Geolocate the browser and store lat,lng in session if and only if it's not already in session

web2py geolocate

controller:
def index()  
    return dict(latitude=session.latitude, longitude=session.longitude)

def set_location():
    session.latitude = request.vars.lat
    session.longitude = request.vars.lng


default/index.html:

{{extend 'layout.html'}}

{{if not session.latitude:}}
<script>
if(navigator.geolocation) 
    {
        navigator.geolocation.getCurrentPosition(postLocation);
        function postLocation(position) 
            {
        jQuery.post( '{{=URL('set_location')}}',{lat: +position.coords.latitude, lng: +position.coords.longitude });
            }
    }
</script>
{{pass}}


{{if 'latitude' in globals():}}
<p>
    Lat: {{=latitude}}
</p>
<p>
    Lng: {{=longitude}}
</p>
{{pass}}

{{=response.toolbar()}}

{{if 'message' in globals():}}
<h3>{{=message}}</h3>

{{elif 'content' in globals():}}
{{=content}}
{{else:}}
{{=BEAUTIFY(response._vars)}}
{{pass}}