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from __future__ import unicode_literals
from django import forms
# While this couples the geographic forms to the GEOS library,
# it decouples from database (by not importing SpatialBackend).
from django.contrib.gis.geos import GEOSException, GEOSGeometry
from django.utils.translation import ugettext_lazy as _
from .widgets import OpenLayersWidget
class GeometryField(forms.Field):
"""
This is the basic form field for a Geometry. Any textual input that is
accepted by GEOSGeometry is accepted by this form. By default,
this includes WKT, HEXEWKB, WKB (in a buffer), and GeoJSON.
"""
widget = OpenLayersWidget
geom_type = 'GEOMETRY'
default_error_messages = {
'required': _('No geometry value provided.'),
'invalid_geom': _('Invalid geometry value.'),
'invalid_geom_type': _('Invalid geometry type.'),
'transform_error': _('An error occurred when transforming the geometry '
'to the SRID of the geometry form field.'),
}
def __init__(self, **kwargs):
# Pop out attributes from the database field, or use sensible
# defaults (e.g., allow None).
self.srid = kwargs.pop('srid', None)
self.geom_type = kwargs.pop('geom_type', self.geom_type)
super(GeometryField, self).__init__(**kwargs)
self.widget.attrs['geom_type'] = self.geom_type
def to_python(self, value):
"""
Transforms the value to a Geometry object.
"""
if value in self.empty_values:
return None
if not isinstance(value, GEOSGeometry):
try:
value = GEOSGeometry(value)
except (GEOSException, ValueError, TypeError):
raise forms.ValidationError(self.error_messages['invalid_geom'], code='invalid_geom')
# Try to set the srid
if not value.srid:
try:
value.srid = self.widget.map_srid
except AttributeError:
if self.srid:
value.srid = self.srid
return value
def clean(self, value):
"""
Validates that the input value can be converted to a Geometry
object (which is returned). A ValidationError is raised if
the value cannot be instantiated as a Geometry.
"""
geom = super(GeometryField, self).clean(value)
if geom is None:
return geom
# Ensuring that the geometry is of the correct type (indicated
# using the OGC string label).
if str(geom.geom_type).upper() != self.geom_type and not self.geom_type == 'GEOMETRY':
raise forms.ValidationError(self.error_messages['invalid_geom_type'], code='invalid_geom_type')
# Transforming the geometry if the SRID was set.
if self.srid and self.srid != -1 and self.srid != geom.srid:
try:
geom.transform(self.srid)
except GEOSException:
raise forms.ValidationError(
self.error_messages['transform_error'], code='transform_error')
return geom
def has_changed(self, initial, data):
""" Compare geographic value of data with its initial value. """
try:
data = self.to_python(data)
initial = self.to_python(initial)
except forms.ValidationError:
return True
# Only do a geographic comparison if both values are available
if initial and data:
data.transform(initial.srid)
# If the initial value was not added by the browser, the geometry
# provided may be slightly different, the first time it is saved.
# The comparison is done with a very low tolerance.
return not initial.equals_exact(data, tolerance=0.000001)
else:
# Check for change of state of existence
return bool(initial) != bool(data)
class GeometryCollectionField(GeometryField):
geom_type = 'GEOMETRYCOLLECTION'
class PointField(GeometryField):
geom_type = 'POINT'
class MultiPointField(GeometryField):
geom_type = 'MULTIPOINT'
class LineStringField(GeometryField):
geom_type = 'LINESTRING'
class MultiLineStringField(GeometryField):
geom_type = 'MULTILINESTRING'
class PolygonField(GeometryField):
geom_type = 'POLYGON'
class MultiPolygonField(GeometryField):
geom_type = 'MULTIPOLYGON'
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