Confused by W3C geolocation example code — will it loop infinitely if a position can’t be found?

Question

I am a bit concerned about the safety of this code example in the W3C Geolocation spec:

// Forcing the user agent to return a fresh cached position.

// Request a position. We only accept cached positions whose age is not
// greater than 10 minutes. If the user agent does not have a fresh
// enough cached position object, it will immediately invoke the error
// callback.
navigator.geolocation.getCurrentPosition(successCallback,
                                         errorCallback,
                                         {maximumAge:600000, timeout:0});

function successCallback(position) {
  // By using the 'maximumAge' option above, the position
  // object is guaranteed to be at most 10 minutes old.
  // By using a 'timeout' of 0 milliseconds, if there is
  // no suitable cached position available, the user agent 
  // will aynchronously invoke the error callback with code
  // TIMEOUT and will not initiate a new position
  // acquisition process.
}

function errorCallback(error) {
  switch(error.code) {
    case error.TIMEOUT:
      // Quick fallback when no suitable cached position exists.
      doFallback();
      // Acquire a new position object.
      navigator.geolocation.getCurrentPosition(successCallback, errorCallback);
      break;
    case ... // treat the other error cases.
  };
}

function doFallback() {
  // No fresh enough cached position available.
  // Fallback to a default position.
}

What happens if the browser genuinely can't return a location fix - for whatever reason - and keeps timing out?

Surely the code will end up in an infinite loop with errorCallback being called over and over again.

I see the doFallback() call but that won't stop errorCallback being called repeatedly. Or will it?

Answer 1

error.code will return POSITION_UNAVAILABLE. The code in the spec is an infinite loop because I guess it is exactly what they want. Imagine a scenario where you are in navigation mode, moving through space. Sometimes, you go through a tunnel and you lost the network and are unable to get any position for a certain amount of time that you do not control. Then when out of the tunnel, it is good to be able to get the position automatically. In a scenario, where you need a one time value, the piece of code will not be useful, but then easy to modify to stop with an error message.