--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/web/lib/django/contrib/gis/forms/fields.py	Wed Jan 20 00:34:04 2010 +0100
@@ -0,0 +1,67 @@
+from django import forms
+from django.utils.translation import ugettext_lazy as _
+
+# While this couples the geographic forms to the GEOS library,
+# it decouples from database (by not importing SpatialBackend).
+from django.contrib.gis.geos import GEOSGeometry
+
+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 = forms.Textarea
+
+    default_error_messages = {
+        'no_geom' : _(u'No geometry value provided.'),
+        'invalid_geom' : _(u'Invalid geometry value.'),
+        'invalid_geom_type' : _(u'Invalid geometry type.'),
+        'transform_error' : _(u'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', 'GEOMETRY')
+        self.null = kwargs.pop('null', True)
+        super(GeometryField, self).__init__(**kwargs)
+
+    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.
+        """
+        if not value:
+            if self.null and not self.required:
+                # The geometry column allows NULL and is not required.
+                return None
+            else:
+                raise forms.ValidationError(self.error_messages['no_geom'])
+
+        # Trying to create a Geometry object from the form value.
+        try:
+            geom = GEOSGeometry(value)
+        except:
+            raise forms.ValidationError(self.error_messages['invalid_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'])
+
+        # Transforming the geometry if the SRID was set.
+        if self.srid:
+            if not geom.srid:
+                # Should match that of the field if not given.
+                geom.srid = self.srid
+            elif self.srid != -1 and self.srid != geom.srid:
+                try:
+                    geom.transform(self.srid)
+                except:
+                    raise forms.ValidationError(self.error_messages['transform_error'])
+
+        return geom