At large search ranges (320 or 640NM range on the 777), the search time can blow up, especially if distant airports are being loaded. Add a time-bounded spatial query, and use it, so performance stays tolerable.
As an opt-in API, allow clients to request partial results, with a time-bounded cutoff. Use this to keep the MapWidget responsive even when many airports are being added to the cache (e.g., zooming out or panning rapidly when zoomed out)
Tolerate Octree leaf children which have been moved outside their leaf's BBox. This is necessary since lazy-loading of ILS and threshold files can cause re-locations even during child traversal, where updating the hierarchy is very complex. Instead, simply tolerate this case, and rely on the real position data (which is correct).
When a position is modified for an in-cache FGPositioned, we need to update the runtime information too, or the Octree code may (rightly) complain that it's seeing inconsistent data. Also make the Octree check an exception throw, and verbose, so this is easier to detect in the future.
Cache the parsed navigation and airport data in a binary file to reduce
startup times and memory consumption (since only referenced FGPositioned
elements are held in memory).
Data will be reimported when the mod-time of any input file is changed.
If a global file is changed (nav.dat, awy.dat, apt.dat, etc), the cache
will be completely rebuilt, which takes approximately 30 seconds on
moderate hardware. (Future work may reduce this).
