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from django.contrib.gis.gdal import OGRException
from django.contrib.gis.geos import GEOSGeometry, GEOSException
from django.forms.widgets import Textarea
from django.template.loader import render_to_string
class OpenLayersWidget(Textarea):
"""
Renders an OpenLayers map using the WKT of the geometry.
"""
def render(self, name, value, attrs=None):
# Update the template parameters with any attributes passed in.
if attrs: self.params.update(attrs)
# Defaulting the WKT value to a blank string -- this
# will be tested in the JavaScript and the appropriate
# interfaace will be constructed.
self.params['wkt'] = ''
# If a string reaches here (via a validation error on another
# field) then just reconstruct the Geometry.
if isinstance(value, basestring):
try:
value = GEOSGeometry(value)
except (GEOSException, ValueError):
value = None
if value and value.geom_type.upper() != self.geom_type:
value = None
# Constructing the dictionary of the map options.
self.params['map_options'] = self.map_options()
# Constructing the JavaScript module name using the ID of
# the GeometryField (passed in via the `attrs` keyword).
self.params['module'] = 'geodjango_%s' % self.params['field_name']
if value:
# Transforming the geometry to the projection used on the
# OpenLayers map.
srid = self.params['srid']
if value.srid != srid:
try:
value.transform(srid)
wkt = value.wkt
except OGRException:
wkt = ''
else:
wkt = value.wkt
# Setting the parameter WKT with that of the transformed
# geometry.
self.params['wkt'] = wkt
return render_to_string(self.template, self.params)
def map_options(self):
"Builds 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)' % str(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
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