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import logging
from django.contrib.gis.gdal import GDALException
from django.contrib.gis.geos import GEOSException, GEOSGeometry
from django.forms.widgets import Textarea
from django.utils import translation
# Creating a template context that contains Django settings
# values needed by admin map templates.
geo_context = {'LANGUAGE_BIDI': translation.get_language_bidi()}
logger = logging.getLogger('django.contrib.gis')
class OpenLayersWidget(Textarea):
"""
Render an OpenLayers map using the WKT of the geometry.
"""
def get_context(self, name, value, attrs):
# Update the template parameters with any attributes passed in.
if attrs:
self.params.update(attrs)
self.params['editable'] = self.params['modifiable']
else:
self.params['editable'] = True
# Defaulting the WKT value to a blank string -- this
# will be tested in the JavaScript and the appropriate
# interface will be constructed.
self.params['wkt'] = ''
# If a string reaches here (via a validation error on another
# field) then just reconstruct the Geometry.
if value and isinstance(value, str):
try:
value = GEOSGeometry(value)
except (GEOSException, ValueError) as err:
logger.error("Error creating geometry from value '%s' (%s)", value, err)
value = None
if (value and value.geom_type.upper() != self.geom_type and
self.geom_type != 'GEOMETRY'):
value = None
# Constructing the dictionary of the map options.
self.params['map_options'] = self.map_options()
# Constructing the JavaScript module name using the name of
# the GeometryField (passed in via the `attrs` keyword).
# Use the 'name' attr for the field name (rather than 'field')
self.params['name'] = name
# note: we must switch out dashes for underscores since js
# functions are created using the module variable
js_safe_name = self.params['name'].replace('-', '_')
self.params['module'] = 'geodjango_%s' % js_safe_name
if value:
# Transforming the geometry to the projection used on the
# OpenLayers map.
srid = self.params['srid']
if value.srid != srid:
try:
ogr = value.ogr
ogr.transform(srid)
wkt = ogr.wkt
except GDALException as err:
logger.error(
"Error transforming geometry from srid '%s' to srid '%s' (%s)",
value.srid, srid, err
)
wkt = ''
else:
wkt = value.wkt
# Setting the parameter WKT with that of the transformed
# geometry.
self.params['wkt'] = wkt
self.params.update(geo_context)
return self.params
def map_options(self):
"""Build the map options hash for the OpenLayers template."""
# JavaScript construction utilities for the Bounds and Projection.
def ol_bounds(extent):
return 'new OpenLayers.Bounds(%s)' % extent
def ol_projection(srid):
return 'new OpenLayers.Projection("EPSG:%s")' % srid
# An array of the parameter name, the name of their OpenLayers
# counterpart, and the type of variable they are.
map_types = [('srid', 'projection', 'srid'),
('display_srid', 'displayProjection', 'srid'),
('units', 'units', str),
('max_resolution', 'maxResolution', float),
('max_extent', 'maxExtent', 'bounds'),
('num_zoom', 'numZoomLevels', int),
('max_zoom', 'maxZoomLevels', int),
('min_zoom', 'minZoomLevel', int),
]
# Building the map options hash.
map_options = {}
for param_name, js_name, option_type in map_types:
if self.params.get(param_name, False):
if option_type == 'srid':
value = ol_projection(self.params[param_name])
elif option_type == 'bounds':
value = ol_bounds(self.params[param_name])
elif option_type in (float, int):
value = self.params[param_name]
elif option_type in (str,):
value = '"%s"' % self.params[param_name]
else:
raise TypeError
map_options[js_name] = value
return map_options