===================
GeoDjango Forms API
===================

.. module:: django.contrib.gis.forms
    :synopsis: GeoDjango forms API.

GeoDjango provides some specialized form fields and widgets in order to visually
display and edit geolocalized data on a map. By default, they use
`OpenLayers`_-powered maps, with a base WMS layer provided by `NASA`_.

.. _OpenLayers: https://openlayers.org/
.. _NASA: https://earthdata.nasa.gov/

Field arguments
===============
In addition to the regular :ref:`form field arguments <core-field-arguments>`,
GeoDjango form fields take the following optional arguments.

``srid``
--------

.. attribute:: Field.srid

    This is the SRID code that the field value should be transformed to. For
    example, if the map widget SRID is different from the SRID more generally
    used by your application or database, the field will automatically convert
    input values into that SRID.

``geom_type``
-------------

.. attribute:: Field.geom_type

    You generally shouldn't have to set or change that attribute which should
    be setup depending on the field class. It matches the OpenGIS standard
    geometry name.

Form field classes
==================

``GeometryField``
-----------------

.. class:: GeometryField

``PointField``
--------------

.. class:: PointField

``LineStringField``
-------------------

.. class:: LineStringField

``PolygonField``
----------------

.. class:: PolygonField

``MultiPointField``
-------------------

.. class:: MultiPointField

``MultiLineStringField``
------------------------

.. class:: MultiLineStringField

``MultiPolygonField``
---------------------

.. class:: MultiPolygonField

``GeometryCollectionField``
---------------------------

.. class:: GeometryCollectionField

Form widgets
============

.. module:: django.contrib.gis.forms.widgets
    :synopsis: GeoDjango widgets API.

GeoDjango form widgets allow you to display and edit geographic data on a
visual map.
Note that none of the currently available widgets supports 3D geometries, hence
geometry fields will fallback using a simple ``Textarea`` widget for such data.

Widget attributes
-----------------

GeoDjango widgets are template-based, so their attributes are mostly different
from other Django widget attributes.


.. attribute:: BaseGeometryWidget.geom_type

    The OpenGIS geometry type, generally set by the form field.

.. attribute:: BaseGeometryWidget.map_height
.. attribute:: BaseGeometryWidget.map_width

    Height and width of the widget map (default is 400x600).

.. attribute:: BaseGeometryWidget.map_srid

    SRID code used by the map (default is 4326).

.. attribute:: BaseGeometryWidget.display_raw

    Boolean value specifying if a textarea input showing the serialized
    representation of the current geometry is visible, mainly for debugging
    purposes (default is ``False``).

.. attribute:: BaseGeometryWidget.supports_3d

    Indicates if the widget supports edition of 3D data (default is ``False``).

.. attribute:: BaseGeometryWidget.template_name

    The template used to render the map widget.

You can pass widget attributes in the same manner that for any other Django
widget. For example::

    from django.contrib.gis import forms

    class MyGeoForm(forms.Form):
        point = forms.PointField(widget=
            forms.OSMWidget(attrs={'map_width': 800, 'map_height': 500}))

Widget classes
--------------

``BaseGeometryWidget``

.. class:: BaseGeometryWidget

    This is an abstract base widget containing the logic needed by subclasses.
    You cannot directly use this widget for a geometry field.
    Note that the rendering of GeoDjango widgets is based on a template,
    identified by the :attr:`template_name` class attribute.

``OpenLayersWidget``

.. class:: OpenLayersWidget

    This is the default widget used by all GeoDjango form fields.
    ``template_name`` is ``gis/openlayers.html``.

    ``OpenLayersWidget`` and :class:`OSMWidget` use the ``openlayers.js`` file
    hosted on the ``cdnjs.cloudflare.com`` content-delivery network. You can
    subclass these widgets in order to specify your own version of the
    ``OpenLayers.js`` file in the ``js`` property of the inner ``Media`` class
    (see :ref:`assets-as-a-static-definition`).

``OSMWidget``

.. class:: OSMWidget

    This widget uses an OpenStreetMap base layer to display geographic objects
    on. Attributes are:

    .. attribute:: template_name

        ``gis/openlayers-osm.html``

    .. attribute:: default_lat
    .. attribute:: default_lon

        The default center latitude and longitude are ``47`` and ``5``,
        respectively, which is a location in eastern France.

    .. attribute:: default_zoom

        The default map zoom is ``12``.

    The :class:`OpenLayersWidget` note about JavaScript file hosting above also
    applies here. See also this `FAQ answer`_ about ``https`` access to map
    tiles.

    .. _FAQ answer: https://help.openstreetmap.org/questions/10920/how-to-embed-a-map-in-my-https-site
