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1 from django.contrib.gis.gdal import OGRException |
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2 from django.contrib.gis.geos import GEOSGeometry, GEOSException |
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3 from django.forms.widgets import Textarea |
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4 from django.template.loader import render_to_string |
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5 |
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6 class OpenLayersWidget(Textarea): |
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7 """ |
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8 Renders an OpenLayers map using the WKT of the geometry. |
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9 """ |
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10 def render(self, name, value, attrs=None): |
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11 # Update the template parameters with any attributes passed in. |
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12 if attrs: self.params.update(attrs) |
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13 |
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14 # Defaulting the WKT value to a blank string -- this |
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15 # will be tested in the JavaScript and the appropriate |
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16 # interfaace will be constructed. |
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17 self.params['wkt'] = '' |
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18 |
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19 # If a string reaches here (via a validation error on another |
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20 # field) then just reconstruct the Geometry. |
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21 if isinstance(value, basestring): |
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22 try: |
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23 value = GEOSGeometry(value) |
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24 except (GEOSException, ValueError): |
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25 value = None |
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26 |
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27 if value and value.geom_type.upper() != self.geom_type: |
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28 value = None |
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29 |
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30 # Constructing the dictionary of the map options. |
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31 self.params['map_options'] = self.map_options() |
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32 |
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33 # Constructing the JavaScript module name using the ID of |
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34 # the GeometryField (passed in via the `attrs` keyword). |
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35 self.params['module'] = 'geodjango_%s' % self.params['field_name'] |
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36 |
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37 if value: |
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38 # Transforming the geometry to the projection used on the |
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39 # OpenLayers map. |
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40 srid = self.params['srid'] |
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41 if value.srid != srid: |
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42 try: |
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43 value.transform(srid) |
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44 wkt = value.wkt |
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45 except OGRException: |
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46 wkt = '' |
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47 else: |
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48 wkt = value.wkt |
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49 |
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50 # Setting the parameter WKT with that of the transformed |
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51 # geometry. |
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52 self.params['wkt'] = wkt |
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53 |
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54 return render_to_string(self.template, self.params) |
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55 |
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56 def map_options(self): |
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57 "Builds the map options hash for the OpenLayers template." |
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58 |
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59 # JavaScript construction utilities for the Bounds and Projection. |
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60 def ol_bounds(extent): |
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61 return 'new OpenLayers.Bounds(%s)' % str(extent) |
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62 def ol_projection(srid): |
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63 return 'new OpenLayers.Projection("EPSG:%s")' % srid |
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64 |
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65 # An array of the parameter name, the name of their OpenLayers |
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66 # counterpart, and the type of variable they are. |
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67 map_types = [('srid', 'projection', 'srid'), |
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68 ('display_srid', 'displayProjection', 'srid'), |
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69 ('units', 'units', str), |
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70 ('max_resolution', 'maxResolution', float), |
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71 ('max_extent', 'maxExtent', 'bounds'), |
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72 ('num_zoom', 'numZoomLevels', int), |
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73 ('max_zoom', 'maxZoomLevels', int), |
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74 ('min_zoom', 'minZoomLevel', int), |
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75 ] |
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76 |
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77 # Building the map options hash. |
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78 map_options = {} |
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79 for param_name, js_name, option_type in map_types: |
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80 if self.params.get(param_name, False): |
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81 if option_type == 'srid': |
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82 value = ol_projection(self.params[param_name]) |
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83 elif option_type == 'bounds': |
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84 value = ol_bounds(self.params[param_name]) |
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85 elif option_type in (float, int): |
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86 value = self.params[param_name] |
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87 elif option_type in (str,): |
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88 value = '"%s"' % self.params[param_name] |
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89 else: |
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90 raise TypeError |
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91 map_options[js_name] = value |
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92 return map_options |