to Django/Wagtail may prefer more technical documentation: 
https://docs.djangoproject.com/en/dev/ref/templates/api/

You should be familiar with Django templating basics before continuing with this documentation.

==========================
Templates
==========================

Every type of page or "content type" in Wagtail is defined as a "model" in a file called ``models.py``. If your site has a blog, you might have a ``BlogPage``  model and another called ``BlogPageListing``. The names of the models are up to the Django developer.

For each page model in ``models.py``, Wagtail assumes an HTML template file exists of (almost) the same name. The Front End developer may need to create these templates themselves by refering to ``models.py`` to infer template names from the models defined therein.

To find a suitable template, Wagtail converts CamelCase names to underscore_case. So for a ``BlogPage``, a template ``blog_page.html`` will be expected. The name of the template file can be overridden per model if necessary.

Template files are assumed to exist here::

    name_of_project/
        name_of_app/
            templates/
                name_of_app/
                    blog_page.html
            models.py


For more information, see the Django documentation for the `application directories template loader`_.

.. _application directories template loader: https://docs.djangoproject.com/en/dev/ref/templates/api/


Page content
~~~~~~~~~~~~

The data/content entered into each page is accessed/output through Django's ``{{ double-brace }}`` notation. Each field from the model must be accessed by prefixing ``self.``. e.g the page title ``{{ self.title }}`` or another field ``{{ self.author }}``.

Additionally ``request.`` is available and contains Django's request object.

==============
Static assets
==============

Static files e.g CSS, JS and images are typically stored here::
    
    name_of_project/
        name_of_app/
            static/
                name_of_app/
                    css/
                    js/
                    images/
            models.py

(The names "css", "js" etc aren't important, only their position within the tree.)    

Any file within the static folder should be inserted into your HTML using the ``{% static %}`` tag. More about it: :ref:`static_tag`.

User images
~~~~~~~~~~~

Images uploaded to Wagtail by its users (as opposed to a developer's static files, above) go into the image library and from there are added to pages via the :doc:`page editor interface </editor_manual/new_pages/inserting_images>`.

Unlike other CMS, adding images to a page does not involve choosing a "version" of the image to use. Wagtail has no predefined image "formats" or "sizes". Instead the template developer defines image manipulation to occur *on the fly* when the image is requested, via a special syntax within the template.

Images from the library **must** be requested using this syntax, but a developer's static images can be added via conventional means e.g ``img`` tags. Only images from the library can be manipulated on the fly.

Read more about the image manipulation syntax here :ref:`image_tag`.


========================
Template tags & filters
========================

In addition to Django's standard tags and filters, Wagtail provides some of it's own, which can be ``load``-ed `as you would any other <https://docs.djangoproject.com/en/dev/topics/templates/#custom-tag-and-filter-libraries>`_


.. _image_tag:

Images (tag)
~~~~~~~~~~~~

The ``image`` tag inserts an XHTML-compatible ``img`` element into the page, setting its ``src``, ``width``, ``height`` and ``alt``. See also :ref:`image_tag_alt`.

The syntax for the tag is thus::

    {% image [image] [method]-[dimension(s)] %}

For example:

.. code-block:: django

    {% load image %}
    ...

    {% image self.photo width-400 %}

    <!-- or a square thumbnail: -->
    {% image self.photo fill-80x80 %}

In the above syntax ``[image]`` is the Django object refering to the image. If your page model defined a field called "photo" then ``[image]`` would probably be ``self.photo``. The ``[method]`` defines which resizing algorithm to use and ``[dimension(s)]`` provides height and/or width values (as ``[width|height]`` or ``[width]x[height]``) to refine that algorithm.

Note that a space separates ``[image]`` and ``[method]``, but not ``[method]`` and ``[dimensions]``: a hyphen between ``[method]`` and ``[dimensions]`` is mandatory. Multiple dimensions must be separated by an ``x``.

The available ``method`` s are:

.. glossary::
    ``max`` 
        (takes two dimensions)

        Fit **within** the given dimensions. 

        The longest edge will be reduced to the equivalent dimension size defined. e.g A portrait image of width 1000, height 2000, treated with the ``max`` dimensions ``1000x500`` (landscape) would result in the image shrunk so the *height* was 500 pixels and the width 250.

    ``min`` 
        (takes two dimensions)

        **Cover** the given dimensions.

        This may result in an image slightly **larger** than the dimensions you specify. e.g A square image of width 2000, height 2000, treated with the ``min`` dimensions ``500x200`` (landscape) would have it's height and width changed to 500, i.e matching the width required, but greater than the height.

    ``width`` 
        (takes one dimension)

        Reduces the width of the image to the dimension specified.

    ``height`` 
        (takes one dimension)

        Resize the height of the image to the dimension specified.. 

    ``fill`` 
        (takes two dimensions)

        Resize and **crop** to fill the **exact** dimensions. 

        This can be particularly useful for websites requiring square thumbnails of arbitrary images. e.g A landscape image of width 2000, height 1000, treated with ``fill`` dimensions ``200x200`` would have it's height reduced to 200, then it's width (ordinarily 400) cropped to 200. 

        **The crop always aligns on the centre of the image.**

.. Note::
    Wagtail *does not allow deforming or stretching images*. Image dimension ratios will always be kept. Wagtail also *does not support upscaling*. Small images forced to appear at larger sizes will "max out" at their their native dimensions.

.. Note::
    Wagtail does not make the "original" version of an image explicitly available. To request it, it's suggested you rely on the lack of upscaling by requesting an image much larger than it's maximum dimensions. e.g to insert an image who's dimensions are uncertain/unknown at it's maximum size, try: ``{% image self.image width-10000 %}``. This assumes the image is unlikely to be larger than 10000px wide.


.. _image_tag_alt:

More control over the ``img`` tag
---------------------------------

In some cases greater control over the ``img`` tag is required, for example to add a custom ``class``. Rather than generating the ``img`` element for you, Wagtail can assign the relevant data to another object using Django's ``as`` syntax:

.. code-block:: django
    
    {% load image %}
    ...
    {% image self.photo width-400 as tmp_photo %}

    <img src="{{ tmp_photo.src }}" width="{{ tmp_photo.width }}" 
        height="{{ tmp_photo.height }}" alt="{{ tmp_photo.alt }}" class="my-custom-class" />


.. _rich-text-filter:

Rich text (filter)
~~~~~~~~~~~~~~~~~~

This filter takes a chunk of HTML content and renders it as safe HTML in the page. Importantly it also expands internal shorthand references to embedded images and links made in the Wagtail editor into fully-baked HTML ready for display.

Only fields using ``RichTextField`` need this applied in the template.

.. code-block:: django

    {% load rich_text %}
    ...
    {{ self.body|richtext }}

.. Note::
    Note that the template tag loaded differs from the name of the filter.

Internal links (tag)
~~~~~~~~~~~~~~~~~~~~

pageurl
--------

Takes a Page object and returns a relative URL (``/foo/bar/``) if within the same site as the current page, or absolute (``http://example.com/foo/bar/``) if not.

.. code-block:: django

    {% load pageurl %}
    ...
    <a href="{% pageurl self.blog_page %}">

slugurl
--------

Takes any ``slug`` as defined in a page's "Promote" tab and returns the URL for the matching Page. Like ``pageurl``, will try to provide a relative link if possible, but will default to an absolute link if on a different site. This is most useful when creating shared page furniture e.g top level navigation or site-wide links.

.. code-block:: django

    {% load slugurl %}
    ...
    <a href="{% slugurl self.your_slug %}">


.. _static_tag:

Static files (tag)
~~~~~~~~~~~~~~~~~~

Used to load anything from your static files directory. Use of this tag avoids rewriting all static paths if hosting arrangements change, as they might between  local and a live environments.

.. code-block:: django

    {% load static %}
    ...
    <img src="{% static "name_of_app/myimage.jpg" %}" alt="My image"/>

Notice that the full path name is not required and the path snippet you enter only need begin with the parent app's directory name.



========================
Wagtail User Bar
========================

This tag provides a contextual flyout menu on the top-right of a page for logged-in users. The menu gives editors the ability to edit the current page or add another at the same level. Moderators are also given the ability to accept or reject a page previewed as part of content moderation.

.. code-block:: django

    {% load wagtailuserbar %}
    ...
    {% wagtailuserbar %}

By default the User Bar appears in the top right of the browser window, flush with the edge. If this conflicts with your design it can be moved with a css rule in your own CSS files e.g to move it down from the top:

.. code-block:: css

    #wagtail-userbar{
       top:200px
    }