restore method
Restores annotation's azimuth and distance; false when unknown or
stale (the annotation moved).
Implementation
bool restore(ArAnnotation annotation) {
final entry = _entries[annotation.uid];
if (entry == null ||
entry.latitude != annotation.position.latitude ||
entry.longitude != annotation.position.longitude) {
return false;
}
annotation.azimuth = entry.azimuth;
annotation.distanceFromUser = entry.distance;
return true;
}